text
stringlengths 128
100k
| source
stringlengths 31
152
|
|---|---|
Racket is a general-purpose, multi-paradigm programming language. The Racket language is a modern dialect of Lisp and a descendant of Scheme. It is designed as a platform for programming language design and implementation. In addition to the core Racket language, Racket is also used to refer to the family of programming languages and set of tools supporting development on and with Racket. Racket is also used for scripting, computer science education, and research.
The Racket platform provides an implementation of the Racket language (including a runtime system, libraries, and compiler supporting several compilation modes: machine code, machine-independent, interpreted, and JIT) along with the DrRacket integrated development environment (IDE) written in Racket. Racket is used by the ProgramByDesign outreach program, which aims to turn computer science into "an indispensable part of the liberal arts curriculum".
The core Racket language is known for its extensive macro system which enables creating embedded and domain-specific languages, language constructs such as classes or modules, and separate dialects of Racket with different semantics.
The platform distribution is free and open-source software distributed under the Apache 2.0 and MIT licenses. Extensions and packages written by the community may be uploaded to Racket's package catalog.
== History ==
=== Development ===
Matthias Felleisen founded PLT Inc. in the mid 1990s, first as a research group, soon after as a project dedicated to producing pedagogic materials for novice programmers (lectures, exercises/projects, software). In January 1995, the group decided to develop a pedagogic programming environment based on Scheme. Matthew Flatt cobbled together MrEd, the original virtual machine for Racket, from libscheme, wxWidgets, and a few other free systems. In the years that followed, a team including Flatt, Robby Findler, Shriram Krishnamurthi, Cormac Flanagan, and many others produced DrScheme, a programming environment for novice Scheme programmers and a research environment for gradual typing. The main development language that DrScheme supported was named PLT Scheme.
In parallel, the team began conducting workshops for high school teachers, training them in program design and functional programming. Field tests with these teachers and their students provided essential clues for directing the development.
Over the following years, PLT added teaching languages, an algebraic stepper, a transparent read–eval–print loop, a constructor-based printer, and many other innovations to DrScheme, producing an application-quality pedagogic program development environment. By 2001, the core team (Felleisen, Findler, Flatt, Krishnamurthi) had also written and published their first textbook, How to Design Programs, based on their teaching philosophy.
The Racket Manifesto details the principles driving the development of Racket, presents the evaluation framework behind the design process, and details opportunities for future improvements.
=== Version history ===
The first generation of PLT Scheme revisions introduced features for programming in the large with both modules and classes. Version 42 introduced units – a first-class module system – to complement classes for large scale development. The class system gained features (e.g. Java-style interfaces) and also lost several features (e.g. multiple inheritance) throughout these versions. The language evolved throughout a number of successive versions, and gaining milestone popularity in Version 53, leading to extensive work and the following Version 100, which would be equivalent to a "1.0" release in current popular version systems.
The next major revision was named Version 200, which introduced a new default module system that cooperates with macros. In particular, the module system ensures that run-time and compile-time computation are separated to support a "tower of languages". Unlike units, these modules are not first-class objects.
Version 300 introduced Unicode support, foreign library support, and refinements to the class system. Later on, the 300 series improved the performance of the language runtime with an addition of a JIT compiler and a switch to a default generational garbage collection.
By the next major release, the project had switched to a more conventional sequence-based version numbering. Version 4.0 introduced the #lang shorthand to specify the language that a module is written in. Further, the revision introduced immutable pairs and lists, support for fine-grained parallelism, and a statically-typed dialect.
On 7 June 2010, PLT Scheme was renamed Racket. The renaming coincided with the release of Version 5.0. Subsequently, the graphical user interface (GUI) backend was rewritten in Racket from C++ in Version 5.1 using native UI toolkits on all platforms. Version 5.2 included a background syntax checking tool, a new plotting library, a database library, and a new extended REPL. Version 5.3 included a new submodule feature for optionally loaded modules, new optimization tools, a JSON library, and other features. Version 5.3.1 introduced major improvements to DrRacket: the background syntax checker was turned on by default and a new documentation preview tool was added.
In version 6.0, Racket released its second-generation package management system. As part of this development, the principal DrRacket and Racket repository was reorganized and split into a large set of small packages, making it possible to install a minimal racket and to install only those packages needed.
Version 7 of Racket was released with a new macro expander written in Racket as part the preparations for supporting moving to the Chez Scheme runtime system and supporting multiple runtime systems.
On 19 November 2019, Racket 7.5 was released. The license of Racket 7.5 was less restrictive. They use now either the Apache 2.0 license or the MIT license.
On 2021 February 13, Racket 8.0 was released. Racket 8.0 marks the first release where Racket with the Chez Scheme runtime system, known as Racket CS, is the default implementation. Racket CS is faster, easier to maintain and develop, backward-compatible with existing Racket programs, and has better parallel garbage collection.
== Features ==
Racket's core language includes macros, modules, lexical closures, tail calls, delimited continuations, parameters (fluid variables), software contracts, green threads and OS threads, and more. The language also comes with primitives, such as eventspaces and custodians, which control resource management and enables the language to act like an operating system for loading and managing other programs. Further extensions to the language are created with the powerful macro system, which together with the module system and custom parsers can control all aspects of a language. Most language constructs in Racket are implemented as macros in the base language. These include a mixin class system, a component (or module) system as expressive as opaque ascription in the ML module system, and pattern matching.
Further, the language features the first contract system for a higher-order programming language.
Racket's contract system is inspired by the Design by Contract work for Eiffel and extends it to work for higher-order values such as first-class functions, objects, reference cells, and so on. For example, an object that is checked by a contract can be ensured to make contract checks when its methods are eventually invoked.
Racket includes both bytecode and JIT (JIT) compilers. The bytecode compiler produces an internal bytecode format run by the Racket virtual machine, and the JIT compiler translates bytecode to machine code at runtime.
Since 2004, the language has also shipped with PLaneT, a package manager that is integrated into the module system so that third-party libraries can be transparently imported and used. Also, PLaneT has a built-in versioning policy to prevent dependency hell.
At the end of 2014, much of Racket's code was moved into a new packaging system separate from the main code base. This new packaging system is serviced by a client program named raco. The new package system provides fewer features than PLaneT; a blog post by Jay McCarthy on the Racket blog explains the rationale for the change and how to duplicate the older system.
=== Integrated language extensibility and macros ===
The features that most clearly distinguish Racket from other languages in the Lisp family are its integrated language extensibility features that support building new domain-specific and general-purpose languages. Racket's extensibility features are built into the module system to allow context-sensitive and module-level control over syntax. For example, the #%app syntactic form can be overridden to change the semantics of function application. Similarly, the #%module-begin form allows arbitrary static analysis of the entire module. Since any module can be used as a language, via the #lang notation, this effectively means that virtually any aspect of the language can be programmed and controlled.
The module-level extensibility features are combined with a Scheme-like hygienic macro system, which provides more features than Lisp's s-expression manipulation system, Scheme 84's hygienic extend-syntax macros, or R5RS's syntax-rules. Indeed, it is fair to say that the macro system is a carefully tuned application programming interface (API) for compiler extensions. Using this compiler API, programmers can add features and entire domain-specific languages in a manner that makes them completely indistinguishable from built-in language constructs.
The macro system in Racket has been used to construct entire language dialects. This includes Typed Racket, which is a gradually typed dialect of Racket that eases the migration from untyped to typed code, Lazy Racket—a dialect with lazy evaluation, and Hackett, which combines Haskell and Racket. The pedagogical programming language Pyret was originally implemented in Racket.
Other dialects include FrTime (functional reactive programming), Scribble (documentation language), Slideshow (presentation language), and several languages for education.
Racket's core distribution provides libraries to aid the development of programming languages. Such languages are not restricted to s-expression based syntax. In addition to conventional readtable-based syntax extensions, the directive #lang enables the invocation of arbitrary parsers, which can be implemented using the parser tools library. See Racket logic programming for an example of such a language.
== Programming environment ==
The language platform provides a self-hosted IDE named DrRacket, a continuation-based web server, a graphical user interface, and other tools. As a viable scripting tool with libraries like common scripting languages, it can be used for scripting the Unix shell. It can parse command-line arguments and execute external tools.
=== DrRacket IDE ===
DrRacket (formerly DrScheme) is widely used among introductory computer science courses that teach Scheme or Racket and is lauded for its simplicity and appeal to beginner programmers. The IDE was originally built for use with the TeachScheme! project (now ProgramByDesign), an outreach effort by Northeastern University and a number of affiliated universities for attracting high school students to computer science courses at the college level.
The editor provides highlighting for syntax and run-time errors, parenthesis matching, a debugger and an algebraic stepper. Its student-friendly features include support for multiple "language levels" (Beginning Student, Intermediate Student and so on). It also has integrated library support, and sophisticated analysis tools for advanced programmers. Further, module-oriented programming is supported with the module browser, a contour view, integrated testing and coverage measurements, and refactoring support. It provides integrated, context-sensitive access to an extensive hyper-linked help system named "Help Desk".
DrRacket is available for Windows, macOS, Unix, and Linux with the X Window System and programs behave similarly on all these platforms.
== Code examples ==
Here is a trivial "Hello, World!" program:
Running this program produces the output:
"Hello, World!"
Here is a slightly less trivial program:
This program, taken from the Racket website, draws a Sierpinski triangle, nested to depth 8.
Using the #lang directive, a source file can be written in different dialects of Racket. Here is an example of the factorial program in Typed Racket, a statically typed dialect of Racket:
== Implementations ==
Racket currently has two implementations. Both support Linux, Windows and MacOS on a variety of architectures and are supported as at version 8.8 (2023). The default implementation uses the Chez Scheme incremental compiler and runtime. The alternate implementation generates platform-independent bytecode and uses Just-in-time compilation to generate machine code as it is loaded.
In addition, there are experimental implementations:
RacketScript is an experimental Racket to JavaScript (ES6) compiler. It allows programmers to use both JavaScript’s and Racket’s ecosystem and aims to make this interoperability as smooth as possible.
Pycket is a Racket implementation generated using the RPython framework.
== Applications and practical use ==
Apart from having a basis in programming language theory, Racket was designed as a general-purpose language for production systems. Thus, the Racket distribution features an extensive library that covers systems and network programming, web development, a uniform interface to the underlying operating system, a dynamic foreign function interface, several flavours of regular expressions, lexer/parser generators, logic programming, and a complete GUI framework.
Racket has several features useful for a commercial language, among them an ability to compile standalone executables under Windows, macOS, and Unix, a profiler and debugger included in the integrated development environment (IDE), and a unit testing framework.
Racket has been used for commercial projects and web applications. A notable example is the Hacker News website, which runs on Arc, which is developed in Racket. Naughty Dog has used it as a scripting language in several video games.
Racket is used to teach students algebra through game design in the Bootstrap program.
== References ==
== Further reading ==
Felleisen et al., 2013. Realm of Racket. No Starch Press.
Felleisen et al., 2003. How to Design Programs. MIT Press.
== External links ==
Official website
|
https://en.wikipedia.org/wiki/Racket_(programming_language)
|
C# (pronounced: C-sharp) ( see SHARP) is a general-purpose high-level programming language supporting multiple paradigms. C# encompasses static typing,: 4 strong typing, lexically scoped, imperative, declarative, functional, generic,: 22 object-oriented (class-based), and component-oriented programming disciplines.
The principal inventors of the C# programming language were Anders Hejlsberg, Scott Wiltamuth, and Peter Golde from Microsoft. It was first widely distributed in July 2000 and was later approved as an international standard by Ecma (ECMA-334) in 2002 and ISO/IEC (ISO/IEC 23270 and 20619) in 2003. Microsoft introduced C# along with .NET Framework and Microsoft Visual Studio, both of which are technically speaking, closed-source. At the time, Microsoft had no open-source products. Four years later, in 2004, a free and open-source project called Microsoft Mono began, providing a cross-platform compiler and runtime environment for the C# programming language. A decade later, Microsoft released Visual Studio Code (code editor), Roslyn (compiler), and the unified .NET platform (software framework), all of which support C# and are free, open-source, and cross-platform. Mono also joined Microsoft but was not merged into .NET.
As of January 2025, the most recent stable version of the language is C# 13.0, which was released in 2024 in .NET 9.0
== Design goals ==
The Ecma standard lists these design goals for C#:
The language is intended to be a simple, modern, general-purpose, object-oriented programming language.
The language, and implementations thereof, should provide support for software engineering principles such as strong type checking, array bounds checking,: 58–59 detection of attempts to use uninitialized variables, and automatic garbage collection.: 563 Software robustness, durability, and programmer productivity are important.
The language is intended for use in developing software components suitable for deployment in distributed environments.
Portability is very important for source code and programmers, especially those already familiar with C and C++.
Support for internationalization: 314 is very important.
C# is intended to be suitable for writing applications for both hosted and embedded systems, ranging from the very large that use sophisticated operating systems, down to the very small having dedicated functions.
Although C# applications are intended to be economical with regard to memory and processing power requirements, the language was not intended to compete directly on performance and size with C or assembly language.
== History ==
During the development of the .NET Framework, the class libraries were originally written using a managed code compiler system named Simple Managed C (SMC). In January 1999, Anders Hejlsberg formed a team to build a new language at the time called COOL, which stood for "C-like Object Oriented Language". Microsoft had considered keeping the name "COOL(C-like Object Oriented Language)" as the final name of the language, but chose not to do so for trademark reasons. By the time the .NET project was publicly announced at the July 2000 Professional Developers Conference, the language had been renamed C#, and the class libraries and ASP.NET runtime were ported to C#.
Hejlsberg is C#'s principal designer and lead architect at Microsoft, and was previously involved with the design of Turbo Pascal, Embarcadero Delphi (formerly CodeGear Delphi, Inprise Delphi and Borland Delphi), and Visual J++. In interviews and technical papers, he has stated that flaws in most major programming languages (e.g. C++, Java, Delphi, and Smalltalk) drove the fundamentals of the Common Language Runtime (CLR), which, in turn, drove the design of the C# language.
James Gosling, who created the Java programming language in 1994, and Bill Joy, a co-founder of Sun Microsystems, the originator of Java, called C# an "imitation" of Java; Gosling further said that "[C# is] sort of Java with reliability, productivity and security deleted."
In July 2000, Hejlsberg said that C# is "not a Java clone" and is "much closer to C++" in its design.
Since the release of C# 2.0 in November 2005, the C# and Java languages have evolved on increasingly divergent trajectories, becoming two quite different languages. One of the first major departures came with the addition of generics to both languages, with vastly different implementations. C# uses of reification to provide "first-class" generic objects that can be used like any other class, with code generation performed at class-load time.
Furthermore, C# has added several major features to accommodate functional-style programming, culminating in the LINQ extensions released with C# 3.0 and its supporting framework of lambda expressions, extension methods, and anonymous types. These features enable C# programmers to use functional programming techniques, such as closures, when it is advantageous to their application. The LINQ extensions and the functional imports help developers reduce the amount of boilerplate code included in common tasks such as querying a database, parsing an XML file, or searching through a data structure, shifting the emphasis onto the actual program logic to help improve readability and maintainability.
C# used to have a mascot called Andy (named after Anders Hejlsberg). It was retired on January 29, 2004.
C# was originally submitted to the ISO/IEC JTC 1 subcommittee SC 22 for review, under ISO/IEC 23270:2003, was withdrawn and was then approved under ISO/IEC 23270:2006. The 23270:2006 is withdrawn under 23270:2018 and approved with this version.
=== Name ===
Microsoft first used the name C# in 1988 for a variant of the C language designed for incremental compilation. That project was not completed, and the name was later reused.
The name "C sharp" was inspired by the musical notation whereby a sharp symbol indicates that the written note should be made a semitone higher in pitch.
This is similar to the language name of C++, where "++" indicates that a variable should be incremented by 1 after being evaluated. The sharp symbol also resembles a ligature of four "+" symbols (in a two-by-two grid), further implying that the language is an increment of C++.
Due to technical limits of display (standard fonts, browsers, etc.), and most keyboard layouts lacking a sharp symbol (U+266F ♯ MUSIC SHARP SIGN (♯)), the number sign (U+0023 # NUMBER SIGN (#)) was chosen to approximate the sharp symbol in the written name of the programming language.
This convention is reflected in the ECMA-334 C# Language Specification.
The "sharp" suffix has been used by a number of other Microsoft .NET compatible/compliant languages that are variants of existing languages, including J# (a .NET language also designed by Microsoft that is derived from Java 1.1), A# (from Ada), and the functional programming language F#. The original implementation of Eiffel for .NET was called Eiffel#, a name retired since the full Eiffel language is now supported. The suffix has also been used for libraries, such as Gtk# (a .NET wrapper for GTK and other GNOME libraries) and Cocoa# (a wrapper for Cocoa).
=== Versions ===
Development of the text for standards (beginning with C# 6) is done on GitHub. C# 7 was submitted to Ecma and approved in December 2023. As of January 2024, the standard for C# 8 is currently under development, referencing the approved language proposals.
== Syntax ==
The core syntax of the C# language is similar to that of other C-style languages such as C, Objective-C, C++ and Java, particularly:
Semicolons are used to denote the end of a statement.
Curly brackets are used to group statements. Statements are commonly grouped into methods (functions), methods into classes, and classes into namespaces.
Variables are assigned using an equals sign, but compared using two consecutive equals signs.
Square brackets are used with arrays, both to declare them and to get a value at a given index in one of them.
"class", "int" and "void" are used to define large-scale (usually main) program functions in scripts most of the time in C-style computer programming languages.
== Distinguishing features ==
Some notable features of C# that distinguish it from C, C++, and Java where noted, are:
=== Portability ===
By design, C# is the programming language that most directly reflects the underlying Common Language Infrastructure (CLI). Most of its intrinsic types correspond to value-types implemented by the CLI (Common Language Infrastructure) framework. However, the language specification does not state the code generation requirements of the compiler: that is, it does not state that a C# compiler must target a Common Language Runtime (CLR), or generate Common Intermediate Language (CIL), or generate any other specific format. Some C# compilers can also generate machine code like traditional compilers of Objective-C, C, C++, Assembly and Fortran.
=== Typing ===
C# supports strongly, implicitly typed variable declarations with the keyword var,: 470 and implicitly typed arrays with the keyword new[] followed by a collection initializer.: 80 : 58
Its type system is split into two families: Value types, like the built-in numeric types and user-defined structs, which are automatically handed over as copies when used as parameters, and reference types, including arrays, instances of classes, and strings, which only hand over a pointer to the respective object. Due to their special handling of the equality operator and their immutability, strings will nevertheless behave as if they were values, for all practical purposes. You can even use them as case labels. Where necessary, value types will be boxed automatically.
C# supports a strict Boolean data type, bool. Statements that take conditions, such as while and if, require an expression of a type that implements the true operator, such as the Boolean type. While C++ also has a Boolean type, it can be freely converted to and from integers, and expressions such as if (a) require only that a is convertible to bool, allowing a to be an int, or a pointer. C# disallows this "integer meaning true or false" approach, on the grounds that forcing programmers to use expressions that return exactly bool can prevent certain types of programming mistakes such as if (a = b) (use of assignment = instead of equality ==).
C# is more type safe than C++. The only implicit conversions by default are those that are considered safe, such as widening of integers. This is enforced at compile-time, during JIT, and, in some cases, at runtime. No implicit conversions occur between Booleans and integers, nor between enumeration members and integers (except for literal 0, which can be implicitly converted to any enumerated type). Any user-defined conversion must be explicitly marked as explicit or implicit, unlike C++ copy constructors and conversion operators, which are both implicit by default.
C# has explicit support for covariance and contravariance in generic types,: 144 : 23 unlike C++ which has some degree of support for contravariance simply through the semantics of return types on virtual methods.
Enumeration members are placed in their own scope.
The C# language does not allow for global variables or functions. All methods and members must be declared within classes. Static members of public classes can substitute for global variables and functions.
Local variables cannot shadow variables of the enclosing block, unlike C and C++, but may shadow type-level names.
=== Metaprogramming ===
Metaprogramming can be achieved in several ways:
Reflection is supported through .NET APIs, which enable scenarios such as type metadata inspection and dynamic method invocation.
Expression trees represent code as an abstract syntax tree, where each node is an expression that can be inspected or executed. This enables dynamic modification of executable code at runtime. Expression trees introduce some homoiconicity to the language.
Attributes, in C# parlance, are metadata that can be attached to types, members, or entire assemblies, equivalent to annotations in Java. Attributes are accessible both to the compiler and to code through reflection, allowing them to adjust their behaviour. Many of the native attributes duplicate the functionality of GCC's and VisualC++'s platform-dependent preprocessor directives.
System.Reflection.Emit namespace, which contains classes that emit metadata and CIL (types, assemblies, etc.) at runtime.
The .NET Compiler Platform (Roslyn) provides API access to language compilation services, allowing for the compilation of C# code from within .NET applications. It exposes APIs for syntactic (lexical) analysis of code, semantic analysis, dynamic compilation to CIL, and code emission.
Source generators, a feature of the Roslyn C# compiler, enable compile time metaprogramming. During the compilation process, developers can inspect the code being compiled with the compiler's API and pass additional generated C# source code to be compiled.
=== Methods and functions ===
A method in C# is a member of a class that can be invoked as a function (a sequence of instructions), rather than the mere value-holding capability of a field (i.e. class or instance variable). As in other syntactically similar languages, such as C++ and ANSI C, the signature of a method is a declaration comprising in order: any optional accessibility keywords (such as private), the explicit specification of its return type (such as int, or the keyword void if no value is returned), the name of the method, and finally, a parenthesized sequence of comma-separated parameter specifications, each consisting of a parameter's type, its formal name and optionally, a default value to be used whenever none is provided. Different from most other languages, call-by-reference parameters have to be marked both at the function definition and at the calling site, and you can choose between ref and out, the latter allowing handing over an uninitialized variable which will have a definite value on return. Additionally, you can specify a variable-sized argument list by applying the params keyword to the last parameter. Certain specific kinds of methods, such as those that simply get or set a field's value by returning or assigning it, do not require an explicitly stated full signature, but in the general case, the definition of a class includes the full signature declaration of its methods.
Like C++, and unlike Java, C# programmers must use the scope modifier keyword virtual to allow methods to be overridden by subclasses. Unlike C++, you have to explicitly specify the keyword override when doing so. This is supposed to avoid confusion between overriding and newly overloading a function (i.e. hiding the former implementation). To do the latter, you have to specify the new keyword. You can use the keyword sealed to disallow further overrides for individual methods or whole classes.
Extension methods in C# allow programmers to use static methods as if they were methods from a class's method table, allowing programmers to virtually add instance methods to a class that they feel should exist on that kind of objects (and instances of the respective derived classes).: 103–105 : 202–203
The type dynamic allows for run-time method binding, allowing for JavaScript-like method calls and run-time object composition.: 114–118
C# has support for strongly-typed function pointers via the keyword delegate. Like the Qt framework's pseudo-C++ signal and slot, C# has semantics specifically surrounding publish-subscribe style events, though C# uses delegates to do so.
C# offers Java-like synchronized method calls, via the attribute [MethodImpl(MethodImplOptions.Synchronized)], and has support for mutually-exclusive locks via the keyword lock.
=== Property ===
C# supports classes with properties. The properties can be simple accesor functions with a backing field, or implement arbitrary getter and setter functions. A property is read-only if there's no setter. Like with fields, there can be class and instance properties. The underlying methods can be virtual or abstract like any other method.
Since C# 3.0 the syntactic sugar of auto-implemented properties is available, where the accessor (getter) and mutator (setter) encapsulate operations on a single field of a class.
=== Namespace ===
A C# namespace provides the same level of code isolation as a Java package or a C++ namespace, with very similar rules and features to a package. Namespaces can be imported with the "using" syntax.
=== Memory access ===
In C#, memory address pointers can only be used within blocks specifically marked as unsafe, and programs with unsafe code need appropriate permissions to run. Most object access is done through safe object references, which always either point to a "live" object or have the well-defined null value; it is impossible to obtain a reference to a "dead" object (one that has been garbage collected), or to an arbitrary block of memory. An unsafe pointer can point to an instance of an unmanaged value type that does not contain any references to objects subject to garbage collections such as class instances, arrays or strings. Code that is not marked as unsafe can still store and manipulate pointers through the System.IntPtr type, but it cannot dereference them.
Managed memory cannot be explicitly freed; instead, it is automatically garbage collected. Garbage collection addresses the problem of memory leaks by freeing the programmer of responsibility for releasing memory that is no longer needed in most cases. Code that retains references to objects longer than is required can still experience higher memory usage than necessary, however once the final reference to an object is released the memory is available for garbage collection.
=== Exceptions ===
A range of standard exceptions are available to programmers. Methods in standard libraries regularly throw system exceptions in some circumstances and the range of exceptions thrown is normally documented. Custom exception classes can be defined for classes allowing handling to be put in place for particular circumstances as needed.
The syntax for handling exceptions is the following:Most of the time people call this a "try-catch" code block, because of the "try" and "catch" functions being used and accessible on all C# versions.Depending on your plans, the "finally" part can be left out. If error handling is not required, the (Exception ex) parameter can be omitted as well. Also, there can be several "catch" parts handling different kinds of exceptions.
Checked exceptions are not present in C# (in contrast to Java). This has been a conscious decision based on the issues of scalability and version management.
=== Polymorphism ===
Unlike C++, C# does not support multiple inheritance, although a class can implement any number of "interfaces" (fully abstract classes). This was a design decision by the language's lead architect to avoid complications and to simplify architectural requirements throughout CLI.
When implementing multiple interfaces that contain a method with the same name and taking parameters of the same type in the same order (i.e. the same signature), similar to Java, C# allows both a single method to cover all interfaces and if necessary specific methods for each interface.
C# also offers function overloading (a.k.a. ad-hoc-polymorphism), i.e. methods with the same name, but distinguishable signatures. Unlike Java, C# additionally supports operator overloading.
Since version 2.0, C# offers parametric polymorphism, i.e. classes with arbitrary or constrained type parameters, e.g. List<T>, a variable-sized array which only can contain elements of type T. There are certain kinds of constraints you can specify for the type parameters: Has to be type X (or one derived from it), has to implement a certain interface, has to be a reference type, has to be a value type, has to implement a public parameterless constructor. Most of them can be combined, and you can specify any number of interfaces.
=== Language Integrated Query (LINQ) ===
C# has the ability to utilize LINQ through the .NET Framework. A developer can query a variety of data sources, provided the IEnumerable<T> interface is implemented on the object. This includes XML documents, an ADO.NET dataset, and SQL databases.
Using LINQ in C# brings advantages like IntelliSense support, strong filtering capabilities, type safety with compile error checking ability, and consistency for querying data over a variety of sources. There are several different language structures that can be utilized with C# and LINQ and they are query expressions, lambda expressions, anonymous types, implicitly typed variables, extension methods, and object initializers.
LINQ has two syntaxes: query syntax and method syntax. However, the compiler always converts the query syntax to method syntax at compile time.
=== Functional programming ===
Though primarily an imperative language, C# always adds functional features over time, for example:
Functions as first-class citizen – C# 1.0 delegates
Higher-order functions – C# 1.0 together with delegates
Anonymous functions – C# 2 anonymous delegates and C# 3 lambdas expressions
Closures – C# 2 together with anonymous delegates and C# 3 together with lambdas expressions
Type inference – C# 3 with implicitly typed local variables var and C# 9 target-typed new expressions new()
List comprehension – C# 3 LINQ
Tuples – .NET Framework 4.0 but it becomes popular when C# 7.0 introduced a new tuple type with language support
Nested functions – C# 7.0
Pattern matching – C# 7.0
Immutability – C# 7.2 readonly struct C# 9 record types and Init only setters
Type classes – C# 12 roles/extensions (in development)
== Common type system ==
C# has a unified type system. This unified type system is called Common Type System (CTS).: Part 2, Chapter 4: The Type System
A unified type system implies that all types, including primitives such as integers, are subclasses of the System.Object class. For example, every type inherits a ToString() method.
=== Categories of data types ===
CTS separates data types into two categories:
Reference types
Value types
Instances of value types neither have referential identity nor referential comparison semantics. Equality and inequality comparisons for value types compare the actual data values within the instances, unless the corresponding operators are overloaded. Value types are derived from System.ValueType, always have a default value, and can always be created and copied. Some other limitations on value types are that they cannot derive from each other (but can implement interfaces) and cannot have an explicit default (parameterless) constructor because they already have an implicit one which initializes all contained data to the type-dependent default value (0, null, or alike). Examples of value types are all primitive types, such as int (a signed 32-bit integer), float (a 32-bit IEEE floating-point number), char (a 16-bit Unicode code unit), decimal (fixed-point numbers useful for handling currency amounts), and System.DateTime (identifies a specific point in time with nanosecond precision). Other examples are enum (enumerations) and struct (user defined structures).
In contrast, reference types have the notion of referential identity, meaning that each instance of a reference type is inherently distinct from every other instance, even if the data within both instances is the same. This is reflected in default equality and inequality comparisons for reference types, which test for referential rather than structural equality, unless the corresponding operators are overloaded (such as the case for System.String). Some operations are not always possible, such as creating an instance of a reference type, copying an existing instance, or performing a value comparison on two existing instances. Nevertheless, specific reference types can provide such services by exposing a public constructor or implementing a corresponding interface (such as ICloneable or IComparable). Examples of reference types are object (the ultimate base class for all other C# classes), System.String (a string of Unicode characters), and System.Array (a base class for all C# arrays).
Both type categories are extensible with user-defined types.
=== Boxing and unboxing ===
Boxing is the operation of converting a value-type object into a value of a corresponding reference type. Boxing in C# is implicit.
Unboxing is the operation of converting a value of a reference type (previously boxed) into a value of a value type. Unboxing in C# requires an explicit type cast. A boxed object of type T can only be unboxed to a T (or a nullable T).
Example:
== Libraries ==
The C# specification details a minimum set of types and class libraries that the compiler expects to have available. In practice, C# is most often used with some implementation of the Common Language Infrastructure (CLI), which is standardized as ECMA-335 Common Language Infrastructure (CLI).
In addition to the standard CLI specifications, there are many commercial and community class libraries that build on top of the .NET framework libraries to provide additional functionality.
C# can make calls to any library included in the List of .NET libraries and frameworks.
== Examples ==
=== Hello World ===
The following is a very simple C# program, a version of the classic "Hello world" example using the top-level statements feature introduced in C# 9:
For code written as C# 8 or lower, the entry point logic of a program must be written in a Main method inside a type:
This code will display this text in the console window:
Hello, world!
Each line has a purpose:
The above line imports all types in the System namespace. For example, the Console class used later in the source code is defined in the System namespace, meaning it can be used without supplying the full name of the type (which includes the namespace).
This line is a comment; it describes and documents the code for the programmer(s).
Above is a class definition for the Program class. Everything that follows between the pair of braces describes that class.The curly brackets demarcate the boundaries of a code block. In this first instance, they are marking the start and end of the Program class.
This declares the class member method where the program begins execution. The .NET runtime calls the Main method. Unlike in Java, the Main method does not need the public keyword, which tells the compiler that the method can be called from anywhere by any class. Writing static void Main(string[] args) is equivalent to writing private static void Main(string[] args). The static keyword makes the method accessible without an instance of Program. Each console application's Main entry point must be declared static otherwise the program would require an instance of Program, but any instance would require a program. To avoid that irresolvable circular dependency, C# compilers processing console applications (like that above) report an error if there is no static Main method. The void keyword declares that Main has no return value. (Note, however, that short programs can be written using Top Level Statements introduced in C# 9, as mentioned earlier.)
This line writes the output. Console is a static class in the System namespace. It provides an interface to the standard input/output, and error streams for console applications. The program calls the Console method WriteLine, which displays on the console a line with the argument, the string "Hello, world!".
=== Generics ===
With .NET 2.0 and C# 2.0, the community got more flexible collections than those in .NET 1.x. In the absence of generics, developers had to use collections such as ArrayList to store elements as objects of unspecified kind, which incurred performance overhead when boxing/unboxing/type-checking the contained items.
Generics introduced a massive new feature in .NET that allowed developers to create type-safe data structures. This shift is particularly important in the context of converting legacy systems, where updating to generics can significantly enhance performance and maintainability by replacing outdated data structures with more efficient, type-safe alternatives.
Example
== Standardization and licensing ==
In August 2001, Microsoft, Hewlett-Packard and Intel co-sponsored the submission of specifications for C# as well as the Common Language Infrastructure (CLI) to the standards organization Ecma International. In December 2001, ECMA released ECMA-334 C# Language Specification. C# became an ISO/IEC standard in 2003 (ISO/IEC 23270:2003 - Information technology — Programming languages — C#). ECMA had previously adopted equivalent specifications as the 2nd edition of C#, in December 2002. In June 2005, ECMA approved edition 3 of the C# specification, and updated ECMA-334. Additions included partial classes, anonymous methods, nullable types, and generics (somewhat similar to C++ templates). In July 2005, ECMA submitted to ISO/IEC JTC 1/SC 22, via the latter's Fast-Track process, the standards and related TRs. This process usually takes 6–9 months.
The C# language definition and the CLI are standardized under ISO/IEC and Ecma standards that provide reasonable and non-discriminatory licensing protection from patent claims.
Microsoft initially agreed not to sue open-source developers for violating patents in non-profit projects for the part of the framework that is covered by the Open Specification Promise. Microsoft has also agreed not to enforce patents relating to Novell products against Novell's paying customers with the exception of a list of products that do not explicitly mention C#, .NET or Novell's implementation of .NET (The Mono Project). However, Novell maintained that Mono does not infringe any Microsoft patents. Microsoft also made a specific agreement not to enforce patent rights related to the Moonlight browser plugin, which depends on Mono, provided it is obtained through Novell.
A decade later, Microsoft began developing free, open-source, and cross-platform tooling for C#, namely Visual Studio Code, .NET Core, and Roslyn. Mono joined Microsoft as a project of Xamarin, a Microsoft subsidiary.
== Implementations ==
Microsoft has developed open-source reference C# compilers and tools. The first compiler, Roslyn, compiles into intermediate language (IL), and the second one, RyuJIT, is a JIT (just-in-time) compiler, which is dynamic and does on-the-fly optimization and compiles the IL into native code for the front-end of the CPU. RyuJIT is open source and written in C++. Roslyn is entirely written in managed code (C#), has been opened up and functionality surfaced as APIs. It is thus enabling developers to create refactoring and diagnostics tools. Two branches of official implementation are .NET Framework (closed-source, Windows-only) and .NET Core (open-source, cross-platform); they eventually converged into one open-source implementation: .NET 5.0. At .NET Framework 4.6, a new JIT compiler replaced the former.
Other C# compilers (some of which include an implementation of the Common Language Infrastructure and .NET class libraries):
Mono, a Microsoft-sponsored project provides an open-source C# compiler, a complete open-source implementation of the CLI (including the required framework libraries as they appear in the ECMA specification,) and a nearly complete implementation of the NET class libraries up to .NET Framework 3.5.
The Elements tool chain from RemObjects includes RemObjects C#, which compiles C# code to .NET's Common Intermediate Language, Java bytecode, Cocoa, Android bytecode, WebAssembly, and native machine code for Windows, macOS, and Linux.
The DotGNU project (now discontinued) also provided an open-source C# compiler, a nearly complete implementation of the Common Language Infrastructure including the required framework libraries as they appear in the ECMA specification, and subset of some of the remaining Microsoft proprietary .NET class libraries up to .NET 2.0 (those not documented or included in the ECMA specification, but included in Microsoft's standard .NET Framework distribution).
The Unity game engine uses C# as its primary scripting language. The Godot game engine has implemented an optional C# module due to a donation of $24,000 from Microsoft.
== See also ==
== Notes ==
== References ==
=== Citations ===
=== Sources ===
Albahari, Joseph (2022). C# 10 in a Nutshell (First ed.). O'Reilly. ISBN 978-1-098-12195-2.
Archer, Tom (2001). "Part 2, Chapter 4: The Type System". Inside C#. Redmond, Washington: Microsoft Press. ISBN 0-7356-1288-9.
Novák, István; Velvart, Andras; Granicz, Adam; Balássy, György; Hajdrik, Attila; Sellers, Mitchel; Hillar, Gastón C.; Molnár, Ágnes; Kanjilal, Joydip (2010). Visual Studio 2010 and .NET 4 Six-in-One. Wrox Press. ISBN 978-0470499481.
Skeet, Jon (2019). C# in Depth (Fourth ed.). Manning. ISBN 978-1617294532.
== Further reading ==
Drayton, Peter; Albahari, Ben; Neward, Ted (2002). C# Language Pocket Reference. O'Reilly. ISBN 0-596-00429-X.
Petzold, Charles (2002). Programming Microsoft Windows with C#. Microsoft Press. ISBN 0-7356-1370-2.
== External links ==
C# Language Specification
C# Programming Guide
ISO C# Language Specification
C# Compiler Platform ("Roslyn") source code
|
https://en.wikipedia.org/wiki/C_Sharp_(programming_language)
|
In computer science, a literal is a textual representation (notation) of a value as it is written in source code. Almost all programming languages have notations for atomic values such as integers, floating-point numbers, and strings, and usually for Booleans and characters; some also have notations for elements of enumerated types and compound values such as arrays, records, and objects. An anonymous function is a literal for the function type.
In contrast to literals, variables or constants are symbols that can take on one of a class of fixed values, the constant being constrained not to change. Literals are often used to initialize variables; for example, in the following, 1 is an integer literal and the three letter string in "cat" is a string literal:
In lexical analysis, literals of a given type are generally a token type, with a grammar rule, like "a string of digits" for an integer literal. Some literals are specific keywords, like true for the Boolean literal "true".
In some object-oriented languages (like ECMAScript), objects can also be represented by literals. Methods of this object can be specified in the object literal using function literals. The brace notation below, which is also used for array literals, is typical for object literals:
== Literals of objects ==
In ECMAScript (as well as its implementations JavaScript or ActionScript), an object with methods can be written using the object literal like this:
These object literals are similar to anonymous classes in other languages like Java.
The JSON data interchange format is based on a subset of the JavaScript object literal syntax, with some additional restrictions (among them requiring all keys to be quoted, and disallowing functions and everything else except data literals). Because of this, almost every valid JSON document (except for some subtleties with escaping) is also valid JavaScript code, a fact exploited in the JSONP technique.
== See also ==
Character literal
Function literal
Here document – a file literal or stream literal
Hexadecimal floating-point literal
Integer literal
String literal
== References ==
|
https://en.wikipedia.org/wiki/Literal_(computer_programming)
|
Sky Atlantic is a British pay television channel owned by Sky Group Limited that launched in 2011 and broadcasts in the United Kingdom and Ireland. The channel airs original British-produced dramas like Fortitude, Tin Star, and Gangs of London but is primarily dedicated to imported programmes from the United States. It has held the domestic rights to HBO programming since 2011, which is set to expire in early 2026, and has previously held the domestic rights to Showtime programming from 2016 to 2021. It is exclusively available on the Sky satellite TV platform (including Sky Go and Now).
Sky Deutschland broadcasts a German-language version of the channel in Germany, Austria, and Switzerland, while Sky Italia broadcasts an Italian-language version of the channel in Italy. Their programming is also dominated by acquired series, usually dubbed in the domestic language. The Italian channel also premieres Sky Originals produced in the country, like Gomorrah, The Young Pope, and ZeroZeroZero.
== Background ==
=== Launch ===
It was announced on 25 October 2010 that Sky Atlantic would launch on Sky channel 108, which was previously occupied by Sky 3. Sky Atlantic launched on 1 February 2011 on Sky in the United Kingdom and Ireland.
At launch, Stuart Murphy was the director of programmes for Sky One, Sky Two, Pick and Sky Atlantic. On 5 May 2011, Elaine Pyke, the head of drama at Sky, was promoted to director of Sky Atlantic, reporting to Murphy. Programmes on the channel are also offered to Sky customers via on-demand channels including the On Demand and Sky Go services and Now. Both BT TV and Virgin Media had held talks with Sky over the new channel but have been unable to agree a carriage deal, in Virgin's case due to pricing.
=== Additional channels ===
A one-hour timeshift of Sky Atlantic started broadcasting on 20 September 2012 on channel 173 as Sky Atlantic +1. It moved to channel 170 on 9 June 2015 as part of a reshuffle which also included the closure of Sky 3D, Sky Livingit becoming Real Lives and Sky Arts 1 and Sky Arts 2 merging to become simply Sky Arts. It moved to channel 217 on 18 July 2017 as part of the Sky Sports reshuffle which included Sky Sports Mix moving to entertainment, and again to 208 on 1 May 2018 as part of Sky's major EPG reshuffle due to Sky Atlantic being channel 108.
Sky Atlantic was available in both standard definition and high definition, the latter on Sky Atlantic HD. Sky Atlantic also utilises the HD swap bouquet system developed by Sky, which switches SD channels with HD channels for HD Pack subscribers, meaning Sky Atlantic HD is on channel 108 and the standard definition version appears on channel 808.
Sky Atlantic VIP was a rewards channel for subscribers of Sky TV who had been with Sky for two or more years and for subscribers who had the Sky Original Bundle (later Sky Entertainment pack, then Sky Signature pack). The HD version also required the HD pack in the UK and the Sky Box Sets pack in Ireland. The channel only broadcast brand new episodes of a popular show a week or so before being shown on the main Sky Atlantic channel. An example of this is when episodes of Riviera were shown first on Sky Atlantic VIP, then a week or so later on Sky Atlantic. Sky Atlantic VIP was under Sky VIP's "See-It-First" offer. Sky VIP is a rewards programme for long-term Sky subscribers. When the channel was not broadcasting a brand new episode of a programme, the channel was off-air resulting in the channel being on-air only for a few hours per week. The channel only broadcast adverts for programmes on Sky channels. The SD version was on Sky channel 994 with the HD version on channel 995. The channel closed on 12 June 2019.
In January 2024, select programming begun being simulcast on Sky Showcase.
=== Acquisitions ===
Sky Atlantic relies heavily on screenings of US television programmes, with more than 50% of all programming coming from HBO. Although the channel mainly screens dramas, blocks in the channel's schedule were dedicated to comedies and movies. The launch of Sky Atlantic in 2011 followed the broadcaster's £150m, five-year deal to buy exclusive UK and Ireland television rights to HBO's entire archive, new HBO programming and a first-look deal on all co-productions. Although it has been renewed since, the exclusivity deal with HBO is set to expire in early 2026, allowing for the launch of the Max streaming service in the UK, Ireland, Germany, Austria, Switzerland, and Italy. In December 2024, a new agreement was made between Sky and Warner Bros. Discovery that allows Sky to maintain life-of-series rights to select HBO programming released before the deal ends, including House of the Dragon, The Last of Us, The White Lotus, Euphoria, and Dune: Prophecy. Sky still planned to make new acquisitions via separate agreements on a programme-by-programme basis, while new series in existing franchises would continue to be released exclusively on Sky but all other future HBO original programming, like the untitled Harry Potter series, would be released on Max.
In January 2016, Sky expanded the acquired programming on Atlantic after purchasing the broadcast rights to Showtime programming; however, Sky Atlantic does not broadcast all Showtime programmes, as some series would later air on Channel 4 as part of a separate deal. The deal with Showtime expired in December 2021, with all future series becoming exclusive to the Paramount+ streaming service which launched in the UK, Ireland, Germany, Austria, Switzerland, and Italy in 2022, while a separate agreement allowed Billions to continue on Sky.
== Current programming ==
=== Drama ===
=== Comedy ===
=== Co-productions ===
=== Acquired programming ===
Dune: Prophecy
Euphoria
The Gilded Age
House of the Dragon
The Last of Us
True Detective
The White Lotus
== Upcoming programming ==
=== Drama ===
=== Comedy ===
=== Acquired programming ===
Task (September 2025)
It – Welcome to Derry (Late 2025)
== Former programming ==
=== Drama ===
=== Comedy ===
=== Unscripted ===
=== Co-productions ===
=== Acquired programming ===
==== HBO programming ====
==== Showtime programming ====
==== Miscellaneous ====
== Most watched programmes ==
The following is a list of the ten most watched programmes on Sky Atlantic (all of them being episodes of Game of Thrones), based on Live +7 data supplied by BARB up to 20 May 2019. The number of viewers does not include repeats or Irish ratings. Additionally, all of these episodes were the most viewed programme of the week on non-terrestrial television in the UK. Game of Thrones is Sky's most popular show.
== Notes ==
== References ==
== External links ==
Official website
|
https://en.wikipedia.org/wiki/Sky_Atlantic
|
In mathematics, the Langlands program is a set of conjectures about connections between number theory and geometry. It was proposed by Robert Langlands (1967, 1970). It seeks to relate Galois groups in algebraic number theory to automorphic forms and representation theory of algebraic groups over local fields and adeles. It was described by Edward Frenkel as the "grand unified theory of mathematics."
== Background ==
The Langlands program is built on existing ideas: the philosophy of cusp forms formulated a few years earlier by Harish-Chandra and Gelfand (1963), the work and Harish-Chandra's approach on semisimple Lie groups, and in technical terms the trace formula of Selberg and others.
What was new in Langlands' work, besides technical depth, was the proposed connection to number theory, together with its rich organisational structure hypothesised (so-called functoriality).
Harish-Chandra's work exploited the principle that what can be done for one semisimple (or reductive) Lie group, can be done for all. Therefore, once the role of some low-dimensional Lie groups such as GL(2) in the theory of modular forms had been recognised, and with hindsight GL(1) in class field theory, the way was open to speculation about GL(n) for general n > 2.
The 'cusp form' idea came out of the cusps on modular curves but also had a meaning visible in spectral theory as "discrete spectrum", contrasted with the "continuous spectrum" from Eisenstein series. It becomes much more technical for bigger Lie groups, because the parabolic subgroups are more numerous.
In all these approaches technical methods were available, often inductive in nature and based on Levi decompositions amongst other matters, but the field remained demanding.
From the perspective of modular forms, examples such as Hilbert modular forms, Siegel modular forms, and theta-series had been developed.
== Objects ==
The conjectures have evolved since Langlands first stated them. Langlands conjectures apply across many different groups over many different fields for which they can be stated, and each field offers several versions of the conjectures. Some versions are vague, or depend on objects such as Langlands groups, whose existence is unproven, or on the L-group that has several non-equivalent definitions.
Objects for which Langlands conjectures can be stated:
Representations of reductive groups over local fields (with different subcases corresponding to archimedean local fields, p-adic local fields, and completions of function fields)
Automorphic forms on reductive groups over global fields (with subcases corresponding to number fields or function fields).
Analogues for finite fields.
More general fields, such as function fields over the complex numbers.
== Conjectures ==
The conjectures can be stated variously in ways that are closely related but not obviously equivalent.
=== Reciprocity ===
The starting point of the program was Emil Artin's reciprocity law, which generalizes quadratic reciprocity. The Artin reciprocity law applies to a Galois extension of an algebraic number field whose Galois group is abelian; it assigns L-functions to the one-dimensional representations of this Galois group, and states that these L-functions are identical to certain Dirichlet L-series or more general series (that is, certain analogues of the Riemann zeta function) constructed from Hecke characters. The precise correspondence between these different kinds of L-functions constitutes Artin's reciprocity law.
For non-abelian Galois groups and higher-dimensional representations of them, L-functions can be defined in a natural way: Artin L-functions.
Langlands' insight was to find the proper generalization of Dirichlet L-functions, which would allow the formulation of Artin's statement in Langland's more general setting. Hecke had earlier related Dirichlet L-functions with automorphic forms (holomorphic functions on the upper half plane of the complex number plane
C
{\displaystyle \mathbb {C} }
that satisfy certain functional equations). Langlands then generalized these to automorphic cuspidal representations, which are certain infinite dimensional irreducible representations of the general linear group GL(n) over the adele ring of
Q
{\displaystyle \mathbb {Q} }
(the rational numbers). (This ring tracks all the completions of
Q
,
{\displaystyle \mathbb {Q} ,}
see p-adic numbers.)
Langlands attached automorphic L-functions to these automorphic representations, and conjectured that every Artin L-function arising from a finite-dimensional representation of the Galois group of a number field is equal to one arising from an automorphic cuspidal representation. This is known as his reciprocity conjecture.
Roughly speaking, this conjecture gives a correspondence between automorphic representations of a reductive group and homomorphisms from a Langlands group to an L-group. This offers numerous variations, in part because the definitions of Langlands group and L-group are not fixed.
Over local fields this is expected to give a parameterization of L-packets of admissible irreducible representations of a reductive group over the local field. For example, over the real numbers, this correspondence is the Langlands classification of representations of real reductive groups. Over global fields, it should give a parameterization of automorphic forms.
=== Functoriality ===
The functoriality conjecture states that a suitable homomorphism of L-groups is expected to give a correspondence between automorphic forms (in the global case) or representations (in the local case). Roughly speaking, the Langlands reciprocity conjecture is the special case of the functoriality conjecture when one of the reductive groups is trivial.
==== Generalized functoriality ====
Langlands generalized the idea of functoriality: instead of using the general linear group GL(n), other connected reductive groups can be used. Furthermore, given such a group G, Langlands constructs the Langlands dual group LG, and then, for every automorphic cuspidal representation of G and every finite-dimensional representation of LG, he defines an L-function. One of his conjectures states that these L-functions satisfy a certain functional equation generalizing those of other known L-functions.
He then goes on to formulate a very general "Functoriality Principle". Given two reductive groups and a (well behaved) morphism between their corresponding L-groups, this conjecture relates their automorphic representations in a way that is compatible with their L-functions. This functoriality conjecture implies all the other conjectures presented so far. It is of the nature of an induced representation construction—what in the more traditional theory of automorphic forms had been called a 'lifting', known in special cases, and so is covariant (whereas a restricted representation is contravariant). Attempts to specify a direct construction have only produced some conditional results.
All these conjectures can be formulated for more general fields in place of
Q
{\displaystyle \mathbb {Q} }
: algebraic number fields (the original and most important case), local fields, and function fields (finite extensions of Fp(t) where p is a prime and Fp(t) is the field of rational functions over the finite field with p elements).
=== Geometric conjectures ===
The geometric Langlands program, suggested by Gérard Laumon following ideas of Vladimir Drinfeld, arises from a geometric reformulation of the usual Langlands program that attempts to relate more than just irreducible representations. In simple cases, it relates l-adic representations of the étale fundamental group of an algebraic curve to objects of the derived category of l-adic sheaves on the moduli stack of vector bundles over the curve.
A 9-person collaborative project led by Dennis Gaitsgory announced a proof of the (categorical, unramified) geometric Langlands conjecture leveraging Hecke eigensheaves as part of the proof.
== Status ==
The Langlands correspondence for GL(1, K) follows from (and are essentially equivalent to) class field theory.
Langlands proved the Langlands conjectures for groups over the archimedean local fields
R
{\displaystyle \mathbb {R} }
(the real numbers) and
C
{\displaystyle \mathbb {C} }
(the complex numbers) by giving the Langlands classification of their irreducible representations.
Lusztig's classification of the irreducible representations of groups of Lie type over finite fields can be considered an analogue of the Langlands conjectures for finite fields.
Andrew Wiles' proof of modularity of semistable elliptic curves over rationals can be viewed as an instance of the Langlands reciprocity conjecture, since the main idea is to relate the Galois representations arising from elliptic curves to modular forms. Although Wiles' results have been substantially generalized, in many different directions, the full Langlands conjecture for
GL
(
2
,
Q
)
{\displaystyle {\text{GL}}(2,\mathbb {Q} )}
remains unproved.
In 1998, Laurent Lafforgue proved Lafforgue's theorem verifying the global Langlands correspondence for the general linear group GL(n, K) for function fields K. This work continued earlier investigations by Drinfeld, who previously addressed the case of GL(2, K) in the 1980s.
In 2018, Vincent Lafforgue established one half of the global Langlands correspondence (the direction from automorphic forms to Galois representations) for connected reductive groups over global function fields.
=== Local Langlands conjectures ===
Philip Kutzko (1980) proved the local Langlands correspondence for the general linear group GL(2, K) over local fields.
Gérard Laumon, Michael Rapoport, and Ulrich Stuhler (1993) proved the local Langlands correspondence for the general linear group GL(n, K) for positive characteristic local fields K. Their proof uses a global argument, realizing smooth admissible representations of interest as the local components of automorphic representations of the group of units of a division algebra over a curve, then using the point-counting formula to study the properties of the global Galois representations associated to these representations.
Michael Harris and Richard Taylor (2001) proved the local Langlands conjectures for the general linear group GL(n, K) for characteristic 0 local fields K. Guy Henniart (2000) gave another proof. Both proofs use a global argument of a similar flavor to the one mentioned in the previous paragraph. Peter Scholze (2013) gave another proof.
=== Fundamental lemma ===
In 2008, Ngô Bảo Châu proved the "fundamental lemma", which was originally conjectured by Langlands and Shelstad in 1983 and being required in the proof of some important conjectures in the Langlands program.
== See also ==
Jacquet–Langlands correspondence
Erlangen program
== Notes ==
== References ==
Arthur, James (2003), "The principle of functoriality", Bulletin of the American Mathematical Society, New Series, 40 (1): 39–53, doi:10.1090/S0273-0979-02-00963-1, ISSN 0002-9904, MR 1943132
Bernstein, J.; Gelbart, S., eds. (2003). An Introduction to the Langlands Program. Boston: Birkhäuser. ISBN 978-3-7643-3211-2.
Gelbart, Stephen (1984), "An elementary introduction to the Langlands program", Bulletin of the American Mathematical Society, New Series, 10 (2): 177–219, doi:10.1090/S0273-0979-1984-15237-6, ISSN 0002-9904, MR 0733692
Frenkel, Edward (2005). "Lectures on the Langlands Program and Conformal Field Theory". arXiv:hep-th/0512172.
Gelfand, I. M. (1963), "Automorphic functions and the theory of representations", Proc. Internat. Congr. Mathematicians (Stockholm, 1962), Djursholm: Inst. Mittag-Leffler, pp. 74–85, MR 0175997
Harris, Michael; Taylor, Richard (2001), The geometry and cohomology of some simple Shimura varieties, Annals of Mathematics Studies, vol. 151, Princeton University Press, ISBN 978-0-691-09090-0, MR 1876802
Henniart, Guy (2000), "Une preuve simple des conjectures de Langlands pour GL(n) sur un corps p-adique", Inventiones Mathematicae, 139 (2): 439–455, Bibcode:2000InMat.139..439H, doi:10.1007/s002220050012, ISSN 0020-9910, MR 1738446, S2CID 120799103
Kutzko, Philip (1980), "The Langlands Conjecture for Gl2 of a Local Field", Annals of Mathematics, 112 (2): 381–412, doi:10.2307/1971151, JSTOR 1971151
Langlands, Robert (1967), Letter to Prof. Weil
Langlands, R. P. (1970), "Problems in the theory of automorphic forms", Lectures in modern analysis and applications, III, Lecture Notes in Math, vol. 170, Berlin, New York: Springer-Verlag, pp. 18–61, doi:10.1007/BFb0079065, ISBN 978-3-540-05284-5, MR 0302614
Laumon, G.; Rapoport, M.; Stuhler, U. (1993), "D-elliptic sheaves and the Langlands correspondence", Inventiones Mathematicae, 113 (2): 217–338, Bibcode:1993InMat.113..217L, doi:10.1007/BF01244308, ISSN 0020-9910, MR 1228127, S2CID 124557672
Mueller, Julia; Shahidi, Freydoon, eds. (2021). The Genesis of the Langlands Program. Cambridge: Cambridge University Press. ISBN 978-1-108-71094-7.
Scholze, Peter (2013), "The Local Langlands Correspondence for GL(n) over p-adic fields", Inventiones Mathematicae, 192 (3): 663–715, arXiv:1010.1540, Bibcode:2013InMat.192..663S, doi:10.1007/s00222-012-0420-5, S2CID 15124490
== External links ==
The work of Robert Langlands
|
https://en.wikipedia.org/wiki/Langlands_program
|
The following are programs broadcast by FX.
== Original programming ==
=== Drama ===
=== Comedy ===
=== Docuseries ===
=== Syndicated programming ===
Family Guy (2021)
Black-ish (2023)
== Upcoming programming ==
=== Drama ===
=== Co-productions ===
=== Pilots ===
==== Drama ====
The Answers
The Bends
The Border
Seven Sisters
Untitled David Chase & Hannah Fidell pilot
Untitled Snowfall spin-off
==== Comedy ====
Peep Show
Untitled Lauren Ludwig pilot
==== Animation ====
The Trenches
=== In development ===
==== Drama ====
Burnfield
Drug Spies
The Shards
Untitled Olivia Colman adaptation
Untitled Sammy the Bull series
== Former programming ==
=== Original programming ===
==== Drama ====
==== Comedy ====
==== Miniseries ====
Thief (2006)
Trust (2018)
Fosse/Verdon (2019)
Justified: City Primeval (2023)
==== Animation ====
The Dick & Paula Celebrity Special (1999)
Archer (2009–16)
Unsupervised (2012)
Chozen (2014)
==== Docuseries ====
Lost & Found (1995–98)
Baseball, Minnesota (1996–98)
The Weekly (2019)
A Wilderness of Error (2020)
Hip Hop Uncovered (2021)
Pride (2021)
Children of the Underground (2022)
Dear Mama (2023)
The Secrets of Hillsong (2023)
Social Studies (2024)
==== Co-productions ====
Taboo (2017)
Mr Inbetween (2018–21)
A Christmas Carol (2019)
Breeders (2020–23)
Black Narcissus (2020)
==== Variety ====
=== Syndicated programming ===
== Live programming ==
The FX Apartment
FX Networks leased the first three floors of the building at 212 Fifth Avenue, which overlooks Madison Square Park in New York City. The first floor contained sales offices and the control room, and the third floor contained production offices. Programming was broadcast from a functional apartment on the second floor. The apartment had several rooms. First was a large common room that contained the living room, dining room, and kitchen areas. Other rooms included a small library, a game room (complete with arcade and pinball machines) and a fully functioning restroom. At the rear of the apartment was a large "ballroom" that served several purposes. A third-floor balcony lined the ballroom. The network's shows would often venture into Madison Square Park for some features, especially in the summer. FX's lease on the building expired on December 31, 1998. All furnishings were auctioned and the building has since been renovated.
Breakfast Time (1994–96)
An off-the-cuff morning show with lifestyle segments and "roving reporters" (aka "Road Warriors") who visited unique sites across the country each day. This was the network's flagship show and utilized every room of the apartment. Hosted by Tom Bergeron, Laurie Hibberd and Bob the Puppet. Aired 7 a.m. to 9 a.m. ET.
Personal fX: The Collectibles Show (1994–98)
The Collectibles Show - similar to Antiques Roadshow, in which collectors would have unique items appraised in-studio, and a "roving reporter" would visit collectors nationwide. Broadcast from the "Dining Room." The last live show to be canceled. Hosted by Claire Carter and John Burke. Aired Noon to 1 p.m. ET.
The Pet Department (1994–98)
A call-in/interview show about domesticated pets. Usually broadcast from the "Game Room." Hosted by Steve Walker, Luann Lee, dog trainer Andrea Arden and fX's pet dog Jack. Suzanne Whang replaced Lee after her departure. Aired 2:30 p.m. to 3:00pm ET.
Under Scrutiny with Jane Wallace (1994–95)
An in-depth news program broadcast each night from the "Library." Given a CableACE Award for news programming in 1995. The first live show to be canceled. Hosted by Jane Wallace. Aired 7 p.m. to 7:30 p.m. ET.
Sound fX (1994–95)
A show dealing with all things music, from the latest major artists to the most creative garage band tactics. Music videos were regularly shown on this show, which originated from the "Ballroom." Hosted by Karyn Bryant, Orlando Jones, and Matt Ostrum. Jeff Probst replaced Jones after his departure. Aired 11 p.m. to Midnight ET.
Backchat (1994–98)
fX ended each broadcast day with a viewer mail show. Viewers could write, call, or e-mail comments about fX and its shows, and the host would spend 30 minutes each night reading and responding to these comments. Broadcast from the "Kitchen." Hosted by Jeff Probst and Jane Fergus. Aired 12:30 a.m. to 1:00 a.m. ET. Near the end of its run, Backchat was pre-taped and moved to 7:30 p.m. to 8:00 p.m. ET.
Some of the young talent discovered on the fX network that have moved on to larger, more successful projects include:
Tom Bergeron (Host, Breakfast Time) - Host of America's Funniest Home Videos, Dancing with the Stars, and Hollywood Squares
Laurie Hibberd (Host, Breakfast Time) - Reporter for CBS's The Early Show and wife of Live with Regis and Kelly producer Michael Gelman.
Orlando Jones (Co-host, Sound fX) - Actor (Evolution, Office Space, MADtv) and perhaps most famous as pitchman for 7 Up.
Jeff Probst (Host, Backchat; Co-host, Sound fX) - Host of Survivor, and The Jeff Probst Show
Phil Keoghan (Road Warrior, Breakfast Time) - Host of The Amazing Race
John Burke (Road Warrior, Personal fX) - Host of E! News Live
Before each show aired, and during commercial breaks, a "channel host" would appear and inform viewers about something upcoming within the episode. Some updates featured trivia about the current show, while some were merely observations. These can be compared to in-vision continuity announcers in Britain.
== Sports ==
=== Former ===
The first venture by fX into sports occurred in September 1995, when The fX Sports Show, an hour-long highlights and analysis show, debuted; it was hosted by Jim Rome and Kevin Frazier, along with the pregame crew and commentators from Fox NFL Sunday providing contributions. Unlike most of fX's other studio programming at the time, it originated from the facilities of Fox Sports in Hollywood, as opposed to the fX Apartment in New York. The show, airing Sunday nights at 11pm, only lasted a single season.
Following Fox's partnering with Liberty Media to form Fox Sports Net, Liberty took an equity stake in fX as well (organized under the banner of Fox/Liberty Networks), resulting in fX becoming the national cable home for Fox Sports programming. This included a package of Major League Baseball games – initially aired on Monday nights before moving to Saturday nights in 1998 – and college football; for a short time, newsbreaks provided by Fox Sports News also began to air during FX's primetime lineup.
FX aired selected NASCAR events from the NEXTEL Cup Series and NASCAR Busch Series from February to June of each year from 2001 to 2006 as part of Fox's NASCAR television package. However, coverage ended after the June 30, 2006, Busch Series race at Daytona International Speedway. When NASCAR signed its new contract effective in 2007, FX was left out as Fox retained its rights and gained the right to broadcast weather-delayed races that aired on the network.
The channel also aired one game in the Major League Baseball postseason from 2001 to 2005, on the first Wednesday night of League Championship Series week when MLB schedules two games at the same time. On that night, Fox distributed one game to local affiliates based on a regional coverage map, and the other game aired on the corresponding cable affiliate of FX, the main DirecTV or Dish Network channel, or an alternate channel on the satellite services.
With a new MLB TV contract signed, again excluding FX, the last such broadcast was scheduled for October 11, 2006, but that night's NLCS game between the St. Louis Cardinals and New York Mets was rained out, making the Detroit Tigers-Oakland Athletics game in the ALCS a national broadcast; FX aired the movie Any Given Sunday instead. Both series were played on October 13, but Fox showed both games, with the ALCS during the day and the NLCS at night. Therefore, the Busch Series race, as mentioned above, is officially the last sports event telecast on FX, at least in the foreseeable future. Future LCS games will be split between Fox and TBS.
Other sports events seen on FX have included the NFL's development league-NFL Europa, formerly the World League of American Football; college football; college basketball; and the World Cup of Hockey in 1996.
With the August 2013 launch of national sports cable network Fox Sports 1, FX no longer serves as a cable outlet for Fox Sports.
=== Current ===
The Walt Disney Company acquired exclusive broadcasting rights to the XFL in 2022 and, beginning with the 2023 season, began to air games on FX, in addition to ESPN and ABC.
== See also ==
FXX
FX Movie Channel
Hulu
== Notes ==
== References ==
|
https://en.wikipedia.org/wiki/List_of_programs_broadcast_by_FX
|
In computing, subject-oriented programming is an object-oriented software paradigm in which the state (fields) and behavior (methods) of objects are not seen as intrinsic to the objects themselves, but are provided by various subjective perceptions ("subjects") of the objects. The term and concepts were first published in September 1993 in a conference paper which was later recognized as being one of the three most influential papers to be presented at the conference between 1986 and 1996. As illustrated in that paper, an analogy is made with the contrast between the philosophical views of Plato and Kant with respect to the characteristics of "real" objects, but applied to software ones. For example, while we may all perceive a tree as having a measurable height, weight, leaf-mass, etc., from the point of view of a bird, a tree may also have measures of relative value for food or nesting purposes, or from the point of view of a tax-assessor, it may have a certain taxable value in a given year. Neither the bird's nor the tax-assessor's additional state information need be seen as intrinsic to the tree, but are added by the perceptions of the bird and tax-assessor, and from Kant's analysis, the same may be true even of characteristics we think of as intrinsic.
Subject-oriented programming advocates the organization of the classes that describe objects into "subjects", which may be composed to form larger subjects. At points of access to fields or methods, several subjects' contributions may be composed. These points were characterized as the join-points of the subjects. For example, if a tree is cut down, the methods involved may need to join behavior in the bird and tax-assessor's subjects with that of the tree's own. It is therefore fundamentally a view of the compositional nature of software development, as opposed to the algorithmic (procedural) or representation-hiding (object) nature.
== Relationships ==
=== Relationship to aspect-oriented programming ===
The introduction of aspect-oriented programming in 1997 raised questions about its relationship to subject-oriented programming, and about the difference between subjects and aspects. These questions were unanswered for some time, but were addressed in the patent on Aspect-oriented programming filed in 1999 in which two points emerge as characteristic differences from earlier art:
the aspect program comprises both a) a cross-cut that comprises a point in the execution where cross-cutting behavior is to be included; and b) a cross-cut action comprising a piece of implementation associated with the cross-cut, the piece of implementation comprising computer readable program code that implements the cross-cutting behavior.
the aspect transparently forces the cross-cutting behavior on object classes and other software entities
In the subject-oriented view, the cross-cut may be placed separately from the aspect (subject) and the behavior is not forced by the aspect, but governed by rules of composition. Hindsight makes it also possible to distinguish aspect-oriented programming by its introduction and exploitation of the concept of a query-like pointcut to externally impose the join-points used by aspects in general ways.
In the presentation of subject-oriented programming, the join-points were deliberately restricted to field access and method call on the grounds that those were the points at which well-designed frameworks were designed to admit functional extension. The use of externally imposed pointcuts is an important linguistic capability, but remains one of the most controversial features of aspect-oriented programming.
=== Relationship to aspect-oriented software development ===
By the turn of the millennium, it was clear that a number of research groups were pursuing different technologies that employed the composition or attachment of separately packaged state and function to form objects. To distinguish the common field of interest from Aspect-Oriented Programming with its particular patent definitions and to emphasize that the compositional technology deals with more than just the coding phase of software development, these technologies were organized together under the term Aspect-Oriented Software Development, and an organization and series on international conferences begun on the subject. Like aspect-oriented programming, subject-oriented programming, composition filters, feature-oriented programming and adaptive methods are considered to be aspect-oriented software development approaches.
== Dimensions ==
=== Multi-dimensional separation of concerns, Hyper/J, and the Concern Manipulation Environment ===
The original formulation of subject-oriented programming deliberately envisioned it as a packaging technology – allowing the space of functions and data types to be extended in either dimension. The first implementations had been for C++, and Smalltalk. These implementations exploited the concepts of software labels and composition rules to describe the joining of subjects.
To address the concern that a better foundation should be provided for the analysis and composition of software not just in terms of its packaging but in terms of the various concerns these packages addressed, an explicit organization of the material was developed in terms of a multi-dimensional "matrix" in which concerns are related to the software units that implement them. This organization is called multi-dimensional separation of concerns, and the paper describing it has been recognized as the most influential paper of the ICSE 1999 Conference.
This new concept was implemented for composing Java software, using the name Hyper/J for the tool.
Composition and the concept of subject can be applied to software artifacts that have no executable semantics, like requirement specifications or documentation. A research vehicle for Eclipse, called the Concern Manipulation Environment (CME), has been described in which tools for query, analysis, modelling, and composition are applied to artifacts in any language or representation, through the use of appropriate plug-in adapters to manipulate the representation.
A successor to the Hyper/J composition engine was developed as part of CME which uses a general approach for the several elements of a composition engine:
a query language with unification to identify join points,
a flexible structural-attachment model,
a nested-graph specification for ordering identified elements,
and a priority ordering specification to resolve conflicts among conflicting rules.
Both Hyper/J and CME are available, from alphaWorks or sourceforge, respectively, but neither is actively supported.
=== Subject-oriented programming as a "third dimension" ===
Method dispatch in object oriented programming can be thought of as "two dimensional" in the sense that the code executed depends on both the method name and the object in question. This can be contrasted with procedural programming, where a procedure name resolves directly, or one dimensionally, onto a subroutine, and also to subject oriented programming, where the sender or subject is also relevant to dispatch, constituting a third dimension.
== See also ==
Separation of concerns
Data, context and interaction
== References ==
== External links ==
Distributed Characteristics of Subject Oriented Programming: An evaluation with the Process and Object-Oriented Paradigms
alphaWorks: HyperJ
Eclipse Archived Technology Projects
Amethyst: a JavaScript library for Subject-Oriented Programming
|
https://en.wikipedia.org/wiki/Subject-oriented_programming
|
In computer programming, event-driven programming is a programming paradigm in which the flow of the program is determined by external events. UI events from mice, keyboards, touchpads and touchscreens, and external sensor inputs are common cases. Events may also be programmatically generated, such as from messages from other programs, notifications from other threads, or other network events.
Event-driven programming is the dominant paradigm used in graphical user interfaces applications and network servers.
In an event-driven application, there is generally an event loop that listens for events and then triggers a callback function when one of those events is detected.
Event-driven programs can be written in any programming language, although the task is easier in languages that provide high-level abstractions.
Although they do not exactly fit the event-driven model, interrupt handling and exception handling have many similarities.
It is important to differentiate between event-driven and message-driven (aka queue driven) paradigms: Event-driven services (e.g. AWS SNS) are decoupled from their consumers. Whereas queue / message driven services (e.g. AWS SQS) are coupled with their consumers.
== Event loop ==
Because the event loop of retrieving/dispatching of events are common amongst applications, many programming frameworks take care of their implementation and expect the user to provide only the code for the event handlers.
RPG, an early programming language from IBM, whose 1960s design concept was similar to event-driven programming discussed above, provided a built-in main I/O loop (known as the "program cycle") where the calculations responded in accordance to 'indicators' (flags) that were set earlier in the cycle.
=== Event handlers ===
The actual logic is contained in event-handler routines. These routines handle the events to which the main program will respond. For example, a single left-button mouse-click on a command button in a GUI program may trigger a routine that will open another window, save data to a database or exit the application. Many IDEs provide the programmer with GUI event templates, allowing the programmer to focus on writing the event code.
Keeping track of history is normally trivial in a sequential program. Because event handlers execute in response to external events, correctly structuring the handlers to work when called in any order can require special attention and planning in an event-driven program.
In addition to writing the event handlers, event handlers also need to be bound to events so that the correct function is called when the event takes place. For UI events, many IDEs combine the two steps: double-click on a button, and the editor creates an (empty) event handler associated with the user clicking the button and opens a text window so you can edit the event handler.
== Common uses ==
Most existing GUI architectures use event-driven programming. Windows has an event loop. The Java AWT framework processes all UI changes on a single thread, called the Event dispatching thread. Similarly, all UI updates in the Java framework JavaFX occur on the JavaFX Application Thread.
Most network servers and frameworks such as Node.js are also event-driven.
== Interrupt and exception handling ==
== See also ==
Autonomous peripheral operation
Dataflow programming
DOM events
Event-driven architecture
Event stream processing (a similar concept)
Hardware description language
Interrupt
Inversion of control
Message-oriented middleware
Programming paradigm
Publish–subscribe pattern
Reactor pattern
Signal programming (a similar concept)
Staged event-driven architecture (SEDA)
Time-triggered system (an alternative architecture for computer systems)
Virtual synchrony, a distributed execution model for event-driven programming
== References ==
== External links ==
Concurrency patterns presentation given at scaleconf
Event-Driven Programming: Introduction, Tutorial, History, tutorial by Stephen Ferg
Event-Driven Programming, tutorial by Alan Gauld
Event Collaboration, article by Martin Fowler
Rethinking Swing Threading, article by Jonathan Simon
The event-driven programming style Archived 2005-02-20 at the Wayback Machine, article by Chris McDonald
Event Driven Programming using Template Specialization, article by Christopher Diggins
Schiffer, S.; Frohlich, J.H. (1994). "Concepts and architecture of Vista-a multiparadigm programming environment". Proceedings of 1994 IEEE Symposium on Visual Languages. pp. 40–47. doi:10.1109/VL.1994.363642. ISBN 0-8186-6660-9. S2CID 15927869.
Event-Driven Programming and Agents, chapter
LabWindows/CVI Resources
Distributed Publish/Subscribe Event System, an open-source example which is in production on MSN.com and Microsoft.com
|
https://en.wikipedia.org/wiki/Event-driven_programming
|
The Fulbright Program, including the Fulbright–Hays Program, is one of several United States cultural exchange programs with the goal of improving intercultural relations, cultural diplomacy, and intercultural competence between the people of the United States and other countries through the mutual exchange of persons, knowledge, and skills. The program was founded by United States Senator J. William Fulbright in 1946, and has been considered as one of the most prestigious scholarships in the United States.
Via the program, competitively selected American citizens including students, scholars, teachers, professionals, scientists, and artists may receive scholarships or grants to study, conduct research, teach, or exercise their talents abroad; and citizens of other countries may qualify to do the same in the United States. The program provides approximately 8,000 grants annually, comprising roughly 1,600 grants to U.S. students, 1,200 to U.S. scholars, 4,000 to foreign students, 900 to foreign visiting scholars, and several hundred to teachers and professionals.
The Fulbright Program is administered by cooperating organizations such as the Institute of International Education and operates in over 160 countries around the world. The Bureau of Educational and Cultural Affairs of the U.S. Department of State sponsors the Fulbright Program and receives funding from the United States Congress via annual appropriation bills. Additional direct and in-kind support comes from partner governments, foundations, corporations, and host institutions both in and outside the U.S. In 49 countries, a bi-national Fulbright Commission administers and oversees the Fulbright Program. In countries that have an active program but no Fulbright Commission, the Public Affairs Section of the U.S. embassy oversees the Fulbright Program. More than 370,000 people have participated in the program since it began; 62 Fulbright alumni have been awarded for a Nobel Prize; 88 have won Pulitzer Prizes.
== History ==
The Fulbright Program's mission is to bring a little more knowledge, a little more reason, and a little more compassion into world affairs and thereby increase the chance that nations will learn at last to live in peace and friendship.
In 1945, Senator J. William Fulbright proposed a bill to use the proceeds from selling surplus U.S. government war property to fund international exchange between the U.S. and other countries. With the crucial timing of the aftermath of the Second World War and with the pressing establishment of the United Nations, the Fulbright Program was an attempt to promote peace and understanding through educational exchange. The bill devised a plan to forgo the debts foreign countries amassed during the war in return for funding an international educational program. It was through the belief that this program would be an essential vehicle to promote peace and mutual understanding between individuals, institutions and future leaders wherever they may be.
In August 1946, Congress created the Fulbright Program in what became the largest education exchange program in history. The program was expanded by the Mutual Educational And Cultural Exchange Act of 1961, known as Fulbright–Hays Act. It made possible participation in international fairs and expositions, including trade and industrial fairs; translations; funding for American studies programs; funds to promote medical, scientific, cultural, and educational research and development; and modern foreign language training.
The program operates on a bi-national basis; each country has entered into an agreement with the U.S. government. The first countries to sign agreements were China in 1947 and Burma, the Philippines, and Greece in 1948.
In March 2024, the Russian government declared the Institute of International Education (IIE) and Cultural Vistas as "undesirable" in Russia. This decision effectively ended the Fulbright Program, which had been established in the USSR during the 1973–74 academic year.
In February 2025, the Trump administration initiated a funding freeze on State Department programs, including the Fulbright Program, disrupting financial support for thousands of scholars. This suspension has left 19,000 participants uncertain about their future, prompting educators to urge Congress to restore funding to these vital international exchange initiatives.
== Program ==
Educational exchange can turn nations into people, contributing as no other form of communication can to the humanizing of international relations.
The Fulbright Program exchanges scholars and students with numerous countries in bilateral partnerships managed by commissions for each country. It provides funding for U.S. persons to visit other countries in the U.S. Student Program, U.S. Scholar Program, Teacher Exchange Program, and others, and enables foreign nationals to visit the United States in programs such as the Foreign Student Program, Visiting Scholar Program, Teacher Exchange Program.
Candidates recommended for Fulbright grants have high academic achievement, a compelling project proposal or statement of purpose, demonstrated leadership potential, and flexibility and adaptability to interact successfully with the host community.
Fulbright grants are awarded in almost all academic disciplines, except clinical medical research involving patient contact. Fulbright grantees' fields of study span the fine arts, humanities, social sciences, mathematics, natural and physical sciences, and professional and applied sciences.
=== Student grants ===
The Fulbright Degree Program funds graduate education for international students wanting to study in the United States. Students apply for the scholarship in their home country and after a long process, they can pursue a Masters or Ph.D. program in the United States.
The Fulbright U.S. Student Program offers fellowships for U.S. graduating college seniors, graduate students, young professionals, and artists to research, study, or teach English abroad for one academic year. The program facilitates cultural exchange through direct interaction on an individual basis in the classroom, field, home, and in routine tasks, allowing the grantee to gain an appreciation of others' viewpoints and beliefs, the way they do things, and the way they think. The application period opens in the spring of each year. Since the inaugural class in 1949, Harvard, Yale, Berkeley, Columbia, and Michigan have been the top producers of U.S. Student Program scholars. Michigan has been the leading producer since 2005.
The Fulbright Foreign Student Program enables graduate students, young professionals, and artists from abroad to conduct research and study in the United States. Some scholarships are renewed after the initial year of study.
The Fulbright Foreign Language Teaching Assistant Program provides opportunities for young English teachers from overseas to refine their teaching skills and broaden their knowledge of U.S. culture and society while strengthening the instruction of foreign languages at colleges and universities in the United States.
The International Fulbright Science and Technology Award, a component of the Fulbright Foreign Student Program, supports doctoral study at leading U.S. institutions in science, technology, engineering or related fields for outstanding foreign students. This program is currently on hiatus.
The Fulbright-mtvU Fellowships award up to four U.S. students the opportunity to study the power of music as a cultural force abroad. Fellows conduct research for one academic year on projects of their own design about a chosen musical aspect. They share their experiences during their Fulbright year via video reports, blogs, and podcasts.
The Fulbright-Clinton Fellowship provides the opportunity for U.S. students to serve in professional placements in foreign government ministries or institutions to gain hands-on public sector experience in participating foreign countries.
The Fulbright Schuman Program awards scholarships to American citizens for research in the European Union with a focus on EU affairs/policy, or the US-EU transatlantic agenda.
=== Scholar grants ===
The Fulbright Distinguished Chair Awards comprise approximately forty distinguished lecturing, distinguished research and distinguished lecturing/research awards ranging from three to 12 months. Fulbright Distinguished Chair Awards are viewed as among the most prestigious appointments in the U.S. Fulbright Scholar Program. Candidates should be eminent scholars and have a significant publication and teaching record.
The Fulbright Bicentennial Chair in American Studies at the University of Helsinki brings scholars of various disciplines to Finland. The Bicentennial Chair is open to senior faculty with outstanding publication and teaching credentials and is also considered to be among the most prestigious Fulbright appointments.
The Fulbright U.S. Scholar Program sends U.S. faculty members, scholars, and professionals abroad to lecture or conduct research for up to a year.
The Fulbright Specialist Program sends U.S. academics and professionals to serve as expert consultants on curriculum, faculty development, institutional planning, and related subjects at overseas institutions for a period of two to six weeks.
The Fulbright Visiting Scholar Program and Fulbright Scholar-in-Residence Program bring foreign scholars to lecture or conduct post-doctoral research for up to a year at U.S. colleges and universities.
The Fulbright Regional Network for Applied Research (NEXUS) Program is a network of junior scholars, professionals, and mid-career applied researchers from the United States, Brazil, Canada, and other Western Hemisphere nations in a year-long program that includes multi-disciplinary, team-based research, a series of three seminar meetings, and a Fulbright exchange experience.
=== Teacher grants ===
The Fulbright Teacher Exchange Program supports one-to-one exchanges of teachers from K–12 schools and a small number of post-secondary institutions.
The Distinguished Fulbright Awards in Teaching Program sends teachers abroad for a semester to pursue individual projects, conduct research, and lead master classes or seminars.
=== Grants for professionals ===
The Hubert H. Humphrey Program brings outstanding mid-career professionals from the developing world and societies in transition to the United States for one year. Fellows participate in a non-degree program of academic study and gain professional experience.
The Fulbright U.S. Scholar Program sends American scholars and professionals abroad to lecture or conduct research for up to a year.
The Fulbright Specialist Program sends U.S. faculty and professionals to serve as expert consultants on curriculum, faculty development, institutional planning, and related subjects at overseas academic institutions for a period of two to six weeks.
The Fulbright U.S. Student Program offers fellowships for U.S. graduating seniors, graduate students, young professionals and artists to study abroad for one academic year. The Program also includes an English Teaching Assistant component.
The Fulbright Foreign Student Program enables graduate students, young professionals and artists from abroad to conduct research and study in the United States. Some scholarships are renewed after the initial year of study.
=== Fulbright–Hays Program ===
The Fulbright–Hays Program is a component of the Fulbright Program funded by a congressional appropriation to the United States Department of Education. It awards grants to individual U.S. K through 14 pre-teachers, teachers and administrators, pre-doctoral students, and post-doctoral faculty, as well as to U.S. institutions and organizations. Funding supports research and training efforts overseas, which focus on non-western foreign languages and area studies. Four Fulbright–Hays grants currently make awards: Fulbright-Hays Doctoral Dissertation Research Abroad, Fulbright–Hays Faculty Research Abroad, Fulbright–Hays Group Projects Abroad and Fulbright–Hays Seminars Abroad.
Fulbright–Hays Doctoral Dissertation Research Abroad fellowships provide grants to U.S. colleges and universities to fund individual doctoral students who conduct research in other countries, in modern foreign languages and area studies for periods of 6–12 months. Fulbright–Hays Faculty Research Abroad fellowships provide grants to U.S. colleges and universities to fund individual faculty who conduct research in other countries, in modern foreign languages and area studies for periods of 3–12 months. Fulbright–Hays Group Projects Abroad provides grants to support overseas projects in training, research, and curriculum development in modern foreign languages and area studies for teachers, students, and faculty engaged in a common endeavor, including short-term seminars, curriculum development, group research or study, or advanced intensive language programs. Fulbright–Hays Seminars Abroad provides individual U.S. educators and administrators opportunities to go abroad as part of a group in the summer to participate in immersive educational and cultural activities and thereby improve their understanding of the peoples and cultures of other countries. Based on their seminar experiences, participants develop cross-cultural curricula for their home educational contexts.
== Administration ==
The program is coordinated by the Bureau of Educational and Cultural Affairs (ECA) of the U.S. Department of State under policy guidelines established by the Fulbright Foreign Scholarship Board (FSB), with the help of 50 bi-national Fulbright commissions, U.S. embassies, and cooperating organizations in the U.S.
The United States Department of State is responsible for managing, coordinating and overseeing the Fulbright program. Bureau of Educational and Cultural Affairs is the bureau in the Department of State that has primary responsibility for the administration of the program.
The United States Department of Education is responsible for managing, coordinating and overseeing the Fulbright–Hays program.
The Fulbright Foreign Scholarship Board is a twelve-member board of educational and public leaders appointed by the President of the United States that determines general policy and direction for the Fulbright Program and approves all candidates nominated for Fulbright Scholarships.
Bi-national Fulbright commissions and foundations, most of which are funded jointly by the U.S. and partner governments, develop priorities for the program, including the numbers and categories of grants. More specifically, they plan and implement educational exchanges, recruit and nominate candidates for fellowships; designate qualified local educational institutions to host Fulbrighters; fundraise; engage alumni; support incoming U.S. Fulbrighters; and, in many countries, operate an information service for the public on educational opportunities in the United States.
In a country active in the program without a Fulbright commission, the Public Affairs Section of the U.S. Embassy administers the Fulbright Program, including recruiting and nominating candidates for grants to the U.S., overseeing U.S. Fulbrighters on their grant in the country, and engaging alumni.
Established in 1919 in the aftermath of World War I, the Institute of International Education was created to catalyze educational exchange. In 1946, the U.S. Department of State invited IIE to administer the graduate student component and CIES to administer the faculty component of the Fulbright Program—IIE's largest program to date.
The Council for International Exchange of Scholars is a division of IIE that administers the Fulbright Scholar Program.
AMIDEAST administers Fulbright Foreign Student grants for grantees from the Middle East and North Africa, excluding Israel.
LASPAU: Affiliated with Harvard University LASPAU brings together a valuable network of individuals, institutions, leaders and organizations devoted to building knowledge-based societies across the Americas. Among other functions, LASPAU administers the Junior Faculty Development Program, a part of the Fulbright Foreign Student Program, for grantees from Central and South America and the Caribbean.
World Learning administers the Fulbright Specialist Program.
American Councils for International Education (ACTR/ACCELS) administers the Junior Faculty Development Program (JFDP), a special academic exchange for grantees from the Caucasus, Central Asia, and Southeast Europe.
The Academy for Educational Development administers the Fulbright Classroom Teacher Exchange Program and the Distinguished Fulbright Awards in Teaching Program.
== Related organizations ==
The Fulbright Association is an organization independent of the Fulbright Program and not associated with the U.S. Department of State. The Fulbright Association was established on February 27, 1977, as a private nonprofit, membership organization with over 9,000 members. Arthur Power Dudden was its founding president. He wanted alumni to educate members of the U.S. Congress and the public about the benefits of advancing increased mutual understanding between the people of the United States and those of other countries. In addition to the Fulbright Association in the U.S., independent Fulbright Alumni associations exist in over 75 countries around the world.
The Fulbright Academy is an organization independent of the Fulbright Program and not associated with the U.S. Department of State. A non-partisan, non-profit organization with members worldwide, the Fulbright Academy focuses on the professional advancement and collaboration needs among the 100,000+ Fulbright alumni in science, technology, and related fields. The Fulbright Academy works with individual and institutional members, Fulbright alumni associations and other organizations interested in leveraging the unique knowledge and skills of Fulbright alumni.
== Bilateral commissions ==
The Fulbright Program has commissions in 49 of the over 160 countries with which it has bilateral partnerships. These foundations are funded jointly by the U.S. and partner governments. The role of the Fulbright Commissions is to plan and implement educational exchanges; recruit and nominate candidates, both domestic and foreign, for fellowships; designate qualified local educational institutions to host Fulbrighters; and support incoming U.S. Fulbrighters while engaging with alumni. Below is a list of current commissions.
== J. William Fulbright Prize for International Understanding ==
The J. William Fulbright Prize for International Understanding is awarded by the Fulbright Association to recognize individuals or organisations which have made extraordinary contributions toward bringing peoples, cultures, or nations to greater understanding of others. Established in 1993, the prize was first awarded to Nelson Mandela.
== Notable alumni ==
Fulbright alumni have occupied key roles in government, academia, and industry. Of the more than 325,000 alumni:
89 have received the Pulitzer Prize
78 have been MacArthur Fellows
62 have received a Nobel Prize
40 have served as head of state or government
10 have been elected to the U.S. Congress
1 has served as secretary general of the United Nations
=== List of selected group of notable Fulbright grant recipients ===
== See also ==
== References ==
== External links ==
U.S. Department of State Fulbright Website, the program's sponsor
Fulbright–Hays information, U.S. Department of Education
Fulbright Scholar Program, grants for university and college faculty, administrators and professionals
Fulbright Teacher Exchange Programs, K–12 Teacher Exchange
Fulbright Foreign Student Program in USA
Directories of past grantees
US Bureau of Educational & Cultural Affairs: International Exchange Alumni
Fulbright Scholar Directory
US Student Program Archived May 16, 2012, at the Wayback Machine
|
https://en.wikipedia.org/wiki/Fulbright_Program
|
Elixir is a functional, concurrent, high-level general-purpose programming language that runs on the BEAM virtual machine, which is also used to implement the Erlang programming language. Elixir builds on top of Erlang and shares the same abstractions for building distributed, fault-tolerant applications. Elixir also provides tooling and an extensible design. The latter is supported by compile-time metaprogramming with macros and polymorphism via protocols.
The community organizes yearly events in the United States, Europe, and Japan, as well as minor local events and conferences.
== History ==
José Valim created the Elixir programming language as a research and development project at Plataformatec. His goals were to enable higher extensibility and productivity in the Erlang VM while maintaining compatibility with Erlang's ecosystem.
Elixir is aimed at large-scale sites and apps. It uses features of Ruby, Erlang, and Clojure to develop a high-concurrency and low-latency language. It was designed to handle large data volumes. Elixir is also used in telecommunications, e-commerce, and finance.
In 2021, the Numerical Elixir effort was announced with the goal of bringing machine learning, neural networks, GPU compilation, data processing, and computational notebooks to the Elixir ecosystem.
== Versioning ==
Each of the minor versions supports a specific range of Erlang/OTP versions. The current stable release version is 1.18.4 .
== Features ==
Compiles to bytecode for the BEAM virtual machine of Erlang. Full interoperability with Erlang code, without runtime impact.
Scalability and fault-tolerance, thanks to Erlang's lightweight concurrency mechanisms
Built-in tooling for managing dependencies, code compilation, running tests, formatting code, remote debugging and more.
An interactive REPL inside running programs, including Phoenix web servers, with code reloading and access to internal state
Everything is an expression
Pattern matching to promote assertive code
Type hints for static analysis tools
Immutable data, with an emphasis, like other functional languages, on recursion and higher-order functions instead of side-effect-based looping
Shared nothing concurrent programming via message passing (actor model)
Lazy and async collections with streams
Railway oriented programming via the with construct
Hygienic metaprogramming by direct access to the abstract syntax tree (AST). Libraries often implement small domain-specific languages, such as for databases or testing.
Code execution at compile time. The Elixir compiler also runs on the BEAM, so modules that are being compiled can immediately run code which has already been compiled.
Polymorphism via a mechanism called protocols. Dynamic dispatch, as in Clojure, however, without multiple dispatch because Elixir protocols dispatch on a single type.
Support for documentation via Python-like docstrings in the Markdown formatting language
Unicode support and UTF-8 strings
== Examples ==
The following examples can be run in an iex shell or saved in a file and run from the command line by typing elixir <filename>.
Classic Hello world example:
Pipe operator:
Pattern matching (a.k.a. destructuring):
Pattern matching with multiple clauses:
List comprehension:
Asynchronously reading files with streams:
Multiple function bodies with guards:
Relational databases with the Ecto library:
Sequentially spawning a thousand processes:
Asynchronously performing a task:
== See also ==
Concurrent computing
Distributed computing
Parallel computing
== References ==
== Further reading ==
Simon St. Laurent; J. Eisenberg (December 22, 2016). Introducing Elixir: Getting Started in Functional Programming 2nd Edition. O'Reilly Media. ISBN 978-1491956779.
Sasa Juric (January 12, 2019). Elixir in Action 2nd Edition. Manning Publications. ISBN 978-1617295027.
|
https://en.wikipedia.org/wiki/Elixir_(programming_language)
|
Ring is a dynamically typed, general-purpose programming language. It can be embedded in C/C++ projects, extended using C/C++ code or used as a standalone language. The supported programming paradigms are imperative, procedural, object-oriented, functional, meta, declarative using nested structures, and natural programming. The language is portable (Windows, Linux, macOS, Android, WebAssembly, etc.) and can be used to create console, GUI, web, game and mobile applications.
== History ==
In 2009, Mahmoud Samir Fayed created a minor domain-specific language called Supernova that focuses on User interface (UI) creation and uses some ideas related to Natural Language Programming, then he realized the need for a new language that is general-purpose and can increase the productivity of natural language creation. Ring aims to offer a language focused on helping the developer with building natural interfaces and declarative DSLs.
== Goals ==
The general goals behind Ring:
Applications programming language.
Productivity and developing high quality solutions that can scale.
Small and flexible language that can be embedded in C/C++ projects.
Simple language that can be used in education and introducing Compiler/VM concepts.
General-Purpose language that can be used for creating domain-specific libraries, frameworks and tools.
Practical language designed for creating the next version of the Programming Without Coding Technology software.
== Examples ==
=== Hello World program ===
The same program can be written using different styles. Here is an example of the standard "Hello, World!" program using four different styles.
The first style:
see "Hello, World!"
The second style:
put "Hello, World!"
The third style:
print("Hello, World!")
Another style: similar to xBase languages like Clipper and Visual FoxPro
? "Hello, World!"
=== Change the keywords and operators ===
Ring supports changing the language keywords and operators.
This could be done many times in the same source file, and is useful for
Translating the keywords from English to other human languages (Non-English-based programming languages)
Customizing the language for use of a favorite style
Porting Legacy code written in other languages
Translate Ring keywords to Japanese
ChangeRingKeyword See 手紙を出す
ChangeRingOperator + そして
改行 = nl
します。 = :します。
手紙を出す "こんにちは、世界" そして 改行 します。
ChangeRingKeyword 手紙を出す See // キーワードの復旧
ChangeRingOperator そして + // 演算子の復旧
Translate Ring keywords to Arabic
ChangeRingKeyword See إطبع
إطبع "Hello, World!"
ChangeRingKeyword إطبع See
Use style similar to the Pascal programming language
=== Loop command ===
The Loop command can take an integer to apply the continue semantics to enclosing outer loops
changeRingKeyword loop continue
count = 2
for x in 1:5
for y = 1 to 2
if x = 3
? "About to execute 'loop', count = " + count
continue count
ok
? "x: " + x + ", y: " + y
next
next
=== Object-oriented programming ===
Ring supports object-oriented programming (classes, objects, composition, inheritance, encapsulation, etc.)
new point { # Create new object from the Point class the access the object using braces
x=10 y=20 z=30 # Set the object attributes
print() # Call the print() method
} # end of object access using braces
class point # Define the class
x y z # Define the attributes (x,y,z)
func print # Define the print() method
? x + nl + y + nl + z # Print the attributes values (nl means printing a new line)
In Ring classes can be defined at runtime using the Eval() function
? "Creating a new class dynamically..."
eval("class DynamicClass a b")
? "Printing the instance..."
? new DynamicClass {a=1 b=2}
== Implementation ==
=== Compiler and virtual machine ===
Ring programs are not interpreted directly from the textual Ring file, but are compiled into bytecode, which is then run on the Ring virtual machine. The compilation process is typically invisible to the user and is performed at run-time, but it can be done offline in order to increase loading performance or reduce the memory footprint of the host environment by leaving out the compiler.
The compiler and the virtual machine are designed using visual programming through the Programming Without Coding Technology software then the C code is generated.
=== Extensions ===
The following are extensions that can be used immediately after the installation of the full installation version (with a file size of about 280 MB for Ring 1.12). Since these are officially provided and maintained on the Ring side, the users are not bothered by library dependencies that may cause problems in other languages, and there is a concern that they can not be used suddenly even if there are destructive language specification changes.
The extensions are implemented in approximately 500,000 lines of C and C++ code.
RingAllegro (Allegro Game Library)
RingConsoleColor (Text coloring library for command prompt or the terminal)
RingCurl (CURL Library)
RingFreeGLUT (FreeGLUT)
RingInternet (Internet related library)
RingLibUV (LibUV-asynchronous I / O library)
RingMurMurHash (Hash Function Library)
RingMySQL (MySQL)
RingODBC (Open Database Connectivity)
RingOpenGL (OpenGL 1.1-4.6)
RingOpenSSL (OpenSSL)
RingPostgreSQL (PostgreSQL)
RingQt (Qt framework)
RingRayLib (raylib)
RingSDL (SDL-Simple DirectMedia Layer Library)
RingSQLite (SQLite)
RingWinAPI (Windows API)
RingWinCREG (Windows Registry)
RingZIP (zip file processing library)
=== Libraries ===
Ring comes with libraries written in Ring itself, such as libraries related to web and game development.
=== Applications ===
Ring is distributed with over 60 applications written in the language.
Some of these applications are
Analog Clock application
Calculator application
The Checkers Game
The Chess Game
Fifteen Puzzle 3D Game
Game 2048
Knight Tour Game
Minesweeper Game
Othello Game
Sokoban Game
Sudoku Game
Tic-tac-toe 3D Game
Video Music Player application
Windows Startup Manager application
=== Tools ===
Ring is distributed with a Standard IDE that includes the following tools:
Ring REPL (Read–eval–print loop)
Ring2EXE (Distributing executable applications)
RingPM (The Ring Package manager)
Ring Notepad (Source-code editor)
Form Designer (WYSIWYG GUI designer)
Ring is also distributed with extensions for many code editors such as Emacs, Notepad++, Geany, Atom, Sublime Text 2, and Visual Studio Code.
=== Documentation ===
Ring is distributed with documentation written using Sphinx. A Japanese translation of the documentation is also available.
== Reception ==
=== Popularity ===
Ring had a rapid rise and fall in popularity as measured by the TIOBE Programming Community Index. In February 2018, Ring broke into the top 50 for the first time (position 45). As of October 2020, Ring holds position 93 on the TIOBE index. Ring is listed by GitHub in the list of programming languages that are actively developed.
=== Criticism ===
Ring critics pointed to some features in Ring that are not common in widely used programming languages.
The list index starts from 1 instead of 0 (See: Zero-based numbering)
Implicit type conversions (See: Implicit type conversions and "type punning")
==== The list index starts from 1 instead of 0 ====
In Ring, the index of the first item in lists and the first character in strings is 1.
cName = "Ring"
? cName[1] # print R
aList = ["One","Two","Three"]
? aList[1] # print One
==== Implicit type conversions ====
The language can automatically convert between numbers and strings.
/*
** Rules:
** <NUMBER> + <STRING> --> <NUMBER>
** <STRING> + <NUMBER> --> <STRING>
*/
x = 10 # x is a number
y = "20" # y is a string
nSum = x + y # nSum is a number (y will be converted to a number)
cMsg = "Sum = " + nSum # cMsg is a string (nSum will be converted to a string)
== See also ==
Tcl
Lua
Python
Ruby
Squirrel
Gambas
Julia
== References ==
== Further reading ==
Fayed, Alohali. (2024) Ring: A Lightweight and Versatile Cross-Platform Dynamic Programming Language Developed Using Visual Programming, Electronics
Ghanem (2021) Developing Poet Software using Ring language (Arabic Book), MetaBook (Egypt - Mansoura)
Ayouni (2020) Beginning Ring Programming, Apress (part of Springer Nature)
Hassouna (2019) Ring Basics (Arabic Book), Hassouna Academy
Sobain (2017) RingWinCReg Extension Documentation, SourceForge
Fayed (2016) The Ring Programming Language, CodeProject
== External links ==
Ring home page
RosettaCode samples
Ring Documentation (Japanese) Archived 2021-10-30 at the Wayback Machine
Online Form Designer (WebAssembly)
|
https://en.wikipedia.org/wiki/Ring_(programming_language)
|
A rewrite in computer programming is the act or result of re-implementing a large portion of existing functionality without re-use of its source code. When the rewrite uses no existing code at all, it is common to speak of a rewrite from scratch.
== Motivations ==
A piece of software is typically rewritten when one or more of the following apply:
its source code is not available or is only available under an incompatible license
its code cannot be adapted to a new target platform
its existing code has become too difficult to handle and extend
the task of debugging it seems too complicated
the programmer finds it difficult to understand its source code
developers learn new techniques or wish to do a big feature overhaul which requires much change
the programming language of the source code has to be changed
== Risks ==
Several software engineers, such as Joel Spolsky have warned against total rewrites, especially under schedule constraints or competitive pressures. While developers may initially welcome the chance to correct historical design mistakes, a rewrite also discards those parts of the design that work as required. A rewrite commits the development team to deliver not just new features, but all those that exist in the previous code, while potentially introducing new bugs or regressions of previously fixed bugs. A rewrite also interferes with the tracking of unfixed bugs in the old version.
The incremental rewrite is an alternative approach, in which developers gradually replace the existing code with calls into a new implementation, expanding that implementation until it fully replaces the old one. This approach avoids a broad loss of functionality during the rewrite. Cleanroom software engineering is another approach, which requires the team to work from an exhaustive written specification of the software's functionality, without access to its code.
== Examples ==
Netscape's project to improve HTML layout in Navigator 4 has been cited as an example of a failed rewrite. The new layout engine (Gecko) had developed independently from Navigator and did not integrate readily with Navigator's code; hence Navigator itself was rewritten around the new engine, breaking many existing features and delaying release by several months. Meanwhile, Microsoft focused on incremental improvements to Internet Explorer and did not face the same obstacles. Ironically, Navigator itself was a successful cleanroom rewrite of NCSA Mosaic overseen by that program's developers. See Browser wars.
Some projects mentioning major rewrites in their history:
== Techniques ==
Strangler fig pattern
== See also ==
Code refactoring
Open source software development
Technical debt
Development hell
Porting
Game engine recreation
Reverse engineering
== References ==
== External links ==
RewriteCodeFromScratch at C2 Wiki
Things You Should Never Do, Part I by Joel Spolsky
|
https://en.wikipedia.org/wiki/Rewrite_(programming)
|
This is a list of television programs currently and formerly broadcast by Cartoon Network in India. The network was launched on 1 May 1995 and airs mainly animated programmings.
== Current programming ==
Ben 10
Ben 10 (2005)
Ben 10: Alien Force
Ben 10: Ultimate Alien
Ben 10: Omniverse
Bionic Max
Courage the Cowardly Dog
Digimon Adventure
Dragon Ball
Dragon Ball Super
Dragon Ball Z
Dragon Ball Z Kai
Grizzy & the Lemmings
Larva
Lamput
My Hero Academia
One Piece
Scooby-Doo
Teen Titans
Teen Titans Go!
The Tom and Jerry Show
== Former programming ==
=== Animated series ===
2 Stupid Dogs
The 13 Ghosts of Scooby-Doo
50/50 Heroes
The Addams Family
The Adventures of Chhota Birbal
The Adventures of Tenali Raman
The Adventures of Tintin
Adventure Time
Akbar and Birbal
The All New Popeye Hour
Alvin and the Chipmunks
Amar Chitra Katha
The Amazing World of Gumball
Andy Pandy
Angelina Ballerina
Angelo Rules
Angry Birds Toons
Animal Control
Animalia
Anpanman
Apple & Onion
Aqua Teen Hunger Force
Archie's Weird Mysteries
Astro Boy
The Avengers: Earth's Mightiest Heroes
Baby Looney Tunes
The Backyardigans
Bakugan Battle Brawlers
Bakugan Battle Brawlers: New Vestroia
Bandbudh Aur Budbak
Batman: The Animated Series
Batman Beyond
Batman: The Brave and the Bold
Batwheels
Battle B-Daman
Be Cool, Scooby-Doo!
Beast Machines: Transformers
Beat Monsters
Ben 10 (2005)
Ben 10 (2016)
Ben 10: Alien Force
Ben 10: Omniverse
Ben 10: Ultimate Alien
Beware the Batman
Beyblade
Beyblade: Metal Fusion
Birdman and the Galaxy Trio
Blue Dragon
Bob the Builder
Bob the Builder: Project: Build It
Bobobo-bo Bo-bobo
Boo!
The Brak Show
The Bugs Bunny Show
Camp Lazlo
Capeta
Captain Planet and the Planeteers
Cardcaptor Sakura
Chowder
Clarence
Cloudy with a Chance of Meatballs
Code Lyoko
Codename: Kids Next Door
Courage the Cowardly Dog
Cow and Chicken
Craig of the Creek
Crime Time
Dabangg
DC Super Hero Girls
DC Super Hero Girls: Super Hero High
Dexter's Laboratory
Digimon
Digimon Adventure
Dragon Ball
Dragon Ball GT
Dragon Ball Kai
Dragon Ball Super
Dragon Ball Z
Dragon Tales
DreamWorks Dragons
Duck Dodgers
Duel Masters
Ed, Edd n Eddy
Ekans – Snakes Awake'
Exchange Student Zero
Fantastic Max
Firehouse Tales
Fish Police
The Flintstones
The Flintstone Comedy Show
The Flintstone Funnies
The Flintstone Kids
Foster's Home for Imaginary Friends
Franklin
Fred Flintstone and Friends
Fukrey Boyzzz
G.I. Joe: A Real American Hero (1983)
G.I. Joe: A Real American Hero (1989)
Galtar and the Golden Lance
Garfield and Friends
Generator Rex
Gon
Green Lantern: The Animated Series
The Grim Adventures of Billy & Mandy
Grim & Evil
Grizzy and the Lemmings
Hagemaru
Harry and His Bucket Full of Dinosaurs
Harvey Birdman, Attorney at Law
He-Man and the Masters of the Universe
Heidi
The Herculoids
Hero: 108
Hi Hi Puffy AmiYumi
Hikari Sentai Maskman
Home Movies
Hong Kong Phooey
Horrid Henry
Hot Wheels: AcceleRacers
Hot Wheels Battle Force 5
I Am Weasel
Inazuma Eleven
Iron Man: Armored Adventures
Jackie Chan Adventures
Jellystone!
The Jetsons
Johnny Bravo
Johnny Test
Jonny Quest
Josie and the Pussycats
Jumanji
Jungle Tales
Justice League
Justice League Action
Justice League Unlimited
Kaiketsu Zorori
Kiba
Kid Krrish
Kipper the Dog
Kiteretsu
The Koala Brothers
Krish, Trish and Baltiboy
Krypto the Superdog
Lamput
The Land Before Time
Larva
League of Super Evil
Legends of Chima
The Legend of Snow White
Lego Ninjago: Masters of Spinjitzu
The Life and Times of Juniper Lee
Looney Tunes
Looney Tunes Cartoons
The Looney Tunes Show
Maca & Roni
Mad: The Animated Series
Make Way for Noddy
Mao Mao: Heroes of Pure Heart
The Marvelous Misadventures of Flapjack
The Mask: Animated Series
Matt Hatter Chronicles
Max Steel (2000)
Max Steel (2013)
Mechamato
Megas XLR
Men in Black: The Series
Mighty Magiswords
Mike, Lu & Og
Miss Spider's Sunny Patch Friends
Mix Master
Mixels
Mobile Suit Gundam
Moby Dick and Mighty Mightor
The Moxy Show
Mr. Bean: The Animated Series
Mr. Magoo
¡Mucha Lucha!
The Mummy: The Animated Series
My Gym Partner's a Monkey
My Hero Academia
My Knight and Me
Naruto
Nate Is Late
The New Adventures of Captain Planet
The New Adventures of Hanuman'
The New Adventures of Jonny Quest
The New Adventures of Speed Racer
The New Batman Adventures
The New Fred and Barney Show
The New Scooby and Scrappy-Doo Show
The New Scooby-Doo Movies
Ninja Robots
Obocchama Kun
Oggy and the Cockroaches
OK K.O.! Let's Be Heroes
One Piece
Oswald
Over the Garden Wall
Ozzy & Drix
The Pebbles and Bamm-Bamm Show
The Perils of Penelope Pitstop
Pet Alien
Pingu
Pinky and the Brain
Pinky, Elmyra & the Brain
The Plucky Duck Show
Pokémon
Popeye and Son
Popeye the Sailor
The Popeye Show
The Porky Pig Show
Postman Pat
The Powerpuff Girls (1998)
The Powerpuff Girls (2016)
Powerpuff Girls Z
A Pup Named Scooby-Doo
The Real Adventures of Jonny Quest
Regular Show
Richie Rich
Ricochet Rabbit & Droop-a-Long
The Road Runner Show
Robotboy
Roll No 21
Rubbadubbers
Running Man
Sabrina: The Animated Series
Samurai Jack
Scooby-Doo and Guess Who?
Scooby-Doo! Mystery Incorporated
Scooby-Doo and Scrappy-Doo (1979)
Scooby-Doo and Scrappy-Doo (1980)
The Scooby-Doo Show
Scooby-Doo, Where Are You!
Sealab 2021
Secret Mountain Fort Awesome
The Secret Saturdays
Shaggy & Scooby-Doo Get a Clue!
Shazzan
Sheep in the Big City
Sitting Ducks
Skunk Fu!
The Smurfs
Sonic Boom
Space Ghost
Space Ghost Coast to Coast
The Spectacular Spider-Man
Spider-Man: The New Animated Series
Star Wars: Clone Wars
Star Wars: The Clone Wars
Static Shock
Steven Universe
Steven Universe Future
Strawberry Shortcake
Stuart Little: The Animated Series
Summer Camp Island
Super Bheem
Super Friends
The Super Hero Squad Show
Super Shiro
Superman: The Animated Series
Supernoobs
SWAT Kats: The Radical Squadron
The Sylvester & Tweety Mysteries
Sym-Bionic Titan
Taffy
Taz-Mania
TDPI
Teen Titans
Teen Titans Go!
Teenage Mutant Ninja Turtles
Thomas & Friends
ThunderCats (1985)
ThunderCats (2011)
ThunderCats Roar
Tik Tak Tail
Time Squad
Tiny Toon Adventures
Tom and Jerry
Tom and Jerry (2023)
The Tom and Jerry Comedy Show
Tom & Jerry Kids
Tom and Jerry in New York
The Tom and Jerry Show (1975)
The Tom and Jerry Show (2014)
Tom and Jerry Tales
Top Cat
Transformers: Animated
Transformers: Armada
Transformers: Cybertron
Transformers: Cyberverse
Transformers: Energon
Transformers: Prime
Transformers: Robots in Disguise
Trouble Chocolate
Ultimate Muscle
Uncle Grandpa
Unikitty!
Victor and Valentino
We Baby Bears
We Bare Bears
What a Cartoon!
What's New, Scooby-Doo?
Whatever Happened to... Robot Jones?
Wolverine and the X-Men
Wow! Wow! Wubbzy!
Xiaolin Chronicles
Xiaolin Showdown
X-Men: Evolution
Yo-kai Watch
The Yogi Bear Show
Yogi's Treasure Hunt
Young Justice
Zatch Bell!
=== Live-action/mixed ===
Cambala Investigation Agency
Chouseishin Gransazer
Galli Galli Sim Sim
Genseishin Justirisers
Sazer X
Skatoony
Teletubbies
== Films ==
Arnab aur Jadui Locket (2014)
Bhootraja Aur Ronnie 2 (2014)
Chakra: The Invincible (2013)
Kid Krrish (2013)
Kid Krrish: Mission Bhutan (2014)
Kid Krrish: Mystery in Mongolia (2014)
Kid Krrish: Shakalaka Africa (2015)
Krishna: The Birth (2006)
Krishna in Vrindavan (2006)
Krishna: Kansa Vadha (2006)
Krishna: Maakhan Chor (2006)
My Name Is Raj (2011)
My Name Is Raj 2 (2012)
My Name Is Raj 3: Attack of Demons (2013)
My Name Is Raj 4: Vizukama Ki Takaar (2014)
My Name is Raj 5: Return of Zohak (2015)
Vikram Betal (2005)
Tripura - The Three Cities of Maya (2011)
== Specials ==
Mangal Pandey Special (2005)
Johnny Goes to Bollywood (2009)
Kris Aur Sharukhan Khan Ki Dilwale Bollywood Class (2015)
Oggy Ki Birthday Party (2015)
Dragon Ball Z Blockbuster (2023)
== Programming blocks ==
== See also ==
List of programmes broadcast by Discovery Kids (India)
== References ==
== External links ==
Cartoon Network India official website
|
https://en.wikipedia.org/wiki/List_of_programmes_broadcast_by_Cartoon_Network_(India)
|
Programming languages can be grouped by the number and types of paradigms supported.
== Paradigm summaries ==
A concise reference for the programming paradigms listed in this article.
Concurrent programming – have language constructs for concurrency, these may involve multi-threading, support for distributed computing, message passing, shared resources (including shared memory), or futures
Actor programming – concurrent computation with actors that make local decisions in response to the environment (capable of selfish or competitive behaviour)
Constraint programming – relations between variables are expressed as constraints (or constraint networks), directing allowable solutions (uses constraint satisfaction or simplex algorithm)
Dataflow programming – forced recalculation of formulas when data values change (e.g. spreadsheets)
Declarative programming – describes what computation should perform, without specifying detailed state changes cf. imperative programming (functional and logic programming are major subgroups of declarative programming)
Distributed programming – have support for multiple autonomous computers that communicate via computer networks
Functional programming – uses evaluation of mathematical functions and avoids state and mutable data
Generic programming – uses algorithms written in terms of to-be-specified-later types that are then instantiated as needed for specific types provided as parameters
Imperative programming – explicit statements that change a program state
Logic programming – uses explicit mathematical logic for programming
Metaprogramming – writing programs that write or manipulate other programs (or themselves) as their data, or that do part of the work at compile time that would otherwise be done at runtime
Template metaprogramming – metaprogramming methods in which a compiler uses templates to generate temporary source code, which is merged by the compiler with the rest of the source code and then compiled
Reflective programming – metaprogramming methods in which a program modifies or extends itself
Object-oriented programming – uses data structures consisting of data fields and methods together with their interactions (objects) to design programs
Class-based – object-oriented programming in which inheritance is achieved by defining classes of objects, versus the objects themselves
Prototype-based – object-oriented programming that avoids classes and implements inheritance via cloning of instances
Pipeline programming – a simple syntax change to add syntax to nest function calls to language originally designed with none
Rule-based programming – a network of rules of thumb that comprise a knowledge base and can be used for expert systems and problem deduction & resolution
Visual programming – manipulating program elements graphically rather than by specifying them textually (e.g. Simulink); also termed diagrammatic programming
== Language overview ==
== See also ==
Programming paradigm
List of programming languages by type
Domain-specific language
Domain-specific multimodeling
== Notes ==
== Citations ==
== References ==
Jim Coplien, Multiparadigm Design for C++, Addison-Wesley Professional, 1998.
|
https://en.wikipedia.org/wiki/Comparison_of_multi-paradigm_programming_languages
|
In computer science and software programming, a value is the representation of some entity that can be manipulated by a program. The members of a type are the values of that type.
The "value of a variable" is given by the corresponding mapping in the environment. In languages with assignable variables, it becomes necessary to distinguish between the r-value (or contents) and the l-value (or location) of a variable.
In declarative (high-level) languages, values have to be referentially transparent. This means that the resulting value is independent of the location of the expression needed to compute the value. Only the contents of the location (the bits, whether they are 1 or 0) and their interpretation are significant.
== Value category ==
Despite its name, in the C++ language standards this terminology is used to categorize expressions, not values.: 8.2.1
=== Assignment: l-values and r-values ===
Some languages use the idea of l-values and r-values, deriving from the typical mode of evaluation on the left and right-hand side of an assignment statement. An l-value refers to an object that persists beyond a single expression. An r-value is a temporary value that does not persist beyond the expression that uses it.
The notion of l-values and r-values was introduced by Combined Programming Language (CPL). The notions in an expression of r-value, l-value, and r-value/l-value are analogous to the parameter modes of input parameter (has a value), output parameter (can be assigned), and input/output parameter (has a value and can be assigned), though the technical details differ between contexts and languages.
=== R-values and addresses ===
In many languages, notably the C family, l-values have storage addresses that are programmatically accessible to the running program (e.g., via some address-of operator like "&" in C/C++), meaning that they are variables or de-referenced references to a certain memory location. R-values can be l-values (see below) or non-l-values—a term only used to distinguish from l-values. Consider the C expression 4 + 9. When executed, the computer generates an integer value of 13, but because the program has not explicitly designated where in the computer this 13 is stored, the expression is a non l-value. On the other hand, if a C program declares a variable x and assigns the value of 13 to x, then the expression x has a value of 13 and is an l-value.
In C, the term l-value originally meant something that could be assigned to (hence the name, indicating it is on the left side of the assignment operator), but since the reserved word const (constant) was added to the language, the term is now 'modifiable l-value'. In C++11 a special semantic-glyph && exists ( not to be confused with the && operator used for logical operations ), to denote the use/access of the expression's address for the compiler only; i.e., the address cannot be retrieved using the address-of & operator during the run-time of the program (see the use of move semantics). The addition of move semantics complicated the value classification taxonomy by adding to it the concept of an xvalue (expiring value) which refers to an object near the end of its lifetime whose resources can be reused (typically by moving them). This also lead to the creation of the categories glvalue (generalized lvalue) which are lvalues and xvalues and prvalues (pure rvalues) which are rvalues that are not xvalues.
This type of reference can be applied to all r-values including non-l-values as well as l-values. Some processors provide one or more instructions which take an immediate value, sometimes referred to as "immediate" for short. An immediate value is stored as part of the instruction which employs it, usually to load into, add to, or subtract from, a register. The other parts of the instruction are the opcode, and destination. The latter may be implicit. (A non-immediate value may reside in a register, or be stored elsewhere in memory, requiring the instruction to contain a direct or indirect address [e.g., index register address] to the value.)
The l-value expression designates (refers to) an object. A non-modifiable l-value is addressable, but not assignable. A modifiable l-value allows the designated object to be changed as well as examined. An r-value is any expression, a non-l-value is any expression that is not an l-value. One example is an "immediate value" (see above) and consequently not addressable.
== In assembly language ==
A value can be virtually any kind of data by a given data type, for instance a string, a digit, a single letter.
Processors often support more than one size of immediate data, e.g. 8 or 16 bit, employing a unique opcode and mnemonic for each instruction variant. If a programmer supplies a data value that will not fit, the assembler issues an "Out of range" error message. Most assemblers allow an immediate value to be expressed as ASCII, decimal, hexadecimal, octal, or binary data. Thus, the ASCII character 'A' is the same as 65 or 0x41. The byte order of strings may differ between processors, depending on the assembler and computer architecture.
== Notes ==
== References ==
Mitchell, John C. (1996). Foundations for Programming Languages. The MIT Press. ISBN 0-262-13321-0.
Strachey, Christopher (2000). "Fundamental Concepts in Programming Languages". Higher-Order and Symbolic Computation. 13: 11–49. doi:10.1023/A:1010000313106. S2CID 14124601.
== External links ==
Value Object
Transfer Object Pattern
|
https://en.wikipedia.org/wiki/Value_(computer_science)
|
Invariant-based programming is a programming methodology where specifications and invariants are written before the actual program statements. Writing down the invariants during the programming process has a number of advantages: it requires the programmer to make their intentions about the program behavior explicit before actually implementing it, and invariants can be evaluated dynamically during execution to catch common programming errors. Furthermore, if strong enough, invariants can be used to prove the correctness of the program based on the formal semantics of program statements. A combined programming and specification language, connected to a powerful formal proof system, will generally be required for full verification of non-trivial programs. In this case a high degree of automation of proofs is also possible.
In most existing programming languages the main organizing structures are control flow blocks such as for loops, while loops and if statements. Such languages may not be ideal for invariants-first programming, since they force the programmer to make decisions about control flow before writing the invariants. Furthermore, most programming languages do not have good support for writing specifications and invariants, since they lack quantifier operators and one can typically not express higher order properties.
The idea of developing the program together with its proof originated from E.W. Dijkstra. Actually writing invariants before program statements has been considered in a number of different forms by M.H. van Emden, J.C. Reynolds and R-J Back.
== See also ==
Eiffel (programming language)
== References ==
|
https://en.wikipedia.org/wiki/Invariant-based_programming
|
In mathematical optimization, linear-fractional programming (LFP) is a generalization of linear programming (LP). Whereas the objective function in a linear program is a linear function, the objective function in a linear-fractional program is a ratio of two linear functions. A linear program can be regarded as a special case of a linear-fractional program in which the denominator is the constant function 1.
Formally, a linear-fractional program is defined as the problem of maximizing (or minimizing) a ratio of affine functions over a polyhedron,
maximize
c
T
x
+
α
d
T
x
+
β
subject to
A
x
≤
b
,
{\displaystyle {\begin{aligned}{\text{maximize}}\quad &{\frac {\mathbf {c} ^{T}\mathbf {x} +\alpha }{\mathbf {d} ^{T}\mathbf {x} +\beta }}\\{\text{subject to}}\quad &A\mathbf {x} \leq \mathbf {b} ,\end{aligned}}}
where
x
∈
R
n
{\displaystyle \mathbf {x} \in \mathbb {R} ^{n}}
represents the vector of variables to be determined,
c
,
d
∈
R
n
{\displaystyle \mathbf {c} ,\mathbf {d} \in \mathbb {R} ^{n}}
and
b
∈
R
m
{\displaystyle \mathbf {b} \in \mathbb {R} ^{m}}
are vectors of (known) coefficients,
A
∈
R
m
×
n
{\displaystyle A\in \mathbb {R} ^{m\times n}}
is a (known) matrix of coefficients and
α
,
β
∈
R
{\displaystyle \alpha ,\beta \in \mathbb {R} }
are constants. The constraints have to restrict the feasible region to
{
x
|
d
T
x
+
β
>
0
}
{\displaystyle \{\mathbf {x} |\mathbf {d} ^{T}\mathbf {x} +\beta >0\}}
, i.e. the region on which the denominator is positive. Alternatively, the denominator of the objective function has to be strictly negative in the entire feasible region.
== Motivation by comparison to linear programming ==
Both linear programming and linear-fractional programming represent optimization problems using linear equations and linear inequalities, which for each problem-instance define a feasible set. Fractional linear programs have a richer set of objective functions. Informally, linear programming computes a policy delivering the best outcome, such as maximum profit or lowest cost. In contrast, a linear-fractional programming is used to achieve the highest ratio of outcome to cost, the ratio representing the highest efficiency. For example, in the context of LP we maximize the objective function profit = income − cost and might obtain maximum profit of $100 (= $1100 of income − $1000 of cost). Thus, in LP we have an efficiency of $100/$1000 = 0.1. Using LFP we might obtain an efficiency of $10/$50 = 0.2 with a profit of only $10, but only requiring $50 of investment.
== Transformation to a linear program ==
Any linear-fractional program can be transformed into a linear program, assuming that the feasible region is non-empty and bounded, using the Charnes–Cooper transformation. The main idea is to introduce a new non-negative variable
t
{\displaystyle t}
to the program which will be used to rescale the constants involved in the program (
α
,
β
,
b
{\displaystyle \alpha ,\beta ,\mathbf {b} }
). This allows us to require that the denominator of the objective function (
d
T
x
+
β
{\displaystyle \mathbf {d} ^{T}\mathbf {x} +\beta }
) equals 1. (To understand the transformation, it is instructive to consider the simpler special case with
α
=
β
=
0
{\displaystyle \alpha =\beta =0}
.)
Formally, the linear program obtained via the Charnes–Cooper transformation uses the transformed variables
y
∈
R
n
{\displaystyle \mathbf {y} \in \mathbb {R} ^{n}}
and
t
≥
0
{\displaystyle t\geq 0}
:
maximize
c
T
y
+
α
t
subject to
A
y
≤
b
t
d
T
y
+
β
t
=
1
t
≥
0.
{\displaystyle {\begin{aligned}{\text{maximize}}\quad &\mathbf {c} ^{T}\mathbf {y} +\alpha t\\{\text{subject to}}\quad &A\mathbf {y} \leq \mathbf {b} t\\&\mathbf {d} ^{T}\mathbf {y} +\beta t=1\\&t\geq 0.\end{aligned}}}
A solution
x
{\displaystyle \mathbf {x} }
to the original linear-fractional program can be translated to a solution of the transformed linear program via the equalities
y
=
1
d
T
x
+
β
⋅
x
and
t
=
1
d
T
x
+
β
.
{\displaystyle \mathbf {y} ={\frac {1}{\mathbf {d} ^{T}\mathbf {x} +\beta }}\cdot \mathbf {x} \quad {\text{and}}\quad t={\frac {1}{\mathbf {d} ^{T}\mathbf {x} +\beta }}.}
Conversely, a solution for
y
{\displaystyle \mathbf {y} }
and
t
{\displaystyle t}
of the transformed linear program can be translated to a solution of the original linear-fractional program via
x
=
1
t
y
.
{\displaystyle \mathbf {x} ={\frac {1}{t}}\mathbf {y} .}
== Duality ==
Let the dual variables associated with the constraints
A
y
−
b
t
≤
0
{\displaystyle A\mathbf {y} -\mathbf {b} t\leq \mathbf {0} }
and
d
T
y
+
β
t
−
1
=
0
{\displaystyle \mathbf {d} ^{T}\mathbf {y} +\beta t-1=0}
be denoted by
u
{\displaystyle \mathbf {u} }
and
λ
{\displaystyle \lambda }
, respectively. Then the dual of the LFP above is
minimize
λ
subject to
A
T
u
+
λ
d
=
c
−
b
T
u
+
λ
β
≥
α
u
∈
R
+
m
,
λ
∈
R
,
{\displaystyle {\begin{aligned}{\text{minimize}}\quad &\lambda \\{\text{subject to}}\quad &A^{T}\mathbf {u} +\lambda \mathbf {d} =\mathbf {c} \\&-\mathbf {b} ^{T}\mathbf {u} +\lambda \beta \geq \alpha \\&\mathbf {u} \in \mathbb {R} _{+}^{m},\lambda \in \mathbb {R} ,\end{aligned}}}
which is an LP and which coincides with the dual of the equivalent linear program resulting from the Charnes–Cooper transformation.
== Properties and algorithms ==
The objective function in a linear-fractional problem is both quasiconcave and quasiconvex (hence quasilinear) with a monotone property, pseudoconvexity, which is a stronger property than quasiconvexity. A linear-fractional objective function is both pseudoconvex and pseudoconcave, hence pseudolinear. Since an LFP can be transformed to an LP, it can be solved using any LP solution method, such as the simplex algorithm (of George B. Dantzig), the criss-cross algorithm, or interior-point methods.
== Notes ==
== Sources ==
Murty, Katta G. (1983). "3.10 Fractional programming (pp. 160–164)". Linear programming. New York: John Wiley & Sons, Inc. pp. xix+482. ISBN 978-0-471-09725-9. MR 0720547.
== Further reading ==
Bajalinov, E. B. (2003). Linear-Fractional Programming: Theory, Methods, Applications and Software. Boston: Kluwer Academic Publishers.
Barros, Ana Isabel (1998). Discrete and fractional programming techniques for location models. Combinatorial Optimization. Vol. 3. Dordrecht: Kluwer Academic Publishers. pp. xviii+178. ISBN 978-0-7923-5002-6. MR 1626973.
Martos, Béla (1975). Nonlinear programming: Theory and methods. Amsterdam-Oxford: North-Holland Publishing Co. p. 279. ISBN 978-0-7204-2817-9. MR 0496692.
Schaible, S. (1995). "Fractional programming". In Reiner Horst and Panos M. Pardalos (ed.). Handbook of global optimization. Nonconvex optimization and its applications. Vol. 2. Dordrecht: Kluwer Academic Publishers. pp. 495–608. ISBN 978-0-7923-3120-9. MR 1377091.
Stancu-Minasian, I. M. (1997). Fractional programming: Theory, methods and applications. Mathematics and its applications. Vol. 409. Translated by Victor Giurgiutiu from the 1992 Romanian. Dordrecht: Kluwer Academic Publishers Group. pp. viii+418. ISBN 978-0-7923-4580-0. MR 1472981.
|
https://en.wikipedia.org/wiki/Linear-fractional_programming
|
In aspect-oriented software development, cross-cutting concerns are aspects of a program that affect several modules, without the possibility of being encapsulated in any of them.
These concerns often cannot be cleanly decomposed from the rest of the system in both the design and implementation, and can result in either scattering (code duplication), tangling (significant dependencies between systems), or both.
For instance, if writing an application for handling medical records, the indexing of such records is a core concern, while logging a history of changes to the record database or user database, or an authentication system, would be cross-cutting concerns since they interact with more parts of the program.
== Background ==
Cross-cutting concerns are parts of a program that rely on or must affect many other parts of the system. They form the basis for the development of aspects. Such cross-cutting concerns do not fit cleanly into object-oriented programming or procedural programming.
Cross-cutting concerns can be directly responsible for tangling, or system inter-dependencies, within a program. Because procedural and functional language constructs consist entirely of procedure calling, there is no semantic through which two goals (the capability to be implemented and the related cross-cutting concern) can be addressed simultaneously. As a result, the code addressing the cross-cutting concern must be scattered, or duplicated, across the various related locations, resulting in a loss of modularity.
Aspect-oriented programming aims to encapsulate cross-cutting concerns into aspects to retain modularity. This allows for the clean isolation and reuse of code addressing the cross-cutting concern. By basing designs on cross-cutting concerns, software engineering benefits can include modularity and simplified maintenance.
== Examples ==
Examples of concerns that tend to be cross-cutting include:
Business rules
Caching
Code mobility
Data validation
Domain-specific optimizations
Environment variables and other global configuration settings
Error detection and correction
Internationalization and localization which includes Language localisation
Information security
Logging
Memory management
Monitoring
Persistence
Product features
Real-time constraints
Synchronization
Transaction processing
Context-sensitive help
Privacy
Computer security
== See also ==
Separation of concerns
Aspect-oriented programming
Code refactoring (restructuring software)
Database normalization (minimize needlessly replicated data)
Multiple inheritance
Microservices
Orthogonalization (mathematical normalization)
== References ==
== Bibliography ==
Kiczales, Gregor; Lamping, John; Mendhekar, Anurag; Maeda, John; Lopes, Cristina; Longtier, Jean-Marc; Irwin (1997). "Aspect-Oriented Programming". Proceedings of the 11th European Conference on Object-Oriented Programming (ECOOP 1997): 220–242.
US patent 6467086, Kiczales et al., "Aspect-oriented programming", issued 2002-10-15
Li, Harry; Krishnamurthi, Shriram; Fisler, Kathi (2002). "Verifying Cross-Cutting Features as Open Systems". ACM SIGSOFT Software Engineering Notes. 27 (6): 89–98. CiteSeerX 10.1.1.8.9445. doi:10.1145/605466.605481. S2CID 52835673.
Parnas, David L. (December 1972). "On the Criteria To Be Used in Decomposing Systems into Modules". Communications of the ACM. 15 (12): 1053–1058. CiteSeerX 10.1.1.90.8963. doi:10.1145/361598.361623. S2CID 53856438.
Tarr, Peri; Ossher, Harold; Harrison, William; Sutton, Stanley M. Jr. (1999). "N degrees of separation: Multi-dimensional separation of concerns". Proceedings of the 1999 International Conference on Software Engineering (IEEE Cat. No.99CB37002). Los Angeles, California, USA: IEEE Computer Society Press. pp. 107–119. CiteSeerX 10.1.1.89.1641. doi:10.1109/ICSE.1999.841000. ISBN 978-1-58113-074-4.
== Further reading ==
Laddad, R. (2003): AspectJ in Action, Practical Aspect-Oriented Programming, Manning Publications Co.
== External links ==
AOSD.net's glossary of aspect oriented terms (via Internet Archive Wayback Machine; AOSD.net has become Modularity).
AspectJ [1], an Aspect-Oriented extension to the Java programming language
Bergmans, L., M. Aksit (2001): Composing Multiple Concerns Using Composition Filters, https://web.archive.org/web/20170909131212/http://trese.cs.utwente.nl/ (24 July 2004)
Berg, K. van den, Conejero, J. and Chitchyan, R. (2005). AOSD Ontology 1.0 ‐ Public Ontology of Aspect‐Orientation. AOSD Europe Network of Excellence, http://eprints.eemcs.utwente.nl/10220/01/BergConChi2005.pdf
Here is an example of handling a cross-cutting concern: https://web.archive.org/web/20161220151503/https://www.captechconsulting.com/blogs/a-persistence-pattern-using-threadlocal-and-ejb-interceptors
|
https://en.wikipedia.org/wiki/Cross-cutting_concern
|
Dennis MacAlistair Ritchie (September 9, 1941 – c. October 12, 2011) was an American computer scientist. He created the C programming language and the Unix operating system and B language with long-time colleague Ken Thompson. Ritchie and Thompson were awarded the Turing Award from the Association for Computing Machinery (ACM) in 1983, the IEEE Richard W. Hamming Medal from the Institute of Electrical and Electronics Engineers (IEEE) in 1990, and the National Medal of Technology from President Bill Clinton in 1999.
Ritchie was the head of Lucent Technologies System Software Research Department when he retired in 2007.
== Early life and education ==
Dennis Ritchie was born in Bronxville, New York. His father was Alistair E. Ritchie, a longtime Bell Labs scientist and co-author of The Design of Switching Circuits on switching circuit theory. As a child, Dennis moved with his family to Summit, New Jersey, where he graduated from Summit High School. He graduated from Harvard University with degrees in physics and applied mathematics in 1963.
== Career ==
In 1967, Ritchie began working at the Bell Labs Computing Science Research Center. In 1968, he completed a draft of his PhD thesis on "Computational Complexity and Program Structure" at Harvard under the supervision of Patrick C. Fischer. However, Ritchie never officially received his PhD degree. In 2020, the Computer History Museum worked with Ritchie's family and Fischer's family and found a copy of the lost dissertation.
During the 1960s, Ritchie and Ken Thompson worked on the Multics operating system at Bell Labs. Thompson then found an old PDP-7 machine and developed his own application programs and operating system from scratch, aided by Ritchie and others. In 1970, Brian Kernighan suggested the name "Unix", a pun on the name "Multics". To supplement assembly language with a system-level programming language, Thompson created B. Later, B was replaced by C, created by Ritchie, who continued to contribute to the development of Unix and C for many years.
During the 1970s, Ritchie collaborated with James Reeds and Robert Morris on a ciphertext-only attack on the M-209 US cipher machine that could solve messages of at least 2000–2500 letters. Ritchie relates that, after discussions with the National Security Agency, the authors decided not to publish it, as they were told that the principle applied to machines still in use by foreign governments.
Ritchie was also involved with the development of the operating systems Plan 9 and Inferno, and the programming language Limbo.
As part of an AT&T restructuring in the mid-1990s, Ritchie was transferred to Lucent Technologies, where he retired in 2007 as head of System Software Research Department.
== C and Unix ==
Ritchie created the C programming language and was one of the developers of the Unix operating system. With Brian Kernighan, he co-wrote the book The C Programming Language, which is often referred to as K&R after their initials. Ritchie worked together with Ken Thompson, who is credited with writing the original version of Unix; one of Ritchie's contributions to Unix was its porting to different machines and platforms. They were so influential on Research Unix that Doug McIlroy later wrote, "The names of Ritchie and Thompson may safely be assumed to be attached to almost everything not otherwise attributed."
Nowadays, the C language is widely used in application, operating system, and embedded system development, and its influence is seen in most modern programming languages. C is a low-level language with constructs closely translating to the hardware's instruction set. However, it is not tied to any given hardware, making it easy to write programs on any machine that supports C. Moreover, C is a high-level programming language with constructs mapping to data structures in application software.
C influenced several other languages and derivatives, such as C++, Objective-C used by Apple, C# used by Microsoft, and Java used in corporate environments extensively and by Android. Ritchie and Thompson used C to write Unix, which has been influential in establishing many computing concepts and principles that are adopted widely.
In an interview from 1999, Ritchie clarified that he saw Linux and Berkeley Software Distribution (BSD) operating systems as a continuation of the basis of the Unix operating system, and as derivatives of Unix:
I think the Linux phenomenon is quite delightful, because it draws so strongly on the basis that Unix provided. Linux seems to be among the healthiest of the direct Unix derivatives, though there are also the various BSD systems as well as the more official offerings from the workstation and mainframe manufacturers.
In the same interview, he stated that he viewed Unix and Linux as "the continuation of ideas that were started by Ken and me and many others, many years ago."
== Awards ==
In 1983, Ritchie and Thompson received the Turing Award "for their development of generic operating systems theory and specifically for the implementation of the UNIX operating system". Ritchie's Turing Award lecture was titled "Reflections on Software Research". In 1990, both Ritchie and Thompson received the IEEE Richard W. Hamming Medal from the Institute of Electrical and Electronics Engineers (IEEE), "for the origination of the UNIX operating system and the C programming language".
In 1997, both Ritchie and Thompson were made Fellows of the Computer History Museum, "for co-creation of the UNIX operating system, and for development of the C programming language."
On April 21, 1999, Thompson and Ritchie jointly received the National Medal of Technology of 1998 from President Bill Clinton for co-inventing the UNIX operating system and the C programming language which, according to the citation for the medal, "led to enormous advances in computer hardware, software, and networking systems and stimulated growth of an entire industry, thereby enhancing American leadership in the Information Age".
In 2005, the Industrial Research Institute awarded Ritchie its Achievement Award in recognition of his contribution to science and technology, and to society generally, with his development of the Unix operating system.
In 2011, Ritchie, along with Thompson, was awarded the Japan Prize for Information and Communications for his work in the development of the Unix operating system.
== Death ==
Ritchie was found dead on October 12, 2011, at the age of 70 at his home in Berkeley Heights, New Jersey, where he lived alone. First news of his death came from his former colleague, Rob Pike. He had been in frail health for several years following treatment for prostate cancer and heart disease. News of Ritchie's death was largely overshadowed by the media coverage of the death of Apple co-founder Steve Jobs, which occurred the week before.
== Legacy ==
Following Ritchie's death, computer historian Paul E. Ceruzzi stated:
Ritchie was under the radar. His name was not a household name at all, but... if you had a microscope and could look in a computer, you'd see his work everywhere inside.
In an interview shortly after Ritchie's death, long-time colleague Brian Kernighan said Ritchie never expected C to be so significant.
Kernighan told The New York Times "The tools that Dennis built—and their direct descendants—run pretty much everything today." Kernighan reminded readers of how important a role C and Unix had played in the development of later high-profile projects, such as the iPhone. Other testimonials to his influence followed.
Reflecting upon his death, a commentator compared the relative importance of Steve Jobs and Ritchie, concluding that "[Ritchie's] work played a key role in spawning the technological revolution of the last forty years—including technology on which Apple went on to build its fortune." Another commentator said, "Ritchie, on the other hand, invented and co-invented two key software technologies which make up the DNA of effectively every single computer software product we use directly or even indirectly in the modern age. It sounds like a wild claim, but it really is true." Another said, "many in computer science and related fields knew of Ritchie's importance to the growth and development of, well, everything to do with computing,..."
The Fedora 16 Linux distribution, which was released about a month after he died, was dedicated to his memory. FreeBSD 9.0, released January 12, 2012, was also dedicated in his memory.
Asteroid 294727 Dennisritchie, discovered by astronomers Tom Glinos and David H. Levy in 2008, was named in his memory. The official naming citation was published by the Minor Planet Center on 7 February 2012 (Minor Planet Circulars (M.P.C.) 78272).
== Notable works ==
B language
C language on which many succeeding languages and technologies are based.
Unix multiuser operating system. Several workalikes (commonly referred to as Unix-like systems) have been developed based on Unix's design. Some follow POSIX standards, again based on Unix.
Unix Programmer's Manual (1971)
The C Programming Language (sometimes referred to as K&R; 1978 with Brian Kernighan)
== Publications and academic papers ==
Ritchie has been the author or contributor to about 50 academic papers, books and textbooks and which have had over 15,000 citations.
Here are some of his most cited works:
The C Programming Language, BW Kernighan, DM Ritchie, Prentice Hall, Englewood Cliffs, New Jersey (1978)
Programming languages, D Ritchie (1978)
The UNIX time-sharing system, DM Ritchie, K Thompson, Classic operating systems, 195-220 (2001)
Advanced Programming in the Unix Environment, WR Stevens, SA Rago, DM Ritchie, Addison-Wesley (1992, 2008)
== See also ==
List of pioneers in computer science
== References ==
== External links ==
Official website, Bell Labs
"The C Family of Languages: Interview with Dennis Ritchie, Bjarne Stroustrup, and James Gosling" – article in Java Report, 5(7), July 2000 and C++ Report, 12(7), July/August 2000
"The Guru" – article in Linux Magazine, June 2001
Dennis Ritchie's video interview June 2011
|
https://en.wikipedia.org/wiki/Dennis_Ritchie
|
In computer programming, an enumerated type (also called enumeration, enum, or factor in the R programming language, a status variable in the JOVIAL programming language, and a categorical variable in statistics) is a data type consisting of a set of named values called elements, members, enumeral, or enumerators of the type. The enumerator names are usually identifiers that behave as constants in the language. An enumerated type can be seen as a degenerate tagged union of unit type. A variable that has been declared as having an enumerated type can be assigned any of the enumerators as a value. In other words, an enumerated type has values that are different from each other, and that can be compared and assigned, but are not generally specified by the programmer as having any particular concrete representation in the computer's memory; compilers and interpreters can represent them arbitrarily.
== Description ==
For example, the four suits in a deck of playing cards may be four enumerators named Club, Diamond, Heart, and Spade, belonging to an enumerated type named suit. If a variable V is declared having suit as its data type, one can assign any of those four values to it.
Although the enumerators are usually distinct, some languages may allow the same enumerator to be listed twice in the type's declaration. The names of enumerators need not be semantically complete or compatible in any sense. For example, an enumerated type called color may be defined to consist of the enumerators Red, Green, Zebra, Missing, and Bacon. In some languages, the declaration of an enumerated type also intentionally defines an ordering of its members (High, Medium and Low priorities); in others, the enumerators are unordered (English, French, German and Spanish supported languages); in others still, an implicit ordering arises from the compiler concretely representing enumerators as integers.
Some enumerator types may be built into the language. The Boolean type, for example is often a pre-defined enumeration of the values False and True. A unit type consisting of a single value may also be defined to represent null. Many languages allow users to define new enumerated types.
Values and variables of an enumerated type are usually implemented with some integer type as the underlying representation. Some languages, especially system programming languages, allow the user to specify the bit combination to be used for each enumerator, which can be useful to efficiently represent sets of enumerators as fixed-length bit strings. In type theory, enumerated types are often regarded as tagged unions of unit types. Since such types are of the form
1
+
1
+
⋯
+
1
{\displaystyle 1+1+\cdots +1}
, they may also be written as natural numbers.
== Rationale ==
Some early programming languages did not originally have enumerated types. If a programmer wanted a variable, for example myColor, to have a value of red, the variable red would be declared and assigned some arbitrary value, usually an integer constant. The variable red would then be assigned to myColor. Other techniques assigned arbitrary values to strings containing the names of the enumerators.
These arbitrary values were sometimes referred to as magic numbers since there often was no explanation as to how the numbers were obtained or whether their actual values were significant. These magic numbers could make the source code harder for others to understand and maintain.
Enumerated types, on the other hand, make the code more self-documenting. Depending on the language, the compiler could automatically assign default values to the enumerators thereby hiding unnecessary detail from the programmer. These values may not even be visible to the programmer (see information hiding). Enumerated types can also prevent a programmer from writing illogical code such as performing mathematical operations on the values of the enumerators. If the value of a variable that was assigned an enumerator were to be printed, some programming languages could also print the name of the enumerator rather than its underlying numerical value. A further advantage is that enumerated types can allow compilers to enforce semantic correctness. For instance:
myColor = TRIANGLE
can be forbidden, whilst
myColor = RED
is accepted, even if TRIANGLE and RED are both internally represented as 1.
Conceptually, an enumerated type is similar to a list of nominals (numeric codes), since each possible value of the type is assigned a distinctive natural number. A given enumerated type is thus a concrete implementation of this notion. When order is meaningful and/or used for comparison, then an enumerated type becomes an ordinal type.
== Conventions ==
Programming languages tend to have their own, oftentimes multiple, programming styles and naming conventions. The variable assigned to an enumeration is usually a noun in singular form, and frequently follows either a PascalCase or uppercase convention, while lowercase and others are seen less frequently.
== Syntax in several programming languages ==
=== Pascal and syntactically similar languages ===
==== Pascal ====
In Pascal, an enumerated type can be implicitly declared by listing the values in a parenthesised list:
The declaration will often appear in a type synonym declaration, such that it can be used for multiple variables:
The order in which the enumeration values are given matters. An enumerated type is an ordinal type, and the pred and succ functions will give the prior or next value of the enumeration, and ord can convert enumeration values to their integer representation. Standard Pascal does not offer a conversion from arithmetic types to enumerations, however. Extended Pascal offers this functionality via an extended succ function. Some other Pascal dialects allow it via type-casts. Some modern descendants of Pascal, such as Modula-3, provide a special conversion syntax using a method called VAL; Modula-3 also treats BOOLEAN and CHAR as special pre-defined enumerated types and uses ORD and VAL for standard ASCII decoding and encoding.
Pascal style languages also allow enumeration to be used as array index:
==== Ada ====
In Ada, the use of "=" was replaced with "is" leaving the definition quite similar:
In addition to Pred, Succ, Val and Pos Ada also supports simple string conversions via Image and Value.
Similar to C-style languages Ada allows the internal representation of the enumeration to be specified:
Unlike C-style languages Ada also allows the number of bits of the enumeration to be specified:
Additionally, one can use enumerations as indexes for arrays, like in Pascal, but there are attributes defined for enumerations
Like Modula-3 Ada treats Boolean and Character as special pre-defined (in package "Standard") enumerated types. Unlike Modula-3 one can also define own character types:
=== C and syntactically similar languages ===
==== C ====
The original K&R dialect of the programming language C had no enumerated types. In C, enumerations are created by explicit definitions (the enum keyword by itself does not cause allocation of storage) which use the enum keyword and are reminiscent of struct and union definitions:
C exposes the integer representation of enumeration values directly to the programmer. Integers and enum values can be mixed freely, and all arithmetic operations on enum values are permitted. It is even possible for an enum variable to hold an integer that does not represent any of the enumeration values. In fact, according to the language definition, the above code will define Clubs, Diamonds, Hearts, and Spades as constants of type int, which will only be converted (silently) to enum cardsuit if they are stored in a variable of that type.
C also allows the programmer to choose the values of the enumeration constants explicitly, even without type. For example,
could be used to define a type that allows mathematical sets of suits to be represented as an enum cardsuit by bitwise logic operations.
Since C23, the underlying type of an enumeration can be specified by the programmer:
==== C# ====
Enumerated types in the C# programming language preserve most of the "small integer" semantics of C's enums. Some arithmetic operations are not defined for enums, but an enum value can be explicitly converted to an integer and back again, and an enum variable can have values that were not declared by the enum definition. For example, given
the expressions CardSuit.Diamonds + 1 and CardSuit.Hearts - CardSuit.Clubs are allowed directly (because it may make sense to step through the sequence of values or ask how many steps there are between two values), but CardSuit.Hearts * CardSuit.Spades is deemed to make less sense and is only allowed if the values are first converted to integers.
C# also provides the C-like feature of being able to define specific integer values for enumerations. By doing this it is possible to perform binary operations on enumerations, thus treating enumeration values as sets of flags. These flags can be tested using binary operations or with the enum type's builtin 'HasFlag' method.
The enumeration definition defines names for the selected integer values and is syntactic sugar, as it is possible to assign to an enum variable other integer values that are not in the scope of the enum definition.
==== C++ ====
C++ has enumeration types that are directly inherited from C's and work mostly like these, except that an enumeration is a real type in C++, giving added compile-time checking. Also (as with structs), the C++ enum keyword is combined with a typedef, so that instead of naming the type enum name, simply name it name. This can be simulated in C using a typedef: typedef enum {Value1, Value2} name;
C++11 also provides a second kind of enumeration, called a scoped enumeration. These are type-safe: the enumerators are not implicitly converted to an integer type. Among other things, this allows I/O streaming to be defined for the enumeration type. Another feature of scoped enumerations is that the enumerators do not leak, so usage requires prefixing with the name of the enumeration (e.g., Color::Red for the first enumerator in the example below), unless a using enum declaration (introduced in C++20) has been used to bring the enumerators into the current scope. A scoped enumeration is specified by the phrase enum class (or enum struct). For example:
The underlying type of an enumeration is an implementation-defined integral type that is large enough to hold all enumerated values; it does not have to be the smallest possible type. The underlying type can be specified directly, which allows "forward declarations" of enumerations:
==== Go ====
Go uses the iota keyword to create enumerated constants.
==== Java ====
The J2SE version 5.0 of the Java programming language added enumerated types whose declaration syntax is
similar to that of C:
The Java type system, however, treats enumerations as a type separate from integers, and intermixing of enum and integer values is not allowed. In fact, an enum type in Java is actually a special compiler-generated class rather than an arithmetic type, and enum values behave as global pre-generated instances of that class. Enum types can have instance methods and a constructor (the arguments of which can be specified separately for each enum value). All enum types implicitly extend the Enum abstract class. An enum type cannot be instantiated directly.
Internally, each enum value contains an integer, corresponding to the order in which they are declared in the source code, starting from 0. The programmer cannot set a custom integer for an enum value directly, but one can define overloaded constructors that can then assign arbitrary values to self-defined members of the enum class. Defining getters allows then access to those self-defined members. The internal integer can be obtained from an enum value using the ordinal() method, and the list of enum values of an enumeration type can be obtained in order using the values() method. It is generally discouraged for programmers to convert enums to integers and vice versa. Enumerated types are Comparable, using the internal integer; as a result, they can be sorted.
The Java standard library provides utility classes to use with enumerations. The EnumSet class implements a Set of enum values; it is implemented as a bit array, which makes it very compact and as efficient as explicit bit manipulation, but safer. The EnumMap class implements a Map of enum values to object. It is implemented as an array, with the integer value of the enum value serving as the index.
==== Perl ====
Dynamically typed languages in the syntactic tradition of C (e.g., Perl or JavaScript) do not, in general, provide enumerations. But in Perl programming the same result can be obtained with the shorthand strings list and hashes (possibly slices):
==== Raku ====
Raku (formerly known as Perl 6) supports enumerations. There are multiple ways to declare enumerations in Raku, all creating a back-end Map.
==== PHP ====
Enums were added in PHP version 8.1.
Enumerators may be backed by string or integer values to aid serialization:
The Enum's interface exposes a method that gives a collection of its enumerators and their names. String/integer-backed Enums also expose the backing value and methods to (attempt) deserialization. Users may add further methods.
==== Rust ====
Though Rust uses the enum keyword like C, it uses it to describe tagged unions, which enums can be considered a degenerate form of. Rust's enums are therefore much more flexible and can contain struct and tuple variants.
Like C, Rust also supports specifying the values of each variant,
==== Swift ====
In C, enumerations assign related names to a set of integer values. In Swift, enumerations are much more flexible and need not provide a value for each case of the enumeration. If a value (termed a raw value) is provided for each enumeration case, the value can be a string, a character, or a value of any integer or floating-point type.
Alternatively, enumeration cases can specify associated values of any type to be stored along with each different case value, much as unions or variants do in other languages. One can define a common set of related cases as part of one enumeration, each of which has a different set of values of appropriate types associated with it.
In Swift, enumerations are a first-class type. They adopt many features traditionally supported only by classes, such as computed properties to provide additional information about the enumeration's current value, and instance methods to provide functionality related to the values the enumeration represents. Enumerations can also define initializers to provide an initial case value and can be extended to expand their functionality beyond their original implementation; and can conform to protocols to provide standard functionality.
Unlike C and Objective-C, Swift enumeration cases are not assigned a default integer value when they are created. In the CardSuit example above, clubs, diamonds, hearts, and spades do not implicitly equal 0, 1, 2 and 3. Instead, the different enumeration cases are fully-fledged values in their own right, with an explicitly-defined type of CardSuit.
Multiple cases can appear on a single line, separated by commas:
When working with enumerations that store integer or string raw values, one doesn't need to explicitly assign a raw value for each case because Swift will automatically assign the values.
For instance, when integers are used for raw values, the implicit value for each case is one more than the previous case. If the first case doesn't have a value set, its value is 0. For the CardSuit example, suits can be numbered starting from 1 by writing:
==== TypeScript ====
TypeScript adds an 'enum' data type to JavaScript.
By default, enums number members starting at 0; this can be overridden by setting the value of the first:
All the values can be set:
TypeScript supports mapping the numeric value to its name. For example, this finds the name of the value 2:
==== Python ====
An enum module was added to the Python standard library in version 3.4.
There is also a functional API for creating enumerations with automatically generated indices (starting with one):
Python enumerations do not enforce semantic correctness (a meaningless comparison to an incompatible enumeration always returns False rather than raising a TypeError):
==== Fortran ====
Fortran only has enumerated types for interoperability with C; hence, the semantics is similar to C and, as in C, the enum values are just integers and no further type check is done. The C example from above can be written in Fortran as
==== Visual Basic/VBA ====
Enumerated datatypes in Visual Basic (up to version 6) and VBA are automatically assigned the "Long" datatype and also become a datatype themselves:
Example Code in VB.NET
==== Lisp ====
Common Lisp uses the member type specifier, e.g.,
that states that object is of type cardsuit if it is #'eql to club, diamond, heart or spade. The member type specifier is not valid as a Common Lisp Object System (CLOS) parameter specializer, however. Instead, (eql atom), which is the equivalent to (member atom) may be used (that is, only one member of the set may be specified with an eql type specifier, however, it may be used as a CLOS parameter specializer.) In other words, to define methods to cover an enumerated type, a method must be defined for each specific element of that type.
Additionally,
may be used to define arbitrary enumerated types at runtime. For instance
would refer to a type equivalent to the prior definition of cardsuit, as of course would simply have been using
but may be less confusing with the function #'member for stylistic reasons.
==== Dart ====
Dart has a support for the most basic form of enums and has a syntax that is a lot similar with other languages supporting enums.
Note that the switch operator does not guarantee the completeness of the cases. This means if you omit one case, the compiler will not raise an error.
== Algebraic data type in functional programming ==
In functional programming languages in the ML lineage (e.g., Standard ML (SML), OCaml, and Haskell), an algebraic data type with only nullary constructors can be used to implement an enumerated type. For example (in the syntax of SML signatures):
In these languages the small-integer representation is completely hidden from the programmer, if indeed such a representation is employed by the implementation. However, Haskell has the Enum type class which a type can derive or implement to get a mapping between the type and Int.
== Databases ==
Some databases support enumerated types directly. MySQL provides an enumerated type ENUM with allowable values specified as strings when a table is created. The values are stored as numeric indices with the empty string stored as 0, the first string value stored as 1, the second string value stored as 2, etc. Values can be stored and retrieved as numeric indexes or string values.
Example:
== XML Schema ==
XML Schema supports enumerated types through the enumeration facet used for constraining most primitive datatypes such as strings.
== See also ==
Contrast set
== Notes ==
== References ==
== External links ==
Enumerated types in C/C++
Enumerated types in C#
Enumerated types in Java
Enumerated types in MySQL
Enumerated types in Obix
Enumerated types in PHP
Enumerated types in Swift
Enumerated types in XML
Enumerated types in Visual Basic
|
https://en.wikipedia.org/wiki/Enumerated_type
|
Ghosts is an American television sitcom adapted for CBS from the original British series of the same name by Joe Port and Joe Wiseman, who were also its showrunners. It premiered on October 7, 2021 and was picked up for a full season that month. It was renewed for a second season in January 2022, which premiered on September 29, 2022. It was renewed for a third season in January 2023, which began filming in Montreal on December 2, 2023. The third season, of ten episodes, premiered on February 15, 2024. In March 2024, it was renewed for a fourth season which premiered on October 17, 2024. In February 2025, the series was renewed for a fifth and sixth season.
== Premise ==
Married New Yorkers Samantha "Sam" and Jay Arondekar believe their dreams have come true when they inherit Woodstone Manor, a beautiful country house, from Sophie Brimble, Sam's great aunt, only to find that it is falling apart and inhabited by ghosts of people from different eras of American history who died on the property and are now bound to the area, appearing as they did at the times of their deaths, until they can reach the afterlife. Jay cannot see or hear the ghosts, but Sam can after a near-death experience.
== Cast ==
=== Main ===
==== Living ====
Rose McIver as Samantha "Sam" Arondekar, a freelance journalist who, after an accident that leaves her clinically dead for three minutes, revives with the ability to see, hear, and interact with ghosts. She is loosely based on Alison Cooper from the original British series.
Utkarsh Ambudkar as Jayanth "Jay" Arondekar, Samantha's husband and a chef with many typically "geeky" interests such as comic books, sci-fi films, video games, and Dungeons & Dragons. He often attempts to communicate with the ghosts despite being unable to see or hear them. He is loosely based on Mike Cooper from the original British series.
==== Ghosts ====
Devan Chandler Long as Thorfinn/"Thor", an aggressive, often melodramatic Viking from Norway and the oldest of the ghosts, who set out to explore North America over 1,000 years ago but was left behind by his shipmates due to their counting one shipmate twice and died from a lightning strike conducted by the helmet he wore. He has the ability to manipulate electricity and enjoys watching TV as well as regaling his friends with stories of combat, especially against Danes, and his favorite foods, particularly cod. He has a son named Bjørn, now a ghost on an adjacent property, who married a Danish woman. His previous ghost girlfriends include Luella and "Flat Maria", both of whom have since moved on to the afterlife. He is loosely based on Robin the caveman in the original British series.
Román Zaragoza as Sasappis/"Sass", a cynical Lenape hunter and storyteller, who often serves as the voice of reason for the other ghosts and died in 1513 for reasons unknown. He can influence living people's thoughts by interacting with them as characters in their dreams, making him the only ghost who can directly speak to Jay. He enjoys storytelling, stirring up drama, watching TV, and smelling food, especially pizza, prepared by the living. Despite being the second oldest ghost, he is more aware of the modern world than most and speaks like a modern person because he "pays attention". He died a virgin and is easily embarrassed whenever other ghosts bring it up; however, by the end of Season 4, he has his first intimate experience with Golden Age Hollywood screenwriter Joan.
Brandon Scott Jones as Captain Isaac Higgintoot (née Higginbottom), an initially closeted gay Continental Army officer who died of dysentery at age 35 two weeks after the siege of Fort Ticonderoga and has been largely forgotten by history, making him immensely jealous of the more famous Alexander Hamilton, with whom he became rivals over a neck ruffle they both coveted. The living can smell a foul odor if he passes through them. He is also implied to have been an ineffective leader as he often mentions how he "heroically" surrendered after most of the battles he led. He is inspired mainly by the Captain in the original British series, while his ghost power is similar to that of Mary Guppy the witch trial victim.
Rebecca Wisocky as Henrietta "Hetty" Woodstone, the uptight lady of the manor, Sam's great-great-great-great-aunt, and the daughter of the original owner of the mansion. She takes pride in being wealthy, looks down her nose on the working class and anyone Irish (though she eventually learns she had an Irish grandmother), and experimented with now-illicit drugs throughout her life, including cocaine and morphine. Her husband Elias cheated on her in life with many different women, while her son Thomas was responsible for Alberta's murder. She strangled herself to death at age 45 in 1895 using a telephone cord to avoid being arrested for Elias's crimes, allowing Thomas to escape with his inheritance. Her ghost power is dormant until Season 4: she can interact with the living on St. Patrick’s Day after acknowledging and embracing her Irish heritage. She is based on Lady Fanny Button in the original British series.
Alice Manning as Young Hetty, who could see and hear Thorfinn as a small child and mistook him for an imaginary friend she named "Gordon".
Danielle Pinnock as Alberta Haynes, a flamboyant Prohibition-era lounge singer who was murdered in 1928 by drinking strychnine-laced moonshine; solving her murder is a key plot arc of the second season, and is done as part of Sam's true crime podcast. Her humming can be heard by the living. She can also be heard in full by Alexa devices.
Sheila Carrasco as Susan "Flower" Montero, a cheerful and sweet but naive and forgetful hippie of Hispanic origin who lived in both a commune and a cult in the 1960s. She was mauled to death in 1969 at age 31 by a bear she tried to hug while under the influence of drugs. She can put a living person into a hallucinogenic high if she passes through them, can speak fluent Spanish, and likes being in polyamorous relationships. She shares a closeness and gentle flirtation with Thorfinn, and they start dating later in the second season. Due to Carrasco taking time off work to raise her newborn daughter, Flower goes missing in the third season, causing her friends to mistakenly believe she has moved on to the afterlife, but she is rescued towards the season's end.
Richie Moriarty as Peter "Pete" Martino, a friendly and polite but socially awkward, Italian American travel agent and leader of a uniformed youth group called the Pinecone Troopers, who died at age 40 in 1985 when one of the uniformed girls in his care accidentally shot him through the neck with an arrow. He has an initially unrequited romantic interest in Alberta, and Jay considers him one of his best friends due to many shared interests between them. Among his varied interests are improvisational theater, basketball, Dungeons & Dragons, Star Wars films, and general 1980s culture. He is the only ghost in the main group who can leave the Woodstone property and go anywhere he wants, but if he stays away from the property for too long, he will start to vanish piece-by-piece into oblivion; it is unknown what will happen if he fully disappears. Discovering this power increases his confidence and causes Alberta to become interested in him. He is based on Pat Butcher in the original British series.
Asher Grodman as Trevor Lefkowitz, a wealthy, womanizing, hard-partying, Jewish stockbroker and Wharton School alumnus who worked at Lehman Brothers. The most recently deceased ghost, he died at age 33 in 2000 from a heart attack, caused by an accidental drug overdose, while not wearing pants. Though he claims he lost his pants because he died during a sexual encounter, he simply lent his pants to his friend Adam Pinkus as a good deed. He can physically interact with the corporeal world to a limited degree, usually with only one index finger, if he concentrates hard enough. He is loosely based on Julian Fawcett MP in the original British series, and his initial attraction to Sam is similar to the poet Thomas Thorne's infatuation with Sam's counterpart Alison.
Sam Ashe Arnold as Young Trevor.
=== Recurring ===
==== Ghosts ====
Hudson Thames (Season 1) and Alex Boniello (Seasons 2-present) as the head of Crash, a smooth-talking 1950s-era greaser ghost who was decapitated. He is loosely based on Sir Humphrey Bone in the British version; however, unlike Humphrey, whose head is always present in each appearance, Crash's head goes missing in the pilot episode when Thorfinn accidentally knocks it off his neck. Only his body (played by Matt Keyes) appears until his head is recovered in "Ghost Father of the Bride."
The cholera victim ghosts (also called basement ghosts): an indeterminate number of ghosts who died in a pest house that used to be on the property during a 19th-century cholera outbreak and whose bodies were buried together in a pit. Although they can go upstairs if they wish, their sickly appearances disturb the upstairs ghosts, so they spend all their time in the basement and are experts on the house's heating system. They can all give non-contagious symptoms of cholera for 24 hours to any living person they walk through. They are based on the plague ghosts in the British version, and most share first names with their actors.
Betsy Sodaro as Cholera Victim Nancy, a brash, obnoxious Albany native who spends most of her time berating her fellow victims and thinking of ways to permanently move upstairs.
Stuart Fink as Cholera Victim Stuart
Arthur Holden as Cholera Victim Creepy Dirk. When the ghosts decide to elect a representative to petition Sam rather than make requests individually, Creepy Dirk wins after Isaac's attempt to garner their support for his candidacy. He briefly holds the position until Sam rejects the arrangement.
Cody Crain as Cholera Victim Cody
Nigel Downer as Cholera Victim Nigel
Cat Lemieux as Cholera Victim Catherine
Tyler Alvarez as Cholera Victim Ralph, a teen who starts a relationship with Stephanie the prom ghost, only to move on to the afterlife.
The British Revolutionary ghosts: three ghosts who died in the Revolutionary War and occupy the shed on the property that used to be a barracks, as was agreed upon with Isaac after the war ended. They keep mostly to themselves and come up to the main house to redraw the borderlines every few years.
John Hartman as Lieutenant Colonel Nigel Chessum, the leader of the trio, whom Isaac accidentally shot. They have had secret romantic feelings for one another since they were alive, and they begin a relationship at the end of the first season.
Chad Andrews (Season 1) and Steven Yaffee (Seasons 3-present) as Baxter, Nigel's subordinate who plays a fife.
Christian Daoust as Jenkins, Nigel's subordinate who possesses a musket. He and Nigel had a physical relationship before Nigel and Isaac started dating, and they "liaison" once more when Isaac and Nigel go "on a respite".
Matt Walsh as Elias Woodstone, Hetty's husband, who died from suffocation in a vault that no ghosts can enter or exit. He has the power to make people sexually aroused when he walks through them. After he rants about becoming a permanent nuisance and refusing to change himself, he becomes bound to Hell. He briefly returns in the second season, but, believing he cannot change his behavior, voluntarily recommits himself to Hell. As a reward, he is promoted some time before the fourth season to a demon who collects souls for the Devil, administers torture, and can physically reincarnate, appearing as his usual self in contemporary clothing.
Odessa A'zion as Stephanie, a senior high school student who was murdered on her prom night by a chainsaw killer in 1987. She sleeps in the attic for months at a time, as extended sleep periods are common for ghosts who die in their teen years, and wakes up around the day of her prom night each year. She often tries to seduce Trevor due to being chronologically close to his age, but he rebuffs her advances since she still appears age 17.
Crystle Lightning as Shiki, a Lenape woman on whom Sasappis had a crush in life. As a ghost, she is bound to the land occupied by the publishing office of the Ulster County Review magazine, so Sam and Jay help her establish a long-distance relationship with Sass.
Lindsey Broad as Judy, Henry Farnsby's deceased mother, who now haunts their home.
Christian Jadah as Bjorn, Thorfinn's son, who married a Danish woman and had three children, travelled to find his father, and now haunts the Farnsbys' property, having died at about the same age as Thor. Sam helps him reconnect with his father by having them shout to each other through the windows.
Louis Labonville as Young Bjorn.
Nichole Sakura as Jessica (Season 2), a permanently drunk ghost who died in a car crash while driving under the influence of alcohol and is now bound to a small perimeter around her former car, enabling her to travel more freely than other ghosts can. She has a brief relationship with Sass when Freddy, who bought Jessica's car, begins working as an assistant at the manor.
Caroline Aaron as Carol (guest Seasons 1–2, recurring Season 3-4), Pete's widow, who cheated on him with his best friend Jerry when he was alive. She becomes a new ghost on the Woodstone property in the third season after fatally choking on a doughnut hole. She becomes engaged to Baxter in the third-season finale.
Tara Spencer-Nairn as Young Carol (Season 1)
Allegra Edwards as Donna (Seasons 3-4), a ghost Pete sleeps with in St. Lucia, who is popularly believed to have murdered her husband Gerald in 1982 and fled to the island before dying when an early cell phone struck her on the head. Pete is able to clear her name by interviewing her former neighbor, who witnessed his wife Linda kill Gerald but kept it a secret.
Mary Holland as Patience (Season 4), a mentally unstable, stridently moralistic Puritan ghost banished from her colony for being too Puritanical. She died of blood-letting; fell down a hole with Thor, Sass, and Isaac at some point in the 1890s; and remains stranded in the dirt until she finds a way back into the house in the present. As a result of her mental state, she often shouts her own name when feeling intense emotions. Her ghost power allows her to make walls bleed and write short messages with the blood.
Taylor Ortega as Joan (Season 4), a screenwriter from the Golden Age of Hollywood and one of the first women to pursue a career in this field, whom Pete introduces to Sasappis as a new romantic partner. She died during the 1940s with a flask of whiskey that other ghosts are able to drink briefly before it returns to the flask. Like Pete, she can leave her home property but has enough experience doing so that she can roam for at least a year without ill effect.
==== Living ====
Tristan D. Lalla as Mark, a construction worker involved in renovating Woodstone Manor for Sam and Jay.
Rodrigo Fernandez-Stoll as Todd Pearlman, an obsessive fan of Alberta's who operates a "museum" dedicated to her out of his mother's garage.
Ravi Patel as Lewis, an editor for Ulster County Review who publishes Sam's articles.
Punam Patel as Bela, Jay's sister who is lured on social media by Trevor. Sam tells her the truth about her talking to ghosts, and while Bela is at first skeptical, Sam is able to convince her with the help of the ghosts. In the second season, she begins dating her coworker Eric.
Mark Linn-Baker and Kathryn Greenwood as Henry and Margaret Farnsby, Sam and Jay's swinger neighbors and owners of a rival B&B, who promise to support their permit applications for their renovations. Their house is also haunted by a collection of ghosts from across history, including Henry's mother. They are based on Barclay Beg-Chetwynde and his wife Bunny in the British version.
Eddie Shin as Dr. Park, a therapist for whom Sam translates Thorfinn's psychological problems.
Punkie Johnson and Carolyn Taylor as June and Ally, Sam and Jay's neighbors who run an organic farm called "Cover Crop Farms".
Mike Lane as Freddy (Season 2), a deliveryman hired as an assistant at the Arondekars' B&B.
Jessie Ennis as Kelsey Foster, a con artist who claims to be Sam's cousin and David Woodstone's daughter.
Joy Osmanski as Sharon, a publisher who agrees to publish Isaac's autobiography, but only as a young adult vampire novel.
=== Guests ===
Tacey Adams as Sophie Brimble (née Woodstone), Sam's great aunt and Hetty's great-granddaughter, from whom Sam inherits Woodstone Manor. Upon dying in the series' first scene, she briefly appears a transparent ghost over her corpse before abruptly moving on to the afterlife.
Rachael Harris as Sheryl, Sam's mother, who she sees as a ghost at the restaurant where she died. After she and Sam make peace with each other, she moves on to the afterlife. Her belches, which smell of shrimp, can be smelled by the living.
Jamie Mayers as Winky, a 12-year-old paper boy who was trampled to death by a horse and now haunts the Ulster County Review office with Shiki.
Gregory Zaragoza as Naxasi, Sass's father, who tried to convince him not to be a storyteller.
Rob Huebel as Ari, one of Trevor's former coworkers from Lehman Brothers who comes to the mansion to purchase a timepiece found on Elias's remains.
Blair Penner as young Ari
Mercedes Morris as Clara Brown, a lounge singer and bootlegger whose illegal activities Alberta reported so she could steal a gig from her.
Drew Tarver as Micah, a charismatic cult leader who attempts to manipulate Jay into joining his group so they can move into the mansion.
Hannah Rose May as Molly, an Irish maid with whom Elias had sex when they were alive. She is brought back from the afterlife briefly through a seance, and explains to Hetty that Elias coerced her.
Dallas Goldtooth as Bob, a Lenape man from the Hudson Valley Lenape Culture Center. He corrects the information Sass has given the group about the ancient tree on their land and teaches them about land acknowledgements, and Sass admires his work.
Kelly Craig as Olga, Thorfinn's wife and Bjorn's mother.
Mathew Baynton as an actor starring in a reconstruction of Pete's death.
Rose Abdoo as Paula, the producer of "Dumb Deaths".
Dana Gourrier as Jennifer, a woman who was one of Pete's scout troops that witnessed his death.
Kaliko Kauahi as a liquor license inspector.
Neil Crone as Benjamin Franklin, an American Founding Father and Freemason, with whom Isaac tried to build a good reputation so he could join the society.
Andrew Leeds as Eric, Bela's friend, whom she starts dating in the second season.
Hillary Anne Matthews as Beatrice, Isaac's wife, who knew about his sexuality but cared deeply for him regardless.
Chip Zien as Lenny Lefkowitz, Trevor's father attending Trevor's memorial at Woodstone Manor.
Laraine Newman as Esther Lefkowitz, Trevor's mother attending Trevor's memorial at Woodstone Manor.
Tara Reid as herself attending Trevor's memorial at Woodstone Manor.
Chris Eckert as George, a Puritan ghost in the Farnsby estate who is now open about his homosexuality due to failing to reach the afterlife.
Ashley D. Kelley as Alicia, a lawyer and a descendant of Alberta, who is inspired by her ancestor's work to pursue singing.
David Baby as Jerry, Carol's current husband and Pete's former best friend.
Asia Martin as Theresa, Alberta's sister.
Brooks Brantly as Earl, Alberta's bootlegger boyfriend.
Daniel Rindress-Kay as Thomas Woodstone, Hetty's son and Earl's secret boyfriend, who planted a poisoned whiskey bottle for Alberta to drink when Earl left him for her.
Jeremy Luke as Al Capone, a famous Chicago crime boss, who almost committed suicide with the poisoned whiskey Alberta ultimately drank.
Brian Cook as David Woodstone, Sam's uncle, Sophie's son, and Trevor's former coworker, who dumped Trevor's body into a lake before dying of an aneurysm in the depressing strip club that he now haunts.
Al Connors as Schmitty, another ghost at the strip club who died from eating ill-prepared sushi.
Holly Gauthier-Frankel as Laura, Pete's daughter. She has a son named after her father.
Emily Mitchell as Young Laura.
Douglas Sills as Samuel, Hetty's father, who discouraged her from marrying an artist due to his painting her with her ankle exposed.
Jon Glaser as Jeremy Lefkowitz, Trevor's brother, who refused to take over their father's business.
David Kohlsmith as Young Jeremy.
Lamorne Morris as Saul, a poltergeist and former Negro league baseball player who visits the manor using a guest as his host and starts a brief relationship with Alberta. As a non-traditional ghost, he can travel anywhere by binding himself to different human hosts in near range if he concentrates hard enough. He speculates that his power is a result of his tendency to become overly attached to people in life.
Geoffrey Owens as Gene, a new guest at Woodstone that Saul is tethered to.
Deniz Akdeniz as Chris, an Australian male stripper and part-time DJ hired to perform a lap dance, unknowingly for Isaac, causing Isaac to become attracted to him. He becomes another ghost at Woodstone when his parachute fails during a stunt for Alicia's bachelorette party and he fatally crashes through the roof of Jay's restaurant, and he and Nigel end up competing for his affections. He can use his parachute to fly beyond the ghost boundaries of the property.
Irene White and Adrian Martinez as Gloria and Mike, a ghost couple Pete meets in a DealMart superstore. They were trampled to death in a 2005 Black Friday sale, and Gloria is now stuck carrying a box containing the TV she tried to buy.
Marc-André Boulanger as the Butcher Ghost, the leader of a violent ghost gang that becomes active in the Hudson Valley DealMart after business hours, who was fatally struck in the head with a meat cleaver.
Dean Norris as Frank, Sam's father.
Melinda McGraw as Diane, Frank's new girlfriend.
Matty Cardarople as Jamie, an Internet personality with a video series themed around detonating objects.
Gardiner Millar as Duffy, a Vietnam veteran ghost who haunts his former house, now owned by Jamie.
Connor Ratliff as Scott Morgan, the director of the Hudson Valley Players.
Samantha Boscarino as Marisa, an actress in the Hudson Valley Players in whom Sass becomes romantically interested.
Hayden Finkelshtain as William, an assessor of historical artifacts.
Sakina Jaffrey as Champa Arondekar, Jay's mother, who immigrated from India to America with her husband Mahesh.
Bernard White as Mahesh Arondekar, Jay's father and Champa's husband.
Paul Wight as Gorm, a Viking ghost haunting a historic Norwegian village, now a tourism destination, who belonged to Thorfinn's tribe and died after being shot in the abdomen with an arrow.
Lenny Venito as Anthony, the head of a local mafia branch and Carol's nephew, whose family used Pete's travel agency as a front for laundering its profits.
Nat Faxon as Alexander Hamilton, an American Founding Father with whom Isaac became rivals over a neck ruffle they both sought to buy. The series' depiction of Hamilton is historically inaccurate: he appears as a middle-aged man in the year 1776 and is involved in an early draft of the Declaration of Independence, whereas the real Hamilton was only age 19 or 21 that year and had nothing to do with the document.
Asif Ali as Sunil, Jay's cousin.
Peter New as Janis, a Latvian ghost hunting expert skilled in maintaining and upgrading equipment designed to capture and eviscerate ghosts.
Richie Keen as Adam Pinkus, Trevor's former coworker, who worked as a junior associate at Lehman Brothers, and to whom Trevor lent his pants and boxers after he was hazed by Ari and David Woodstone.
Robert Bazzocchi as young Pinkus
Gideon Adlon as Abby Pinkus, Trevor's biological daughter, born to his once-girlfriend Laurie Goldstein, who later married Pinkus before she died.
Kyle Gatehouse as Richard, Donna's former neighbor, who died with a Walkman that only plays the album Purple Rain and witnessed his wife Linda murder Donna's husband Gerald.
Justin Kirk as Tad, the mayor of Hudson Valley and Stephanie's prom date from the night of her murder, who was knocked unconscious while trying to stop her killer and uses his attempt at heroism to bolster his image. Kirk co-starred on the TV series "Weeds," and his appearance on "Ghosts" marked the 20th episode of its 4th season with a 420-theme.
Stephanie Belding as Melanie del Vecchio, Tad's wife and Stephanie's former friend.
Ben Feldman as Kyle Rosenblatt, another man who can see ghosts after colliding with a bird while riding a roller coaster.
== Episodes ==
=== Series overview ===
=== Season 1 (2021–22) ===
=== Season 2 (2022–23) ===
=== Season 3 (2024) ===
=== Season 4 (2024–25) ===
== Production ==
=== Development ===
On November 29, 2019, CBS announced that they were developing an adaptation of the BBC One series Ghosts. The original British series upon which the series is based was created by Mathew Baynton, Simon Farnaby, Martha Howe-Douglas, Jim Howick, Laurence Rickard, and Ben Willbond for BBC. On February 4, 2020, it was announced that the pilot had been picked up by CBS Studios and was co-produced with BBC Studios and Lionsgate Television. On March 31, 2021, it was announced that the adaptation has been picked up for a full series. In July 2021, it was announced that the series would premiere as a Thursday-night entry on October 7, 2021. On September 23, 2021, CBS changed the premiere to back-to-back episodes. On October 21, 2021, CBS picked up the series for a full season. On December 17, 2021, it was reported that production has been temporarily halted due to a positive case of COVID-19 on the set of the series. On January 24, 2022, CBS renewed the series for a second season which premiered on September 29, 2022. On November 8, 2022, it was announced that the BBC would be airing Ghosts in the United Kingdom under the name of 'Ghosts US' on BBC Three & BBC iPlayer on November 20, 2022. On January 12, 2023, CBS renewed the series for a third season, which premiered on February 15, 2024. On March 12, 2024, the series was renewed for a fourth season which premiered on October 17, 2024. On February 20, 2025, CBS renewed the series for a fifth and sixth season.
=== Casting ===
On March 4, 2020, Rose McIver was cast in a leading role for the pilot. On July 1, 2020, Utkarsh Ambudkar was cast in a main role for the pilot. On December 9, 2020, Brandon Scott Jones, Richie Moriarty, Asher Grodman, Rebecca Wisocky, Sheila Carrasco, Danielle Pinnock and Roman Zaragoza were cast in main roles for the pilot. On May 12, 2021, Devan Chandler Long joined the cast as a series regular.
=== Filming ===
Filming for the third season began in Montreal on December 2, 2023.
== Reception ==
=== Critical response ===
For the first season, the review aggregator website Rotten Tomatoes reported a 93% approval rating with an average rating of 7.3/10, based on 27 critic reviews. The website's critics consensus reads, "Ghosts could stand to ask more of its characters, but an excellent ensemble and a genial wit make for easy, softly spooky viewing." Metacritic, which uses a weighted average, assigned a score of 69 out of 100 based on 13 critics, indicating "generally favorable reviews".
On Rotten Tomatoes, the second season received an approval rating of 100% with an average rating of 8.5/10, based on nine critic reviews.
On Rotten Tomatoes, the third season received an approval rating of 100% with an average rating of 8.1/10, based on seven critic reviews.
=== Ratings ===
==== Overall ====
==== Season 1 ====
==== Season 2 ====
==== Season 3 ====
==== Season 4 ====
=== Accolades ===
== Home media ==
Lionsgate Home Entertainment released the complete first season on Blu-ray and DVD on November 29, 2022.
== Notes ==
== References ==
== External links ==
Official website
Ghosts at IMDb
|
https://en.wikipedia.org/wiki/Ghosts_(American_TV_series)
|
In computer science, cloning refers to the making of an exact copy of an object, frequently under the paradigm of instance-based programming, or object-oriented programming (OOP).
== Shallow copies ==
In most programming languages (exceptions include Ruby), primitive types such as double, float, int, long, etc. simply store their values somewhere in the computer's memory (often the call stack). By using simple assignment, you can copy the contents of the variable to another one:
Copying primitive types in Java or C++:
Many OOP programming languages (including Java, D, ECMAScript, and C#) make use of object references. Object references, which are similar to pointers in other languages, allow for objects to be passed around by address so that the whole object need not be copied.
A Java example, when "copying" an object using simple assignment:
The object is not duplicated, the variables 'original' and 'copy' are actually referring to the same object. In C++, the equivalent code
makes it clear that it is a pointer to the object being copied, not the object itself.
== Cloning ==
The process of actually making another exact replica of the object instead of just its reference is called cloning. In most languages, the language or libraries can facilitate some sort of cloning. In Java, the Object class contains the clone() method, which copies the object and returns a reference to that copied object. Since it is in the Object class, all classes defined in Java will have a clone method available to the programmer (although to function correctly it needs to be overridden at each level it is used).
Cloning an object in Java:
→
C++ objects in general behave like primitive types, so to copy a C++ object one could use the '=' (assignment) operator. There is a default assignment operator provided for all classes, but its effect may be altered through the use of operator overloading. There are dangers when using this technique (see slicing). A method of avoiding slicing can be implementing a similar solution to the Java clone() method for the classes and using pointers. (There is no built-in clone() method.)
A C++ example of object cloning:
A C++ example of object cloning using pointers (to avoid slicing see):
== References ==
|
https://en.wikipedia.org/wiki/Cloning_(programming)
|
In computer science, futures, promises, delays, and deferreds are constructs used for synchronizing program execution in some concurrent programming languages. Each is an object that acts as a proxy for a result that is initially unknown, usually because the computation of its value is not yet complete.
The term promise was proposed in 1976 by Daniel P. Friedman and David Wise,
and Peter Hibbard called it eventual.
A somewhat similar concept future was introduced in 1977 in a paper by Henry Baker and Carl Hewitt.
The terms future, promise, delay, and deferred are often used interchangeably, although some differences in usage between future and promise are treated below. Specifically, when usage is distinguished, a future is a read-only placeholder view of a variable, while a promise is a writable, single assignment container which sets the value of the future. Notably, a future may be defined without specifying which specific promise will set its value, and different possible promises may set the value of a given future, though this can be done only once for a given future. In other cases a future and a promise are created together and associated with each other: the future is the value, the promise is the function that sets the value – essentially the return value (future) of an asynchronous function (promise). Setting the value of a future is also called resolving, fulfilling, or binding it.
== Applications ==
Futures and promises originated in functional programming and related paradigms (such as logic programming) to decouple a value (a future) from how it was computed (a promise), allowing the computation to be done more flexibly, notably by parallelizing it. Later, it found use in distributed computing, in reducing the latency from communication round trips. Later still, it gained more use by allowing writing asynchronous programs in direct style, rather than in continuation-passing style.
== Implicit vs. explicit ==
Use of futures may be implicit (any use of the future automatically obtains its value, as if it were an ordinary reference) or explicit (the user must call a function to obtain the value, such as the get method of java.util.concurrent.Futurein Java). Obtaining the value of an explicit future can be called stinging or forcing. Explicit futures can be implemented as a library, whereas implicit futures are usually implemented as part of the language.
The original Baker and Hewitt paper described implicit futures, which are naturally supported in the actor model of computation and pure object-oriented programming languages like Smalltalk. The Friedman and Wise paper described only explicit futures, probably reflecting the difficulty of efficiently implementing implicit futures on stock hardware. The difficulty is that stock hardware does not deal with futures for primitive data types like integers. For example, an add instruction does not know how to deal with 3 + future factorial(100000). In pure actor or object languages this problem can be solved by sending future factorial(100000) the message +[3], which asks the future to add 3 to itself and return the result. Note that the message passing approach works regardless of when factorial(100000) finishes computation and that no stinging/forcing is needed.
== Promise pipelining ==
The use of futures can dramatically reduce latency in distributed systems. For instance, futures enable promise pipelining, as implemented in the languages E and Joule, which was also called call-stream in the language Argus.
Consider an expression involving conventional remote procedure calls, such as:
t3 := ( x.a() ).c( y.b() )
which could be expanded to
t1 := x.a();
t2 := y.b();
t3 := t1.c(t2);
Each statement needs a message to be sent and a reply received before the next statement can proceed. Suppose, for example, that x, y, t1, and t2 are all located on the same remote machine. In this case, two complete network round-trips to that machine must take place before the third statement can begin to execute. The third statement will then cause yet another round-trip to the same remote machine.
Using futures, the above expression could be written
t3 := (x <- a()) <- c(y <- b())
which could be expanded to
t1 := x <- a();
t2 := y <- b();
t3 := t1 <- c(t2);
The syntax used here is that of the language E, where x <- a() means to send the message a() asynchronously to x. All three variables are immediately assigned futures for their results, and execution proceeds to subsequent statements. Later attempts to resolve the value of t3 may cause a delay; however, pipelining can reduce the number of round-trips needed. If, as in the prior example, x, y, t1, and t2 are all located on the same remote machine, a pipelined implementation can compute t3 with one round-trip instead of three. Because all three messages are destined for objects which are on the same remote machine, only one request need be sent and only one response need be received containing the result. The send t1 <- c(t2) would not block even if t1 and t2 were on different machines to each other, or to x or y.
Promise pipelining should be distinguished from parallel asynchronous message passing. In a system supporting parallel message passing but not pipelining, the message sends x <- a() and y <- b() in the above example could proceed in parallel, but the send of t1 <- c(t2) would have to wait until both t1 and t2 had been received, even when x, y, t1, and t2 are on the same remote machine. The relative latency advantage of pipelining becomes even greater in more complicated situations involving many messages.
Promise pipelining also should not be confused with pipelined message processing in actor systems, where it is possible for an actor to specify and begin executing a behaviour for the next message before having completed processing of the current message.
== Read-only views ==
In some programming languages such as Oz, E, and AmbientTalk, it is possible to obtain a read-only view of a future, which allows reading its value when resolved, but does not permit resolving it:
In Oz, the !! operator is used to obtain a read-only view.
In E and AmbientTalk, a future is represented by a pair of values called a promise/resolver pair. The promise represents the read-only view, and the resolver is needed to set the future's value.
In C++11 a std::future provides a read-only view. The value is set directly by using a std::promise, or set to the result of a function call using std::packaged_task or std::async.
In the Dojo Toolkit's Deferred API as of version 1.5, a consumer-only promise object represents a read-only view.
In Alice ML, futures provide a read-only view, whereas a promise contains both a future and the ability to resolve the future
In .NET System.Threading.Tasks.Task<T> represents a read-only view. Resolving the value can be done via System.Threading.Tasks.TaskCompletionSource<T>.
Support for read-only views is consistent with the principle of least privilege, since it enables the ability to set the value to be restricted to subjects that need to set it. In a system that also supports pipelining, the sender of an asynchronous message (with result) receives the read-only promise for the result, and the target of the message receives the resolver.
== Thread-specific futures ==
Some languages, such as Alice ML, define futures that are associated with a specific thread that computes the future's value. This computation can start either eagerly when the future is created, or lazily when its value is first needed. A lazy future is similar to a thunk, in the sense of a delayed computation.
Alice ML also supports futures that can be resolved by any thread, and calls these promises. This use of promise is different from its use in E as described above. In Alice, a promise is not a read-only view, and promise pipelining is unsupported. Instead, pipelining naturally happens for futures, including ones associated with promises.
== Blocking vs non-blocking semantics ==
If the value of a future is accessed asynchronously, for example by sending a message to it, or by explicitly waiting for it using a construct such as when in E, then there is no difficulty in delaying until the future is resolved before the message can be received or the wait completes. This is the only case to be considered in purely asynchronous systems such as pure actor languages.
However, in some systems it may also be possible to attempt to immediately or synchronously access a future's value. Then there is a design choice to be made:
the access could block the current thread or process until the future is resolved (possibly with a timeout). This is the semantics of dataflow variables in the language Oz.
the attempted synchronous access could always signal an error, for example throwing an exception. This is the semantics of remote promises in E.
potentially, the access could succeed if the future is already resolved, but signal an error if it is not. This would have the disadvantage of introducing nondeterminism and the potential for race conditions, and seems to be an uncommon design choice.
As an example of the first possibility, in C++11, a thread that needs the value of a future can block until it is available by calling the wait() or get() member functions. A timeout can also be specified on the wait using the wait_for() or wait_until() member functions to avoid indefinite blocking. If the future arose from a call to std::async then a blocking wait (without a timeout) may cause synchronous invocation of the function to compute the result on the waiting thread.
== Related constructs ==
Futures are a particular case of the synchronization primitive "events," which can be completed only once. In general, events can be reset to initial empty state and, thus, completed as many times as desired.
An I-var (as in the language Id) is a future with blocking semantics as defined above. An I-structure is a data structure containing I-vars. A related synchronization construct that can be set multiple times with different values is called an M-var. M-vars support atomic operations to take or put the current value, where taking the value also sets the M-var back to its initial empty state.
A concurrent logic variable is similar to a future, but is updated by unification, in the same way as logic variables in logic programming. Thus it can be bound more than once to unifiable values, but cannot be set back to an empty or unresolved state. The dataflow variables of Oz act as concurrent logic variables, and also have blocking semantics as mentioned above.
A concurrent constraint variable is a generalization of concurrent logic variables to support constraint logic programming: the constraint may be narrowed multiple times, indicating smaller sets of possible values. Typically there is a way to specify a thunk that should run whenever the constraint is narrowed further; this is needed to support constraint propagation.
== Relations between the expressiveness of different forms of future ==
Eager thread-specific futures can be straightforwardly implemented in non-thread-specific futures, by creating a thread to calculate the value at the same time as creating the future. In this case it is desirable to return a read-only view to the client, so that only the newly created thread is able to resolve this future.
To implement implicit lazy thread-specific futures (as provided by Alice ML, for example) in terms in non-thread-specific futures, needs a mechanism to determine when the future's value is first needed (for example, the WaitNeeded construct in Oz). If all values are objects, then the ability to implement transparent forwarding objects is sufficient, since the first message sent to the forwarder indicates that the future's value is needed.
Non-thread-specific futures can be implemented in thread-specific futures, assuming that the system supports message passing, by having the resolving thread send a message to the future's own thread. However, this can be viewed as unneeded complexity. In programming languages based on threads, the most expressive approach seems to be to provide a mix of non-thread-specific futures, read-only views, and either a WaitNeeded construct, or support for transparent forwarding.
== Evaluation strategy ==
The evaluation strategy of futures, which may be termed call by future, is non-deterministic: the value of a future will be evaluated at some time between when the future is created and when its value is used, but the precise time is not determined beforehand and can change from run to run. The computation can start as soon as the future is created (eager evaluation) or only when the value is actually needed (lazy evaluation), and may be suspended part-way through, or executed in one run. Once the value of a future is assigned, it is not recomputed on future accesses; this is like the memoization used in call by need.
A lazy future is a future that deterministically has lazy evaluation semantics: the computation of the future's value starts when the value is first needed, as in call by need. Lazy futures are of use in languages which evaluation strategy is by default not lazy. For example, in C++11 such lazy futures can be created by passing the std::launch::deferred launch policy to std::async, along with the function to compute the value.
== Semantics of futures in the actor model ==
In the actor model, an expression of the form future <Expression> is defined by how it responds to an Eval message with environment E and customer C as follows: The future expression responds to the Eval message by sending the customer C a newly created actor F (the proxy for the response of evaluating <Expression>) as a return value concurrently with sending <Expression> an Eval message with environment E and customer C. The default behavior of F is as follows:
When F receives a request R, then it checks to see if it has already received a response (that can either be a return value or a thrown exception) from evaluating <Expression> proceeding as follows:
If it already has a response V, then
If V is a return value, then it is sent the request R.
If V is an exception, then it is thrown to the customer of the request R.
If it does not already have a response, then R is stored in the queue of requests inside the F.
When F receives the response V from evaluating <Expression>, then V is stored in F and
If V is a return value, then all of the queued requests are sent to V.
If V is an exception, then it is thrown to the customer of each of the queued requests.
However, some futures can deal with requests in special ways to provide greater parallelism. For example, the expression 1 + future factorial(n) can create a new future that will behave like the number 1+factorial(n). This trick does not always work. For example, the following conditional expression:
if m>future factorial(n) then print("bigger") else print("smaller")
suspends until the future for factorial(n) has responded to the request asking if m is greater than itself.
== History ==
The future and/or promise constructs were first implemented in programming languages such as MultiLisp and Act 1. The use of logic variables for communication in concurrent logic programming languages was quite similar to futures. These began in Prolog with Freeze and IC Prolog, and became a true concurrency primitive with Relational Language, Concurrent Prolog, guarded Horn clauses (GHC), Parlog, Strand, Vulcan, Janus, Oz-Mozart, Flow Java, and Alice ML. The single-assignment I-var from dataflow programming languages, originating in Id and included in Reppy's Concurrent ML, is much like the concurrent logic variable.
The promise pipelining technique (using futures to overcome latency) was invented by Barbara Liskov and Liuba Shrira in 1988, and independently by Mark S. Miller, Dean Tribble and Rob Jellinghaus in the context of Project Xanadu circa 1989.
The term promise was coined by Liskov and Shrira, although they referred to the pipelining mechanism by the name call-stream, which is now rarely used.
Both the design described in Liskov and Shrira's paper, and the implementation of promise pipelining in Xanadu, had the limit that promise values were not first-class: an argument to, or the value returned by a call or send could not directly be a promise (so the example of promise pipelining given earlier, which uses a promise for the result of one send as an argument to another, would not have been directly expressible in the call-stream design or in the Xanadu implementation). It seems that promises and call-streams were never implemented in any public release of Argus, the programming language used in the Liskov and Shrira paper. Argus development stopped around 1988. The Xanadu implementation of promise pipelining only became publicly available with the release of the source code for Udanax Gold in 1999, and was never explained in any published document. The later implementations in Joule and E support fully first-class promises and resolvers.
Several early actor languages, including the Act series, supported both parallel message passing and pipelined message processing, but not promise pipelining. (Although it is technically possible to implement the last of these features in the first two, there is no evidence that the Act languages did so.)
After 2000, a major revival of interest in futures and promises occurred, due to their use in responsiveness of user interfaces, and in web development, due to the request–response model of message-passing. Several mainstream languages now have language support for futures and promises, most notably popularized by FutureTask in Java 5 (announced 2004) and the async/await constructions in .NET 4.5 (announced 2010, released 2012) largely inspired by the asynchronous workflows of F#, which dates to 2007. This has subsequently been adopted by other languages, notably Dart (2014), Python (2015), Hack (HHVM), and drafts of ECMAScript 7 (JavaScript), Scala, and C++ (2011).
== List of implementations ==
Some programming languages are supporting futures, promises, concurrent logic variables, dataflow variables, or I-vars, either by direct language support or in the standard library.
=== List of concepts related to futures and promises by programming language ===
ABCL/f
Alice ML
AmbientTalk (including first-class resolvers and read-only promises)
C++, starting with C++11: std::future and std::promise
Compositional C++
Crystal (programming language)
Dart (with Future/Completer classes and the keywords await and async)
Elm (programming language) via the Task module
Glasgow Haskell (I-vars and M-vars only)
Id (I-vars and M-vars only)
Io
Java via java.util.concurrent.Future or java.util.concurrent.CompletableFuture
JavaScript as of ECMAScript 2015, and via the keywords async and await since ECMAScript 2017
Lucid (dataflow only)
Some Lisps
Clojure
MultiLisp
.NET via Tasks
C#, since .NET Framework 4.5, via the keywords async and await
Kotlin, however kotlin.native.concurrent.Future is only usually used when writing Kotlin that is intended to run natively
Nim
Oxygene
Oz version 3
Python concurrent.futures, since 3.2, as proposed by the PEP 3148, and Python 3.5 added async and await
R (promises for lazy evaluation, still single threaded)
Racket
Raku
Rust (usually achieved via .await)
Scala via scala.concurrent package
Scheme
Squeak Smalltalk
Strand
Swift (only via third-party libraries)
Visual Basic 11 (via the keywords Async and Await)
Languages also supporting promise pipelining include:
E
Joule
=== List of library-based implementations of futures ===
For Common Lisp:
Blackbird
Eager Future2
lparallel
PCall
For C++:
Boost library
Dlib
Folly
HPX
POCO C++ Libraries (Active Results)
Qt
Seastar
stlab
For C# and other .NET languages: The Parallel Extensions library
For Groovy: GPars
For JavaScript:
Cujo.js' when.js provides promises conforming to the Promises/A+ 1.1 specification
The Dojo Toolkit supplies promises and Twisted style deferreds
MochiKit inspired by Twisted's Deferreds
jQuery's Deferred Object is based on the CommonJS Promises/A design.
AngularJS
node-promise
Q, by Kris Kowal, conforms to Promises/A+ 1.1
RSVP.js, conforms to Promises/A+ 1.1
YUI's promise class conforms to the Promises/A+ 1.0 specification.
Bluebird, by Petka Antonov
The Closure Library's promise package conforms to the Promises/A+ specification.
See Promise/A+'s list for more implementations based on the Promise/A+ design.
For Java:
JDeferred, provides deferred-promise API and behavior similar to jQuery.Deferred object
ParSeq provides task-promise API ideal for asynchronous pipelining and branching, maintained by LinkedIn
For Lua:
The cqueues [1] module contains a Promise API.
For Objective-C: MAFuture, RXPromise, ObjC-CollapsingFutures, PromiseKit, objc-promise, OAPromise,
For OCaml: Lazy module implements lazy explicit futures
For Perl: Future, Promises, Reflex, Promise::ES6, and Promise::XS
For PHP: React/Promise
For Python:
Built-in implementation
pythonfutures
Twisted's Deferreds
For R:
future, implements an extendable future API with lazy and eager synchronous and (multicore or distributed) asynchronous futures
For Ruby:
Concurrent Ruby
Promise gem
libuv gem, implements promises
Celluloid gem, implements futures
future-resource
For Rust:
futures-rs
For Scala:
Twitter's util library
For Swift:
Async framework, implements C#-style async/non-blocking await
FutureKit, implements a version for Apple GCD
FutureLib, pure Swift 2 library implementing Scala-style futures and promises with TPL-style cancellation
Deferred, pure Swift library inspired by OCaml's Deferred
BrightFutures
SwiftCoroutine
For Tcl: tcl-promise
=== Coroutines ===
Futures can be implemented in coroutines or generators, resulting in the same evaluation strategy (e.g., cooperative multitasking or lazy evaluation).
=== Channels ===
Futures can easily be implemented in channels: a future is a one-element channel, and a promise is a process that sends to the channel, fulfilling the future. This allows futures to be implemented in concurrent programming languages with support for channels, such as CSP and Go. The resulting futures are explicit, as they must be accessed by reading from the channel, rather than only evaluation.
== See also ==
Fiber (computer science)
Futex
Pyramid of doom (programming), a design antipattern avoided by promises
== References ==
== External links ==
Concurrency patterns presentation given at scaleconf
Future Value and Promise Pipelining at the Portland Pattern Repository
Easy Threading with Futures in Python
|
https://en.wikipedia.org/wiki/Futures_and_promises
|
In computing, multitasking is the concurrent execution of multiple tasks (also known as processes) over a certain period of time. New tasks can interrupt already started ones before they finish, instead of waiting for them to end. As a result, a computer executes segments of multiple tasks in an interleaved manner, while the tasks share common processing resources such as central processing units (CPUs) and main memory. Multitasking automatically interrupts the running program, saving its state (partial results, memory contents and computer register contents) and loading the saved state of another program and transferring control to it. This "context switch" may be initiated at fixed time intervals (pre-emptive multitasking), or the running program may be coded to signal to the supervisory software when it can be interrupted (cooperative multitasking).
Multitasking does not require parallel execution of multiple tasks at exactly the same time; instead, it allows more than one task to advance over a given period of time. Even on multiprocessor computers, multitasking allows many more tasks to be run than there are CPUs.
Multitasking is a common feature of computer operating systems since at least the 1960s. It allows more efficient use of the computer hardware; when a program is waiting for some external event such as a user input or an input/output transfer with a peripheral to complete, the central processor can still be used with another program. In a time-sharing system, multiple human operators use the same processor as if it was dedicated to their use, while behind the scenes the computer is serving many users by multitasking their individual programs. In multiprogramming systems, a task runs until it must wait for an external event or until the operating system's scheduler forcibly swaps the running task out of the CPU. Real-time systems such as those designed to control industrial robots, require timely processing; a single processor might be shared between calculations of machine movement, communications, and user interface.
Often multitasking operating systems include measures to change the priority of individual tasks, so that important jobs receive more processor time than those considered less significant. Depending on the operating system, a task might be as large as an entire application program, or might be made up of smaller threads that carry out portions of the overall program.
A processor intended for use with multitasking operating systems may include special hardware to securely support multiple tasks, such as memory protection, and protection rings that ensure the supervisory software cannot be damaged or subverted by user-mode program errors.
The term "multitasking" has become an international term, as the same word is used in many other languages such as German, Italian, Dutch, Romanian, Czech, Danish and Norwegian.
== Multiprogramming ==
In the early days of computing, CPU time was expensive, and peripherals were very slow. When the computer ran a program that needed access to a peripheral, the central processing unit (CPU) would have to stop executing program instructions while the peripheral processed the data. This was usually very inefficient. Multiprogramming is a computing technique that enables multiple programs to be concurrently loaded and executed into a computer's memory, allowing the CPU to switch between them swiftly. This optimizes CPU utilization by keeping it engaged with the execution of tasks, particularly useful when one program is waiting for I/O operations to complete.
The Bull Gamma 60, initially designed in 1957 and first released in 1960, was the first computer designed with multiprogramming in mind. Its architecture featured a central memory and a Program Distributor feeding up to twenty-five autonomous processing units with code and data, and allowing concurrent operation of multiple clusters.
Another such computer was the LEO III, first released in 1961. During batch processing, several different programs were loaded in the computer memory, and the first one began to run. When the first program reached an instruction waiting for a peripheral, the context of this program was stored away, and the second program in memory was given a chance to run. The process continued until all programs finished running.
Multiprogramming gives no guarantee that a program will run in a timely manner. Indeed, the first program may very well run for hours without needing access to a peripheral. As there were no users waiting at an interactive terminal, this was no problem: users handed in a deck of punched cards to an operator, and came back a few hours later for printed results. Multiprogramming greatly reduced wait times when multiple batches were being processed.
== Cooperative multitasking ==
Early multitasking systems used applications that voluntarily ceded time to one another. This approach, which was eventually supported by many computer operating systems, is known today as cooperative multitasking. Although it is now rarely used in larger systems except for specific applications such as CICS or the JES2 subsystem, cooperative multitasking was once the only scheduling scheme employed by Microsoft Windows and classic Mac OS to enable multiple applications to run simultaneously. Cooperative multitasking is still used today on RISC OS systems.
As a cooperatively multitasked system relies on each process regularly giving up time to other processes on the system, one poorly designed program can consume all of the CPU time for itself, either by performing extensive calculations or by busy waiting; both would cause the whole system to hang. In a server environment, this is a hazard that makes the entire environment unacceptably fragile.
== Preemptive multitasking ==
Preemptive multitasking allows the computer system to more reliably guarantee to each process a regular "slice" of operating time. It also allows the system to deal rapidly with important external events like incoming data, which might require the immediate attention of one or another process. Operating systems were developed to take advantage of these hardware capabilities and run multiple processes preemptively. Preemptive multitasking was implemented in the PDP-6 Monitor and Multics in 1964, in OS/360 MFT in 1967, and in Unix in 1969, and was available in some operating systems for computers as small as DEC's PDP-8; it is a core feature of all Unix-like operating systems, such as Linux, Solaris and BSD with its derivatives, as well as modern versions of Windows.
Possibly the earliest preemptive multitasking OS available to home users was Microware's OS-9, available for computers based on the Motorola 6809 such as the TRS-80 Color Computer 2, with the operating system supplied by Tandy as an upgrade for disk-equipped systems. Sinclair QDOS on the Sinclair QL followed in 1984, but it was not a big success. Commodore's Amiga was released the following year, offering a combination of multitasking and multimedia capabilities. Microsoft made preemptive multitasking a core feature of their flagship operating system in the early 1990s when developing Windows NT 3.1 and then Windows 95. In 1988 Apple offered A/UX as a UNIX System V-based alternative to the Classic Mac OS. In 2001 Apple switched to the NeXTSTEP-influenced Mac OS X.
A similar model is used in Windows 9x and the Windows NT family, where native 32-bit applications are multitasked preemptively. 64-bit editions of Windows, both for the x86-64 and Itanium architectures, no longer support legacy 16-bit applications, and thus provide preemptive multitasking for all supported applications.
== Real time ==
Another reason for multitasking was in the design of real-time computing systems, where there are a number of possibly unrelated external activities needed to be controlled by a single processor system. In such systems a hierarchical interrupt system is coupled with process prioritization to ensure that key activities were given a greater share of available process time.
== Multithreading ==
Threads were born from the idea that the most efficient way for cooperating processes to exchange data would be to share their entire memory space. Thus, threads are effectively processes that run in the same memory context and share other resources with their parent processes, such as open files. Threads are described as lightweight processes because switching between threads does not involve changing the memory context.
While threads are scheduled preemptively, some operating systems provide a variant to threads, named fibers, that are scheduled cooperatively. On operating systems that do not provide fibers, an application may implement its own fibers using repeated calls to worker functions. Fibers are even more lightweight than threads, and somewhat easier to program with, although they tend to lose some or all of the benefits of threads on machines with multiple processors.
Some systems directly support multithreading in hardware.
== Memory protection ==
Essential to any multitasking system is to safely and effectively share access to system resources. Access to memory must be strictly managed to ensure that no process can inadvertently or deliberately read or write to memory locations outside the process's address space. This is done for the purpose of general system stability and data integrity, as well as data security.
In general, memory access management is a responsibility of the operating system kernel, in combination with hardware mechanisms that provide supporting functionalities, such as a memory management unit (MMU). If a process attempts to access a memory location outside its memory space, the MMU denies the request and signals the kernel to take appropriate actions; this usually results in forcibly terminating the offending process. Depending on the software and kernel design and the specific error in question, the user may receive an access violation error message such as "segmentation fault".
In a well designed and correctly implemented multitasking system, a given process can never directly access memory that belongs to another process. An exception to this rule is in the case of shared memory; for example, in the System V inter-process communication mechanism the kernel allocates memory to be mutually shared by multiple processes. Such features are often used by database management software such as PostgreSQL.
Inadequate memory protection mechanisms, either due to flaws in their design or poor implementations, allow for security vulnerabilities that may be potentially exploited by malicious software.
== Memory swapping ==
Use of a swap file or swap partition is a way for the operating system to provide more memory than is physically available by keeping portions of the primary memory in secondary storage. While multitasking and memory swapping are two completely unrelated techniques, they are very often used together, as swapping memory allows more tasks to be loaded at the same time. Typically, a multitasking system allows another process to run when the running process hits a point where it has to wait for some portion of memory to be reloaded from secondary storage.
== Programming ==
Over the years, multitasking systems have been refined. Modern operating systems generally include detailed mechanisms for prioritizing processes, while symmetric multiprocessing has introduced new complexities and capabilities.
== See also ==
Process state
Task switching
== References ==
|
https://en.wikipedia.org/wiki/Computer_multitasking
|
In programming languages, a closure, also lexical closure or function closure, is a technique for implementing lexically scoped name binding in a language with first-class functions. Operationally, a closure is a record storing a function together with an environment. The environment is a mapping associating each free variable of the function (variables that are used locally, but defined in an enclosing scope) with the value or reference to which the name was bound when the closure was created. Unlike a plain function, a closure allows the function to access those captured variables through the closure's copies of their values or references, even when the function is invoked outside their scope.
== History and etymology ==
The concept of closures was developed in the 1960s for the mechanical evaluation of expressions in the λ-calculus and was first fully implemented in 1970 as a language feature in the PAL programming language to support lexically scoped first-class functions.
Peter Landin defined the term closure in 1964 as having an environment part and a control part as used by his SECD machine for evaluating expressions. Joel Moses credits Landin with introducing the term closure to refer to a lambda expression with open bindings (free variables) that have been closed by (or bound in) the lexical environment, resulting in a closed expression, or closure. This use was subsequently adopted by Sussman and Steele when they defined Scheme in 1975, a lexically scoped variant of Lisp, and became widespread.
Sussman and Abelson also use the term closure in the 1980s with a second, unrelated meaning: the property of an operator that adds data to a data structure to also be able to add nested data structures. This use of the term comes from mathematics use, rather than the prior use in computer science. The authors consider this overlap in terminology to be "unfortunate."
== Anonymous functions ==
The term closure is often used as a synonym for anonymous function, though strictly, an anonymous function is a function literal without a name, while a closure is an instance of a function, a value, whose non-local variables have been bound either to values or to storage locations (depending on the language; see the lexical environment section below).
For example, in the following Python code:
the values of a and b are closures, in both cases produced by returning a nested function with a free variable from the enclosing function, so that the free variable binds to the value of parameter x of the enclosing function. The closures in a and b are functionally identical. The only difference in implementation is that in the first case we used a nested function with a name, g, while in the second case we used an anonymous nested function (using the Python keyword lambda for creating an anonymous function). The original name, if any, used in defining them is irrelevant.
A closure is a value like any other value. It does not need to be assigned to a variable and can instead be used directly, as shown in the last two lines of the example. This usage may be deemed an "anonymous closure".
The nested function definitions are not themselves closures: they have a free variable which is not yet bound. Only once the enclosing function is evaluated with a value for the parameter is the free variable of the nested function bound, creating a closure, which is then returned from the enclosing function.
Lastly, a closure is only distinct from a function with free variables when outside of the scope of the non-local variables, otherwise the defining environment and the execution environment coincide and there is nothing to distinguish these (static and dynamic binding cannot be distinguished because the names resolve to the same values). For example, in the program below, functions with a free variable x (bound to the non-local variable x with global scope) are executed in the same environment where x is defined, so it is immaterial whether these are actually closures:
This is most often achieved by a function return, since the function must be defined within the scope of the non-local variables, in which case typically its own scope will be smaller.
This can also be achieved by variable shadowing (which reduces the scope of the non-local variable), though this is less common in practice, as it is less useful and shadowing is discouraged. In this example f can be seen to be a closure because x in the body of f is bound to the x in the global namespace, not the x local to g:
== Applications ==
The use of closures is associated with languages where functions are first-class objects, in which functions can be returned as results from higher-order functions, or passed as arguments to other function calls; if functions with free variables are first-class, then returning one creates a closure. This includes functional programming languages such as Lisp and ML, and many modern, multi-paradigm languages, such as Julia, Python, and Rust. Closures are also often used with callbacks, particularly for event handlers, such as in JavaScript, where they are used for interactions with a dynamic web page.
Closures can also be used in a continuation-passing style to hide state. Constructs such as objects and control structures can thus be implemented with closures. In some languages, a closure may occur when a function is defined within another function, and the inner function refers to local variables of the outer function. At run-time, when the outer function executes, a closure is formed, consisting of the inner function's code and references (the upvalues) to any variables of the outer function required by the closure.
=== First-class functions ===
Closures typically appear in languages with first-class functions—in other words, such languages enable functions to be passed as arguments, returned from function calls, bound to variable names, etc., just like simpler types such as strings and integers. For example, consider the following Scheme function:
In this example, the lambda expression (lambda (book) (>= (book-sales book) threshold)) appears within the function best-selling-books. When the lambda expression is evaluated, Scheme creates a closure consisting of the code for the lambda expression and a reference to the threshold variable, which is a free variable inside the lambda expression.
The closure is then passed to the filter function, which calls it repeatedly to determine which books are to be added to the result list and which are to be discarded. Because the closure has a reference to threshold, it can use that variable each time filter calls it. The function filter might be defined in a separate file.
Here is the same example rewritten in JavaScript, another popular language with support for closures:
The arrow operator => is used to define an arrow function expression, and an Array.filter method instead of a global filter function, but otherwise the structure and the effect of the code are the same.
A function may create a closure and return it, as in this example:
Because the closure in this case outlives the execution of the function that creates it, the variables f and dx live on after the function derivative returns, even though execution has left their scope and they are no longer visible. In languages without closures, the lifetime of an automatic local variable coincides with the execution of the stack frame where that variable is declared. In languages with closures, variables must continue to exist as long as any existing closures have references to them. This is most commonly implemented using some form of garbage collection.
=== State representation ===
A closure can be used to associate a function with a set of "private" variables, which persist over several invocations of the function. The scope of the variable encompasses only the closed-over function, so it cannot be accessed from other program code. These are analogous to private variables in object-oriented programming, and in fact closures are similar to stateful function objects (or functors) with a single call-operator method.
In stateful languages, closures can thus be used to implement paradigms for state representation and information hiding, since the closure's upvalues (its closed-over variables) are of indefinite extent, so a value established in one invocation remains available in the next. Closures used in this way no longer have referential transparency, and are thus no longer pure functions; nevertheless, they are commonly used in impure functional languages such as Scheme.
=== Other uses ===
Closures have many uses:
Because closures delay evaluation—i.e., they do not "do" anything until they are called—they can be used to define control structures. For example, all of Smalltalk's standard control structures, including branches (if/then/else) and loops (while and for), are defined using objects whose methods accept closures. Users can easily define their own control structures also.
In languages which implement assignment, multiple functions can be produced that close over the same environment, enabling them to communicate privately by altering that environment. In Scheme:
Closures can be used to implement object systems.
Note: Some speakers call any data structure that binds a lexical environment a closure, but the term usually refers specifically to functions.
== Implementation and theory ==
Closures are typically implemented with a special data structure that contains a pointer to the function code, plus a representation of the function's lexical environment (i.e., the set of available variables) at the time when the closure was created. The referencing environment binds the non-local names to the corresponding variables in the lexical environment at the time the closure is created, additionally extending their lifetime to at least as long as the lifetime of the closure. When the closure is entered at a later time, possibly with a different lexical environment, the function is executed with its non-local variables referring to the ones captured by the closure, not the current environment.
A language implementation cannot easily support full closures if its run-time memory model allocates all automatic variables on a linear stack. In such languages, a function's automatic local variables are deallocated when the function returns. However, a closure requires that the free variables it references survive the enclosing function's execution. Therefore, those variables must be allocated so that they persist until no longer needed, typically via heap allocation, rather than on the stack, and their lifetime must be managed so they survive until all closures referencing them are no longer in use.
This explains why, typically, languages that natively support closures also use garbage collection. The alternatives are manual memory management of non-local variables (explicitly allocating on the heap and freeing when done), or, if using stack allocation, for the language to accept that certain use cases will lead to undefined behaviour, due to dangling pointers to freed automatic variables, as in lambda expressions in C++11 or nested functions in GNU C. The funarg problem (or "functional argument" problem) describes the difficulty of implementing functions as first class objects in a stack-based programming language such as C or C++. Similarly in D version 1, it is assumed that the programmer knows what to do with delegates and automatic local variables, as their references will be invalid after return from its definition scope (automatic local variables are on the stack) – this still permits many useful functional patterns, but for complex cases needs explicit heap allocation for variables. D version 2 solved this by detecting which variables must be stored on the heap, and performs automatic allocation. Because D uses garbage collection, in both versions, there is no need to track usage of variables as they are passed.
In strict functional languages with immutable data (e.g. Erlang), it is very easy to implement automatic memory management (garbage collection), as there are no possible cycles in variables' references. For example, in Erlang, all arguments and variables are allocated on the heap, but references to them are additionally stored on the stack. After a function returns, references are still valid. Heap cleaning is done by incremental garbage collector.
In ML, local variables are lexically scoped, and hence define a stack-like model, but since they are bound to values and not to objects, an implementation is free to copy these values into the closure's data structure in a way that is invisible to the programmer.
Scheme, which has an ALGOL-like lexical scope system with dynamic variables and garbage collection, lacks a stack programming model and does not suffer from the limitations of stack-based languages. Closures are expressed naturally in Scheme. The lambda form encloses the code, and the free variables of its environment persist within the program as long as they can possibly be accessed, and so they can be used as freely as any other Scheme expression.
Closures are closely related to Actors in the Actor model of concurrent computation where the values in the function's lexical environment are called acquaintances. An important issue for closures in concurrent programming languages is whether the variables in a closure can be updated and, if so, how these updates can be synchronized. Actors provide one solution.
Closures are closely related to function objects; the transformation from the former to the latter is known as defunctionalization or lambda lifting; see also closure conversion.
== Differences in semantics ==
=== Lexical environment ===
As different languages do not always have a common definition of the lexical environment, their definitions of closure may vary also. The commonly held minimalist definition of the lexical environment defines it as a set of all bindings of variables in the scope, and that is also what closures in any language have to capture. However the meaning of a variable binding also differs. In imperative languages, variables bind to relative locations in memory that can store values. Although the relative location of a binding does not change at runtime, the value in the bound location can. In such languages, since closure captures the binding, any operation on the variable, whether done from the closure or not, are performed on the same relative memory location. This is often called capturing the variable "by reference". Here is an example illustrating the concept in ECMAScript, which is one such language:
Function foo and the closures referred to by variables f and g all use the same relative memory location signified by local variable x.
In some instances the above behaviour may be undesirable, and it is necessary to bind a different lexical closure. Again in ECMAScript, this would be done using the Function.bind().
=== Example 1: Reference to an unbound variable ===
=== Example 2: Accidental reference to a bound variable ===
For this example the expected behaviour would be that each link should emit its id when clicked; but because the variable 'e' is bound to the scope above, and lazy evaluated on click, what actually happens is that each on click event emits the id of the last element in 'elements' bound at the end of the for loop.
Again here variable e would need to be bound by the scope of the block using handle.bind(this) or the let keyword.
On the other hand, many functional languages, such as ML, bind variables directly to values. In this case, since there is no way to change the value of the variable once it is bound, there is no need to share the state between closures—they just use the same values. This is often called capturing the variable "by value". Java's local and anonymous classes also fall into this category—they require captured local variables to be final, which also means there is no need to share state.
Some languages enable choosing between capturing the value of a variable or its location. For example, in C++11, captured variables are either declared with [&], which means captured by reference, or with [=], which means captured by value.
Yet another subset, lazy functional languages such as Haskell, bind variables to results of future computations rather than values. Consider this example in Haskell:
The binding of r captured by the closure defined within function foo is to the computation (x / y)—which in this case results in division by zero. However, since it is the computation that is captured, and not the value, the error only manifests when the closure is invoked, and then attempts to use the captured binding.
=== Closure leaving ===
Yet more differences manifest themselves in the behavior of other lexically scoped constructs, such as return, break and continue statements. Such constructs can, in general, be considered in terms of invoking an escape continuation established by an enclosing control statement (in case of break and continue, such interpretation requires looping constructs to be considered in terms of recursive function calls). In some languages, such as ECMAScript, return refers to the continuation established by the closure lexically innermost with respect to the statement—thus, a return within a closure transfers control to the code that called it. However, in Smalltalk, the superficially similar operator ^ invokes the escape continuation established for the method invocation, ignoring the escape continuations of any intervening nested closures. The escape continuation of a particular closure can only be invoked in Smalltalk implicitly by reaching the end of the closure's code. These examples in ECMAScript and Smalltalk highlight the difference:
The above code snippets will behave differently because the Smalltalk ^ operator and the JavaScript return operator are not analogous. In the ECMAScript example, return x will leave the inner closure to begin a new iteration of the forEach loop, whereas in the Smalltalk example, ^x will abort the loop and return from the method foo.
Common Lisp provides a construct that can express either of the above actions: Lisp (return-from foo x) behaves as Smalltalk ^x, while Lisp (return-from nil x) behaves as JavaScript return x. Hence, Smalltalk makes it possible for a captured escape continuation to outlive the extent in which it can be successfully invoked. Consider:
When the closure returned by the method foo is invoked, it attempts to return a value from the invocation of foo that created the closure. Since that call has already returned and the Smalltalk method invocation model does not follow the spaghetti stack discipline to facilitate multiple returns, this operation results in an error.
Some languages, such as Ruby, enable the programmer to choose the way return is captured. An example in Ruby:
Both Proc.new and lambda in this example are ways to create a closure, but semantics of the closures thus created are different with respect to the return statement.
In Scheme, definition and scope of the return control statement is explicit (and only arbitrarily named 'return' for the sake of the example). The following is a direct translation of the Ruby sample.
== Closure-like constructs ==
Some languages have features which simulate the behavior of closures. In languages such as C++, C#, D, Java, Objective-C, and Visual Basic (.NET) (VB.NET), these features are the result of the language's object-oriented paradigm.
=== Callbacks (C) ===
Some C libraries support callbacks. This is sometimes implemented by providing two values when registering the callback with the library: a function pointer and a separate void* pointer to arbitrary data of the user's choice. When the library executes the callback function, it passes along the data pointer. This enables the callback to maintain state and to refer to information captured at the time it was registered with the library. The idiom is similar to closures in functionality, but not in syntax. The void* pointer is not type safe so this C idiom differs from type-safe closures in C#, Haskell or ML.
Callbacks are used extensively in graphical user interface (GUI) widget toolkits to implement event-driven programming by associating general functions of graphical widgets (menus, buttons, check boxes, sliders, spinners, etc.) with application-specific functions implementing the specific desired behavior for the application.
==== Nested function and function pointer (C) ====
With a GNU Compiler Collection (GCC) extension, a nested function can be used and a function pointer can emulate closures, provided the function does not exit the containing scope. The next example is invalid because adder is a top-level definition (depending on compiler version, it could produce a correct result if compiled with no optimizing, i.e., at -O0):
But moving adder (and, optionally, the typedef) in main makes it valid:
If executed this now prints 11 as expected.
=== Local classes and lambda functions (Java) ===
Java enables classes to be defined inside methods. These are called local classes. When such classes are not named, they are known as anonymous classes (or anonymous inner classes). A local class (either named or anonymous) may refer to names in lexically enclosing classes, or read-only variables (marked as final) in the lexically enclosing method.
The capturing of final variables enables capturing variables by value. Even if the variable to capture is non-final, it can always be copied to a temporary final variable just before the class.
Capturing of variables by reference can be emulated by using a final reference to a mutable container, for example, a one-element array. The local class will not be able to change the value of the container reference, but it will be able to change the contents of the container.
With the advent of Java 8's lambda expressions, the closure causes the above code to be executed as:
Local classes are one of the types of inner class that are declared within the body of a method. Java also supports inner classes that are declared as non-static members of an enclosing class. They are normally referred to just as "inner classes". These are defined in the body of the enclosing class and have full access to instance variables of the enclosing class. Due to their binding to these instance variables, an inner class may only be instantiated with an explicit binding to an instance of the enclosing class using a special syntax.
Upon execution, this will print the integers from 0 to 9. Beware to not confuse this type of class with the nested class, which is declared in the same way with an accompanied usage of the "static" modifier; those have not the desired effect but are instead just classes with no special binding defined in an enclosing class.
As of Java 8, Java supports functions as first class objects. Lambda expressions of this form are considered of type Function<T,U> with T being the domain and U the image type. The expression can be called with its .apply(T t) method, but not with a standard method call.
=== Blocks (C, C++, Objective-C 2.0) ===
Apple introduced blocks, a form of closure, as a nonstandard extension into C, C++, Objective-C 2.0 and in Mac OS X 10.6 "Snow Leopard" and iOS 4.0. Apple made their implementation available for the GCC and clang compilers.
Pointers to block and block literals are marked with ^. Normal local variables are captured by value when the block is created, and are read-only inside the block. Variables to be captured by reference are marked with __block. Blocks that need to persist outside of the scope they are created in may need to be copied.
=== Delegates (C#, VB.NET, D) ===
C# anonymous methods and lambda expressions support closure:
Visual Basic .NET, which has many language features similar to those of C#, also supports lambda expressions with closures:
In D, closures are implemented by delegates, a function pointer paired with a context pointer (e.g. a class instance, or a stack frame on the heap in the case of closures).
D version 1, has limited closure support. For example, the above code will not work correctly, because the variable a is on the stack, and after returning from test(), it is no longer valid to use it (most probably calling foo via dg(), will return a 'random' integer). This can be solved by explicitly allocating the variable 'a' on heap, or using structs or class to store all needed closed variables and construct a delegate from a method implementing the same code. Closures can be passed to other functions, as long as they are only used while the referenced values are still valid (for example calling another function with a closure as a callback parameter), and are useful for writing generic data processing code, so this limitation, in practice, is often not an issue.
This limitation was fixed in D version 2 - the variable 'a' will be automatically allocated on the heap because it is used in the inner function, and a delegate of that function can escape the current scope (via assignment to dg or return). Any other local variables (or arguments) that are not referenced by delegates or that are only referenced by delegates that do not escape the current scope, remain on the stack, which is simpler and faster than heap allocation. The same is true for inner's class methods that reference a function's variables.
=== Function objects (C++) ===
C++ enables defining function objects by overloading operator(). These objects behave somewhat like functions in a functional programming language. They may be created at runtime and may contain state, but they do not implicitly capture local variables as closures do. As of the 2011 revision, the C++ language also supports closures, which are a type of function object constructed automatically from a special language construct called lambda-expression. A C++ closure may capture its context either by storing copies of the accessed variables as members of the closure object or by reference. In the latter case, if the closure object escapes the scope of a referenced object, invoking its operator() causes undefined behavior since C++ closures do not extend the lifetime of their context.
=== Inline agents (Eiffel) ===
Eiffel includes inline agents defining closures. An inline agent is an object representing a routine, defined by giving the code of the routine in-line. For example, in
the argument to subscribe is an agent, representing a procedure with two arguments; the procedure finds the country at the corresponding coordinates and displays it. The whole agent is "subscribed" to the event type click_event for a
certain button, so that whenever an instance of the event type occurs on that button – because a user has clicked the button – the procedure will be executed with the mouse coordinates being passed as arguments for x and y.
The main limitation of Eiffel agents, which distinguishes them from closures in other languages, is that they cannot reference local variables from the enclosing scope. This design decision helps in avoiding ambiguity when talking about a local variable value in a closure - should it be the latest value of the variable or the value captured when the agent is created? Only Current (a reference to current object, analogous to this in Java), its features, and arguments of the agent can be accessed from within the agent body. The values of the outer local variables can be passed by providing additional closed operands to the agent.
=== C++Builder __closure reserved word ===
Embarcadero C++Builder provides the reserved word __closure to provide a pointer to a method with a similar syntax to a function pointer.
Standard C allows writing a typedef for a pointer to a function type using the following syntax:In a similar way, a typedef can be declared for a pointer to a method using this syntax:
== See also ==
== Notes ==
== References ==
== External links ==
Original "Lambda Papers": A classic series of papers by Guy L. Steele Jr. and Gerald Jay Sussman discussing, among other things, the versatility of closures in the context of Scheme (where they appear as lambda expressions).
Gafter, Neal (28 January 2007). "A Definition of Closures".
Bracha, Gilad; Gafter, Neal; Gosling, James; von der Ahé, Peter. "Closures for the Java Programming Language (v0.5)".
Closures: An article about closures in dynamically typed imperative languages, by Martin Fowler.
Collection closure methods: An example of a technical domain where using closures is convenient, by Martin Fowler.
|
https://en.wikipedia.org/wiki/Closure_(computer_programming)
|
In mathematics, an invariant is a property of a mathematical object (or a class of mathematical objects) which remains unchanged after operations or transformations of a certain type are applied to the objects. The particular class of objects and type of transformations are usually indicated by the context in which the term is used. For example, the area of a triangle is an invariant with respect to isometries of the Euclidean plane. The phrases "invariant under" and "invariant to" a transformation are both used. More generally, an invariant with respect to an equivalence relation is a property that is constant on each equivalence class.
Invariants are used in diverse areas of mathematics such as geometry, topology, algebra and discrete mathematics. Some important classes of transformations are defined by an invariant they leave unchanged. For example, conformal maps are defined as transformations of the plane that preserve angles. The discovery of invariants is an important step in the process of classifying mathematical objects.
== Examples ==
A simple example of invariance is expressed in our ability to count. For a finite set of objects of any kind, there is a number to which we always arrive, regardless of the order in which we count the objects in the set. The quantity—a cardinal number—is associated with the set, and is invariant under the process of counting.
An identity is an equation that remains true for all values of its variables. There are also inequalities that remain true when the values of their variables change.
The distance between two points on a number line is not changed by adding the same quantity to both numbers. On the other hand, multiplication does not have this same property, as distance is not invariant under multiplication.
Angles and ratios of distances are invariant under scalings, rotations, translations and reflections. These transformations produce similar shapes, which is the basis of trigonometry. In contrast, angles and ratios are not invariant under non-uniform scaling (such as stretching). The sum of a triangle's interior angles (180°) is invariant under all the above operations. As another example, all circles are similar: they can be transformed into each other and the ratio of the circumference to the diameter is invariant (denoted by the Greek letter π (pi)).
Some more complicated examples:
The real part and the absolute value of a complex number are invariant under complex conjugation.
The tricolorability of knots.
The degree of a polynomial is invariant under a linear change of variables.
The dimension and homology groups of a topological object are invariant under homeomorphism.
The number of fixed points of a dynamical system is invariant under many mathematical operations.
Euclidean distance is invariant under orthogonal transformations.
Area is invariant under linear maps which have determinant ±1 (see Equiareal map § Linear transformations).
Some invariants of projective transformations include collinearity of three or more points, concurrency of three or more lines, conic sections, and the cross-ratio.
The determinant, trace, eigenvectors, and eigenvalues of a linear endomorphism are invariant under a change of basis. In other words, the spectrum of a matrix is invariant under a change of basis.
The principal invariants of tensors do not change with rotation of the coordinate system (see Invariants of tensors).
The singular values of a matrix are invariant under orthogonal transformations.
Lebesgue measure is invariant under translations.
The variance of a probability distribution is invariant under translations of the real line. Hence the variance of a random variable is unchanged after the addition of a constant.
The fixed points of a transformation are the elements in the domain that are invariant under the transformation. They may, depending on the application, be called symmetric with respect to that transformation. For example, objects with translational symmetry are invariant under certain translations.
The integral
∫
M
K
d
μ
{\textstyle \int _{M}K\,d\mu }
of the Gaussian curvature
K
{\displaystyle K}
of a two-dimensional Riemannian manifold
(
M
,
g
)
{\displaystyle (M,g)}
is invariant under changes of the Riemannian metric
g
{\displaystyle g}
. This is the Gauss–Bonnet theorem.
=== MU puzzle ===
The MU puzzle is a good example of a logical problem where determining an invariant is of use for an impossibility proof. The puzzle asks one to start with the word MI and transform it into the word MU, using in each step one of the following transformation rules:
If a string ends with an I, a U may be appended (xI → xIU)
The string after the M may be completely duplicated (Mx → Mxx)
Any three consecutive I's (III) may be replaced with a single U (xIIIy → xUy)
Any two consecutive U's may be removed (xUUy → xy)
An example derivation (with superscripts indicating the applied rules) is
MI →2 MII →2 MIIII →3 MUI →2 MUIUI →1 MUIUIU →2 MUIUIUUIUIU →4 MUIUIIUIU → ...
In light of this, one might wonder whether it is possible to convert MI into MU, using only these four transformation rules. One could spend many hours applying these transformation rules to strings. However, it might be quicker to find a property that is invariant to all rules (that is, not changed by any of them), and that demonstrates that getting to MU is impossible. By looking at the puzzle from a logical standpoint, one might realize that the only way to get rid of any I's is to have three consecutive I's in the string. This makes the following invariant interesting to consider:
The number of I's in the string is not a multiple of 3.
This is an invariant to the problem, if for each of the transformation rules the following holds: if the invariant held before applying the rule, it will also hold after applying it. Looking at the net effect of applying the rules on the number of I's and U's, one can see this actually is the case for all rules:
The table above shows clearly that the invariant holds for each of the possible transformation rules, which means that whichever rule one picks, at whatever state, if the number of I's was not a multiple of three before applying the rule, then it will not be afterwards either.
Given that there is a single I in the starting string MI, and one is not a multiple of three, one can then conclude that it is impossible to go from MI to MU (as the number of I's will never be a multiple of three).
== Invariant set ==
A subset S of the domain U of a mapping T: U → U is an invariant set under the mapping when
x
∈
S
⟺
T
(
x
)
∈
S
.
{\displaystyle x\in S\iff T(x)\in S.}
The elements of S are not necessarily fixed, even though the set S is fixed in the power set of U. (Some authors use the terminology setwise invariant, vs. pointwise invariant, to distinguish between these cases.)
For example, a circle is an invariant subset of the plane under a rotation about the circle's center. Further, a conical surface is invariant as a set under a homothety of space.
An invariant set of an operation T is also said to be stable under T. For example, the normal subgroups that are so important in group theory are those subgroups that are stable under the inner automorphisms of the ambient group.
In linear algebra, if a linear transformation T has an eigenvector v, then the line through 0 and v is an invariant set under T, in which case the eigenvectors span an invariant subspace which is stable under T.
When T is a screw displacement, the screw axis is an invariant line, though if the pitch is non-zero, T has no fixed points.
In probability theory and ergodic theory, invariant sets are usually defined via the stronger property
x
∈
S
⇔
T
(
x
)
∈
S
.
{\displaystyle x\in S\Leftrightarrow T(x)\in S.}
When the map
T
{\displaystyle T}
is measurable, invariant sets form a sigma-algebra, the invariant sigma-algebra.
== Formal statement ==
The notion of invariance is formalized in three different ways in mathematics: via group actions, presentations, and deformation.
=== Unchanged under group action ===
Firstly, if one has a group G acting on a mathematical object (or set of objects) X, then one may ask which points x are unchanged, "invariant" under the group action, or under an element g of the group.
Frequently one will have a group acting on a set X, which leaves one to determine which objects in an associated set F(X) are invariant. For example, rotation in the plane about a point leaves the point about which it rotates invariant, while translation in the plane does not leave any points invariant, but does leave all lines parallel to the direction of translation invariant as lines. Formally, define the set of lines in the plane P as L(P); then a rigid motion of the plane takes lines to lines – the group of rigid motions acts on the set of lines – and one may ask which lines are unchanged by an action.
More importantly, one may define a function on a set, such as "radius of a circle in the plane", and then ask if this function is invariant under a group action, such as rigid motions.
Dual to the notion of invariants are coinvariants, also known as orbits, which formalizes the notion of congruence: objects which can be taken to each other by a group action. For example, under the group of rigid motions of the plane, the perimeter of a triangle is an invariant, while the set of triangles congruent to a given triangle is a coinvariant.
These are connected as follows: invariants are constant on coinvariants (for example, congruent triangles have the same perimeter), while two objects which agree in the value of one invariant may or may not be congruent (for example, two triangles with the same perimeter need not be congruent). In classification problems, one might seek to find a complete set of invariants, such that if two objects have the same values for this set of invariants, then they are congruent.
For example, triangles such that all three sides are equal are congruent under rigid motions, via SSS congruence, and thus the lengths of all three sides form a complete set of invariants for triangles. The three angle measures of a triangle are also invariant under rigid motions, but do not form a complete set as incongruent triangles can share the same angle measures. However, if one allows scaling in addition to rigid motions, then the AAA similarity criterion shows that this is a complete set of invariants.
=== Independent of presentation ===
Secondly, a function may be defined in terms of some presentation or decomposition of a mathematical object; for instance, the Euler characteristic of a cell complex is defined as the alternating sum of the number of cells in each dimension. One may forget the cell complex structure and look only at the underlying topological space (the manifold) – as different cell complexes give the same underlying manifold, one may ask if the function is independent of choice of presentation, in which case it is an intrinsically defined invariant. This is the case for the Euler characteristic, and a general method for defining and computing invariants is to define them for a given presentation, and then show that they are independent of the choice of presentation. Note that there is no notion of a group action in this sense.
The most common examples are:
The presentation of a manifold in terms of coordinate charts – invariants must be unchanged under change of coordinates.
Various manifold decompositions, as discussed for Euler characteristic.
Invariants of a presentation of a group.
=== Unchanged under perturbation ===
Thirdly, if one is studying an object which varies in a family, as is common in algebraic geometry and differential geometry, one may ask if the property is unchanged under perturbation (for example, if an object is constant on families or invariant under change of metric).
== Invariants in computer science ==
In computer science, an invariant is a logical assertion that is always held to be true during a certain phase of execution of a computer program. For example, a loop invariant is a condition that is true at the beginning and the end of every iteration of a loop.
Invariants are especially useful when reasoning about the correctness of a computer program. The theory of optimizing compilers, the methodology of design by contract, and formal methods for determining program correctness, all rely heavily on invariants.
Programmers often use assertions in their code to make invariants explicit. Some object oriented programming languages have a special syntax for specifying class invariants.
=== Automatic invariant detection in imperative programs ===
Abstract interpretation tools can compute simple invariants of given imperative computer programs. The kind of properties that can be found depend on the abstract domains used. Typical example properties are single integer variable ranges like 0<=x<1024, relations between several variables like 0<=i-j<2*n-1, and modulus information like y%4==0. Academic research prototypes also consider simple properties of pointer structures.
More sophisticated invariants generally have to be provided manually.
In particular, when verifying an imperative program using the Hoare calculus, a loop invariant has to be provided manually for each loop in the program, which is one of the reasons that this approach is generally impractical for most programs.
In the context of the above MU puzzle example, there is currently no general automated tool that can detect that a derivation from MI to MU is impossible using only the rules 1–4. However, once the abstraction from the string to the number of its "I"s has been made by hand, leading, for example, to the following C program, an abstract interpretation tool will be able to detect that ICount%3 cannot be 0, and hence the "while"-loop will never terminate.
== See also ==
== Notes ==
== References ==
== External links ==
"Applet: Visual Invariants in Sorting Algorithms" Archived 2022-02-24 at the Wayback Machine by William Braynen in 1997
|
https://en.wikipedia.org/wiki/Invariant_(mathematics)
|
A raster graphics editor (also called bitmap graphics editor) is a computer program that allows users to create and edit images interactively on the computer screen and save them in one of many raster graphics file formats (also known as bitmap images) such as JPEG, PNG, and GIF.
== Comparison to vector graphic editors ==
Vector graphics editors are often contrasted with raster graphics editors, yet their capabilities complement each other. The technical difference between vector and raster editors stem from the difference between vector and raster images. Vector graphics are created mathematically, using geometric formulas. Each element is created and manipulated numerically; essentially using Cartesian coordinates for the placement of key points, and then a mathematical algorithm to connect the dots and define the colors.
Raster images include digital photos. A raster image is made up of rows and columns of dots, called pixels, and is generally more photo-realistic. This is the standard form for digital cameras; whether it be a .raw file or .jpg file, the concept is the same. The image is represented pixel by pixel, like a microscopic jigsaw puzzle.
Vector editors tend to be better suited for graphic design, page layout, typography, logos, sharp-edged artistic illustrations, e.g., cartoons, clip art, complex geometric patterns, technical illustrations, diagramming and flowcharting.
Advanced raster editors, like GIMP and Adobe Photoshop, use vector methods (mathematics) for general layout and elements such as text, but are equipped to deal with raster images down to the pixel and often have special capabilities in doing so, such as brightness/contrast, and even adding "lighting" to a raster image or photograph.
== Popular editors ==
Adobe Photoshop: Industry standard for photography, design, and digital art
GIMP: Free, open-source alternative with similar features to Photoshop
Corel Painter: Focuses on digital painting with traditional art simulation
Affinity Photo: Professional-grade tools with a one-time purchase model
Procreate(iOS): Popular app for digital painting on iPad
Krita : A popular software for Windows.
== Common features ==
Select a region for editing
Draw lines with simulated brushes of different color, size, shape and pressure
Fill a region with a single color, gradient of colors, or a texture
Select a color using different color models, e.g., RGB, HSV, or by using a color dropper
Edit and convert between various color models.
Add typed letters in various font styles
Remove imperfections from photo images
Composite editing using layers
Apply filters for effects including sharpening and blurring
Convert between various image file formats
== See also ==
Comparison of raster graphics editors
Vector graphics editor
Texture mapping
Text editor
3D modeling
== References ==
== External links ==
Media related to Raster graphics software at Wikimedia Commons
|
https://en.wikipedia.org/wiki/Raster_graphics_editor
|
In computer programming, a mirror is a reflection mechanism that is completely decoupled from the object whose structure is being introspected. This is as opposed to traditional reflection, for example in Java, where one introspects an object using methods from the object itself (e.g. getClass()).
Mirrors adhere to the qualities of encapsulation, stratification and ontological correspondence.
== Benefits ==
Decoupling the reflection mechanism from the objects themselves allows for a few benefits:
The object's interface is not polluted, so there is no danger of breaking reflection by overriding a reflective method.
There can be different mirror systems.
The mirror system can be removed entirely (potentially allowing for optimizations).
A mirror system can operate on remote code, since it is not coupled with a particular machine.
== Languages that use mirrors ==
Dart, via its reflect function.
Inko, via its std::mirror module.
Rubinius (Ruby implementation), via its Rubinius::Mirror.reflect method.
Scala
Swift, via its reflect function.
== References ==
|
https://en.wikipedia.org/wiki/Mirror_(programming)
|
In computer science, a type signature or type annotation defines the inputs and outputs of a function, subroutine or method. A type signature includes the number, types, and order of the function's arguments. One important use of a type signature is for function overload resolution, where one particular definition of a function to be called is selected among many overloaded forms.
== Examples ==
=== C/C++ ===
In C and C++, the type signature is declared by what is commonly known as a function prototype. In C/C++, a function declaration reflects its use; for example, a function pointer with the signature (int)(char, double) would be called as:
=== Erlang ===
In Erlang, type signatures may be optionally declared, as:
For example:
=== Haskell ===
A type signature in Haskell generally takes the following form:
Notice that the type of the result can be regarded as everything past the first supplied argument. This is a consequence of currying, which is made possible by Haskell's support for first-class functions; this function requires two inputs where one argument is supplied and the function is "curried" to produce a function for the argument not supplied. Thus, calling f x, where f :: a -> b -> c, yields a new function f2 :: b -> c that can be called f2 b to produce c.
The actual type specifications can consist of an actual type, such as Integer, or a general type variable that is used in parametric polymorphic functions, such as a, or b, or anyType. So we can write something like:
functionName :: a -> a -> ... -> a
Since Haskell supports higher-order functions, functions can be passed as arguments. This is written as:
functionName :: (a -> a) -> a
This function takes in a function with type signature a -> a and returns data of type a out.
=== Java ===
In the Java virtual machine, internal type signatures are used to identify methods and classes at the level of the virtual machine code.
Example: The method String String.substring(int, int) is represented in bytecode as Ljava/lang/String.substring(II)Ljava/lang/String;.
The signature of the main method looks like this:
And in the disassembled bytecode, it takes the form of Lsome/package/Main/main:([Ljava/lang/String;)V
The method signature for the main() method contains three modifiers:
public indicates that the main() method can be called by any object.
static indicates that the main() method is a class method.
void indicates that the main() method has no return value.
== Signature ==
A function signature consists of the function prototype. It specifies the general information about a function like the name, scope and parameters. Many programming languages use name mangling in order to pass along more semantic information from the compilers to the linkers. In addition to mangling, there is an excess of information in a function signature (stored internally to most compilers) which is not readily available, but may be accessed.
Understanding the notion of a function signature is an important concept for all computer science studies.
Modern object orientation techniques make use of interfaces, which are essentially templates made from function signatures.
C++ uses function overloading with various signatures.
The practice of multiple inheritance requires consideration of the function signatures to avoid unpredictable results. Computer science theory, and the concept of polymorphism in particular, make much use of the concept of function signature.
In the C programming language, a signature is roughly equivalent to its prototype definition.
In the ML family of programming languages, "signature" is used as a keyword referring to a construct of the module system that plays the role of an interface.
== Method signature ==
In computer programming, especially object-oriented programming, a method is commonly identified by its unique method signature, which usually includes the method name and the number, types, and order of its parameters. A method signature is the smallest type of a method.
=== Examples ===
==== C/C++ ====
In C/C++, the method signature is the method name and the number and type of its parameters, but it is possible to have a last parameter that consists of an array of values:
Manipulation of these parameters can be done by using the routines in the standard library header <stdarg.h>.
In C++, the return type can also follow the parameter list, which is referred to as a trailing return type. The difference is only syntactic; in either case, the resulting signature is identical:
==== C# ====
Similar to the syntax of C, method signatures in C# are composed of a name and the number and type of its parameters, where the last parameter may be an array of values:
==== Java ====
In Java, a method signature is composed of a name and the number, type, and order of its parameters. Return types and thrown exceptions are not considered to be a part of the method signature, nor are the names of parameters; they are ignored by the compiler for checking method uniqueness.
The method signatures help distinguish overloaded methods (methods with the same name) in a class. Return types are not included in overloading. Only method signatures should be used to distinguish overloaded methods.
For example, the following two methods have different signatures:
The following two methods both have the same signature:
==== Julia ====
In Julia, function signatures take the following form:
The types in the arguments are used for the multiple dispatch. The return type is validated when the function returns a value, and a runtime exception is raised if the type of the value does not agree with the specified type.
Abstract types are allowed and are encouraged for implementing general behavior that is common to all subtypes. The above function can therefore be rewritten as follows. In this case, the function can accept any Integer and Real subtypes accordingly.
Types are completely optional in function arguments. When unspecified, it is equivalent to using the type Any, which is the super-type of all types. It is idiomatic to specify argument types but not return type.
==== Objective-C ====
In the Objective-C programming language, method signatures for an object are declared in the interface header file. For example,
defines a method initWithInt that returns a general object (an id) and takes one integer argument. Objective-C only requires a type in a signature to be explicit when the type is not id; this signature is equivalent:
==== Rust ====
In Rust, function signatures take the following form:
== See also ==
Argument of a function – Input to a mathematical function
== References ==
|
https://en.wikipedia.org/wiki/Type_signature
|
IC programming is the process of transferring a software or firmware into an integrated circuit (IC), typically to enable the chip to perform specific tasks or functions. The process of IC programming usually requires an IC programmer, also known as a chip programmer, device programmer, or PROM writer, which is an electronic device used to load data into the non-volatile memory of programmable ICs.
IC programming can be performed either off-board, where the IC is removed from its PCB and programmed externally, or on-board, where the IC is programmed while still mounted on the device's circuit board. IC programming is essential in providing the ability to program a range of programmable ICs used in diverse applications, from consumer electronics to industrial systems.
The common types of programmable chips include:
Programmable Read-Only Memory (PROM)
Erasable Programmable Read-Only Memory (EPROM)
Electrically Erasable Programmable Read-Only Memory (EEPROM)
Flash memory
Field Programmable Gate Arrays (FPGA)
Microcontroller Units (MCU)
== Notes ==
|
https://en.wikipedia.org/wiki/IC_programming
|
The Advisory Committee on the Future of the United States Space Program, commonly known as the Augustine Committee, was a 1990 space policy group requested by Vice President Dan Quayle, chairman of the National Space Council. The objective of the committee was to evaluate the long-term future of NASA and the United States civilian space program. The committee's final report (known as the Augustine Report) recommended that the space program should comprise five activities—space science, Earth science, human spaceflight, space technology and space transportation—with space science as the highest priority for funding. It also proposed an unmanned launch vehicle to replace some Space Shuttle launches, and a scaled-back redesign of space station Freedom.
== Original recommendations ==
In its original report, the committee ranked five space activities in order of priority:
Space science
Technology development
Earth science
Unmanned launch vehicle
Human spaceflight
At a dinner with Vice President Quayle and committee members, Office of Management and Budget director Richard Darman argued that the low priority projects would be eliminated during the budget process. The committee members decided to change their report. Space science was still given first priority, but the other activities were assigned equal priority behind space science.
After discussing the Space Shuttle Challenger disaster the executive summary of the committee's report recommended, "saving the Space Shuttle for those missions requiring human presence."
== Members ==
The committee had twelve members in total, with one chairman and one vice chairman.
Norman Augustine (chairman), CEO of Martin Marietta
Laurel L. Wilkening (vice chairman), provost of the University of Washington
Edward Aldridge, president of the McDonnell Douglas Electronic Systems Company
Joseph Allen, former astronaut and president of Space Industries International
D. James Baker, president of Joint Oceanographic Institutions
Edward Boland, former Massachusetts congressman
Daniel Fink, former senior vice president of General Electric
Don Fuqua, president of the Aerospace Industries Association of America
Robert Herres, former commander of the United States Space Command
David Kearns, chairman of Xerox
Louis Lanzerotti, chairman of the Space Studies Board
Thomas Paine, former NASA administrator
== See also ==
Criticism of the Space Shuttle program
Review of United States Human Space Flight Plans Committee
Space Exploration Initiative
== References ==
== External links ==
Report of the Advisory Committee on the Future of the U.S. Space Program NASA History Division
Principal Recommendations of the Augustine Commission, 1990 NASA Public Affairs Office
|
https://en.wikipedia.org/wiki/Augustine_Committee
|
GOL TV is an American TV sports channel dedicated to soccer owned by GOLTV Inc., based in Coral Gables, Florida. The network broadcasts Portugal Primeira Liga, Liga 1, and Campeonato Uruguay matches.
The network was among the first to start a trend of bilingual broadcasting among networks to serve both English language and Spanish language customers, a strategy since emulated by competitor beIN Sports with their English and Spanish networks and BabyFirst TV. GOL TV maintains one main feed with both English and Spanish language audio and bilingual promotional advertising (though paid programming can vary between English and Spanish and is not cross-translated). Some providers offer the two feeds as separate channels, while others present it as one channel with language selection handled by the viewer at the set-top box through the provider's secondary audio program (SAP) feature.
== Ownership ==
GOL TV is a corporation of Florida, in the United States. As of 2012, Enzo Francescoli was its CEO and managing director.
== Carriage ==
As of January 10, 2024, GOL TV is no longer on Spectrum, and is available on Spanish language packages on DirecTV and AT&T U-verse. As of October 1, 2018, GOL TV is no longer included in Verizon Fios' channel line-up. Cox removed it from the lineup on April 1, 2019.
== Talent ==
All based at Montevideo, Uruguay
In English:
Nino Torres: play-by-play (lead)
Piero Montalvo: play-by-play
Manuel Oyola: play-by-play
Juan Pablo Borges: General Announcer and voice of Portugol, Tu Fútbol Uruguay and GoGoGoal
In Spanish:
Bruno Piñeiro: All Portuguese matches as lead narrator. Also Spanish voice of Tu Fútbol Uruguay
Mauricio Raggiotto: All Portuguese matches as commentator. Also voice of Portugol and GoGoGoal
== Programs ==
=== UEFA ===
Primeira Liga (Portugal)
KNVB Cup
=== CONMEBOL ===
Peruvian Primera División (one or two matches each week, broadcast taken from GOLPERU)
Uruguayan Primera División
=== Other programs ===
Tu Fútbol - A weekly series that provides a recap and highlights of league matches from Uruguay. Tu Fútbol: Uruguay airs on Monday at 7:30 p.m. ET.
Portugol - A weekly series showcasing a full recap and highlights of the Portuguese Primeira Liga. The program airs every Tuesday night starting at 7:30 p.m. ET.
Foot Brazil - A weekly series that provides a recap and highlights of all the games from the São Paulo State Championship and the Brasileirão Serie A, as well as interviews with the biggest stars of Brazilian soccer. It airs on Wednesdays at 7 p.m. and 10 p.m. ET.
The Football Review
Clubland
=== Former programs ===
Campeonato Brasileiro, Campeonato Paulista
Spanish La Liga (2004-2012), Copa del Rey
Dutch Eredivisie
UEFA Europa League
CONCACAF qualifiers for the Gold Cup and FIFA World Cup
Lamar Hunt U.S. Open Cup Final
German Bundesliga
Coppa Italia
Supercoppa Italiana
Ecuadorian Serie A
== GOL TV HD ==
GOL TV HD is a 1080i high definition simulcast of GOL TV that launched on August 1, 2010. Time Warner Cable in New York City added it on August 27, 2010.
== See also ==
GolTV Canada
GOL TV (Latin American)
== References ==
== External links ==
"Gol TV Celebrates First Anniversary"
Official site
Gol TV Canada
Gol TV Latinoamérica
|
https://en.wikipedia.org/wiki/GOL_TV
|
A chrestomathy ( kreh-STOM-ə-thee; from the Ancient Greek χρηστομάθεια khrēstomátheia 'desire of learning', from χρηστός khrēstós 'useful' + μανθάνω manthánō 'learn') is a collection of selected literary passages (usually from a single author); a selection of literary passages from a foreign language assembled for studying the language; or a text in various languages, used especially as an aid in learning a subject.
In philology or in the study of literature, it is a type of reader that presents a sequence of example texts, selected to demonstrate the development of language or literary style. It is different from an anthology because of its didactic purpose.
== Examples ==
Bernhard Dorn, A Chrestomathy of the Pushtū or Afghan language, St. Petersburg: Imperial Academy of Sciences, 1847
H. L. Mencken, A Mencken Chrestomathy: His Own Selection of his Choicest Writing, New York: Alfred P. Knopf, 1949
L. L. Zamenhof, Fundamenta Krestomatio de la Lingvo Esperanto, Paris: Hachette, 1903
Edward Ullendorff, A Tigrinya Chrestomathy, Stuttgart: Steiner Werlag Wiesbaden GmbH, 1985.
Bilingual Greek-Latin Grammar, by Georgios Dimitriou, 1785, that contained personal observations, Epistles and Maxims, as well as biographies of notable men.
Rosetta Code, "a programming chrestomathy site", which "present[s] solutions to the same task in as many different [computer] languages as possible".
The Ibis Chrestomathy, dealing "solely with words that have a claim to naturalization within the English language".
Heather Christle, The Crying Book, Catapult: 2019. Explores the subject of crying and tears in a numbered series of extremely short essays.
== See also ==
Lord's Prayer § Use as a language comparison tool
Parallel text
Text corpus
== References ==
|
https://en.wikipedia.org/wiki/Chrestomathy
|
In mathematics, the floor function is the function that takes as input a real number x, and gives as output the greatest integer less than or equal to x, denoted ⌊x⌋ or floor(x). Similarly, the ceiling function maps x to the least integer greater than or equal to x, denoted ⌈x⌉ or ceil(x).
For example, for floor: ⌊2.4⌋ = 2, ⌊−2.4⌋ = −3, and for ceiling: ⌈2.4⌉ = 3, and ⌈−2.4⌉ = −2.
The floor of x is also called the integral part, integer part, greatest integer, or entier of x, and was historically denoted [x] (among other notations). However, the same term, integer part, is also used for truncation towards zero, which differs from the floor function for negative numbers.
For an integer n, ⌊n⌋ = ⌈n⌉ = n.
Although floor(x + 1) and ceil(x) produce graphs that appear exactly alike, they are not the same when the value of x is an exact integer. For example, when x = 2.0001, ⌊2.0001 + 1⌋ = ⌈2.0001⌉ = 3. However, if x = 2, then ⌊2 + 1⌋ = 3, while ⌈2⌉ = 2.
== Notation ==
The integral part or integer part of a number (partie entière in the original) was first defined in 1798 by Adrien-Marie Legendre in his proof of the Legendre's formula.
Carl Friedrich Gauss introduced the square bracket notation [x] in his third proof of quadratic reciprocity (1808). This remained the standard in mathematics until Kenneth E. Iverson introduced, in his 1962 book A Programming Language, the names "floor" and "ceiling" and the corresponding notations ⌊x⌋ and ⌈x⌉. (Iverson used square brackets for a different purpose, the Iverson bracket notation.) Both notations are now used in mathematics, although Iverson's notation will be followed in this article.
In some sources, boldface or double brackets ⟦x⟧ are used for floor, and reversed brackets ⟧x⟦ or ]x[ for ceiling.
The fractional part is the sawtooth function, denoted by {x} for real x and defined by the formula
{x} = x − ⌊x⌋
For all x,
0 ≤ {x} < 1.
These characters are provided in Unicode:
U+2308 ⌈ LEFT CEILING (⌈, ⌈)
U+2309 ⌉ RIGHT CEILING (⌉, ⌉)
U+230A ⌊ LEFT FLOOR (⌊, ⌊)
U+230B ⌋ RIGHT FLOOR (⌋, ⌋)
In the LaTeX typesetting system, these symbols can be specified with the \lceil, \rceil, \lfloor, and \rfloor commands in math mode. LaTeX has supported UTF-8 since 2018, so the Unicode characters can now be used directly. Larger versions are\left\lceil, \right\rceil, \left\lfloor, and \right\rfloor.
== Definition and properties ==
Given real numbers x and y, integers m and n and the set of integers
Z
{\displaystyle \mathbb {Z} }
, floor and ceiling may be defined by the equations
⌊
x
⌋
=
max
{
m
∈
Z
∣
m
≤
x
}
,
{\displaystyle \lfloor x\rfloor =\max\{m\in \mathbb {Z} \mid m\leq x\},}
⌈
x
⌉
=
min
{
n
∈
Z
∣
n
≥
x
}
.
{\displaystyle \lceil x\rceil =\min\{n\in \mathbb {Z} \mid n\geq x\}.}
Since there is exactly one integer in a half-open interval of length one, for any real number x, there are unique integers m and n satisfying the equation
x
−
1
<
m
≤
x
≤
n
<
x
+
1.
{\displaystyle x-1<m\leq x\leq n<x+1.}
where
⌊
x
⌋
=
m
{\displaystyle \lfloor x\rfloor =m}
and
⌈
x
⌉
=
n
{\displaystyle \lceil x\rceil =n}
may also be taken as the definition of floor and ceiling.
=== Equivalences ===
These formulas can be used to simplify expressions involving floors and ceilings.
⌊
x
⌋
=
m
if and only if
m
≤
x
<
m
+
1
,
⌈
x
⌉
=
n
if and only if
n
−
1
<
x
≤
n
,
⌊
x
⌋
=
m
if and only if
x
−
1
<
m
≤
x
,
⌈
x
⌉
=
n
if and only if
x
≤
n
<
x
+
1.
{\displaystyle {\begin{alignedat}{3}\lfloor x\rfloor &=m\ \ &&{\mbox{ if and only if }}&m&\leq x<m+1,\\\lceil x\rceil &=n&&{\mbox{ if and only if }}&\ \ n-1&<x\leq n,\\\lfloor x\rfloor &=m&&{\mbox{ if and only if }}&x-1&<m\leq x,\\\lceil x\rceil &=n&&{\mbox{ if and only if }}&x&\leq n<x+1.\end{alignedat}}}
In the language of order theory, the floor function is a residuated mapping, that is, part of a Galois connection: it is the upper adjoint of the function that embeds the integers into the reals.
x
<
n
if and only if
⌊
x
⌋
<
n
,
n
<
x
if and only if
n
<
⌈
x
⌉
,
x
≤
n
if and only if
⌈
x
⌉
≤
n
,
n
≤
x
if and only if
n
≤
⌊
x
⌋
.
{\displaystyle {\begin{aligned}x<n&\;\;{\mbox{ if and only if }}&\lfloor x\rfloor &<n,\\n<x&\;\;{\mbox{ if and only if }}&n&<\lceil x\rceil ,\\x\leq n&\;\;{\mbox{ if and only if }}&\lceil x\rceil &\leq n,\\n\leq x&\;\;{\mbox{ if and only if }}&n&\leq \lfloor x\rfloor .\end{aligned}}}
These formulas show how adding an integer n to the arguments affects the functions:
⌊
x
+
n
⌋
=
⌊
x
⌋
+
n
,
⌈
x
+
n
⌉
=
⌈
x
⌉
+
n
,
{
x
+
n
}
=
{
x
}
.
{\displaystyle {\begin{aligned}\lfloor x+n\rfloor &=\lfloor x\rfloor +n,\\\lceil x+n\rceil &=\lceil x\rceil +n,\\\{x+n\}&=\{x\}.\end{aligned}}}
The above are never true if n is not an integer; however, for every x and y, the following inequalities hold:
⌊
x
⌋
+
⌊
y
⌋
≤
⌊
x
+
y
⌋
≤
⌊
x
⌋
+
⌊
y
⌋
+
1
,
⌈
x
⌉
+
⌈
y
⌉
−
1
≤
⌈
x
+
y
⌉
≤
⌈
x
⌉
+
⌈
y
⌉
.
{\displaystyle {\begin{aligned}\lfloor x\rfloor +\lfloor y\rfloor &\leq \lfloor x+y\rfloor \leq \lfloor x\rfloor +\lfloor y\rfloor +1,\\[3mu]\lceil x\rceil +\lceil y\rceil -1&\leq \lceil x+y\rceil \leq \lceil x\rceil +\lceil y\rceil .\end{aligned}}}
=== Monotonicity ===
Both floor and ceiling functions are monotonically non-decreasing functions:
x
1
≤
x
2
⇒
⌊
x
1
⌋
≤
⌊
x
2
⌋
,
x
1
≤
x
2
⇒
⌈
x
1
⌉
≤
⌈
x
2
⌉
.
{\displaystyle {\begin{aligned}x_{1}\leq x_{2}&\Rightarrow \lfloor x_{1}\rfloor \leq \lfloor x_{2}\rfloor ,\\x_{1}\leq x_{2}&\Rightarrow \lceil x_{1}\rceil \leq \lceil x_{2}\rceil .\end{aligned}}}
=== Relations among the functions ===
It is clear from the definitions that
⌊
x
⌋
≤
⌈
x
⌉
,
{\displaystyle \lfloor x\rfloor \leq \lceil x\rceil ,}
with equality if and only if x is an integer, i.e.
⌈
x
⌉
−
⌊
x
⌋
=
{
0
if
x
∈
Z
1
if
x
∉
Z
{\displaystyle \lceil x\rceil -\lfloor x\rfloor ={\begin{cases}0&{\mbox{ if }}x\in \mathbb {Z} \\1&{\mbox{ if }}x\not \in \mathbb {Z} \end{cases}}}
In fact, for integers n, both floor and ceiling functions are the identity:
⌊
n
⌋
=
⌈
n
⌉
=
n
.
{\displaystyle \lfloor n\rfloor =\lceil n\rceil =n.}
Negating the argument switches floor and ceiling and changes the sign:
⌊
x
⌋
+
⌈
−
x
⌉
=
0
−
⌊
x
⌋
=
⌈
−
x
⌉
−
⌈
x
⌉
=
⌊
−
x
⌋
{\displaystyle {\begin{aligned}\lfloor x\rfloor +\lceil -x\rceil &=0\\-\lfloor x\rfloor &=\lceil -x\rceil \\-\lceil x\rceil &=\lfloor -x\rfloor \end{aligned}}}
and:
⌊
x
⌋
+
⌊
−
x
⌋
=
{
0
if
x
∈
Z
−
1
if
x
∉
Z
,
{\displaystyle \lfloor x\rfloor +\lfloor -x\rfloor ={\begin{cases}0&{\text{if }}x\in \mathbb {Z} \\-1&{\text{if }}x\not \in \mathbb {Z} ,\end{cases}}}
⌈
x
⌉
+
⌈
−
x
⌉
=
{
0
if
x
∈
Z
1
if
x
∉
Z
.
{\displaystyle \lceil x\rceil +\lceil -x\rceil ={\begin{cases}0&{\text{if }}x\in \mathbb {Z} \\1&{\text{if }}x\not \in \mathbb {Z} .\end{cases}}}
Negating the argument complements the fractional part:
{
x
}
+
{
−
x
}
=
{
0
if
x
∈
Z
1
if
x
∉
Z
.
{\displaystyle \{x\}+\{-x\}={\begin{cases}0&{\text{if }}x\in \mathbb {Z} \\1&{\text{if }}x\not \in \mathbb {Z} .\end{cases}}}
The floor, ceiling, and fractional part functions are idempotent:
⌊
⌊
x
⌋
⌋
=
⌊
x
⌋
,
⌈
⌈
x
⌉
⌉
=
⌈
x
⌉
,
{
{
x
}
}
=
{
x
}
.
{\displaystyle {\begin{aligned}{\big \lfloor }\lfloor x\rfloor {\big \rfloor }&=\lfloor x\rfloor ,\\{\big \lceil }\lceil x\rceil {\big \rceil }&=\lceil x\rceil ,\\{\big \{}\{x\}{\big \}}&=\{x\}.\end{aligned}}}
The result of nested floor or ceiling functions is the innermost function:
⌊
⌈
x
⌉
⌋
=
⌈
x
⌉
,
⌈
⌊
x
⌋
⌉
=
⌊
x
⌋
{\displaystyle {\begin{aligned}{\big \lfloor }\lceil x\rceil {\big \rfloor }&=\lceil x\rceil ,\\{\big \lceil }\lfloor x\rfloor {\big \rceil }&=\lfloor x\rfloor \end{aligned}}}
due to the identity property for integers.
=== Quotients ===
If m and n are integers and n ≠ 0,
0
≤
{
m
n
}
≤
1
−
1
|
n
|
.
{\displaystyle 0\leq \left\{{\frac {m}{n}}\right\}\leq 1-{\frac {1}{|n|}}.}
If n is positive
⌊
x
+
m
n
⌋
=
⌊
⌊
x
⌋
+
m
n
⌋
,
{\displaystyle \left\lfloor {\frac {x+m}{n}}\right\rfloor =\left\lfloor {\frac {\lfloor x\rfloor +m}{n}}\right\rfloor ,}
⌈
x
+
m
n
⌉
=
⌈
⌈
x
⌉
+
m
n
⌉
.
{\displaystyle \left\lceil {\frac {x+m}{n}}\right\rceil =\left\lceil {\frac {\lceil x\rceil +m}{n}}\right\rceil .}
If m is positive
n
=
⌈
n
1
m
⌉
+
⌈
n
−
1
m
⌉
+
⋯
+
⌈
n
−
m
+
1
m
⌉
,
{\displaystyle n=\left\lceil {\frac {n{\vphantom {1}}}{m}}\right\rceil +\left\lceil {\frac {n-1}{m}}\right\rceil +\dots +\left\lceil {\frac {n-m+1}{m}}\right\rceil ,}
n
=
⌊
n
1
m
⌋
+
⌊
n
+
1
m
⌋
+
⋯
+
⌊
n
+
m
−
1
m
⌋
.
{\displaystyle n=\left\lfloor {\frac {n{\vphantom {1}}}{m}}\right\rfloor +\left\lfloor {\frac {n+1}{m}}\right\rfloor +\dots +\left\lfloor {\frac {n+m-1}{m}}\right\rfloor .}
For m = 2 these imply
n
=
⌊
n
1
2
⌋
+
⌈
n
1
2
⌉
.
{\displaystyle n=\left\lfloor {\frac {n{\vphantom {1}}}{2}}\right\rfloor +\left\lceil {\frac {n{\vphantom {1}}}{2}}\right\rceil .}
More generally, for positive m (See Hermite's identity)
⌈
m
x
⌉
=
⌈
x
⌉
+
⌈
x
−
1
m
⌉
+
⋯
+
⌈
x
−
m
−
1
m
⌉
,
{\displaystyle \lceil mx\rceil =\left\lceil x\right\rceil +\left\lceil x-{\frac {1}{m}}\right\rceil +\dots +\left\lceil x-{\frac {m-1}{m}}\right\rceil ,}
⌊
m
x
⌋
=
⌊
x
⌋
+
⌊
x
+
1
m
⌋
+
⋯
+
⌊
x
+
m
−
1
m
⌋
.
{\displaystyle \lfloor mx\rfloor =\left\lfloor x\right\rfloor +\left\lfloor x+{\frac {1}{m}}\right\rfloor +\dots +\left\lfloor x+{\frac {m-1}{m}}\right\rfloor .}
The following can be used to convert floors to ceilings and vice versa (with m being positive)
⌈
n
1
m
⌉
=
⌊
n
+
m
−
1
m
⌋
=
⌊
n
−
1
m
⌋
+
1
,
{\displaystyle \left\lceil {\frac {n{\vphantom {1}}}{m}}\right\rceil =\left\lfloor {\frac {n+m-1}{m}}\right\rfloor =\left\lfloor {\frac {n-1}{m}}\right\rfloor +1,}
⌊
n
1
m
⌋
=
⌈
n
−
m
+
1
m
⌉
=
⌈
n
+
1
m
⌉
−
1
,
{\displaystyle \left\lfloor {\frac {n{\vphantom {1}}}{m}}\right\rfloor =\left\lceil {\frac {n-m+1}{m}}\right\rceil =\left\lceil {\frac {n+1}{m}}\right\rceil -1,}
For all m and n strictly positive integers:
∑
k
=
1
n
−
1
⌊
k
m
n
⌋
=
(
m
−
1
)
(
n
−
1
)
+
gcd
(
m
,
n
)
−
1
2
,
{\displaystyle \sum _{k=1}^{n-1}\left\lfloor {\frac {km}{n}}\right\rfloor ={\frac {(m-1)(n-1)+\gcd(m,n)-1}{2}},}
which, for positive and coprime m and n, reduces to
∑
k
=
1
n
−
1
⌊
k
m
n
⌋
=
1
2
(
m
−
1
)
(
n
−
1
)
,
{\displaystyle \sum _{k=1}^{n-1}\left\lfloor {\frac {km}{n}}\right\rfloor ={\tfrac {1}{2}}(m-1)(n-1),}
and similarly for the ceiling and fractional part functions (still for positive and coprime m and n),
∑
k
=
1
n
−
1
⌈
k
m
n
⌉
=
1
2
(
m
+
1
)
(
n
−
1
)
,
{\displaystyle \sum _{k=1}^{n-1}\left\lceil {\frac {km}{n}}\right\rceil ={\tfrac {1}{2}}(m+1)(n-1),}
∑
k
=
1
n
−
1
{
k
m
n
}
=
1
2
(
n
−
1
)
.
{\displaystyle \sum _{k=1}^{n-1}\left\{{\frac {km}{n}}\right\}={\tfrac {1}{2}}(n-1).}
Since the right-hand side of the general case is symmetrical in m and n, this implies that
⌊
m
1
n
⌋
+
⌊
2
m
n
⌋
+
⋯
+
⌊
(
n
−
1
)
m
n
⌋
=
⌊
n
1
m
⌋
+
⌊
2
n
m
⌋
+
⋯
+
⌊
(
m
−
1
)
n
m
⌋
.
{\displaystyle \left\lfloor {\frac {m{\vphantom {1}}}{n}}\right\rfloor +\left\lfloor {\frac {2m}{n}}\right\rfloor +\dots +\left\lfloor {\frac {(n-1)m}{n}}\right\rfloor =\left\lfloor {\frac {n{\vphantom {1}}}{m}}\right\rfloor +\left\lfloor {\frac {2n}{m}}\right\rfloor +\dots +\left\lfloor {\frac {(m-1)n}{m}}\right\rfloor .}
More generally, if m and n are positive,
⌊
x
1
n
⌋
+
⌊
m
+
x
n
⌋
+
⌊
2
m
+
x
n
⌋
+
⋯
+
⌊
(
n
−
1
)
m
+
x
n
⌋
=
⌊
x
1
m
⌋
+
⌊
n
+
x
m
⌋
+
⌊
2
n
+
x
m
⌋
+
⋯
+
⌊
(
m
−
1
)
n
+
x
m
⌋
.
{\displaystyle {\begin{aligned}&\left\lfloor {\frac {x{\vphantom {1}}}{n}}\right\rfloor +\left\lfloor {\frac {m+x}{n}}\right\rfloor +\left\lfloor {\frac {2m+x}{n}}\right\rfloor +\dots +\left\lfloor {\frac {(n-1)m+x}{n}}\right\rfloor \\[5mu]=&\left\lfloor {\frac {x{\vphantom {1}}}{m}}\right\rfloor +\left\lfloor {\frac {n+x}{m}}\right\rfloor +\left\lfloor {\frac {2n+x}{m}}\right\rfloor +\cdots +\left\lfloor {\frac {(m-1)n+x}{m}}\right\rfloor .\end{aligned}}}
This is sometimes called a reciprocity law.
Division by positive integers gives rise to an interesting and sometimes useful property. Assuming
m
,
n
>
0
{\displaystyle m,n>0}
,
m
≤
⌊
x
n
⌋
⟺
n
≤
⌊
x
m
⌋
⟺
n
≤
⌊
x
⌋
m
.
{\displaystyle m\leq \left\lfloor {\frac {x}{n}}\right\rfloor \iff n\leq \left\lfloor {\frac {x}{m}}\right\rfloor \iff n\leq {\frac {\lfloor x\rfloor }{m}}.}
Similarly,
m
≥
⌈
x
n
⌉
⟺
n
≥
⌈
x
m
⌉
⟺
n
≥
⌈
x
⌉
m
.
{\displaystyle m\geq \left\lceil {\frac {x}{n}}\right\rceil \iff n\geq \left\lceil {\frac {x}{m}}\right\rceil \iff n\geq {\frac {\lceil x\rceil }{m}}.}
Indeed,
m
≤
⌊
x
n
⌋
⟹
m
≤
x
n
⟹
n
≤
x
m
⟹
n
≤
⌊
x
m
⌋
⟹
…
⟹
m
≤
⌊
x
n
⌋
,
{\displaystyle m\leq \left\lfloor {\frac {x}{n}}\right\rfloor \implies m\leq {\frac {x}{n}}\implies n\leq {\frac {x}{m}}\implies n\leq \left\lfloor {\frac {x}{m}}\right\rfloor \implies \ldots \implies m\leq \left\lfloor {\frac {x}{n}}\right\rfloor ,}
keeping in mind that
⌊
x
n
⌋
=
⌊
⌊
x
⌋
n
⌋
.
{\textstyle \left\lfloor {\frac {x}{n}}\right\rfloor =\left\lfloor {\frac {\lfloor x\rfloor }{n}}\right\rfloor .}
The second equivalence involving the ceiling function can be proved similarly.
=== Nested divisions ===
For a positive integer n, and arbitrary real numbers m and x:
⌊
⌊
x
m
⌋
n
⌋
=
⌊
x
m
n
⌋
⌈
⌈
x
m
⌉
n
⌉
=
⌈
x
m
n
⌉
.
{\displaystyle {\begin{aligned}\left\lfloor {\frac {\left\lfloor {\frac {x}{m}}\right\rfloor }{n}}\right\rfloor &=\left\lfloor {\frac {x}{mn}}\right\rfloor \\[4px]\left\lceil {\frac {\left\lceil {\frac {x}{m}}\right\rceil }{n}}\right\rceil &=\left\lceil {\frac {x}{mn}}\right\rceil .\end{aligned}}}
=== Continuity and series expansions ===
None of the functions discussed in this article are continuous, but all are piecewise linear: the functions
⌊
x
⌋
{\displaystyle \lfloor x\rfloor }
,
⌈
x
⌉
{\displaystyle \lceil x\rceil }
, and
{
x
}
{\displaystyle \{x\}}
have discontinuities at the integers.
⌊
x
⌋
{\displaystyle \lfloor x\rfloor }
is upper semi-continuous and
⌈
x
⌉
{\displaystyle \lceil x\rceil }
and
{
x
}
{\displaystyle \{x\}}
are lower semi-continuous.
Since none of the functions discussed in this article are continuous, none of them have a power series expansion. Since floor and ceiling are not periodic, they do not have uniformly convergent Fourier series expansions. The fractional part function has Fourier series expansion
{
x
}
=
1
2
−
1
π
∑
k
=
1
∞
sin
(
2
π
k
x
)
k
{\displaystyle \{x\}={\frac {1}{2}}-{\frac {1}{\pi }}\sum _{k=1}^{\infty }{\frac {\sin(2\pi kx)}{k}}}
for x not an integer.
At points of discontinuity, a Fourier series converges to a value that is the average of its limits on the left and the right, unlike the floor, ceiling and fractional part functions: for y fixed and x a multiple of y the Fourier series given converges to y/2, rather than to x mod y = 0. At points of continuity the series converges to the true value.
Using the formula
⌊
x
⌋
=
x
−
{
x
}
{\displaystyle \lfloor x\rfloor =x-\{x\}}
gives
⌊
x
⌋
=
x
−
1
2
+
1
π
∑
k
=
1
∞
sin
(
2
π
k
x
)
k
{\displaystyle \lfloor x\rfloor =x-{\frac {1}{2}}+{\frac {1}{\pi }}\sum _{k=1}^{\infty }{\frac {\sin(2\pi kx)}{k}}}
for x not an integer.
== Applications ==
=== Mod operator ===
For an integer x and a positive integer y, the modulo operation, denoted by x mod y, gives the value of the remainder when x is divided by y. This definition can be extended to real x and y, y ≠ 0, by the formula
x
mod
y
=
x
−
y
⌊
x
y
⌋
.
{\displaystyle x{\bmod {y}}=x-y\left\lfloor {\frac {x}{y}}\right\rfloor .}
Then it follows from the definition of floor function that this extended operation satisfies many natural properties. Notably, x mod y is always between 0 and y, i.e.,
if y is positive,
0
≤
x
mod
y
<
y
,
{\displaystyle 0\leq x{\bmod {y}}<y,}
and if y is negative,
0
≥
x
mod
y
>
y
.
{\displaystyle 0\geq x{\bmod {y}}>y.}
=== Quadratic reciprocity ===
Gauss's third proof of quadratic reciprocity, as modified by Eisenstein, has two basic steps.
Let p and q be distinct positive odd prime numbers, and let
m
=
1
2
(
p
−
1
)
,
{\displaystyle m={\tfrac {1}{2}}(p-1),}
n
=
1
2
(
q
−
1
)
.
{\displaystyle n={\tfrac {1}{2}}(q-1).}
First, Gauss's lemma is used to show that the Legendre symbols are given by
(
q
p
)
=
(
−
1
)
⌊
q
p
⌋
+
⌊
2
q
p
⌋
+
⋯
+
⌊
m
q
p
⌋
,
(
p
q
)
=
(
−
1
)
⌊
p
q
⌋
+
⌊
2
p
q
⌋
+
⋯
+
⌊
n
p
q
⌋
.
{\displaystyle {\begin{aligned}\left({\frac {q}{p}}\right)&=(-1)^{\left\lfloor {\frac {q}{p}}\right\rfloor +\left\lfloor {\frac {2q}{p}}\right\rfloor +\dots +\left\lfloor {\frac {mq}{p}}\right\rfloor },\\[5mu]\left({\frac {p}{q}}\right)&=(-1)^{\left\lfloor {\frac {p}{q}}\right\rfloor +\left\lfloor {\frac {2p}{q}}\right\rfloor +\dots +\left\lfloor {\frac {np}{q}}\right\rfloor }.\end{aligned}}}
The second step is to use a geometric argument to show that
⌊
q
p
⌋
+
⌊
2
q
p
⌋
+
⋯
+
⌊
m
q
p
⌋
+
⌊
p
q
⌋
+
⌊
2
p
q
⌋
+
⋯
+
⌊
n
p
q
⌋
=
m
n
.
{\displaystyle \left\lfloor {\frac {q}{p}}\right\rfloor +\left\lfloor {\frac {2q}{p}}\right\rfloor +\dots +\left\lfloor {\frac {mq}{p}}\right\rfloor +\left\lfloor {\frac {p}{q}}\right\rfloor +\left\lfloor {\frac {2p}{q}}\right\rfloor +\dots +\left\lfloor {\frac {np}{q}}\right\rfloor =mn.}
Combining these formulas gives quadratic reciprocity in the form
(
p
q
)
(
q
p
)
=
(
−
1
)
m
n
=
(
−
1
)
p
−
1
2
q
−
1
2
.
{\displaystyle \left({\frac {p}{q}}\right)\left({\frac {q}{p}}\right)=(-1)^{mn}=(-1)^{{\frac {p-1}{2}}{\frac {q-1}{2}}}.}
There are formulas that use floor to express the quadratic character of small numbers mod odd primes p:
(
2
p
)
=
(
−
1
)
⌊
p
+
1
4
⌋
,
(
3
p
)
=
(
−
1
)
⌊
p
+
1
6
⌋
.
{\displaystyle {\begin{aligned}\left({\frac {2}{p}}\right)&=(-1)^{\left\lfloor {\frac {p+1}{4}}\right\rfloor },\\[5mu]\left({\frac {3}{p}}\right)&=(-1)^{\left\lfloor {\frac {p+1}{6}}\right\rfloor }.\end{aligned}}}
=== Rounding ===
For an arbitrary real number
x
{\displaystyle x}
, rounding
x
{\displaystyle x}
to the nearest integer with tie breaking towards positive infinity is given by
rpi
(
x
)
=
⌊
x
+
1
2
⌋
=
⌈
1
2
⌊
2
x
⌋
⌉
;
{\displaystyle {\text{rpi}}(x)=\left\lfloor x+{\tfrac {1}{2}}\right\rfloor =\left\lceil {\tfrac {1}{2}}\lfloor 2x\rfloor \right\rceil ;}
rounding towards negative infinity is given as
rni
(
x
)
=
⌈
x
−
1
2
⌉
=
⌊
1
2
⌈
2
x
⌉
⌋
.
{\displaystyle {\text{rni}}(x)=\left\lceil x-{\tfrac {1}{2}}\right\rceil =\left\lfloor {\tfrac {1}{2}}\lceil 2x\rceil \right\rfloor .}
If tie-breaking is away from 0, then the rounding function is
ri
(
x
)
=
sgn
(
x
)
⌊
|
x
|
+
1
2
⌋
{\displaystyle {\text{ri}}(x)=\operatorname {sgn}(x)\left\lfloor |x|+{\tfrac {1}{2}}\right\rfloor }
(where
sgn
{\displaystyle \operatorname {sgn} }
is the sign function), and rounding towards even can be expressed with the more cumbersome
⌊
x
⌉
=
⌊
x
+
1
2
⌋
+
⌈
1
4
(
2
x
−
1
)
⌉
−
⌊
1
4
(
2
x
−
1
)
⌋
−
1
,
{\displaystyle \lfloor x\rceil =\left\lfloor x+{\tfrac {1}{2}}\right\rfloor +\left\lceil {\tfrac {1}{4}}(2x-1)\right\rceil -\left\lfloor {\tfrac {1}{4}}(2x-1)\right\rfloor -1,}
which is the above expression for rounding towards positive infinity
rpi
(
x
)
{\displaystyle {\text{rpi}}(x)}
minus an integrality indicator for
1
4
(
2
x
−
1
)
{\displaystyle {\tfrac {1}{4}}(2x-1)}
.
Rounding a real number
x
{\displaystyle x}
to the nearest integer value forms a very basic type of quantizer – a uniform one. A typical (mid-tread) uniform quantizer with a quantization step size equal to some value
Δ
{\displaystyle \Delta }
can be expressed as
Q
(
x
)
=
Δ
⋅
⌊
x
Δ
+
1
2
⌋
{\displaystyle Q(x)=\Delta \cdot \left\lfloor {\frac {x}{\Delta }}+{\frac {1}{2}}\right\rfloor }
,
=== Number of digits ===
The number of digits in base b of a positive integer k is
⌊
log
b
k
⌋
+
1
=
⌈
log
b
(
k
+
1
)
⌉
.
{\displaystyle \lfloor \log _{b}{k}\rfloor +1=\lceil \log _{b}{(k+1)}\rceil .}
=== Number of strings without repeated characters ===
The number of possible strings of arbitrary length that doesn't use any character twice is given by
(
n
)
0
+
⋯
+
(
n
)
n
=
⌊
e
n
!
⌋
{\displaystyle (n)_{0}+\cdots +(n)_{n}=\lfloor en!\rfloor }
where:
n > 0 is the number of letters in the alphabet (e.g., 26 in English)
the falling factorial
(
n
)
k
=
n
(
n
−
1
)
⋯
(
n
−
k
+
1
)
{\displaystyle (n)_{k}=n(n-1)\cdots (n-k+1)}
denotes the number of strings of length k that don't use any character twice.
n! denotes the factorial of n
e = 2.718... is Euler's number
For n = 26, this comes out to 1096259850353149530222034277.
=== Factors of factorials ===
Let n be a positive integer and p a positive prime number. The exponent of the highest power of p that divides n! is given by a version of Legendre's formula
⌊
n
p
⌋
+
⌊
n
p
2
⌋
+
⌊
n
p
3
⌋
+
⋯
=
n
−
∑
k
a
k
p
−
1
{\displaystyle \left\lfloor {\frac {n}{p}}\right\rfloor +\left\lfloor {\frac {n}{p^{2}}}\right\rfloor +\left\lfloor {\frac {n}{p^{3}}}\right\rfloor +\dots ={\frac {n-\sum _{k}a_{k}}{p-1}}}
where
n
=
∑
k
a
k
p
k
{\textstyle n=\sum _{k}a_{k}p^{k}}
is the way of writing n in base p. This is a finite sum, since the floors are zero when pk > n.
=== Beatty sequence ===
The Beatty sequence shows how every positive irrational number gives rise to a partition of the natural numbers into two sequences via the floor function.
=== Euler's constant (γ) ===
There are formulas for Euler's constant γ = 0.57721 56649 ... that involve the floor and ceiling, e.g.
γ
=
∫
1
∞
(
1
⌊
x
⌋
−
1
x
)
d
x
,
{\displaystyle \gamma =\int _{1}^{\infty }\left({1 \over \lfloor x\rfloor }-{1 \over x}\right)\,dx,}
γ
=
lim
n
→
∞
1
n
∑
k
=
1
n
(
⌈
n
k
⌉
−
n
k
)
,
{\displaystyle \gamma =\lim _{n\to \infty }{\frac {1}{n}}\sum _{k=1}^{n}\left(\left\lceil {\frac {n}{k}}\right\rceil -{\frac {n}{k}}\right),}
and
γ
=
∑
k
=
2
∞
(
−
1
)
k
⌊
log
2
k
⌋
k
=
1
2
−
1
3
+
2
(
1
4
−
1
5
+
1
6
−
1
7
)
+
3
(
1
8
−
⋯
−
1
15
)
+
⋯
{\displaystyle \gamma =\sum _{k=2}^{\infty }(-1)^{k}{\frac {\left\lfloor \log _{2}k\right\rfloor }{k}}={\tfrac {1}{2}}-{\tfrac {1}{3}}+2\left({\tfrac {1}{4}}-{\tfrac {1}{5}}+{\tfrac {1}{6}}-{\tfrac {1}{7}}\right)+3\left({\tfrac {1}{8}}-\cdots -{\tfrac {1}{15}}\right)+\cdots }
=== Riemann zeta function (ζ) ===
The fractional part function also shows up in integral representations of the Riemann zeta function. It is straightforward to prove (using integration by parts) that if
φ
(
x
)
{\displaystyle \varphi (x)}
is any function with a continuous derivative in the closed interval [a, b],
∑
a
<
n
≤
b
φ
(
n
)
=
∫
a
b
φ
(
x
)
d
x
+
∫
a
b
(
{
x
}
−
1
2
)
φ
′
(
x
)
d
x
+
(
{
a
}
−
1
2
)
φ
(
a
)
−
(
{
b
}
−
1
2
)
φ
(
b
)
.
{\displaystyle \sum _{a<n\leq b}\varphi (n)=\int _{a}^{b}\varphi (x)\,dx+\int _{a}^{b}\left(\{x\}-{\tfrac {1}{2}}\right)\varphi '(x)\,dx+\left(\{a\}-{\tfrac {1}{2}}\right)\varphi (a)-\left(\{b\}-{\tfrac {1}{2}}\right)\varphi (b).}
Letting
φ
(
n
)
=
n
−
s
{\displaystyle \varphi (n)=n^{-s}}
for real part of s greater than 1 and letting a and b be integers, and letting b approach infinity gives
ζ
(
s
)
=
s
∫
1
∞
1
2
−
{
x
}
x
s
+
1
d
x
+
1
s
−
1
+
1
2
.
{\displaystyle \zeta (s)=s\int _{1}^{\infty }{\frac {{\frac {1}{2}}-\{x\}}{x^{s+1}}}\,dx+{\frac {1}{s-1}}+{\frac {1}{2}}.}
This formula is valid for all s with real part greater than −1, (except s = 1, where there is a pole) and combined with the Fourier expansion for {x} can be used to extend the zeta function to the entire complex plane and to prove its functional equation.
For s = σ + it in the critical strip 0 < σ < 1,
ζ
(
s
)
=
s
∫
−
∞
∞
e
−
σ
ω
(
⌊
e
ω
⌋
−
e
ω
)
e
−
i
t
ω
d
ω
.
{\displaystyle \zeta (s)=s\int _{-\infty }^{\infty }e^{-\sigma \omega }(\lfloor e^{\omega }\rfloor -e^{\omega })e^{-it\omega }\,d\omega .}
In 1947 van der Pol used this representation to construct an analogue computer for finding roots of the zeta function.
=== Formulas for prime numbers ===
The floor function appears in several formulas characterizing prime numbers. For example, since
⌊
n
m
⌋
−
⌊
n
−
1
m
⌋
=
{
1
if
m
divides
n
0
otherwise
,
{\displaystyle \left\lfloor {\frac {n}{m}}\right\rfloor -\left\lfloor {\frac {n-1}{m}}\right\rfloor ={\begin{cases}1&{\text{if }}m{\text{ divides }}n\\0&{\text{otherwise}},\end{cases}}}
it follows that a positive integer n is a prime if and only if
∑
m
=
1
∞
(
⌊
n
m
⌋
−
⌊
n
−
1
m
⌋
)
=
2.
{\displaystyle \sum _{m=1}^{\infty }\left(\left\lfloor {\frac {n}{m}}\right\rfloor -\left\lfloor {\frac {n-1}{m}}\right\rfloor \right)=2.}
One may also give formulas for producing the prime numbers. For example, let pn be the n-th prime, and for any integer r > 1, define the real number α by the sum
α
=
∑
m
=
1
∞
p
m
r
−
m
2
.
{\displaystyle \alpha =\sum _{m=1}^{\infty }p_{m}r^{-m^{2}}.}
Then
p
n
=
⌊
r
n
2
α
⌋
−
r
2
n
−
1
⌊
r
(
n
−
1
)
2
α
⌋
.
{\displaystyle p_{n}=\left\lfloor r^{n^{2}}\alpha \right\rfloor -r^{2n-1}\left\lfloor r^{(n-1)^{2}}\alpha \right\rfloor .}
A similar result is that there is a number θ = 1.3064... (Mills' constant) with the property that
⌊
θ
3
⌋
,
⌊
θ
9
⌋
,
⌊
θ
27
⌋
,
…
{\displaystyle \left\lfloor \theta ^{3}\right\rfloor ,\left\lfloor \theta ^{9}\right\rfloor ,\left\lfloor \theta ^{27}\right\rfloor ,\dots }
are all prime.
There is also a number ω = 1.9287800... with the property that
⌊
2
ω
⌋
,
⌊
2
2
ω
⌋
,
⌊
2
2
2
ω
⌋
,
…
{\displaystyle \left\lfloor 2^{\omega }\right\rfloor ,\left\lfloor 2^{2^{\omega }}\right\rfloor ,\left\lfloor 2^{2^{2^{\omega }}}\right\rfloor ,\dots }
are all prime.
Let π(x) be the number of primes less than or equal to x. It is a straightforward deduction from Wilson's theorem that
π
(
n
)
=
∑
j
=
2
n
⌊
(
j
−
1
)
!
+
1
j
−
⌊
(
j
−
1
)
!
j
⌋
⌋
.
{\displaystyle \pi (n)=\sum _{j=2}^{n}{\Biggl \lfloor }{\frac {(j-1)!+1}{j}}-\left\lfloor {\frac {(j-1)!}{j}}\right\rfloor {\Biggr \rfloor }.}
Also, if n ≥ 2,
π
(
n
)
=
∑
j
=
2
n
⌊
1
∑
k
=
2
j
⌊
⌊
j
k
⌋
k
j
⌋
⌋
.
{\displaystyle \pi (n)=\sum _{j=2}^{n}\left\lfloor {\frac {1}{\displaystyle \sum _{k=2}^{j}\left\lfloor \left\lfloor {\frac {j}{k}}\right\rfloor {\frac {k}{j}}\right\rfloor }}\right\rfloor .}
None of the formulas in this section are of any practical use.
=== Solved problems ===
Ramanujan submitted these problems to the Journal of the Indian Mathematical Society.
If n is a positive integer, prove that
⌊
n
3
⌋
+
⌊
n
+
2
6
⌋
+
⌊
n
+
4
6
⌋
=
⌊
n
2
⌋
+
⌊
n
+
3
6
⌋
,
{\displaystyle \left\lfloor {\tfrac {n}{3}}\right\rfloor +\left\lfloor {\tfrac {n+2}{6}}\right\rfloor +\left\lfloor {\tfrac {n+4}{6}}\right\rfloor =\left\lfloor {\tfrac {n}{2}}\right\rfloor +\left\lfloor {\tfrac {n+3}{6}}\right\rfloor ,}
⌊
1
2
+
n
+
1
2
⌋
=
⌊
1
2
+
n
+
1
4
⌋
,
{\displaystyle \left\lfloor {\tfrac {1}{2}}+{\sqrt {n+{\tfrac {1}{2}}}}\right\rfloor =\left\lfloor {\tfrac {1}{2}}+{\sqrt {n+{\tfrac {1}{4}}}}\right\rfloor ,}
⌊
n
+
n
+
1
⌋
=
⌊
4
n
+
2
⌋
.
{\displaystyle \left\lfloor {\sqrt {n}}+{\sqrt {n+1}}\right\rfloor =\left\lfloor {\sqrt {4n+2}}\right\rfloor .}
Some generalizations to the above floor function identities have been proven.
=== Unsolved problem ===
The study of Waring's problem has led to an unsolved problem:
Are there any positive integers k ≥ 6 such that
3
k
−
2
k
⌊
(
3
2
)
k
⌋
>
2
k
−
⌊
(
3
2
)
k
⌋
−
2
?
{\displaystyle 3^{k}-2^{k}{\Bigl \lfloor }{\bigl (}{\tfrac {3}{2}}{\bigr )}^{k}{\Bigr \rfloor }>2^{k}-{\Bigl \lfloor }{\bigl (}{\tfrac {3}{2}}{\bigr )}^{k}{\Bigr \rfloor }-2\ ?}
Mahler has proved there can only be a finite number of such k; none are known.
== Computer implementations ==
In most programming languages, the simplest method to convert a floating point number to an integer does not do floor or ceiling, but truncation. The reason for this is historical, as the first machines used ones' complement and truncation was simpler to implement (floor is simpler in two's complement). FORTRAN was defined to require this behavior and thus almost all processors implement conversion this way. Some consider this to be an unfortunate historical design decision that has led to bugs handling negative offsets and graphics on the negative side of the origin.
An arithmetic right-shift of a signed integer
x
{\displaystyle x}
by
n
{\displaystyle n}
is the same as
⌊
x
2
n
⌋
{\displaystyle \left\lfloor {\tfrac {x}{2^{n}}}\right\rfloor }
. Division by a power of 2 is often written as a right-shift, not for optimization as might be assumed, but because the floor of negative results is required. Assuming such shifts are "premature optimization" and replacing them with division can break software.
Many programming languages (including C, C++, C#, Java,
Julia,
PHP, R, and Python) provide standard functions for floor and ceiling, usually called floor and ceil, or less commonly ceiling. The language APL uses ⌊x for floor. The J Programming Language, a follow-on to APL that is designed to use standard keyboard symbols, uses <. for floor and >. for ceiling.
ALGOL usesentier for floor.
In Microsoft Excel the function INT rounds down rather than toward zero, while FLOOR rounds toward zero, the opposite of what "int" and "floor" do in other languages. Since 2010 FLOOR has been changed to error if the number is negative. The OpenDocument file format, as used by OpenOffice.org, Libreoffice and others, INT and FLOOR both do floor, and FLOOR has a third argument to reproduce Excel's earlier behavior.
== See also ==
Bracket (mathematics)
Integer-valued function
Step function
Modulo operation
== Citations ==
== References ==
J.W.S. Cassels (1957), An introduction to Diophantine approximation, Cambridge Tracts in Mathematics and Mathematical Physics, vol. 45, Cambridge University Press
Crandall, Richard; Pomerance, Carl (2001), Prime Numbers: A Computational Perspective, New York: Springer, ISBN 0-387-94777-9
Graham, Ronald L.; Knuth, Donald E.; Patashnik, Oren (1994), Concrete Mathematics, Reading Ma.: Addison-Wesley, ISBN 0-201-55802-5
Hardy, G. H.; Wright, E. M. (1980), An Introduction to the Theory of Numbers (Fifth edition), Oxford: Oxford University Press, ISBN 978-0-19-853171-5
Nicholas J. Higham, Handbook of writing for the mathematical sciences, SIAM. ISBN 0-89871-420-6, p. 25
ISO/IEC. ISO/IEC 9899::1999(E): Programming languages — C (2nd ed), 1999; Section 6.3.1.4, p. 43.
Iverson, Kenneth E. (1962), A Programming Language, Wiley
Lemmermeyer, Franz (2000), Reciprocity Laws: from Euler to Eisenstein, Berlin: Springer, ISBN 3-540-66957-4
Ramanujan, Srinivasa (2000), Collected Papers, Providence RI: AMS / Chelsea, ISBN 978-0-8218-2076-6
Ribenboim, Paulo (1996), The New Book of Prime Number Records, New York: Springer, ISBN 0-387-94457-5
Michael Sullivan. Precalculus, 8th edition, p. 86
Titchmarsh, Edward Charles; Heath-Brown, David Rodney ("Roger") (1986), The Theory of the Riemann Zeta-function (2nd ed.), Oxford: Oxford U. P., ISBN 0-19-853369-1
== External links ==
"Floor function", Encyclopedia of Mathematics, EMS Press, 2001 [1994]
Štefan Porubský, "Integer rounding functions", Interactive Information Portal for Algorithmic Mathematics, Institute of Computer Science of the Czech Academy of Sciences, Prague, Czech Republic, retrieved 24 October 2008
Weisstein, Eric W. "Floor Function". MathWorld.
Weisstein, Eric W. "Ceiling Function". MathWorld.
|
https://en.wikipedia.org/wiki/Floor_and_ceiling_functions
|
A program is a set of instructions used to control the behavior of a machine. Examples of such programs include:
The sequence of cards used by a Jacquard loom to produce a given pattern within weaved cloth. Invented in 1801, it used holes in punched cards to represent sewing loom arm movements in order to generate decorative patterns automatically.
A computer program (software) is a list of instructions to be executed by a computer.
Barrels, punched cards and music rolls encoding music to be played by player pianos, fairground organs, barrel organs and music boxes.
The automatic flute player, which was invented in the 9th century by the Banū Mūsā brothers in Baghdad, is the first known example of a programmable machine. The work of the Banu Musa was influenced by their Hellenistic forebears, but it also makes significant improvements over Greek creation. The pinned-barrel mechanism, which allowed for programmable variations in the rhythm and melody of the music, was the key contribution given by the Banu Musa. In 1206, the Muslim inventor Al-Jazari (in the Artuqid Sultnate) described a drum machine which may have been an example of a programmable automaton.
The execution of a program is a series of actions following the instructions it contains. Each instruction produces effects that alter the state of the machine according to its predefined meaning.
While some machines are called programmable, for example a programmable thermostat or a musical synthesizer, they are in fact just devices which allow their users to select among a fixed set of a variety of options, rather than being controlled by programs written in a language (be it textual, visual or otherwise).
== References ==
|
https://en.wikipedia.org/wiki/Program_(machine)
|
Numerical analysis is the study of algorithms that use numerical approximation (as opposed to symbolic manipulations) for the problems of mathematical analysis (as distinguished from discrete mathematics). It is the study of numerical methods that attempt to find approximate solutions of problems rather than the exact ones. Numerical analysis finds application in all fields of engineering and the physical sciences, and in the 21st century also the life and social sciences like economics, medicine, business and even the arts. Current growth in computing power has enabled the use of more complex numerical analysis, providing detailed and realistic mathematical models in science and engineering. Examples of numerical analysis include: ordinary differential equations as found in celestial mechanics (predicting the motions of planets, stars and galaxies), numerical linear algebra in data analysis, and stochastic differential equations and Markov chains for simulating living cells in medicine and biology.
Before modern computers, numerical methods often relied on hand interpolation formulas, using data from large printed tables. Since the mid-20th century, computers calculate the required functions instead, but many of the same formulas continue to be used in software algorithms.
The numerical point of view goes back to the earliest mathematical writings. A tablet from the Yale Babylonian Collection (YBC 7289), gives a sexagesimal numerical approximation of the square root of 2, the length of the diagonal in a unit square.
Numerical analysis continues this long tradition: rather than giving exact symbolic answers translated into digits and applicable only to real-world measurements, approximate solutions within specified error bounds are used.
== Applications ==
The overall goal of the field of numerical analysis is the design and analysis of techniques to give approximate but accurate solutions to a wide variety of hard problems, many of which are infeasible to solve symbolically:
Advanced numerical methods are essential in making numerical weather prediction feasible.
Computing the trajectory of a spacecraft requires the accurate numerical solution of a system of ordinary differential equations.
Car companies can improve the crash safety of their vehicles by using computer simulations of car crashes. Such simulations essentially consist of solving partial differential equations numerically.
In the financial field, (private investment funds) and other financial institutions use quantitative finance tools from numerical analysis to attempt to calculate the value of stocks and derivatives more precisely than other market participants.
Airlines use sophisticated optimization algorithms to decide ticket prices, airplane and crew assignments and fuel needs. Historically, such algorithms were developed within the overlapping field of operations research.
Insurance companies use numerical programs for actuarial analysis.
== History ==
The field of numerical analysis predates the invention of modern computers by many centuries. Linear interpolation was already in use more than 2000 years ago. Many great mathematicians of the past were preoccupied by numerical analysis, as is obvious from the names of important algorithms like Newton's method, Lagrange interpolation polynomial, Gaussian elimination, or Euler's method. The origins of modern numerical analysis are often linked to a 1947 paper by John von Neumann and Herman Goldstine,
but others consider modern numerical analysis to go back to work by E. T. Whittaker in 1912.
To facilitate computations by hand, large books were produced with formulas and tables of data such as interpolation points and function coefficients. Using these tables, often calculated out to 16 decimal places or more for some functions, one could look up values to plug into the formulas given and achieve very good numerical estimates of some functions. The canonical work in the field is the NIST publication edited by Abramowitz and Stegun, a 1000-plus page book of a very large number of commonly used formulas and functions and their values at many points. The function values are no longer very useful when a computer is available, but the large listing of formulas can still be very handy.
The mechanical calculator was also developed as a tool for hand computation. These calculators evolved into electronic computers in the 1940s, and it was then found that these computers were also useful for administrative purposes. But the invention of the computer also influenced the field of numerical analysis, since now longer and more complicated calculations could be done.
The Leslie Fox Prize for Numerical Analysis was initiated in 1985 by the Institute of Mathematics and its Applications.
== Key concepts ==
=== Direct and iterative methods ===
Direct methods compute the solution to a problem in a finite number of steps. These methods would give the precise answer if they were performed in infinite precision arithmetic. Examples include Gaussian elimination, the QR factorization method for solving systems of linear equations, and the simplex method of linear programming. In practice, finite precision is used and the result is an approximation of the true solution (assuming stability).
In contrast to direct methods, iterative methods are not expected to terminate in a finite number of steps, even if infinite precision were possible. Starting from an initial guess, iterative methods form successive approximations that converge to the exact solution only in the limit. A convergence test, often involving the residual, is specified in order to decide when a sufficiently accurate solution has (hopefully) been found. Even using infinite precision arithmetic these methods would not reach the solution within a finite number of steps (in general). Examples include Newton's method, the bisection method, and Jacobi iteration. In computational matrix algebra, iterative methods are generally needed for large problems.
Iterative methods are more common than direct methods in numerical analysis. Some methods are direct in principle but are usually used as though they were not, e.g. GMRES and the conjugate gradient method. For these methods the number of steps needed to obtain the exact solution is so large that an approximation is accepted in the same manner as for an iterative method.
As an example, consider the problem of solving
3x3 + 4 = 28
for the unknown quantity x.
For the iterative method, apply the bisection method to f(x) = 3x3 − 24. The initial values are a = 0, b = 3, f(a) = −24, f(b) = 57.
From this table it can be concluded that the solution is between 1.875 and 2.0625. The algorithm might return any number in that range with an error less than 0.2.
=== Conditioning ===
Ill-conditioned problem: Take the function f(x) = 1/(x − 1). Note that f(1.1) = 10 and f(1.001) = 1000: a change in x of less than 0.1 turns into a change in f(x) of nearly 1000. Evaluating f(x) near x = 1 is an ill-conditioned problem.
Well-conditioned problem: By contrast, evaluating the same function f(x) = 1/(x − 1) near x = 10 is a well-conditioned problem. For instance, f(10) = 1/9 ≈ 0.111 and f(11) = 0.1: a modest change in x leads to a modest change in f(x).
=== Discretization ===
Furthermore, continuous problems must sometimes be replaced by a discrete problem whose solution is known to approximate that of the continuous problem; this process is called 'discretization'. For example, the solution of a differential equation is a function. This function must be represented by a finite amount of data, for instance by its value at a finite number of points at its domain, even though this domain is a continuum.
== Generation and propagation of errors ==
The study of errors forms an important part of numerical analysis. There are several ways in which error can be introduced in the solution of the problem.
=== Round-off ===
Round-off errors arise because it is impossible to represent all real numbers exactly on a machine with finite memory (which is what all practical digital computers are).
=== Truncation and discretization error ===
Truncation errors are committed when an iterative method is terminated or a mathematical procedure is approximated and the approximate solution differs from the exact solution. Similarly, discretization induces a discretization error because the solution of the discrete problem does not coincide with the solution of the continuous problem. In the example above to compute the solution of
3
x
3
+
4
=
28
{\displaystyle 3x^{3}+4=28}
, after ten iterations, the calculated root is roughly 1.99. Therefore, the truncation error is roughly 0.01.
Once an error is generated, it propagates through the calculation. For example, the operation + on a computer is inexact. A calculation of the type
a
+
b
+
c
+
d
+
e
{\displaystyle a+b+c+d+e}
is even more inexact.
A truncation error is created when a mathematical procedure is approximated. To integrate a function exactly, an infinite sum of regions must be found, but numerically only a finite sum of regions can be found, and hence the approximation of the exact solution. Similarly, to differentiate a function, the differential element approaches zero, but numerically only a nonzero value of the differential element can be chosen.
=== Numerical stability and well-posed problems ===
An algorithm is called numerically stable if an error, whatever its cause, does not grow to be much larger during the calculation. This happens if the problem is well-conditioned, meaning that the solution changes by only a small amount if the problem data are changed by a small amount. To the contrary, if a problem is 'ill-conditioned', then any small error in the data will grow to be a large error.
Both the original problem and the algorithm used to solve that problem can be well-conditioned or ill-conditioned, and any combination is possible.
So an algorithm that solves a well-conditioned problem may be either numerically stable or numerically unstable. An art of numerical analysis is to find a stable algorithm for solving a well-posed mathematical problem.
== Areas of study ==
The field of numerical analysis includes many sub-disciplines. Some of the major ones are:
=== Computing values of functions ===
One of the simplest problems is the evaluation of a function at a given point. The most straightforward approach, of just plugging in the number in the formula is sometimes not very efficient. For polynomials, a better approach is using the Horner scheme, since it reduces the necessary number of multiplications and additions. Generally, it is important to estimate and control round-off errors arising from the use of floating-point arithmetic.
=== Interpolation, extrapolation, and regression ===
Interpolation solves the following problem: given the value of some unknown function at a number of points, what value does that function have at some other point between the given points?
Extrapolation is very similar to interpolation, except that now the value of the unknown function at a point which is outside the given points must be found.
Regression is also similar, but it takes into account that the data are imprecise. Given some points, and a measurement of the value of some function at these points (with an error), the unknown function can be found. The least squares-method is one way to achieve this.
=== Solving equations and systems of equations ===
Another fundamental problem is computing the solution of some given equation. Two cases are commonly distinguished, depending on whether the equation is linear or not. For instance, the equation
2
x
+
5
=
3
{\displaystyle 2x+5=3}
is linear while
2
x
2
+
5
=
3
{\displaystyle 2x^{2}+5=3}
is not.
Much effort has been put in the development of methods for solving systems of linear equations. Standard direct methods, i.e., methods that use some matrix decomposition are Gaussian elimination, LU decomposition, Cholesky decomposition for symmetric (or hermitian) and positive-definite matrix, and QR decomposition for non-square matrices. Iterative methods such as the Jacobi method, Gauss–Seidel method, successive over-relaxation and conjugate gradient method are usually preferred for large systems. General iterative methods can be developed using a matrix splitting.
Root-finding algorithms are used to solve nonlinear equations (they are so named since a root of a function is an argument for which the function yields zero). If the function is differentiable and the derivative is known, then Newton's method is a popular choice. Linearization is another technique for solving nonlinear equations.
=== Solving eigenvalue or singular value problems ===
Several important problems can be phrased in terms of eigenvalue decompositions or singular value decompositions. For instance, the spectral image compression algorithm is based on the singular value decomposition. The corresponding tool in statistics is called principal component analysis.
=== Optimization ===
Optimization problems ask for the point at which a given function is maximized (or minimized). Often, the point also has to satisfy some constraints.
The field of optimization is further split in several subfields, depending on the form of the objective function and the constraint. For instance, linear programming deals with the case that both the objective function and the constraints are linear. A famous method in linear programming is the simplex method.
The method of Lagrange multipliers can be used to reduce optimization problems with constraints to unconstrained optimization problems.
=== Evaluating integrals ===
Numerical integration, in some instances also known as numerical quadrature, asks for the value of a definite integral. Popular methods use one of the Newton–Cotes formulas (like the midpoint rule or Simpson's rule) or Gaussian quadrature. These methods rely on a "divide and conquer" strategy, whereby an integral on a relatively large set is broken down into integrals on smaller sets. In higher dimensions, where these methods become prohibitively expensive in terms of computational effort, one may use Monte Carlo or quasi-Monte Carlo methods (see Monte Carlo integration), or, in modestly large dimensions, the method of sparse grids.
=== Differential equations ===
Numerical analysis is also concerned with computing (in an approximate way) the solution of differential equations, both ordinary differential equations and partial differential equations.
Partial differential equations are solved by first discretizing the equation, bringing it into a finite-dimensional subspace. This can be done by a finite element method, a finite difference method, or (particularly in engineering) a finite volume method. The theoretical justification of these methods often involves theorems from functional analysis. This reduces the problem to the solution of an algebraic equation.
== Software ==
Since the late twentieth century, most algorithms are implemented in a variety of programming languages. The Netlib repository contains various collections of software routines for numerical problems, mostly in Fortran and C. Commercial products implementing many different numerical algorithms include the IMSL and NAG libraries; a free-software alternative is the GNU Scientific Library.
Over the years the Royal Statistical Society published numerous algorithms in its Applied Statistics (code for these "AS" functions is here);
ACM similarly, in its Transactions on Mathematical Software ("TOMS" code is here).
The Naval Surface Warfare Center several times published its Library of Mathematics Subroutines (code here).
There are several popular numerical computing applications such as MATLAB, TK Solver, S-PLUS, and IDL as well as free and open-source alternatives such as FreeMat, Scilab, GNU Octave (similar to Matlab), and IT++ (a C++ library). There are also programming languages such as R (similar to S-PLUS), Julia, and Python with libraries such as NumPy, SciPy and SymPy. Performance varies widely: while vector and matrix operations are usually fast, scalar loops may vary in speed by more than an order of magnitude.
Many computer algebra systems such as Mathematica also benefit from the availability of arbitrary-precision arithmetic which can provide more accurate results.
Also, any spreadsheet software can be used to solve simple problems relating to numerical analysis.
Excel, for example, has hundreds of available functions, including for matrices, which may be used in conjunction with its built in "solver".
== See also ==
== Notes ==
== References ==
=== Citations ===
=== Sources ===
== External links ==
=== Journals ===
Numerische Mathematik, volumes 1–..., Springer, 1959–
volumes 1–66, 1959–1994 (searchable; pages are images). (in English and German)
Journal on Numerical Analysis (SINUM), volumes 1–..., SIAM, 1964–
=== Online texts ===
"Numerical analysis", Encyclopedia of Mathematics, EMS Press, 2001 [1994]
Numerical Recipes, William H. Press (free, downloadable previous editions)
First Steps in Numerical Analysis (archived), R.J.Hosking, S.Joe, D.C.Joyce, and J.C.Turner
CSEP (Computational Science Education Project), U.S. Department of Energy (archived 2017-08-01)
Numerical Methods, ch 3. in the Digital Library of Mathematical Functions
Numerical Interpolation, Differentiation and Integration, ch 25. in the Handbook of Mathematical Functions (Abramowitz and Stegun)
Tobin A. Driscoll and Richard J. Braun: Fundamentals of Numerical Computation (free online version)
=== Online course material ===
Numerical Methods (Archived 28 July 2009 at the Wayback Machine), Stuart Dalziel University of Cambridge
Lectures on Numerical Analysis, Dennis Deturck and Herbert S. Wilf University of Pennsylvania
Numerical methods, John D. Fenton University of Karlsruhe
Numerical Methods for Physicists, Anthony O’Hare Oxford University
Lectures in Numerical Analysis (archived), R. Radok Mahidol University
Introduction to Numerical Analysis for Engineering, Henrik Schmidt Massachusetts Institute of Technology
Numerical Analysis for Engineering, D. W. Harder University of Waterloo
Introduction to Numerical Analysis, Doron Levy University of Maryland
Numerical Analysis - Numerical Methods (archived), John H. Mathews California State University Fullerton
|
https://en.wikipedia.org/wiki/Numerical_analysis
|
Oberon is a general-purpose programming language first published in 1987 by Niklaus Wirth and the latest member of the Wirthian family of ALGOL-like languages (Euler, ALGOL W, Pascal, Modula, and Modula-2). Oberon was the result of a concentrated effort to increase the power of Modula-2, the direct successor of Pascal, and simultaneously to reduce its complexity. Its principal new feature is the concept of data type extension of record types. It permits constructing new data types on the basis of existing ones and to relate them, deviating from the dogma of strict static typing of data. Type extension is Wirth's way of inheritance reflecting the viewpoint of the parent site. Oberon was developed as part of the implementation of an operating system, also named Oberon at ETH Zurich in Switzerland. The name was inspired both by the Voyager space probe's pictures of the moon of the planet Uranus, named Oberon, and because Oberon is famous as the king of the elves.
Oberon was maintained by Wirth and the latest Project Oberon compiler update is dated 6 March 2020.
== Design ==
Oberon is designed with a motto attributed to Albert Einstein in mind: "Make things as simple as possible, but not simpler." The principal guideline was to concentrate on features that are basic and essential and to omit ephemeral issues. Another factor was recognition of the growth of complexity in languages such as C++ and Ada. In contrast to these, Oberon emphasizes the use of the library concept to extend the language. Enumeration and subrange types, which were present in Modula-2, were omitted, and set types are limited to sets of integers. All imported items must be qualified by the name of the module where they are declared. Low-level facilities are highlighted by only allowing them to be used in a module which includes the identifier SYSTEM in its import list. Strict type checking, even across modules, and index checking at runtime, null pointer checking, and the safe type extension concept largely allow programming to rely on the language rules alone.
The intent of this strategy was to produce a language that is easier to learn, simpler to implement, and very efficient. Oberon compilers have been viewed as compact and fast, while providing code quality comparable to commercial compilers.
== Characteristics ==
Features characterizing the Oberon language include:
Case sensitive syntax with uppercase keywords
Type-extension with type test
Modules and separate compiling
String operations
Isolating unsafe code
Support for system programming
== Object orientation ==
Oberon supports extension of record types for the construction of abstractions and heterogeneous structures. In contrast to the later dialects, Oberon-2 and Active Oberon, the original Oberon lacks a dispatch mechanism as a language feature but has it as a programming technique or design pattern. This gives great flexibility in OOP. In the Oberon operating system, two programming techniques are used together for the dispatch call: Method suite and Message handler.
=== Method suite ===
In this technique, a table of procedure variables is defined and a global variable of this type is declared in the extended module and assigned back in the generic module:
MODULE Figures; (* Abstract module *)
TYPE
Figure* = POINTER TO FigureDesc;
Interface* = POINTER TO InterfaceDesc;
InterfaceDesc* = RECORD
draw* : PROCEDURE (f : Figure);
clear* : PROCEDURE (f : Figure);
mark* : PROCEDURE (f : Figure);
move* : PROCEDURE (f : Figure; dx, dy : INTEGER);
END;
FigureDesc* = RECORD
if : Interface;
END;
PROCEDURE Init* (f : Figure; if : Interface);
BEGIN
f.if := if
END Init;
PROCEDURE Draw* (f : Figure);
BEGIN
f.if.draw(f)
END Draw;
(* Other procedures here *)
END Figures.
We extend the generic type Figure to a specific shape:
MODULE Rectangles;
IMPORT Figures;
TYPE
Rectangle* = POINTER TO RectangleDesc;
RectangleDesc* = RECORD
(Figures.FigureDesc)
x, y, w, h : INTEGER;
END;
VAR
if : Figures.Interface;
PROCEDURE New* (VAR r : Rectangle);
BEGIN
NEW(r);
Figures.Init(r, if)
END New;
PROCEDURE Draw* (f : Figure);
VAR
r : Rectangle;
BEGIN
r := f(Rectangle); (* f AS Rectangle *)
(* ... *)
END Draw;
(* Other procedures here *)
BEGIN (* Module initialisation *)
NEW(if);
if.draw := Draw;
if.clear := Clear;
if.mark := Mark;
if.move := Move
END Rectangles.
Dynamic dispatch is only done via procedures in Figures module that is the generic module.
=== Message handler ===
This technique consists of replacing the set of methods with a single procedure, which discriminates among the various methods:
MODULE Figures; (* Abstract module *)
TYPE
Figure* = POINTER TO FigureDesc;
Message* = RECORD END;
DrawMsg* = RECORD (Message) END;
ClearMsg* = RECORD (Message) END;
MarkMsg* = RECORD (Message) END;
MoveMsg* = RECORD (Message) dx*, dy* : INTEGER END;
Handler* = PROCEDURE (f : Figure; VAR msg : Message);
FigureDesc* = RECORD
(* Abstract *)
handle : Handler;
END;
PROCEDURE Handle* (f : Figure; VAR msg : Message);
BEGIN
f.handle(f, msg)
END Handle;
PROCEDURE Init* (f : Figure; handle : Handler);
BEGIN
f.handle := handle
END Init;
END Figures.
We extend the generic type Figure to a specific shape:
MODULE Rectangles;
IMPORT Figures;
TYPE
Rectangle* = POINTER TO RectangleDesc;
RectangleDesc* = RECORD
(Figures.FigureDesc)
x, y, w, h : INTEGER;
END;
PROCEDURE Draw* (r : Rectangle);
BEGIN
(* ... *)
END Draw;
(* Other procedures here *)
PROCEDURE Handle* (f: Figure; VAR msg: Figures.Message);
VAR
r : Rectangle;
BEGIN
r := f(Rectangle);
IF msg IS Figures.DrawMsg THEN Draw(r)
ELSIF msg IS Figures.MarkMsg THEN Mark(r)
ELSIF msg IS Figures.MoveMsg THEN Move(r, msg(Figures.MoveMsg).dx, msg(Figures.MoveMsg).dy)
ELSE (* ignore *)
END
END Handle;
PROCEDURE New* (VAR r : Rectangle);
BEGIN
NEW(r);
Figures.Init(r, Handle)
END New;
END Rectangles.
In the Oberon operating system both of these techniques are used for dynamic dispatch. The first one is used for a known set of methods; the second is used for any new methods declared in the extension module. For example, if the extension module Rectangles were to implement a new Rotate() procedure, within the Figures module it could only be called via a message handler.
== Implementations and variants ==
=== Oberon ===
No-cost implementations of Oberon (the language) and Oberon (the operating system) can be found on the Internet (several are from ETHZ itself).
=== Oberon-2 ===
A few changes were made to the first released specification. For example, object-oriented programming (OOP) features were added, the FOR loop was reinstated. The result was Oberon-2. One release, named Native Oberon which includes an operating system, and can directly boot on IBM PC compatible class hardware. A .NET implementation of Oberon with some added minor .NET-related extensions was also developed at ETHZ. In 1993, an ETHZ university spin-off company brought a dialect of Oberon-2 to the market named Oberon-L. In 1997, it was renamed Component Pascal.
Oberon-2 compilers developed by ETH include versions for Microsoft Windows, Linux, Solaris, and classic Mac OS. Implementations from other sources exist for some other operating systems, including Atari TOS and AmigaOS.
There is an Oberon-2 Lex scanner and Yacc parser by Stephen J Bevan of Manchester University, UK, based on the one in the Mössenböck and Wirth reference. It is at version 1.4.
Other compilers include Oxford Oberon-2, which also understands Oberon-07, and Vishap Oberon. The latter is based on Josef Templ's Oberon to C language source-to-source compiler (transpiler) named Ofront, which in turn is based on the OP2 Compiler developed by Regis Crelier at ETHZ.
=== Oberon-07 ===
Oberon-07, defined by Niklaus Wirth in 2007 and revised in 2008, 2011, 2013, 2014, 2015, and 2016 is based on the original version of Oberon rather than Oberon-2. The main changes are: explicit numeric conversion functions (e.g., FLOOR and FLT) must be used; the WITH, LOOP and EXIT statements were omitted; WHILE statements were extended; CASE statements can be used for type extension tests; RETURN statements can only be connected to the end of a function; imported variables and structured value parameters are read-only; and, arrays can be assigned without using COPY.
Oberon-07 compilers have been developed for use with many different computer systems. Wirth's compiler targets a reduced instruction set computer (RISC) processor of his own design that was used to implement the 2013 version of the Project Oberon operating system on a Xilinx field-programmable gate array (FPGA) Spartan-3 board. Ports of the RISC processor to FPGA Spartan-6, Spartan-7, Artix-7 and a RISC emulator for Windows (compilable on Linux and macOS, and binaries available for Windows) also exist. OBNC compiles via C and can be used on any Portable Operating System Interface (POSIX) compatible operating system. The commercial Astrobe implementation targets STM ARM Cortex-M0, M3, M4, M7 and Raspberry Pi RP2040 and RP2350 microcontrollers. The Patchouli compiler produces 64-bit Windows binaries. Oberon-07M produces 32-bit Windows binaries and implements revision 2008 of the language. Akron's produces binaries for both Windows and Linux. OberonJS translates Oberon to JavaScript. There is online IDE for Oberon. oberonc is an implementation for the Java virtual machine.
=== Active Oberon ===
Active Oberon is yet another variant of Oberon, which adds objects (with object-centered access protection and local activity control), system-guarded assertions, preemptive priority scheduling and a changed syntax for methods (named type-bound procedures in Oberon vocabulary). Objects may be active, which means that they may be threads or processes. Further, Active Oberon has a way to implement operators (including overloading), an advanced syntax for using arrays (see OberonX language extensions and Proceedings of the 7th Joint Modular Languages Conference 2006 Oxford, UK), and knows about namespaces. The operating system A2 (formerly Active Object System (AOS), then Bluebottle), especially the kernel, synchronizes and coordinates different active objects.
ETHZ has released Active Oberon which supports active objects, and the operating systems based thereon (Active Object System (AOS), Bluebottle, A2), and environment (JDK, HTTP, FTP, etc.) for the language. As with many prior designs from ETHZ, versions of both are available for download on the Internet. As of 2003, supported central processing units (CPUs) include single and dual core x86, and StrongARM.
=== Related languages ===
Development continued on languages in this family. A further extension of Oberon-2 was originally named Oberon/L but later renamed to Component Pascal (CP). CP was developed for Windows and classic Mac OS by Oberon microsystems, a commercial spin-off company from ETHZ, and for .NET by Queensland University of Technology. Further, the languages Lagoona and Obliq carry Oberon methods into specialized areas.
Later .NET development efforts at ETHZ focused on a new language named Zonnon. This includes the features of Oberon and restores some from Pascal (enumerated types, built-in IO) but has some syntactic differences. Other features include support for active objects, operator overloading, and exception handling.
Oberon-V (originally named Seneca, after Seneca the Younger) is a descendant of Oberon designed for numerical applications on supercomputers, especially vector or pipelined architectures. It includes array constructors and an ALL statement.
== See also ==
Oberon (operating system)
A2 (operating system)
Oberon on Wikibooks
== Resources ==
=== General ===
Official website (latest available copy at archive org) at ETH-Zürich
Niklaus Wirth's Oberon Page at ETH-Zürich
Oberon Page at SSW, Linz
Oberon: The Programming Language at Ulm
Project Oberon, The Design of an Operating System and a Compiler, book in PDF by Niklaus Wirth and Jürg Gutknecht, 2005 Edition
Oberon Language Genealogy
Astrobe ARM Oberon-07 Development System
Oberon System V4 for HP OpenVMS Alpha with source code upward-compatible 64 bit addressing
64 bit Oberon-2 compiler for OpenVMS Alpha
Oxford Oberon-2 Compiler and its User Manual
Free Oberon-07 IDE Free Oberon-07 IDE for Windows, Macintosh, and Linux with syntax colouring, semantic navigation and source code debugger
Oberon article by Joseph Templ in the January 1994 issue of Dr.Dobbs
=== Evolution of Oberon ===
Modula-2 and Oberon Wirth (2005)
The Programming Language Oberon Wirth, (1988/90)
The Programming Language Oberon (Oberon-7, Revised Oberon) Wirth, (2016, most current language report)
Differences between Oberon-07 and Oberon Wirth (2011)
The Programming Language Oberon-2 H. Mössenböck, N. Wirth, Institut für Computersysteme, ETH Zürich, January 1992
Differences between Oberon and Oberon-2 Mössenböck and Wirth (1991)
What's New in Component Pascal (Changes from Oberon-2 to CP), Pfister (2001)
== References ==
|
https://en.wikipedia.org/wiki/Oberon_(programming_language)
|
Euclid is an imperative programming language for writing verifiable programs. It was designed in the mid-1970s by Butler Lampson and James G. Mitchell at the Xerox PARC lab in collaboration with Jim Horning at the University of Toronto, Ralph L. London at USC ISI and Gerald J. Popek at UCLA. The implementation was led by Ric Holt at the University of Toronto and James Cordy was the principal programmer for the first implementation of the compiler. It was originally designed for the Motorola 6809 microprocessor. It was considered innovative for the time; the compiler development team had a $2 million budget over 2 years and was commissioned by the Defense Advanced Research Projects Agency of the U.S. Department of Defense and the Canadian Department of National Defence. It was used for a few years at I. P. Sharp Associates, MITRE Corporation, SRI International and various other international institutes for research in systems programming and secure software systems.
Euclid is descended from Pascal, Mesa, Alphard, CLU, Gypsy, BCPL, Modula, LIS, and SUE. Functions in Euclid are closed scopes, may not have side effects, and must explicitly declare imports. Euclid also disallows gotos, floating point numbers, global assignments, nested functions and aliases, and none of the actual parameters to a function can refer to the same memory cell (which Euclid calls a "variable"). Euclid implements modules as types. Descendants of Euclid include the Concurrent Euclid programming language and the Turing programming language.
== External links ==
B.W. Lampson, J.J. Horning, R.L. London, J.G. Mitchell and G.J. Popek 1977. Report on the programming language Euclid. SIGPLAN Notices 12, 2 (February 1977), 1-79.
R.C. Holt, D.B. Wortman, J.R. Cordy and D.R. Crowe 1978. The Euclid Language: a progress report. In Proceedings of the 1978 Annual Conference (Washington, D.C., United States, December 04 - 06, 1978), 111-115.
D.B. Wortman and J.R. Cordy 1981. Early experiences with Euclid. In Proc. 5th international Conference on Software Engineering (San Diego, California, United States, March 09 - 12, 1981), 27-32.
|
https://en.wikipedia.org/wiki/Euclid_(programming_language)
|
Apache Pig
is a high-level platform for creating programs that run on Apache Hadoop. The language for this platform is called Pig Latin. Pig can execute its Hadoop jobs in MapReduce, Apache Tez, or Apache Spark. Pig Latin abstracts the programming from the Java MapReduce idiom into a notation which makes MapReduce programming high level, similar to that of SQL for relational database management systems. Pig Latin can be extended using user-defined functions (UDFs) which the user can write in Java, Python, JavaScript, Ruby or Groovy and then call directly from the language.
== History ==
Apache Pig was originally developed at Yahoo Research around 2006 for researchers to have an ad hoc way of creating and executing MapReduce jobs on very large data sets. In 2007, it was moved into the Apache Software Foundation.
=== Naming ===
Regarding the naming of the Pig programming language, the name was chosen arbitrarily and stuck because it was memorable, easy to spell, and for novelty.
The story goes that the researchers working on the project initially referred to it simply as 'the language'. Eventually they needed to call it something. Off the top of his head, one researcher suggested Pig, and the name stuck. It is quirky yet memorable and easy to spell. While some have hinted that the name sounds coy or silly, it has provided us with an entertaining nomenclature, such as Pig Latin for the language, Grunt for the shell, and PiggyBank for the CPAN-like shared repository.
== Example ==
Below is an example of a "Word Count" program in Pig Latin:
The above program will generate parallel executable tasks which can be distributed across multiple machines in a Hadoop cluster to count the number of words in a dataset such as all the webpages on the internet.
== Pig vs SQL ==
In comparison to SQL, Pig
has a nested relational model,
uses lazy evaluation,
uses extract, transform, load (ETL),
is able to store data at any point during a pipeline,
declares execution plans,
supports pipeline splits, thus allowing workflows to proceed along DAGs instead of strictly sequential pipelines.
On the other hand, it has been argued DBMSs are substantially faster than the MapReduce system once the data is loaded, but that loading the data takes considerably longer in the database systems. It has also been argued RDBMSs offer out of the box support for column-storage, working with compressed data, indexes for efficient random data access, and transaction-level fault tolerance.
Pig Latin is procedural and fits very naturally in the pipeline paradigm while SQL is instead declarative. In SQL users can specify that data from two tables must be joined, but not what join implementation to use (You can specify the implementation of JOIN in SQL, thus "... for many SQL applications the query writer may not have enough knowledge of the data or enough expertise to specify an appropriate join algorithm."). Pig Latin allows users to specify an implementation or aspects of an implementation to be used in executing a script in several ways. In effect, Pig Latin programming is similar to specifying a query execution plan, making it easier for programmers to explicitly control the flow of their data processing task.
SQL is oriented around queries that produce a single result. SQL handles trees naturally, but has no built in mechanism for splitting a data processing stream and applying different operators to each sub-stream. Pig Latin script describes a directed acyclic graph (DAG) rather than a pipeline.
Pig Latin's ability to include user code at any point in the pipeline is useful for pipeline development. If SQL is used, data must first be imported into the database, and then the cleansing and transformation process can begin.
== See also ==
Apache Hive
Sawzall — similar tool from Google
== References ==
== External links ==
Official website
|
https://en.wikipedia.org/wiki/Apache_Pig
|
Univision (Spanish pronunciation: [uniβiˈsjon] ) is a Mexican American Spanish-language free-to-air television network owned by TelevisaUnivision. It is the United States' largest provider of Spanish-language content. The network's programming is aimed at the Latino public and includes telenovelas and other drama series, sports, sitcoms, reality and variety series, news programming, and imported Spanish-language feature films. Univision is headquartered in Midtown Manhattan, New York City, and has its major studios, production facilities, and business operations based in Doral, Florida (near Miami).
Univision is available on pay television providers throughout most of the United States, with local stations in over 60 markets with large Latin American communities. Most of these stations air full local newscasts and other local programming in addition to network shows; in major markets such as Los Angeles, Miami, and New York City, the local newscasts carried by the network's owned-and-operated stations and affiliates are equally competitive with their English-language counterparts ratings-wise.
Randy Falco, who was executive vice president and COO since January 2011, took over as CEO in June that year after the departure of president and CEO Joe Uva in April 2011. In March 2018, Falco announced that he would be retiring and stepping down after seven years as CEO.
In May 2018, Vincent L. Sadusky, having previously been CEO of Media General Inc. and CFO and Treasurer of Telemundo Communications Inc., took over as CEO, replacing Falco.
In February 2020, Searchlight Capital Partners and ForgeLight acquired a 64% majority stake in Univision, with Televisa keeping their 36% minority stake. In December 2020, former Viacom CFO Wade Davis replaced Sadusky as CEO.
== History ==
=== Beginning as Spanish International Network ===
Univision's roots can be traced back to 1955, when Raoul A. Cortez started KCOR-TV, an independent station in San Antonio, Texas, which was the nation's first Spanish-only TV outlet. The station was not profitable during its early years, and in 1961, Cortez sold KCOR-TV – now known as KWEX-TV – to a group headed by Mexican entertainment mogul Emilio Azcárraga Vidaurreta, owner of Mexico-based Telesistema Mexicano (the forerunner of Televisa). Cortez's son-in-law Emilio Nicolás Sr., who helped produce variety programs for the station, held a 20% stake and remained as KWEX general manager for three decades. The new owners helped to turn around the station's fortunes by heavily investing in programming, most of it sourced from Telesistema Mexicano.
On September 29, 1962, Azcárraga and his partners launched a second Spanish-language station, KMEX-TV, in Los Angeles. KWEX and KMEX formed the nucleus of the Azcárraga-owned Spanish International Network (SIN), created in late 1962. SIN was the first television network in the United States to broadcast its programming in a language other than English. From 1963 until 1987, SIN was managed from offices in New York by Rene Anselmo, a U.S. native who had worked for Azcárraga in Mexico City for eight years as head of Telesistema's programming export subsidiary. Having supervised the launch of KMEX, Anselmo spearheaded SIN's expansion, first into the New York City area, when it founded WXTV in Paterson, New Jersey (licensed in 1965 and launched in 1968), next in Fresno, California (licensed in 1969 and launched in 1972 as KFTV), and then by acquiring WLTV in Miami in 1971. That year, Azcárraga and his partners incorporated these five stations (separately from SIN) as the Spanish International Communications Corporation (SICC), with Anselmo named as president.
Over the next 15 years, SIN and SICC would create other top-rated Spanish-language television stations throughout the United States; these included KTVW in Phoenix and KDTV in San Francisco (both owned by Anselmo) and a part-time affiliation with WCIU-TV in Chicago. The Mexican ownership interest in SIN and SICC transferred posthumously from Emilio Azcárraga Vidaurreta to his son, Emilio Azcárraga Milmo, in 1972. On July 4, 1976, the network began distributing its national feed via satellite, which originally was delivered as a superstation-type feed of San Antonio's KWEX-TV, before eventually switching to a direct programming feed of SIN, allowing cable television providers to carry the network on their systems at little cost. Between the mid-1970s and late-1980s, SIN began affiliating with startup Spanish-language stations in markets such as Dallas–Fort Worth (KUVN) and Houston (KXLN), as well as with independent stations that previously broadcast in English.
In Chicago, SIN moved its programming from WCIU-TV to new full-time affiliate WSNS-TV in July 1985. After WSNS was sold to Telemundo in 1988, what had become Univision moved its programming back to WCIU-TV, which agreed to air Univision programming on weekday evenings and weekends. In 1994, the network purchased English-language independent WGBO-TV after WCIU-TV turned down Univision's request to become a full-time affiliate in favor of maintaining its longtime multi-ethnic programming format. WGBO-TV became an Univision-owned station on December 31, 1994.
=== Relaunch as Univision ===
1986 became a pivotal year for the Spanish International Network and its owned-and-operated station group; in 1987, Nicolas sold his stake in the network to a partnership of Hallmark Cards and Televisa for 25 years, which formed Univision Holdings Inc. to operate the network and its stations. The Federal Communications Commission and SIN's competitors had long questioned whether the relationship between SIN and the Azcárraga family was impermissibly tight. Both the FCC and other Spanish-language broadcasters had long suspected that Televisa was merely using Nicolas to skirt FCC rules prohibiting foreign ownership of broadcast media.
The FCC and the U.S. Justice Department eventually encouraged a sale of the network to a properly constituted domestic organization. Spanish International Communications ultimately began discussions with various prospective buyers, culminating in Hallmark Cards (which owned a 63.5% interest), private equity firm First Chicago Venture Capital (which acquired 21.5%) and several other private investors (which collectively owned the remaining 15% held in a trust) purchasing the SIN stations for $600 million, while forming a new relationship with Televisa for the distribution of programs; the new group also adopted a new name for the network, Univision.
The first reference to the new Univision name was in "América, esta es tu canción", a song interpreted by Lucerito on her 1982 album Te prometo. The lyric that mentions the network is "cantaremos al mundo fantástico mágico de Univisión" ("we'll sing to the fantastic, magical world of Univision").
The initial logo under the Univision name Spanish International Network, that was used from 1987 to 1989; the logo was similar in resemblance to Televisa's station logo. Televisa still uses this logo today.
Joaquin Blaya, the network's new chief executive officer, would sign agreements to carry two programs that would change the face of the network. He signed contracts to develop programs hosted by Cristina Saralegui (who became the host of the long-running talk show El Show de Cristina ("The Cristina Show"), which aired on the network for 22 years) and Chilean-born Mario Kreutzberger – better known as Don Francisco (who brought his popular variety series Sábado Gigante ("Giant Saturday") to the U.S., which aired on Univision for 29 years until its cancellation in September 2015) – for the network. Univision also began production of its first morning program, Mundo Latino, which was anchored by Cuban natives Lucy Pereda and Frank Moro; Moro left the network to move to Mexico to continue his career as a soap opera actor, the network then brought in Jorge Ramos to replace him.
To appeal to Hispanics and Latinos of all nationalities, the network soon instituted a policy of maintaining neutrality with its use of Spanish dialects, slang and humor on its domestically produced programs, enforcing program producers to limit the use of humor and slang relatable only to a specific Hispanic nationality. It also prohibited the use of English in its programming or advertisements (outside of product titles and dialogue featured in film trailers), most obvious in the use of Spanish equivalent placenames such as "Nueva York" rather than New York. In 1988, Blaya also substantially ramped up production of American-based programs on Univision's lineup, reducing the share of programming imported from Latin America (most of which came from Televisa) on its schedule. With this, the network began producing programs for a national audience in mind, resulting in Univision's schedule consisting of 50% foreign programming and 50% U.S.-produced programming.
The first such program, TV Mujer ("Woman TV"), was a magazine-style talk show aimed at American Hispanic women, originally hosted by Pereda and Gabriel Traversari, featuring a mix of cooking and entertainment segments. The following year, Pereda was replaced as co-host by Mexican-American Lauri Flores, who previously swas director of programming, promotions, special events and public information at Houston affiliate KXLN-TV – where she also hosted a local community affairs program, Entre Nos. During Flores' tenure as host of TV Mujer, the program remained the #1 daytime show on Spanish-language television, outperforming its competition in its time period by 33%. Telemundo's Dia a Dia, which debuted prior to the premiere of TV Mujer, saw its ratings diminish as a result. Sábado Gigante model Jackie Nespral was added as host of the program for its final year on the network; she was originally hired as a fill-in co-host while Flores went on maternity leave, before becoming a full-time host during the show's final season. TV Mujer inspired a series of other programs, including Hola, America ("Hello, America") and Al Mediodia ("At Noon"), which never garnered the ratings of the original concept and were ultimately canceled.
However, the network's fortunes began to wane following the Hallmark purchase, when Televisa terminated its programming agreement with Univision, taking along with it the company's popular telenovelas. The network opted to replace the Mexican-produced serials with novelas produced in South America; however, viewership for its telenovelas declined with the programming shift. To make matters worse, with limited revenue from advertising, the sale to Hallmark left Univision with a huge debt load to cover. On February 1, 1990, Univision Holdings disclosed that it had failed to make an interest payment of about $10 million (totaling about $3 million to be paid to its bank lenders and about $7 million to holders of its junk-bond debt) that was due a day prior as part of its efforts to restructure its debt, citing insufficient cash flow for the missed payments. At the time, Univision had owed about $315 million to a group of banks led by Continental Bank of Chicago, about $135 million in senior subordinated zero-coupon debt and $105 million in 13 3/8% in outstanding subordinated debentures.
On March 30, Univision filed a motion in U.S. Bankruptcy Court to seek Chapter 11 creditor protection and financial reorganization unless it could convince its bondholders to accept an increased offer by Hallmark Cards Inc., in which they would receive $131 million for a face value of $270 million in securities on a blended basis, following an initial bid that was widely turned down by the bondholders. The holders of two different series of Univision Holdings' debt accepted the bid and tendered their securities by April 13, preventing the bankruptcy protection proceedings, with Hallmark's offer to purchase the debt securities being completed by April 25.
=== Revamp and competition with Telemundo in the 1990s and 2000s ===
On April 8, 1992, Hallmark sold Univision to a group that included Los Angeles-based investor A. Jerrold Perenchio (a former partner in Norman Lear's Embassy Communications, who was outbid by the Hallmark-led consortium for the network in 1987), Emilio Azcárraga Milmo, and brothers Ricardo and Gustavo Cisneros (co-owners of Venezuelan broadcaster Venevision) for $550 million, in order to refocus its television operation efforts on cable provider Cencom Cable Associates, which it acquired the previous year for about $500 million. In order to comply with FCC rules on foreign ownership of television stations, the deal was structured to give Perenchio a controlling 75% interest in Univision's station group and 50% ownership of the network itself; Azcárraga and the Cisneroses held a 25% stake in the network and a 12.5% stake in the station group. The deal placed Univision under common ownership with competing cable channel Galavisión, which the Azcárraga-run Grupo Televisa owned at the time. The Cisneroses' ownership of stake in Univision led to the broadcast of Venevision telenovelas from Venezuela, & eventually, to the co-production partnership of Venevision International and Univision of telenovelas. The consortium ended up selling Univision for $13.7 billion in 2007.
The sale raised concerns by several Latino activist groups such as the National Hispanic Media Coalition – which subsequently filed a petition to the FCC to deny the sale of Univision and its television stations – that it would lead to a drastic reduction in Univision's domestically originated programming output in favor of lower-cost, imported Latin American content, and allow Azcárraga to potentially expand control of American Spanish language television in the manner of Televisa's near-monopoly in Mexican media. Indeed, this concern was effectively confirmed in the release of an FCC filing for the Perenchio-Televisa-Venevision purchase in which Perenchio indicated "the programs offered[...] by Televisa and Venevision will include at least a quantity of programs sufficient to fill a 24-hour-a-day, seven-day-a-week broadcast schedule", with local content consisting only of newscasts. This led Joaquin Blaya to resign from his role as Univision's president in May 1992 – after Perenchio had earlier assured him that the amount of domestic national programming on the network and its nine owned-and-operated stations would not be reduced before the filing was disclosed – concerned that it would limit opportunities to increase the amount of local programming content on Univision's stations.
Blaya was then hired by Telemundo as its president and chief executive officer, and was subsequently joined by four other Univision senior executives on that network's production and management team. The FCC expedited its review of the deal, and approved the purchase on September 30, 1992, stating that the consortium was quantified to acquire Univision and that it was "unconvinced" by the petitioners' arguments that it would dilute the amount of American programming on the network. Subsequently, in January 1993, Univision canceled three U.S.-produced programs – the newsmagazines Portada ("Cover Story") and Al Mediodía and the variety series Charytin International – resulting in the layoffs of 70 production staffers based at Univision's Miami headquarters and at Al Mediodía's base in Los Angeles; although two of the three programs were replaced by Televisa series (Portada was replaced in its Wednesday night slot with the variety series El Nuevo Show ("The New Show"), a Los Angeles-based series hosted by Paul Rodriguez, which had aired on Saturdays for several years prior), Univision executives cited that all three programs were discontinued due to low ratings and not because of any plan to eschew American programming with imported content. Televisa and Venevision's stakes in the network in exchange the two foreign partners get 14.7% of Univision's revenue also gave Univision access to a broad selection of programs from Televisa and Venevision are locked up until 2017.
In 1993, Univision owner Jerry Perenchio, in a swift and unprecedented move, after the acquisition, appointed a 27-year-old, Los Angeles native, Venezuelan-born, Miguel Banojian, known for his in-depth of the U.S. and Latin American Hispanic market, his impeccable professional skills, as well as his proven successful ratings track records to turn around the operations of the station group, but mainly Univision's West Coast flagship KMEX-Channel 34 Los Angeles, generating at the time of purchase of the company, approximately 40% of the overall Univision revenue. Under Banojian, the network increased monetary investments in the stations, expanding staff and resources, introducing new sets for its newscasts, hiring and appointing KVEA's main anchor Jesus Javier, reporter Pepe Barreto also from KVEA, as well as hiring Andrea Kutyas, joining news anchor Eduardo Quezada, who worked at KMEX from 1975 to 2003, to lead and reshape KMEX's 11 p.m. newscast, which became the #1 late news in the Los Angeles Market. The overall re-organization effort, included, the purchasing of new live production equipment, updated production units, new master control equipment; new station antennas with more transmission power and a new studio located in Westchester, replacing the Hollywood studio which served from 1962 to March 1993. Same year, A Mexico City-based "MEDIA HUB CENTER ALLIANCE" was created by Televisa AND KMEX; both companies shared its operational, technical and resources strengths to increase market presence, Miguel Banojian representing KMEX, Alejandro Burillo Azcarraga, Shareholder & Executive VP of Televisa and Félix Cortés Camarillo VP of News & Production operations of Televisa, signed the alliance which included shared news bureaus in Mexico City, Los Angeles, Tijuana, San Francisco, Dallas, and Houston; Such alliance locked a leasing agreement of "Two" 24 hours transponders from its newly launched Geostationary "Intelsat 601", which served the satellite sharing between the two countries; the newly created satellite hub was later used by both networks to share programming and sales needs. One of the iconic marketing move to revamp the then dying "KMEX" station, Mr. Banojian and the KMEX group of engineers, also designed, created and launched what became, "The first U.S Hispanic Aerial Newsgathering operation", which included a brand new helicopter with call sign "Aguila 1" ("Eagle one" in its English translation). The news sets, production equipment, master control equipment, and antenna were upgraded. With all these operational moves, not only did KMEX-34 poise itself to acquire 70% of the Hispanic market share in Los Angeles market against its competitors including Telemundo, but achieved something unprecedented in U.S. television history: KMEX Channel 34 became the first Spanish-language television station ever to outperform English-language network stations (like NBC station KNBC, CBS station KCBS-TV, ABC station KABC-TV and Fox station KTTV) and overcame what had been Telemundo's national competitive edge against Univision. That year, Univision increased its advertising rates and was able to increase its cash flow, which allowed to go on to a purchase mode, acquiring KXLN, the first Spanish-language television station in the Houston market. Perenchio also invested $37 million, in conjunction with rival Telemundo, to develop the National Hispanic Television Index, a ratings system created by A.C. Nielsen to track viewership of Spanish language television networks. Perenchio also implemented new programming requirements in which non-sports programs were no longer allowed to run 20 minutes over their allotted timeslot.
Jesus Javier was hired as KVEA's main anchor, joined by reporter Pepe Barreto. Andrea Kuyas and veteran (1975 to 2003) KMEX news anchor Eduardo Quezada led the 11 p.m. newscast, which became the #1 late news in the Los Angeles market.
Also in 1993, KMEX agreed to share operational and technical resources with Televisa to enhance market presence. Banojian representing KMEX, with Televisa executive VP Alejandro Burillo Azcarraga, and Félix Cortés Camarillo, Televisa News and Production VP signed the "Media Hub Center Alliance", which included shared news bureaus in Mexico City, Los Angeles, Tijuana, San Francisco, Dallas, and Houston. The alliance leased two 24-hour transponders on the new Intelsat 601 to share programming and ads.
KMEX also purchased a new helicopter "Aguila 1" ("Eagle 1"), becoming the first Hispanic station in the U.S. to add aerial capability.
Univision increased its advertising rates and subsequently was able to acquire KXLN, the first Spanish-language television station in the Houston market. Perenchio also invested $37 million, in conjunction with Telemundo and A.C. Nielsen, to develop the National Hispanic Television Index to track viewership in Spanish language markets. Perenchio also implemented new programming requirements in which non-sports programs were no longer allowed to run 20 minutes over their allotted timeslot.[5]
In 1996, Perenchio took Univision Holdings public for the first time. Univision also appointed Mario Rodriguez as its president of programming; Rodriguez developed a strategy to provide programming that would appeal to both Latino immigrants and native citizens, and increased domestic programming production (much of which consisted primarily of news, talk, and variety shows) to encompass 52% of the network's schedule. Univision also adopted the standard Latin American model of programming its prime-time telenovela lineup to appeal to different target audiences (with novelas aimed children airing at 7:00 p.m., those aimed teenagers at 8:00 p.m. and novelas targeted toward adults scheduled at 9:00 p.m. Eastern and Pacific). The following year, the network appointed former Housing and Urban Development secretary Henry Cisneros as its president and CEO, a post he remained in until his resignation in 2000 to head American CityVista, a contracting company that builds residential communities in inner cities.
At the same time, citing its dominance in the Spanish-language television market, having consistently beaten Telemundo and other smaller Spanish language networks in the ratings, the network decided to refocus its efforts on attracting Hispanic and Latinos viewers who preferred watching programs on English language broadcast and cable networks to grow its viewership further. The strategy helped Univision to nearly double its ratings during prime time by 1998, ranking as the fifth most-watched American broadcast network by the 1998–99 season (beating fledgling English-language networks UPN and The WB), as it steadily began to attract bilingual viewers away from the English-language networks. In September 1998, the network added two new shows to shore up its struggling afternoon lineup leading into the highly rated Cristina. While one of the programs – the game show El Bla-Blazo – lasted only a few years, it experienced more long-term success with the newsmagazine that followed it, El Gordo y La Flaca ("The Scoop and the Skinny", although alternately translated as "The Fat Man and the Skinny Girl"), a Miami-based entertainment news program hosted by Raul De Molina and Lili Estefan, who had become popular with viewers for their entertainment reports on the network's news programs.
In June 2001, Univision entered into a local marketing agreement (LMA) with Raycom Media to operate two television stations in Puerto Rico, WLII in Caguas and WSUR in Ponce, as part of a planned and protracted purchase of the two stations. At the time, WLII had long maintained an LMA with another Puerto Rican station, WSTE, which Univision maintained. Also around this time, Univision resumed its broadcast expansion by converting several television stations that it had acquired into affiliates of the network, including those in Raleigh, North Carolina (WUVC), Baltimore, Maryland (WQAW), Cleveland, Ohio (WQHS), Philadelphia, Pennsylvania (WUVP) and Atlanta, Georgia (WUVG) – including one acquired from USA Broadcasting that had previously been affiliated with the Home Shopping Network, which was left out of the group's charter affiliation deals for Univision Communications' secondary network TeleFutura (now UniMás) when it launched in January of that year. Both WLII and WSUR were sold to Univision Communications outright in 2005. Since that point, Univision also signed affiliation agreements with television stations owned by other media companies in cities such as Detroit, Seattle, Portland, Oregon, Minneapolis, Oklahoma City, Nashville and Kansas City – expanding its affiliate body further outside the Univision-owned stations and stations owned by Entravision Communications.
In June 2002, Univision acquired Dallas-based Hispanic Broadcasting Corp., owner of Spanish language radio stations in markets such as New York City (WADO), Los Angeles (KLVE), San Antonio (KGSX, now KMYO) and Dallas (KESS), in a $3.5 billion all-stock transaction. Following the FCC's long-awaited approval of the acquisition, the group was renamed Univision Radio. The negotiations to merge the two companies followed years of on-again/off-again negotiations in which each company made an offer to acquire the other, as well as occasional takeover attempts of other television and radio station groups (HBC once attempted to broker a deal to merge with the Spanish Broadcasting System, and made a failed attempt to acquire Telemundo before Sony Pictures Entertainment and Liberty Media acquired that network in 1998).
In April 2003, KMEX news anchor Eduardo Quezada left for KVEA and spent three years working as a news anchor before retiring in 2006; his oldest son, Eduardo Quezada Jr., is one of the news writers and editors at KMEX.
In late 2004, a feud began between Perenchio and Televisa head Emilio Azcárraga Jean, regarding Univision's continual editing of Televisa's programming, and the failure to pay for rights to broadcast Televisa-produced sports and specials. The feud intensified to the point where Grupo Televisa filed a breach of contract lawsuit against Univision in a U.S. federal court in June 2005, accusing the network of several actions, including "unauthorized editing" of Televisa programming; Televisa also barred its most famous stars from appearing on any Univision-produced series and specials. Rumors also circulated that Univision would form a partnership with Televisa's longtime rival TV Azteca, which for a short period of time, bought airtime rights and allowed its video footage to be used on Univision's news programs.
During the 2000s, Univision also lost several key on-air personalities to Telemundo, including longtime weekend news anchor María Antonieta Collins (who left to host the morning program Cada Dia), Primer Impacto anchor María Celeste Arrarás (who became the host of a similarly formatted newsmagazine, Al Rojo Vivo) and sports announcers Andrés Cantor (known to many Americans for his exuberant announcement of "Goal!" during football matches) and Norberto Longo. By the middle of the decade, Univision overtook UPN and The WB – which shut down in September 2006 and were replaced by The CW, which Univision also outranks – as the fifth highest-rated network in total viewership; since then, it also sometimes posts higher viewership in the key age demographics of Adults 18–34 and Adults 18–49.
Other key on-air personalities that join Telemundo from Univision or Televisa in the 2000s are Lucero, Pedro Fernandez, Kate del Castillo, Aracely Arámbula, Raúl González, Blanca Soto, Laura Flores, Ana María Canseco, Cristina Saralegui, Fernando Fiore, Rodner Figueroa, who was fired for making reference from the movie Planet of the Apes, to Michelle Obama, Barbara Bermudo, who was laid by network, Don Francisco, Natalia Cruz, Maria Elena Salinas, who was stepped down in December 2017 after 36 years of news service, Arantxa Loizaga Lourdes Stephen, Felix Fernandez, who was laid off by network, Jorge Ramos, who was stepped down in December 2024 after 40 years of news service and Maity Interiano, who was laid off by network.
On April 7, 2005, Univision aired Selena ¡VIVE! ("Selena Lives!"), a three-hour tribute concert in honor of slain singer Selena (who was murdered via gunshot in March 1995 by a fan who worked as part of her managerial staff). The concert earned a 35.9 Nielsen household rating, becoming the highest-rated program that night on all of the network television as well as the most-watched Spanish-language program in American television history.
On February 9, 2006, Univision Communications announced that it was putting itself up for sale. News Corporation chairman Rupert Murdoch stated that his company was considering buying Univision, but backed off that position (the company had already owned duopolies in several markets, and could not acquire the existing Univision stations in any event as FCC rules prohibit common ownership of three television stations in a single market except in cases where a market has 20 full-power stations, and sell some of its stations to get below the FCC's 39% market reach cap for any individual station owner). Other expected bidders included Grupo Televisa (which would have had to acquire the network under a partnership, due to FCC laws that restrict ownership of a television station or network by a foreign company to a percentage of no more than 25%), Time Warner, CBS Corporation, Viacom, The Walt Disney Company, Bill Gates, and several private equity firms. The Tribune Company was rumored to be interested in buying Univision's sister network TeleFutura.
On June 27, 2006, Univision Communications was acquired by Broadcasting Media Partners Inc. – a consortium of investment firms led by the Haim Saban-owned Saban Capital Group (which had previously owned Saban Entertainment until its sale to The Walt Disney Company in June 2001, as part of News Corporation's sale of Fox Family Worldwide), TPG Capital, L.P., Providence Equity Partners, Madison Dearborn Partners and Thomas H. Lee Partners – for $12.3 billion (increasing to $13.7 billion or $36.25 per share by the sale's closure), plus the assumption of $1.4 billion in debt. The sale received federal approval and was formally consummated on March 27, 2007.
The buyout left the company with a debt level of twelve times its annual cash flow, which was twice the debt incurred in buyouts that occurred over the previous two years. However, Univision's shareholders filed two class action lawsuits against Univision Communications and its board members to stop the buyout – one of which claimed that the board members structured the deal to only benefit the company's insiders and not average stockholders, while the other was filed on behalf of a shareholder identified as L A Murphy, who claimed that the board put its own personal interests and the interests of the winning bidder ahead of shareholders, and also failed to adequately evaluate the company's worth. Additional lawsuits were filed in the meantime, including one against the Univision Records division for heavy-handed tactics, and a suit filed by a winner of a $30,000 makeover prize in a contest held by the network's morning program ¡Despierta América! who alleged that Univision broke its own contest rules.
On June 25, 2007, with the finale of La Fea Más Bella ("The Prettiest Ugly Girl", a telenovela based on the Colombian series Yo Soy Betty, la Fea), Univision led all U.S. broadcast networks – English and Spanish – with a 3.0 rating out of 9 share, placing as the second most-watched network television program that week. Later that year, Univision hosted the first Spanish-language presidential debate in the United States at the University of Miami, featuring candidates vying for the Democratic nomination. In May 2008, Univision Music Group was sold to Universal Music Group and combined with the latter's Latin music label to become Universal Music Latin Entertainment.
In 2009, the network sponsored a countdown in Times Square, similar to the New Year's Eve event. On the evening of June 12, at 11:59 p.m. Eastern Time, a 60-second countdown appeared on the Jumbotron-size screen in the Manhattan district to mark the shutdown of full-power analog television signals in the Eastern Time Zone, culminating in the message "BIENVENIDOS A LA ERA DIGITAL" ("welcome to the digital era"). The countdown was aired live by the network during Ultima Hora: Una Nueva Era, a special edition of its late-evening newscast Noticiero Univision: Ultima Hora. The ball was lighted in white but was not dropped, remaining positioned at the bottom where the lighted "2009" sign also remained, despite the four-month delay of the digital television transition from February 17. On December 7 of that year, Univision announced it would launch an in-house production division, Univision Studios, a Doral, Florida-based company that would produce original programming content for Univision and TeleFutura; former RTVE president Luis Fernandez was appointed to lead the new division.
=== 2010s ===
During the first week of September 2011, the network reached a milestone, earning its first #1 ranking in the ratings among all American broadcast television networks – English and Spanish – in the 18–49 age demographic, assisted by a prime time soccer match between Mexico and Ecuador and the season finale of the Colombian reality game show Desafío: La Gran Batalla ("Challenge: The Great Battle"), along with the English networks having traditionally weak programming that time of year, prior to the launch of the fall television season.
In October 2011, Televisa reached an agreement to acquire a 5% ownership stake in Univision (marking the third time that the company held equity in Univision Communications in its history), with the option of expanding its interest in the future. As part of the deal, Televisa also signed a long-term extension to its program licensing agreement with Univision – which runs through at least 2020, through with an option to extend it to 2025 or later – which expanded upon the previous agreement, which was set to expire in 2017, to give Univision rights to stream Televisa content via the internet and on mobile platforms and covers key rights to matches from Mexican soccer leagues.
On October 17, 2012, Univision Communications unveiled an updated corporate logo, which was adopted on-air by the Univision network during the broadcast of its New Year's Eve countdown program ¡Feliz 2013! ("Happy 2013!") on December 31. The new logo shares the multicolored quadrant design of the previous logo (which had been used since January 1990), but now resembles a three-dimensional heart to represent its new slogan, "El latido del corazón hispano de Estados Unidos" ("The Hispanic Heartbeat of the United States"). The revised logo's new three-dimensional shape was intended to represent Univision's recent growth as a "360-degree", multi-platform media company, while its seamless form represented the unity of Hispanic cultures.
On May 8, 2012, Univision and ABC News announced that the two companies would jointly create an English-language digital cable and satellite news channel, later given the name Fusion in February 2013, that would be primarily aimed at English-speaking Hispanic and Latino American audiences; Fusion was launched on October 28, 2013.
During the 2010s, the network reached viewership parity with the five major English-language U.S. broadcast television networks.
=== 2020s ===
In February 2020, Searchlight Capital Partners, LP (“Searchlight”), a global private investment firm, and ForgeLight LLC (“ForgeLight”), an operating and investment company focused on the media and consumer technology sectors, acquired 64% ownership stake of Univision, Televisa to maintain its 36% stake in Univision, and appointed former Viacom EVP and CFO Wade Davis as its CEO. The US federal government approved the foreign acquisition under specific conditions around safeguards of personal identifiable information of US consumers.
In April 2021, Televisa announced that their ownership stake in Univision would increase to 45% and would merge its media, content, and production assets with Univision, creating its new parent company TelevisaUnivision.
In November 2021, Univision reacquired local stations in Tampa, Florida, Orlando, Florida and Washington, D.C., from affiliate operator Entravision.
On September 27, 2023, Univision co-hosted the second Republican primary debate, alongside Fox Business and Rumble, from the Ronald Reagan Presidential Library in Simi Valley, California, with its anchor, Ilia Calderón, serving as a moderator alongside Stuart Varney and Dana Perino.
On November 7, 2023, TelevisaUnivision CEO Wade Davis, as well as TelevisaUnivision Mexico co-CEOs Bernardo Gómez Martínez and Alfonso de Angoitia Noriega, met with former President Donald Trump at his residence in Mar-a-Lago. And on November 9, the network aired a special hourlong exclusive interview with him, with Enrique Acevedo of N+ as the interviewer. Due to a new unannounced policy prohibiting opposition advertising in single candidate interviews, the network abruptly canceled President Joe Biden’s campaign ads which were set to air on network affiliates in Nevada, Arizona, Pennsylvania, and Florida during the Trump interview. The network also canceled a scheduled response with Maca Casado, Biden’s Hispanic media director, which was set to air after the Trump interview. In the days following the interview, Univision’s most prominent news anchor, León Krauze, left the network after 13 years of working with them, prompting many to believe that his departure was due to the way that Univision handled the Trump interview. The Washington Post reported that Jared Kushner, Trump’s son-in-law, helped arrange the event and was in the room with the TelevisaUnivision executive. Well-known Latino artists and activists like political commentator and co-host of The View Ana Navarro and comedian, actor and host of The Daily Show John Leguizamo have been taking to social media to encourage people to boycott Univision due to the gracious tone of the interview, the softball questions asked during the interview, and the lack of follow-up questions, with some even calling Univision “MAGAvision”. More than 80 organizations, including prominent Latino groups such as the Mexican American Legal Defense and Educational Fund (MALDEF), America’s Voice and the Coalition for Humane Immigrant Rights, signed an open letter to Davis and other TelevisaUnivision executives, sharply criticizing the interview.
In August 2024, Univision welcomed two new affiliates, WHMB-TV in Indianapolis and WHME-TV in South Bend, both in Indiana.
== Programming ==
Univision operates on a 164-hour network programming schedule, which it adopted in January 2013. The network's base programming feed provides general entertainment programming on an uninterrupted 24-hour schedule each weekday, from 5:00 to 6:00 a.m. Monday through Friday and 8:00 a.m. to 5:00 a.m. Eastern and Pacific Time on Saturdays and Sundays (the first three hours of the secondary weekend schedule on Saturday and Sunday mornings, starting at 8:00 a.m. Eastern and Pacific Time, is occupied by the children's programming block "Planeta U"). The remaining weekend time periods are filled with infomercials (prior to 2013, the network had programmed a full 168-hour schedule, with reruns of past Televisa-produced entertainment programs filling the two hours on Saturday and Sundays now occupied by paid programming).
Although Univision's owned-and-operated stations and affiliates largely rely on the network's master feed to fill their daily broadcast schedule, many of its stations also produce their own local programming, usually in the form of newscasts and public affairs programs (production of local infotainment programming, and leasing of brokered programs such as direct response and religious content, is at the station's discretion). Many Univision stations usually air limited local news programming, which are commonly reserved for early and late evening timeslots on Monday through Friday nights, with the master feed incorporating alternate programming that news programming may pre-empt on its broadcast outlets during these designated time periods (as well as others in which stations carry additional local programs); some of its stations may also air newscasts on weekday mornings (these are mainly limited to the network's O&Os and affiliates in larger markets) and/or on weekend evenings.
The majority of Univision's programming consists of telenovelas and series produced by Televisa, the majority of which originated on the company's flagship network in Mexico, Las Estrellas. Normally, the telenovelas would be on Las Estrellas for a few weeks, then airing in the United States on Univision, causing a delay. Prior to 2009, Univision had also broadcast telenovelas and other programs produced by Venezuelan broadcaster Venevisión. Otherwise, Univision produces a moderate amount of original programming, including the reality competition series Nuestra Belleza Latina ("Our Latin Beauty"), La Banda ("The Band") and Mi Pongo Mi Pie ("I Stand Up"); national news programming; entertainment news shows El Gordo y La Flaca and Sal y pimienta ("Salt and Pepper"); and sports discussion program República Deportiva ("Sports Republic"). Univision also operates its own television production unit, Univision Studios, which its corporate parent launched in 2009 and produces original content for the network.
The network's signature program, the variety show Sabado Gigante, hosted by Don Francisco, aired on Univision every Saturday night from April 12, 1986 to September 19, 2015 (its final episode was broadcast live in the U.S., Mexico and in Chile, where the program originated in 1962); in addition, from September 2004 to May 2015, Univision aired Clásicos de Sábado Gigante ("Giant Saturday Classics"), an early Sunday morning program consisting of condensed two-hour episodes of the series on an approximately one-year delay from their original broadcast. After Sabado Gigante ended its 29-year run on the network, Univision continued the Saturday evening variety tradition with its move of the Televisa-produced music and game show Sabadazo – which it had aired on Saturday afternoons since the show moved from sister network TeleFutura (now UniMás) in September 2012 – into part of Gigante's former time slot on October 17, 2015, before reverting to an afternoon slot and being replaced by the investigative news program Crónicas De Sábado after four months due to low ratings. As such, Univision is one of only two American television networks that airs the first-run program during Saturday prime time (CBS is the only other, although ABC, Fox and occasionally NBC broadcast live sporting events during Saturday prime on certain weeks of the year).
Univision also typically airs drama and variety series in the afternoon (telenovelas that appeal to teen or pre-teen audiences previously aired on early Saturday afternoons until 2011). Scripted series and variety shows (such as Bailando por un Sueño ("Dancing for a Dream"), Como Dice el Dicho ("As the Proverb Goes") and El Chavo Animado ("El Chavo: The Animated Series")) largely make up Univision's weekend lineup. Reality programming became a focal point of the network's Sunday primetime schedule beginning in 2007, with the debut of the beauty pageant competition series Nuestra Belleza Latina ("Our Latin Beauty"). Sitcoms, once a major part of the network's schedule, have a reduced presence on Univision in recent years; since 2008, the network has only obtained rights to two comedies produced by Televisa since that time (Durmiendo con mi Jefe ("Sleeping with My Boss") and Todo en Incluido ("All Inclusive"), both of which began airing on Univision in 2014), although it continues to air comedies that are no longer in production to which Univision continues to maintain U.S. distribution rights (including the family sitcom La Familia P. Luche and the sketch comedies La Hora Pico, Desmadruga2 and its spin-off Estrella2), mainly in overnight and select weekend timeslots.
Although its reliance on them has greatly decreased since 2009, the network also airs some feature films, generally older Mexican imported films from the 1960s to the 1980s, which occasionally air in weekend timeslots not occupied by afternoon football events or Sunday evening reality programs (this is in contrast to UniMás and Telemundo, which both air Spanish-dubbed versions of films produced for the English-language market, although Telemundo also airs Mexican-produced films in overnight timeslots). Until September 2009, when the network began ceding the time period to telenovelas, Univision filled the 10:00 p.m. (Eastern and Pacific Time) hour on Monday through Fridays with various programs each night (including Cristina, Don Francisco Presenta ("Don Francisco Presents"), the newsmagazine Aqui y Ahora ("Here and Now") and Televisa-produced sitcoms and sketch comedies), mirroring the scheduling of English language broadcast networks.
=== Distribution agreements ===
=== English subtitles ===
On January 30, 2012, Univision became the second Spanish language network in the United States to provide English closed captions transmitted over the CC3 caption channel, and the third network overall to provide CC3 captions in any form. The captions are intended to attract Hispanic viewers and others who are not fluent in Spanish, and primarily appear during the network's evening telenovela block each Monday through Friday from 7:00 to 11:00 p.m. Eastern and Pacific Time. Some weekend evening programs (such as Nuestra Belleza Latina) also utilize English captions, in addition to the native Spanish-language captions on the CC1 caption stream.
Prior to Univision gaining these captions, competing network Telemundo has carried English subtitles during its entire weeknight prime time schedule from September 2003 to October 2008 and again since March 2009. And in an inverse manner, upon the launch of the now-defunct Qubo Channel in 2007, most of its programming included CC3 Spanish subtitles in addition to its native CC1 English subtitles.
Unlike the respective CC3 captions transmitted by both Telemundo and Qubo Channel, Univision does not include these captions during most repeat broadcasts of telenovelas airing outside of the network's prime time schedule following the program's original run on the network.
=== Content editing ===
In 2004, Univision published a list of words it edited from programs broadcast by the network (mostly those acquired from Televisa and other distributors) to comply with broadcast decency standards set by the Federal Communications Commission. The words affected had no negative connotations in some Spanish-speaking countries, but had obscene connotations in other countries.
In June 2005, Grupo Televisa filed a lawsuit against Univision in a U.S. federal court, accusing the network of several actions, including "unauthorized editing" of Televisa programming. Since 2013, Univision has edited various telenovelas aired within its prime time schedule if a telenovela does not garner sufficient ratings; as such, scenes from a single program (such examples include Qué Bonito Amor ("Beautiful Love"), La Tempestad ("The Storm"), De Que te Quiero, te Quiero ("Head Over Heels") and La Malquerida ("The Unloved")) comprising 1½ to three episodes are sometimes removed and combined to fit into a one-hour timeslot. In 2015, the network implemented further content edits, removing scenes incorporating forms of physical violence or situations of a sexual nature or incorporating substance use involving minors on some of its telenovelas and anthology serials (such as La Rosa de Guadalupe and Como Dice el Dicho), regardless of the integrality of such depictions to the episode's plotline.
=== News programming ===
The network operates a news division, Noticias Univision ("Univision News"), which produces the network's flagship newscast Noticiero Univision, which airs in the form of two daily half-hour early and late evening broadcasts (the late-evening newscast formerly maintained a in-depth, investigative focused program Noticiero Univision Ultima Hora ("Noticiero Univision: Last Hour") from 2002 to 2008, under anchor Enrique Gratas, before reverting to the format of its early evening edition); it also produces the morning news and lifestyle program ¡Despierta América! ("Wake Up America!"), the late afternoon newsmagazine series Primer Impacto (which originally aired as a seven-day-a-week broadcast until 2007, and produces a condensed half-hour edition Primer Impacto Extra, which airs in place of late local newscasts on affiliates without their own news department or which choose to preempt regularly scheduled local newscasts on certain holidays) and the Sunday morning talk show Al Punto ("To the Point").
In 1987, Univision appointed Roberto FE Soto – a former producer at NBC News – to produce a revamped flagship evening newscast, Noticiero Univision, becoming the network's youngest executive; the network also reassigned Ramos and hired veteran journalist Maria Elena Salinas to co-anchor the evolving network newscast. Univision eventually decided to expand its news programming to afternoons; in 1992, the network debuted Noticias y Más ("News and More"), anchored by Nespral, Ambrosio Hernandez and Raúl Peimbert; Myrka Dellanos joined the program after Nespral's departure later that year. Hernandez and Peimbert left Univision in 1993 to join Telemundo, while Nespral became co-host of the weekend edition of NBC's Today. Univision had other plans for the moribund show: the network revamped its format, changed its name and its theme music, and hired Puerto Rican-born María Celeste Arrarás as a weekend reporter to serve as Dellanos' partner; the retooled newsmagazine series became Primer Impacto ("First Impact") in February 1994. For 14 years, from 1996 to 2009, John Lippman was Senior Vice President for News and Operations at Univision Television.
On April 14, 1997, Univision launched ¡Despierta América! as a Spanish-language competitor to NBC's Today, ABC's Good Morning America and CBS This Morning. The program – which originally ran for three hours, before expanding to four in 2013 – is known for coining the catch phrase, "échate pa' acá" ("Come here"), which is also the name of an entertainment segment focusing news and gossip about Latin entertainers. This format was later carried over to another show, Un Nuevo Día, when Telemundo retooled that program originally known as ¡Levantate! in 2013. ¡Despierta América! has since developed its own style of reporting news of various topics, such as immigration, sports, consumer, health, lifestyle, fashion, beauty and entertainment content.
Today, Univision's news programs typically outrank its Spanish-language competitors, with the early-evening edition of Noticiero Univision often placing ahead of its English-language rivals (NBC Nightly News, ABC World News Tonight and the CBS Evening News) among viewers in the 18–49 demographic. Most of Univision's owned-and-operated stations and affiliates produce their own local programming, usually in the form of local newscasts and public affairs programs. Newscasts aired on the network's stations are usually broadcast in early and late evening timeslots – with many non-O&Os not owned by Univision Communications and Entravision Communications airing them only on Monday through Fridays – although some O&Os and affiliates also air newscasts on weekday mornings and/or weekend evenings (with morning newscasts being limited mainly to the network's larger-market O&Os and affiliates).
=== Sports ===
The network also maintains a sports division, Univision Deportes, which is responsible for the production of sports content on Univision, UniMás, Galavisión and its dedicated cable-satellite sports channel Univision Deportes Network. For the main Univision broadcast network, the division produces soccer matches from Liga MX (which have aired since 1987), select matches involving the Mexico and United States men's national teams, as well as tournament matches from the CONCACAF Gold Cup (the rights to which it assumed in 2000) and Copa América (which began airing in 1993). The network formerly held the Spanish language broadcast rights to the FIFA World Cup from 1970 until 2014 and the FIFA Women's World Cup from 1999 until 2011, with the rights migrating to Telemundo and NBC Universo beginning with the 2015 Women's World Cup.
In addition, the division also produces the weekly sports talk program República Deportiva, a Sunday daytime program that debuted in April 1999 with a companion late-night edition premiering in January 2015; and the weeknightly sports highlight/discussion program Contacto Deportivo ("Contact Sports"), which debuted in 2002 on what was then Telefutura, before moving to the main Univision network on March 2, 2015.
=== Children's programming ===
Children's programming has played a part in Univision's programming since its initial roots as the Spanish International Network. From 1962 until 2004, the bulk of SIN/Univision's children's programming was derived of mainly live-action and animated programming from Televisa and other content partners.
The network's first foray into children's programming, "Univision Infantiles", and featured Spanish-language dubs of the Japanese anime shows (Future Boy Conan and Voltron: Defender of the Universe). In June 1989, Univision launched a weekday and Saturday morning block, Univision y Los Niños, was in partnership of DIC Entertainment (Jayce and the Wheeled Warriors, Kidd Video, Rainbow Brite and The Adventures of Teddy Ruxpin). The block was discontinued in September 15, 1990, it was replaced with "Platavision", and it was carried with some DIC-produced shows. In 1991, Univision introduced "Chispavision", featuring the notable program was El Show de Xuxa ("The Xuxa Show"), a variety-based series starring the Southern Brazilian entertainer, which became a hit in the U.S. when it debuted on the network in 1992 (Xuxa would subsequently star in an American syndicated version of the program that aired for one season from 1993 to 1994).
In April 1995, Univision test-marketed Plaza Sésamo ("Sesame Plaza"), Televisa and Children's Television Workshop's (now Sesame Workshop) Spanish-language adaptation of Sesame Street featuring a mix of original segments featuring characters based on its U.S.-based parent series and dubbed interstitials from the aforementioned originating program, on its owned-and-operated stations in Los Angeles, Dallas and Miami. The success of the test run led the network to begin airing the program nationally beginning on December 11 of that year; the program aired on Univision until 2002, when it moved to its newly created sister network TeleFutura as part of its "Mi Tele" ("My TV") block (the Univision network resumed its relationship with the now-Sesame Workshop when it debuted the U.S.-based Spanish language spin-off Sesame Amigos ("Sesame Friends") in August 2015). The network aired its children's programs on weekday and Saturday mornings until April 1997, when Univision relegated its children's programming exclusively to Saturday mornings to make room for its new morning news/talk/lifestyle program ¡Despierta América!.
On March 30, 1996, after the children's block was hiatus since 1993, Univision debuted La Piñata Loca with the host by the comedian, George Ortuzar and entering into an agreement with Hanna-Barbera. A block featuring Spanish dubs of the animated series programming. The sub-block was launched within Saturday morning, "Giorgiomania" and featuring of the cartoon series, Cro (attempt with the based on "Sesame Street" was developed by Children's Television Workshop; now Sesame Workshop). The blocks were discontinued after February 27, 2000, when it was George "O" left Univision before the ending by the air, it was replaced with "¡De Cabeza!" debuted on October 7, 2000, which featured a mix of acquired programming from various provides, including Film Roman (Bruno the Kid and The Twisted Tales of Felix the Cat) and MB Producciones ("Mimi & Mr. Bobo") as well as some Japanese anime series such as Tenchi Universe and Lost Universe part of its inaugural lineup.
In 2003, Univision reduced the amount of children's programming on its schedule, reserving weekend morning and Saturday early afternoon timeslots for youth-oriented telenovelas. Following an agency investigation resulting from complaints by the United Church of Christ and the National Hispanic Media Coalition during license renewal proceedings for a Univision-owned television station in 2005, in February 2007, the FCC levied a $24 million fine – the largest single FCC fine filed against any corporation to that point – against the network's 24 owned-and-operated stations for circumventing federal guidelines requiring broadcast television stations and networks to air at least three hours of educational programming aimed at children by claiming the novelas (with the Televisa-produced Cómplices Al Rescate ("Friends to the Rescue") specifically cited as one example, due to the incorporation of occasional adult themes in some plotlines and complex subplots that were not suitable for younger children) as compliant educational programs in Children's Television Act filings for 116 weeks between 2004 and early 2006. The fine was paid as a component of a settlement that preceded the FCC's approval of Univision's acquisition by Broadcasting Media Partners Inc. to resolve then-pending license renewal applications for O&Os WQHS-TV in Cleveland and KDTV in San Francisco.
Through Univision's agreement to carry more programming that directly complies with the Children's Television Act's educational requirements in its payment of the fine, on March 3, 2008, the network launched a Saturday morning children's programming block, Planeta U ("Planet U"), consisting of Spanish-dubbed versions of American children's programs, with Dora the Explorer (which previously aired on competitor Telemundo via that network's "Nickelodeon en Telemundo" and "Telemundo Kids" blocks respectively), Go, Diego, Go!, Pinky Dinky Doo, Jakers! The Adventures of Piggley Winks, Inspector Gadget's Field Trip and Beakman's World as part of its inaugural lineup.
Before Walt Disney Television entered into an agreement with Univision, a sub-block during the first two hours of the block, "Disney Junior en Univision", debuted within "Planeta U" on June 28, 2014, featuring dubbed versions of Disney Junior original series (with Mickey Mouse Clubhouse and Handy Manny as the first to air as part of the sub-block; the latter's dub incorporates basic instruction in English words and phrases instead of those in Spanish, as the English version features).
=== Specials ===
Univision broadcasts several annual specials, including rights to several major Latin American award shows; through its programming agreement with Televisa, the network has held the U.S. broadcast rights to Premios TVyNovelas, a co-production of Televisa and the television publication TVyNovelas that honors the year's Mexican television programs, including telenovelas, since 1983. The 2013 telecast on April 28 of that year was the first to air simultaneously on Univision and the program's originating broadcaster in Mexico, Canal de las Estrellas.
Since 1989, the network has served as the broadcaster of Premio Lo Nuestro ("Our Thing Awards"), an awards show established by the network to honor the previous year's top artists in Latin music, with nominees initially selected by Univision and Billboard and winners decided by viewers (after Billboard created its own Latin Awards ceremony in 1994, the nominees and winners were selected by a poll conducted among program directors of Spanish-language radio stations throughout the United States, with results were tabulated and certified by Arthur Andersen).
In 2004, the network launched Premios Juventud ("Youthfulness Awards"), a viewer-decided awards show (similar in format and identical in target audience to the Teen Choice Awards) honoring Hispanics and Latinos in film, music, sports, fashion and pop culture. On August 24, 2005, Univision acquired the rights to broadcast the Latin Grammy Awards (which aired on the network for the first time exclusively in Spanish on November 3 of that year), after organizers with the Latin Recording Academy chose to end its four-year relationship with CBS (having canceled the 2001 broadcast following the September 11 attacks) were rebuffed by executives with that network in efforts to retool the show to better cater to a Hispanic audience; the Latin Recording Academy extended its agreement with Univision to televise the Latin Grammys for six years on June 26, 2012.
On October 1, 2012, Univision and Fundación Teletón announced the creation of Fundación Teletón USA, a foundation to benefit rehabilitation centers specializing in research and medical treatment of children with disabilities, cancer and autism around the United States. The partnership resulted in the development of Teletón USA, a 28-hour telethon based on the televised benefit created by Don Francisco – who has hosted the U.S. version since its inception – that originated in Chile in 1978, which was modeled after the now-discontinued telethons benefitting the Muscular Dystrophy Association that were started by Jerry Lewis. The first event on December 14 and 15, 2012 – which was watched by a cumulative 13.9 million viewers through its simulcast on Univision and co-owned radio network Univision America, and via live streaming on Univision.com and the UVideos platforms – raised US$8,150,625 (exceeding its initial goal of US$7 million).
Univision also broadcasts an annual New Year's Eve special, ¡Feliz!, as well as Spanish-language coverage of the Rose Parade.
== Stations ==
As of June 2018, Univision has 27 owned-and-operated stations, and current and pending affiliation agreements with 37 additional television stations, encompassing 25 states, the District of Columbia and the U.S. possession of Puerto Rico. The network has an estimated national reach of 58.35% of all households in the United States (or 182,330,440 Americans with at least one television set), making Univision the largest American Spanish broadcast television network by population reach percentage. Univision maintains affiliations with low-power stations (broadcasting either in analog or digital) in several markets, including a few larger markets such as San Diego (KBNT-CD and its repeater KHAX-LD), Minneapolis−St. Paul (WUMN-LD), and Kansas City (KUKC-LD). In certain other markets, these low-power affiliates also maintain digital simulcasts on a subchannel of a co-owned/co-managed full-power television station.
Currently outside of Univision's core O&O group, Entravision Communications is the network's largest affiliate operator by numerical total and market reach, owning or providing services to 13 primary affiliates of the network (including a station in one top-ten market Boston. In other areas of the U.S., Univision provides a national cable network feed that is distributed directly to cable, satellite and IPTV providers as an alternative method of distribution in markets without either the availability or the demand for a locally based owned-and-operated or affiliate station.
== Related services ==
=== Current sister channels ===
==== UniMás ====
UniMás is a companion Spanish-language broadcast television network that is owned by Univision Communications, which originally launched on January 14, 2002, as TeleFutura; the network adopted its current name on January 7, 2013. The network features programming aimed at young males between the ages of 18 and 35, featuring a mix of telenovelas, soccer events, reruns of classic novelas and comedy series and feature films (primarily Spanish-dubbed versions of American films). As Telefutura, the network carried a similar programming format, including telenovelas produced by Televisa, Coral Productions, Venevision, RCTV, RCN and Rede Globo.
==== Galavisión ====
Galavisión is a cable and satellite network that originally launched on April 2, 1979, as a premium channel that carried classic and recent Spanish-language films (primarily those produced in Mexico) as well as Spanish-dubbed versions of recent American-produced films. The network converted into a general entertainment basic cable channel in 1984, offering programming sourced from Televisa (some of which originally aired on the then-Spanish International Network, and are now sourced from Televisa's Mexican-based networks Canal de las Estrellas, FOROtv, Gala TV and TeleHit) and SIN. During the mid-1990s, Galavisión incorporated some English-language programs to its lineup, as well as select news programs from the Televisa-owned cable news channel ECO. The network airs a mix of telenovelas and comedy series, as well as news, sports and specials originating from the Televisa networks. Other than the fact that both networks carry Televisa-produced programs, Galavisión is not related to Mexico-based Gala TV, which formerly went by the same name as the U.S. channel until 2014.
==== TUDN ====
TUDN is a sports channel operated in partnership between Univision and Televisa; it originally launched in 2012 as the Univision Deportes Network (UDN), serving as an overflow channel for Univision's existing sports rights (including Liga MX and the UEFA Champions League), as well as carrying programming sub-licensed from Televisa Deportes Network. In 2019, both services re-launched as the joint venture TUDN (referring to "Televisa Univision Deportes Network", but with the first two letters pronounced as the pronoun "tu"), signifying a larger degree of collaboration between the two services for studio programming and shared event rights. Univision Deportes Network officially rebranded as TUDN on July 20, 2019.
==== Fusion TV ====
Fusion TV is an American pay television news and satire channel owned by Fusion Media Group, a multi-platform media company owned by Univision Communications, which relies in part on the resources of its parent company's news division, Noticias Univision. In addition to conventional television distribution, Fusion is streamed online and on mobile platforms to subscribers of participating cable and satellite providers.
==== Univision tlnovelas ====
Univision tlnovelas is a digital cable and satellite network that launched on March 1, 2012. The channel carries a mix of first-run and repeat broadcasts of telenovelas sourced from Televisa's program library, in El Canal y las Estrellas, including those that were never previously aired in the United States, as well as content produced by Univision.
=== Video-on-demand services ===
Univision provides video on demand access for delayed viewing of full episodes of the network's programming through various means, including its TV Everywhere service UVideos, a traditional VOD service – called Univision on Demand – which is carried on most traditional cable and IPTV providers, and through content deals with Hulu and iTunes. and Verizon's go90 platform. Due to restrictions imposed on the streaming service by Univision Communications, Hulu limits day-after-air streaming of newer episodes of Univision's programs to subscribers of its subscription service until eight days after their initial broadcast, in order to encourage live or same-week (via both DVR and cable on demand) viewing. Like the video-on-demand television services provided by the other U.S. broadcast networks, Univision on Demand disables fast forwarding for content provided through the service.
==== UVideos ====
On October 29, 2012, Univision launched UVideos, a multi-platform streaming service – which incorporates a user interface accessible to and advertising aimed at both Spanish and English speakers – that originally encompassed a dedicated website at UVideos.com and a mobile app for smartphones and tablet computers supporting the Apple iOS and Android platforms (with programs streamable over 3G and WiFi networks). The service provides full-length episodes of Univision programs (including those produced by Televisa) as well as programs aired on sister networks UniMás and Galavisión, with the most recent episodes usually being made available for streaming on the service (as well as Univision on Demand) the day after their original broadcast to subscribers of participating pay television providers (such as Comcast, Verizon FiOS and Time Warner Cable) using an ISP account via an authenticated user login. The service also includes select original digital content, user-enabled English subtitling for most programs (except for excerpts from Noticiero Univision broadcasts) as well as a social stream featuring viewer comments from the UVideos and other social media platforms, which are time-synched to the user's local time zone to mimic a live relay to the user as posted during the program's original broadcast.
==== Univision NOW ====
On November 18, 2015, Univision launched Univision NOW, an over-the-top subscription video on demand streaming service, which features program content from both Univision and UniMás. Designed as a standalone offering that does not require an existing pay television subscription in order to access, the service is initially available via a dedicated website (univisionnow.com), as well as apps for iOS and Android devices. Available for subscription rates of either $5.99 per month or $59.99 per year, although prospective users can access content through a seven-day free trial, It can also be accessed by using a television provider. Univision NOW is identical to UVideos in terms of content and features, offering a catalog of telenovelas, news programming, reality series, awards shows and archived football matches (due to content restrictions imposed upon by Univision's content distributors, some entertainment programming seen on Univision and UniMás is not available on the service, and is not available for purchase in Puerto Rico, despite Univision's ownership of WLII-DT in the territory).
New episodes of prime time series aired on Univision and UniMás – both original content and programs from their distribution partners – are made available for streaming the day after their broadcast on the two linear television networks and are accessible for seven days following their airdate. In addition to providing full-length episodes of Univision and UniMás programs, the service allows live programming streams from both networks and newscast streams from local Univision owned-and-operated stations in certain markets (with its stations in New York City, Los Angeles and Houston initially being available); the live streams include a DVR-style "rewind" feature that allows users to replay programming from those streams up to 72 hours after their broadcast as well as push notifications to notify subscribers when live breaking news coverage is available. In November 2016 it began adding exclusive content, using the name Univision NOW Originals, with most exclusive content being telenovelas that have not aired on the Univision or UniMas channels, including Sin rastro de ti, Corazón que miente, and most recently, Las amazonas.
=== Univision HD ===
Univision's master feed is transmitted in 1080i high definition, the native resolution format for Univision Communications' network television properties. However, three Univision-affiliated stations transmit the network feed in 480i standard definition; two of the stations (Fort Myers affiliate WLZE-LD and Nashville affiliate WLLC-LD) are primary feed Univision affiliates that have not yet made technical upgrades to their transmission equipment to allow content to be presented in HD, while the third (Hartford affiliate WUVN) runs a standard-definition simulcast of its main HD feed on a digital subchannel.
Univision launched its high definition simulcast feed at 12:02 a.m. Eastern and Pacific Time on New Year's Day, January 1, 2010, on its East and West Coast flagship stations in New York City and Los Angeles, WXTV-DT and KMEX-DT. The first Univision program to be televised in high definition was that day's broadcast of the Tournament of Roses Parade. On January 18, 2010, Univision debuted the first telenovela to be broadcast in HD on the network, Hasta que el Dinero nos Separe ("Until Money Do Us Part"); the telenovelas Un Gancho Al Corazón ("A Hook to the Heart") and Sortilegio ("Love Spell") also began airing in high definition on that date. The network's coverage of the 2010 FIFA World Cup became the first sports event on Univision to be broadcast in HD.
Most of the network's programming is presented in HD As of October 2015 (including most telenovelas; sports programs, including football events and the sports analysis/variety program Republica Deportiva; news programs Noticiero Univision, Primer Impacto, ¡Despierta América!, El Gorda y La Flaca and Al Punto; variety series such as Nuestra Belleza Latina, La Banda and Sabadazo; and select movies) is broadcast by the network in high definition; exceptions exist with certain telenovelas, sitcoms and variety series as well as select children's programs aired as part of the "Planeta U" block produced prior to 2008 that air in reruns, which continue to be presented in their native 4:3 standard definition format. DirecTV added the East Coast HD feed on April 28, 2010. Dish Network added the HD feed on May 12, 2010.
Univision did not fully broadcast in a 16:9 presentation (except for Noticiero Univision: Edición Digital where it is resented in a 16:9 format, select programs such as Vino el amor, and most sporting events by both of the networks although Univision's (and Unimás's) on screen on screen graphics remains orientated in mixed 4:3 and 16:9 presentation for some of its on-screen graphics) until October 1, 2018, when it and UniMás repositioned their on-screen graphics into a 16:9-orientation.
With the deployment of ATSC 3.0, some Univision stations began broadcasting at 1080p such as WUVC-DT in Fayetteville, North Carolina, which broadcasts at 1080p through WRDC in Durham, North Carolina and KSTR-DT in Irving, Texas, which is an UniMás station that simulcasts its sister station, KUVN-DT at 1080p.
=== Other channels distributed by Univision ===
Univision distributes several of Televisa's domestic Mexican broadcast and cable networks in the United States via cable, IPTV and satellite as part of 'Spanish' or 'Latino' tiers requiring additional fees, with American advertising, promotional ads and public service announcements overlaid by Univision.
Bandamax - Banda, Norteño and Regional Mexican music videos
De Película - Modern-day Mexican films
De Película Clásico - Classic Mexican films
FOROtv - Noticieros Televisa rolling news programming
RMS - Modern music videos
TeleHit - Modern pop/rap music videos and comedy programming
=== Univision America ===
Univision America is a Spanish-language talk radio network that is distributed by Univision parent Univision Communications, which was launched on July 4, 2012, with affiliations with nine AM radio stations in Los Angeles, San Francisco and San Diego, California; Dallas and Houston, Texas; Chicago, Illinois, Las Vegas, Nevada; and Orlando and Miami, Florida. The network features talk shows focusing on issues of importance to Hispanic and Latino Americans, and produces features hourly national and international news updates. As of October 2015, Univision America has ten affiliates, all or which are owned by Univision Communications' radio division Univision Radio; it is also distributed nationwide to other areas without a local affiliate via iHeartRadio.
== International broadcasts ==
=== Mexico ===
Univision programming is available in Mexico through affiliates in markets located within proximity to the Mexico–United States border (such as KBNT-CD/San Diego (and repeater KHAX-LD); KUVE-DT/Tucson, Arizona; KINT-TV/El Paso, KLDO-TV/Laredo and KNVO/McAllen), whose signals are readily receivable over-the-air in border areas of northern Mexico. Some U.S.-based border affiliates are also available on subscription television providers throughout the country, including in the Mexico City area include WLTV of Miami, WXTV of the New York City and KMEX of Los Angeles.
=== Colombia ===
In Colombia, Univision programming is available on many cable and satellite providers in that country via either Miami and New York City owned-and-operated stations WLTV or WXTV, along with UniMás, Galavisión and TUDN in that country.
=== Ecuador ===
In Ecuador, Univision programming is available on many cable and satellite providers in that country via either Miami and New York City owned-and-operated stations WLTV or WXTV, along with UniMás, Galavisión and TUDN in that country.
=== Peru ===
In Peru, Univision programming is available on many cable and satellite providers in that country via either Miami and New York City owned-and-operated stations WLTV or WXTV, along with UniMás, Galavisión and TUDN in that country.
=== Canada ===
The U.S.-based Univision network maintains a very limited over-the-air presence in Canada outside of Seattle affiliate KVOS, within parts of the Vancouver market, and Cleveland owned-and-operated station WQHS-DT, within areas within the London, Ontario, market.
On January 28, 2014, Toronto-based Corus Entertainment announced that it would relaunch its cable and satellite specialty channel TLN en Español (a Spanish-language spinoff of Telelatino, which launched on October 23, 2007, and already carried select programs broadcast by Univision through separate programming agreements) as a Canadian version of Univision through a brand licensing agreement with the U.S. network's parent, Univision Communications; the network was relaunched as Univision Canada on May 5, 2014.
=== Caribbean ===
In the Caribbean, Univision is broadcast on affiliated station WLII-DT in Caguas-San Juan and satellite stations WSUR-DT in Ponce and WOLE-DT in Aguadilla; these stations are owned by Liberman Media Group and broadcast under the TeleOnce branding. These stations, which were owned by Univision from 2005 to 2020, do not carry the complete main Univision programming schedule as seen in the United States mainland, offering a mix of programs seen on the main network feed (with some programs airing at different times than in the continental U.S.). In addition, Univision programming is available on many cable and satellite providers in other parts of the Caribbean via either Miami owned-and-operated station WLTV or WLII.
== Carriage disputes ==
Univision, UniMás, Galavisión, Univision Deportes Network and Univision tlnovelas were dropped by AT&T U-verse on March 4, 2016, because of a carriage dispute. Although AT&T also has DirecTV as a subsidiary of AT&T, along with U-Verse, despite being in the process to integrate with DirecTV and U-Verse, DirecTV customers were not affected, as they were taken in a different deal, which had been agreed to before the dispute ever occurred. All of Univision's channels and cable networks were later returned to the U-verse lineup on March 24, 2016.
On January 27, 2017, Charter Spectrum (along with Time Warner Cable and Bright House, which merged with Charter Communications in 2016) faced another dispute with Univision, warning Charter Communications that Univision could be removed from Charter by January 31, 2017. Prior to then, Univision sued Charter over pay carriage rates at the New York Supreme Court in July 2016. On January 31, 2017, Charter customers lost access to all of Univision's channels, including UniMás, UDN, and Galavisión (including access to its Owned-and-Operated Stations via Charter). On February 2, the New York Superior Court ordered Univision to end the blackout on Charter as negotiations continue. This blackout affects all Univision affiliates, even if Univision does not own them, so this dispute includes all stations owned by Entravision Communications, even if Entravision was not involved in the dispute.
On October 16, 2017, at around 5 PM EDT, Verizon FiOS, without any warning, pulled Univision, along with UniMás, UDN, and Galavisión despite the extension of an agreement arranged by the two. It also caused FOROtv to be removed during the dispute as well, despite not being owned by Univision.
On Sunday, July 1, 2018, Univision entered into a dispute with Dish Network and Sling TV. Dish and Sling subscribers lost access to Univision and UniMás east and west channels, affiliated stations, Galavision, Univision Deportes Network, ForoTV news channel and Univisíon tlnovelas channel. Many subscribers cancelled their subscription to Dish or Sling and switched to DirecTV, other streaming TV service, or to a cable provider that offered the Univision-owned channels. On April 1, 2019, a new agreement was reached between Univision Communications and Dish, restoring the channels that had been removed from the lineup, This does not affect Sling TV subscribers.
== See also ==
List of Spanish-language television networks in the United States
List of United States television networks
Telemundo
== References ==
== Further reading ==
Allen, Craig. Univision, Telemundo, and the Rise of Spanish- Language Television in the United States (University of Florida Press, 2020) online review
Álvarez-González, Janet. "Structural Characteristics of the 50 Highest–Rated Television Shows Broadcast by Univision and Telemundo Network for the Hispanic Markets in the United States and Puerto Rico." Journal of Spanish Language Media 3 (2010): 92-122. online
Avilés-Santiago, Manuel G., and Jillian M. Báez. " 'Targeting Billennials': Billenials, linguistic flexibility, and the new language politics of Univision." Communication Culture & Critique 12.1 (2019): 128-146. online
Benamou, Catherine L. "Spanish-Language Television and Diaspora in Detroit and Los Angeles: Toward Latinx Media Enfranchisement." Television & New Media 24.3 (2023): 316-335.
Constantakis-Valdés, Patricia. "Univisión and Telemundo on the campaign trail: 1988." in The mass media and Latino politics. (Routledge, 2009) pp. 157-179. online
Gibens, Guillermo. "Univision and Telemundo: Spanish language television leaders in the United States." in The handbook of Spanish language media (Routledge, 2009). 237-244. online
Moreno Esparza, Gabriel Alberto. "Televisa and Univision, 50 years of media post-nationalism." Global Media and Communication 7.1 (2011): 62-68. online
Nuñez, Luis V. Spanish language media after the Univision-Hispanic Broadcasting (Nova Publishers, 2006) online.
Rodriguez, America. "Objectivity and ethnicity in the production of the Noticiero Univision." Critical Studies in Media Communication 13.1 (1996): 59-81.
Serratore, Nicole. "How Do You Say Big Media in Spanish-Spanish-Language Media Regulation and the Implications of the Univision-Hispanic Broadcasting Merger on the Public Interest." Fordham Intellectual Property, Media and Entertainment Law Journal 15 (2004): 203+ online.
== External links ==
Official website (in Spanish)
Official corporate website (in English)
Spanish International Network historical website (in English)
Univision Archived 2009-02-21 at the Wayback Machine, from the Museum of Broadcast Communications websites
|
https://en.wikipedia.org/wiki/Univision
|
Secure Network Programming (SNP) is a prototype of the first Secure Sockets Layer, designed and built in 1993 by the Networking Research Laboratory at the University of Texas at Austin, led by Simon S. Lam. This work was published in the 1994 USENIX Summer Technical Conference. For this project, the authors won the 2004 ACM Software System Award.
Simon S. Lam was inducted into the Internet Hall of Fame (2023) for "inventing secure sockets in 1991 and implementing the first secure sockets layer, named SNP, in 1993."
This work began in 1991 as a theoretical investigation by the Networking Research Laboratory on the formal meaning of a protocol layer satisfying an upper interface specification as a service provider and a lower interface specification as a service consumer. A case study of adding a security layer between the application and network layers was presented.
The Networking Research Laboratory received a grant from the National Security Agency in June 1991 to investigate how to apply their theory of modules and interfaces to security verification. At that time, there were three well-known authentication systems built (MIT's Kerberos) or being developed (DEC's SPX and IBM's KryptoKnight). All of these systems suffered from a common drawback; namely, they did not export a clean and easy-to-use interface that could be readily used by Internet applications. For example, it would take a tremendous amount of effort to "kerberize" an existing distributed application.
Toward the goal of "secure network programming for the masses", the inventors of SNP conceived secure sockets as a high-level abstraction suitable for securing Internet applications. In 1993, they designed and built a prototype of SNP. Designed as an application sublayer on top of sockets, SNP provides a user interface closely resembling sockets. This resemblance was by design so that security could be retrofitted into existing socket programs with only minor modifications. Also, with such a sublayer carefully designed and its implementation thoroughly debugged, it can be easily used by any Internet application that uses sockets for end-to-end communications. This is a natural idea in hindsight but, in 1993, it was novel and a major departure from mainstream network security research at that time.
SNP's secure sockets support both stream and datagram semantics with security guarantees (i.e., data origin authenticity, data destination authenticity, data integrity, and data confidentiality). Many of the ideas and design choices in SNP can be found in subsequent secure sockets layers, including: placing authenticated communication endpoints in the application layer, use of public-key cryptography for authentication, a handshake protocol for establishing session state including a shared secret, use of symmetric-key cryptography for data confidentiality, and managing contexts and credentials in the secure sockets layer.
The paper presented on June 8, 1994 at the USENIX Summer Technical Conference includes the system design together with performance measurement results from the prototype implementation to clearly demonstrate the practicality of a secure sockets layer.
SNP pioneered secure sockets for Internet applications in general, independently and concurrently with the design and development of the HTTP protocol for the world-wide web which was still in its infancy in 1993. Subsequent secure socket layers (SSL by Netscape and TLS by IETF), implemented several years later using the architecture and key ideas first presented in SNP, enabled secure e-commerce between browsers and servers. Today, many other Internet applications (including email) use HTTPS, which consists of HTTP running over a secure sockets layer.
== References ==
As of 2023-05-10, this article is derived in whole or in part from Networking Research Laboratory. The copyright holder has licensed the content in a manner that permits reuse under CC BY-SA 3.0 and GFDL. All relevant terms must be followed. The original text was at "A brief history of the first secure sockets layer"
|
https://en.wikipedia.org/wiki/Secure_Network_Programming
|
A synchronous programming language is a computer programming language optimized for programming reactive systems.
Computer systems can be sorted in three main classes:
Transformational systems take some inputs, process them, deliver their outputs, and terminate their execution. A typical example is a compiler.
Interactive systems interact continuously with their environment, at their own speed. A typical example is the web.
Reactive systems interact continuously with their environment, at a speed imposed by the environment. A typical example is the automatic flight control system of modern airplanes. Reactive systems must therefore react to stimuli from the environment within strict time bounds. For this reason they are often also called real-time systems, and are found often in embedded systems.
Synchronous programming, also called synchronous reactive programming (SRP), is a computer programming paradigm supported by synchronous programming languages. The principle of SRP is to make the same abstraction for programming languages as the synchronous abstraction in digital circuits. Synchronous circuits are indeed designed at a high level of abstraction where the timing characteristics of the electronic transistors are neglected. Each gate of the circuit (or, and, ...) is therefore assumed to compute its result instantaneously, each wire is assumed to transmit its signal instantaneously. A synchronous circuit is clocked and at each tick of its clock, it computes instantaneously its output values and the new values of its memory cells (latches) from its input values and the current values of its memory cells. In other words, the circuit behaves as if the electrons were flowing infinitely fast. The first synchronous programming languages were invented in France in the 1980s: Esterel, Lustre, and SIGNAL. Since then, many other synchronous languages have emerged.
The synchronous abstraction makes reasoning about time in a synchronous program a lot easier, thanks to the notion of logical ticks: a synchronous program reacts to its environment in a sequence of ticks, and computations within a tick are assumed to be instantaneous, i.e., as if the processor executing them were infinitely fast. The statement "a||b" is therefore abstracted as the package "ab" where "a" and "b" are simultaneous. To take a concrete example, the Esterel statement "'every 60 second emit minute" specifies that the signal "minute" is exactly synchronous with the 60-th occurrence of the signal "second". At a more fundamental level, the synchronous abstraction eliminates the non-determinism resulting from the interleaving of concurrent behaviors. This allows deterministic semantics, therefore making synchronous programs amenable to formal analysis, verification and certified code generation, and usable as formal specification formalisms.
In contrast, in the asynchronous model of computation, on a sequential processor, the statement "a||b" can be either implemented as "a;b" or as "b;a". This is known as the interleaving-based non determinism. The drawback with an asynchronous model is that it intrinsically forbids deterministic semantics (e.g., race conditions), which makes formal reasoning such as analysis and verification more complex. Nonetheless, asynchronous formalisms are very useful to model, design and verify distributed systems, because they are intrinsically asynchronous.
Also in contrast are systems with processes that basically interact synchronously. An example would be systems based on the Communicating sequential processes (CSP) model, which allows deterministic (external) and nondeterministic (internal) choice.
== Synchronous languages ==
Argos
Atom (a domain-specific language in Haskell for hard realtime embedded programming)
Averest
Blech
ChucK (a synchronous reactive programming language for audio)
Esterel
LabVIEW
LEA
Lustre
PLEXIL
SIGNAL (a dataflow-oriented synchronous language enabling multi-clock specifications)
SOL
SyncCharts
== See also ==
Asynchronous programming
Concurrency (computer science)
== References ==
Nicolas Halbwachs. "Synchronous programming of reactive systems". Kluwer Academic Publishers, 1993. http://www-verimag.imag.fr/~halbwach/newbook.pdf
== External links ==
The Synchronous group at Verimag lab.
The SIGNAL programming language.
Unification of Synchronous and Asynchronous Models for Parallel Programming Languages —Proposes parallel languages based on C, lets programmers specify and manage parallelism on a broad range of computer architectures.
|
https://en.wikipedia.org/wiki/Synchronous_programming_language
|
Chance Constrained Programming (CCP) is a mathematical optimization approach used to handle problems under uncertainty. It was first introduced by Charnes and Cooper in 1959 and further developed by Miller and Wagner in 1965. CCP is widely used in various fields, including finance, engineering, and operations research, to optimize decision-making processes where certain constraints need to be satisfied with a specified probability.
== Theoretical Background ==
Chance Constrained Programming involves the use of probability and confidence levels to handle uncertainty in optimization problems. It distinguishes between single and joint chance constraints:
Single Chance Constraints: These constraints ensure that each individual constraint is satisfied with a certain probability.
Joint Chance Constraints: These constraints ensure that all constraints are satisfied simultaneously with a certain probability.
== Mathematical Formulation ==
A general chance constrained optimization problem can be formulated as follows:
min
f
(
x
,
u
,
ξ
)
s.t.
g
(
x
,
u
,
ξ
)
=
0
,
Pr
{
h
(
x
,
u
,
ξ
)
≥
0
}
≥
α
{\displaystyle \min f(x,u,\xi ){\text{s.t. }}g(x,u,\xi )=0,\Pr\{h(x,u,\xi )\geq 0\}\geq \alpha }
Here,
f
{\displaystyle f}
is the objective function,
g
{\displaystyle g}
represents the equality constraints,
h
{\displaystyle h}
represents the inequality constraints,
x
{\displaystyle x}
represents the state variables,
u
{\displaystyle u}
represents the control variables,
ξ
{\displaystyle \xi }
represents the uncertain parameters, and
α
{\displaystyle \alpha }
is the confidence level.
Common objective functions in CCP involve minimizing the expected value of a cost function, possibly combined with minimizing the variance of the cost function.
== Solution Approaches ==
To solve CCP problems, the stochastic optimization problem is often relaxed into an equivalent deterministic problem. There are different approaches depending on the nature of the problem:
Linear CCP: For linear systems, the feasible region is typically convex, and the problem can be solved using linear programming techniques.
Nonlinear CCP: For nonlinear systems, the main challenge lies in computing the probabilities and their gradients. These problems often require nonlinear programming solvers.
Dynamic Systems: Dynamic systems involve time-dependent uncertainties, and the solution approach must account for the propagation of uncertainty over time.
== Practical Applications ==
Chance constrained programming is used in engineering for process optimisation under uncertainty and production planning and in finance for portfolio selection. It has been applied to renewable energy integration, generating flight trajectory for UAVs, and robotic space exploration.
=== Process Optimization Under Uncertainty ===
CCP is used in chemical and process engineering to optimize operations considering uncertainties in operating conditions and model parameters. For example, in optimizing the design and operation of chemical plants, CCP helps in achieving desired performance levels while accounting for uncertainties in feedstock quality, demand, and environmental conditions.
=== Production Planning and Operations ===
In production planning, CCP can optimize production schedules and resource allocation under demand uncertainty. A typical problem formulation involves maximizing profit while ensuring that production constraints are satisfied with a certain probability.
=== Chance-Constrained Portfolio Selection ===
Chance-constrained portfolio selection is an approach to portfolio selection under loss aversion which is based on CCP. The goal is to maximize expected returns while ensuring that the portfolio's risk (e.g., variance or downside risk) stays within acceptable levels with a certain probability. This approach allows investors to consider the uncertainty in asset returns and make more informed investment decisions.
== References ==
|
https://en.wikipedia.org/wiki/Chance_constrained_programming
|
Tea is a high-level scripting language for the Java environment. It combines features of Scheme, Tcl, and Java.
== Features ==
Integrated support for all major programming paradigms.
Functional programming language.
Functions are first-class objects.
Scheme-like closures are intrinsic to the language.
Support for object-oriented programming.
Modular libraries with autoloading on-demand facilities.
Large base of core functions and classes.
String and list processing.
Regular expressions.
File and network I/O.
Database access.
XML processing.
100% pure Java.
The Tea interpreter is implemented in Java.
Tea runs anywhere with a Java 1.6 JVM or higher.
Java reflection features allow the use of Java libraries directly from Tea code.
Intended to be easily extended in Java. For example, Tea supports relational database access through JDBC, regular expressions through GNU Regexp, and an XML parser through a SAX parser (XML4J for example).
== Interpreter alternatives ==
Tea is a proprietary language. Its interpreter is subject to a non-free license. A project called "destea", which released as Language::Tea in CPAN, provides an alternative by generating Java code based on the Tea code.
TeaClipse is an open-source compiler that uses a JavaCC-generated parser to parse and then compile Tea source to the proprietary Tea bytecode.
== References ==
== External links ==
Tea Home Page
"destea" code converter
|
https://en.wikipedia.org/wiki/Tea_(programming_language)
|
Broadcast syndication is the practice of content owners leasing the right to broadcast their content to other television stations or radio stations, without having an official broadcast network to air it on. It is common in the United States where broadcast programming is scheduled by television networks with local independent affiliates. Syndication is less widespread in the rest of the world, as most countries have centralized networks or television stations without local affiliates. Shows can be syndicated internationally, although this is less common.
Three common types of syndication are: first-run syndication, which is programming that is broadcast for the first time as a syndicated show and is made specifically for the purpose of selling it into syndication; Off-network syndication (colloquially called a "rerun"), which is the licensing of a program whose first airing was on stations inside the television network that produced it, or in some cases a program that was first-run syndicated, to other stations; and public broadcasting syndication.
== Types ==
=== First-run syndication ===
In first-run syndication, a program is broadcast for the first time as a syndicated show. Often these programs are made specifically to sell directly into syndication and not made for any particular network.
=== Off-network syndication ===
In off-network syndication, a program whose first airing was on network television (or, in some cases, first-run syndication) is licensed for local broadcast on individual stations. Reruns are usually found on stations affiliated with smaller networks like The CW or MyNetworkTV, especially since these networks broadcast one less hour of prime time network programming than the Big Four television networks and far less network-provided daytime television (none at all for these networks). A show usually enters off-network syndication when it has built up about four seasons' worth or between 80 and 100 episodes, though for some genres the number could be as low as 65. Successful shows in syndication can cover production costs and make a profit, even if the first run of the show was not profitable.
=== Public broadcasting syndication ===
This type of syndication has arisen in the U.S. as a parallel service to member stations of the Public Broadcasting Service (PBS) and the handful of independent public broadcasting stations. This form of syndication more closely resembles the news agency model, where nominally competing networks share resources and rebroadcast each other's programs. For example, National Public Radio (NPR) stations commonly air the Public Radio Exchange's This American Life, which may contain stories produced by NPR journalists.
== Process ==
When syndicating a show, the production company, or a distribution company called a syndicator, attempts to license the show to one station in each media market or area, or to a commonly owned station group, within the country and internationally. If successful, this can be lucrative, but the syndicator may only be able to license the show in a small percentage of the markets. Syndication differs from licensing the show to a television network. Once a network picks up a show, it is usually guaranteed to run on most or all the network's affiliates on the same day of the week and at the same time (in a given time zone, in countries where this is a concern). Some production companies create their shows and license them to networks at a loss, at least at first, hoping that the series will succeed and that eventual off-network syndication will turn a profit for the show. A syndicated program is licensed to stations for "cash" (the stations purchase the rights to local insertion some or all of the advertisements at their level); given to stations for access to airtime (wherein the syndicators get the advertising revenue); or the combination of both. The trade of program for airtime is called "barter."
In the United States (as a result of continued relaxation of station ownership regulations since the 1970s), syndicated programs are usually licensed to stations on a group level, with multiple stations owned and/or operated by the same broadcasting group carrying the program in different markets (except in areas where another station holds the market rights to the program) – making it increasingly more efficient for syndicators to gain widespread national clearances for their programs. Many syndicated programs are traditionally sold first to one of six "key" station groups (ABC Owned Television Stations, NBC Owned Television Stations, CBS Television Stations, Fox Television Stations, Telemundo Station Group, and Televisa Univision), allowing their programs to gain clearances in the largest U.S. TV markets (such as New York City, Los Angeles, San Francisco and Philadelphia, where all six aforementioned groups each own stations), before striking deals with other major and smaller station owners. Shows airing in first-run syndication that are carried primarily by an owned-and-operated station of a network may sometimes be incorrectly referenced as a network program, especially if said network's syndication wing distributes the program, regardless to its distribution to stations of varying network affiliations and despite the fact it is not part of an individual network's base schedule.
Since the early 2000s, some programs being proposed for national distribution in first-run syndication have been test marketed on a selected number of or all stations owned by certain major station group, allowing the distributor to determine whether a national roll-out is feasible based on the ratings accrued in the selected markets where the program is being aired.
While market penetration can vary widely and revenues can be unreliable, the producers often enjoy more content freedom in the absence of network's standards and practices departments; frequently, some innovative ideas are explored by first-run syndicated programming which the networks are leery of giving airtime to. Meanwhile, top-rated syndicated shows in the United States usually have a domestic market reach as high as 98%. Very often, series that are aired in syndication have reduced running times. For example, a standard American sitcom runs 22 minutes, but in syndication it may be reduced to 20 minutes to make room for more commercials.
Syndication can take the form of either weekly or daily syndication. Game shows, some "tabloid" and entertainment news shows, and talk shows are broadcast daily on weekdays, while most other first-run syndicated shows are broadcast on a weekly basis and are usually aired on weekends only. Big discussion occurred in the 1990s and 2000s about whether previously aired episodes of a show could become syndicated while new episodes of it continued to air on its original network. There had been much opposition to this idea and it was generally viewed to lead to the death of the show. However, licensing a program for syndication actually resulted in the increased popularity for shows that remained in production. A prime example is Law & Order.
== First-run syndication in the U.S. ==
As with radio in the U.S., television networks, particularly in their early years, did not offer a full day's worth of programming for their affiliates, even in the evening or "prime time" hours. In the early days of television, this was less of an issue, as there were in most markets fewer TV stations than there were networks (at the time four), which meant that the stations that did exist affiliated with multiple networks and, when not airing network or local programs, typically sign-on and sign-off. The loosening of licensing restrictions, and the subsequent passage of the All-Channel Receiver Act, meant that by the early 1960s, the situation had reversed. There were now more stations than the networks—now down to three in number after the failure of the DuMont Television Network—could serve. Some stations were not affiliated with any network, operating as independent stations. Both groups sought to supplement their locally produced programming with content that could be flexibly scheduled. The development of videotape and, much later, enhanced satellite down link access furthered these options. While most past first-run syndicated shows were shown only in syndication, some canceled network shows continued to be produced for first-run syndication or were revived for syndication several years after their original cancellation. Until about 1980, most syndicated series were distributed to stations either on 16mm film prints (off-network reruns, feature films, and cartoons) or videotape (topical series such as the talk shows of Mike Douglas and Merv Griffin, and variety and quiz shows).
Ziv Television Programs, after establishing itself as a major radio syndicator, was the first major first-run television syndicator, creating several long-lived series in the 1950s and selling them directly to regional sponsors, who in turn sold the shows to local stations. Ziv's first major TV hit was The Cisco Kid. Ziv had the foresight to film The Cisco Kid in color, even though color TV was still in its infancy and most stations did not yet support the technology. Among the most widely seen Ziv offerings were Sea Hunt, I Led Three Lives, Highway Patrol and Ripcord. Some first-run syndicated series were picked up by networks in the 1950s and early 1960s, such as the Adventures of Superman and Mr. Ed. The networks began syndicating their reruns in the late 1950s, and first-run syndication shrank sharply for a decade. Some stalwart series continued, including Death Valley Days; other ambitious projects were also to flourish, however briefly, such as The Play of the Week (1959–1961), produced by David Susskind (of the syndicated talk show Open End and also producer of such network fare as NYPD).
Among other syndicated series of the 1950s were MCA's The Abbott and Costello Show (vaudeville-style comedy) and Guild Films' Liberace (musical variety) and Life With Elizabeth, a domestic situation comedy that introduced Betty White to a national audience. In addition to the Adventures of Superman, many other series were based on comic strips and aimed at the juvenile audience, including Flash Gordon, Dick Tracy, Sheena, Queen of the Jungle, and Joe Palooka. Original juvenile adventure series included Captain Gallant of the Foreign Legion, Cowboy G-Men, and Ramar of the Jungle. Series based on literary properties included Sherlock Holmes, Long John Silver (based on Treasure Island), and The Three Musketeers. Several of these were co-productions between American and European (usually British) companies. Crusader Rabbit pioneered in the area of first-run animated series; followed by Bucky and Pepito, Colonel Bleep, Spunky and Tadpole, Q. T. Hush, and others. (All of these were five-minute shorts designed to be placed within locally hosted kiddie shows.) Syndicated sports programming included Championship Bowling and All-Star Golf, both produced by Chicago-based Walter Schwimmer Inc.
In addition to regular series, syndicators also offered packages of feature films, cartoons, and short subjects originally made for movie theaters. Until late in the 1950s, however, much of the theatrical product available consisted of low-budget secondary features (mainly Westerns) with relatively few notable stars. One syndication company, National Telefilm Associates, attempted to create a "NTA Film Network" of stations showing its lineup of first-run series, which included syndicated programs such as Police Call (1955), How to Marry a Millionaire (1957–1959), The Passerby, Man Without a Gun (1957–1959), and This Is Alice (1958). The venture lasted five years and closed down in 1961.
By the late 1960s, a de facto two-tiered system had developed in the United States, with the major network affiliates (usually on longer-range VHF stations) consistently drawing more viewers than their UHF, independent counterparts; syndicators thus hoped to get their programs onto the major network stations, where spots in the lineup were far more scarce. Federal Communications Commission (FCC) rulings in 1971 curtailed the American networks' ability to schedule programming in what has become known as the "fringe time", notably the 7–8 p.m. (Eastern and Pacific Time) hour of "prime time", with the stated hope that this might encourage more local programming of social and cultural relevance to communities (off-network syndicated repeats were also banned); some projects of this sort came to fruition, though these were usually relatively commercial and slick efforts such as Group W's Evening/PM Magazine franchise, and such pre-existing national projects as the brief commercial-television run of William F. Buckley Jr.'s interview/debate series Firing Line. The more obvious result was an increase in Canadian-produced syndicated dramatic series, such as Dusty's Trail and the Colgate-sponsored Dr. Simon Locke. Game shows, often evening editions of network afternoon series, flourished, and a few odd items such as Wild Kingdom, canceled by NBC in 1971, had a continuing life as syndicated programming tailor-made for the early fringe.
=== 1970s and 1980s ===
In 1971, the U.S. FCC passed the Prime Time Access Rule and Financial Interest and Syndication Rules, which prevented networks from programming one particular hour of prime time programming on its television stations each night and required the networks to spin off their syndication arms as independent companies. Although the intent of the rule was to encourage local stations to produce their own programs for this time slot, budgetary limits instead prompted stations to buy syndicated programs to fill the slot. This, coupled with an increase in UHF independent stations, caused a boom in the syndication market. In the 1970s, first-run syndication continued to be an odd mix: cheaply produced, but not always poor quality, "filler" programming. These included the dance-music show Soul Train, and 20th Century Fox's That's Hollywood, a television variation on the popular That's Entertainment! theatrically released collections of film clips from the Metro-Goldwyn-Mayer library.
There were also many imported programs distributed this way. These include the documentary series Wild, Wild World of Animals (repackaged by Time Life with narration by William Conrad) and Thames Television's sober and necessarily grim The World at War. The Starlost (1973) was a Canadian series, apparently modified from the vision of science fiction writers Harlan Ellison and Ben Bova. Britain's ITC Entertainment, headed by Lew Grade, made UFO (1970) and Space: 1999 (1975). These two series were created by Gerry Anderson (and his associates), previously best known for Supermarionation (a combination of puppetry and animation) series such as Thunderbirds. The most successful syndicated show in the United States in the 1970s was probably The Muppet Show, also from Lew Grade's company. Animated series from the 1980s Dogtanian and the Three Muskehounds and Around the World with Willy Fog came from Spanish animation production company BRB Internacional and their Japanese co-producers Nippon Animation.
Game shows thrived in syndication during the decade. Nightly versions of What's My Line?, Truth or Consequences, Beat the Clock and To Tell the Truth premiered in the late 1960s and found loyal audiences for many years. Several daytime network games began producing once-a-week nighttime versions for broadcast in the early evening hours, usually with bigger prizes and often featuring different hosts (emcees were limited to appearing on one network and one syndicated game simultaneously) and modified titles (Match Game PM, The $100,000 Name That Tune or The $25,000 Pyramid, for example). A few independent game shows, such as Sports Challenge and Celebrity Bowling, also entered the syndication market around this time. Of these shows, Let's Make a Deal and Hollywood Squares were the first to jump to twice-a-week syndicated versions, in about 1973. Another popular daytime show to have a weekly syndicated version was The Price Is Right, which began concurrently in weekly syndication and on CBS; the syndicated "nighttime" version was hosted by Dennis James for its first five years, after which daytime host Bob Barker took over for another three years of weekly episodes (even though, by this point, the daytime and nighttime shows had diverged noticeably). The nighttime version of Family Feud (1977) quickly jumped from once-weekly to twice, and finally to five-day-a-week airings, and its massive popularity, along with that of new five-day-a-week entries like Jack Barry's The Joker's Wild (1977) and Tic-Tac-Dough (1978), the move of Match Game's daily run from CBS to syndication (1979), and Chuck Barris's increasingly raunchy remakes of his 1960s hits The Newlywed Game and The Dating Game, brought an end (with rare exceptions) to the era of once-a-week games. Also popular in first-run syndication and daytime was The Gong Show, hosted by Barris throughout most of its run (Gary Owens hosted the first syndicated season).
A number of half-hour musical-variety shows were also offered in the early 1970s, generally built around personable middle-of-the-road singers like Bobby Vinton, Bobby Goldsboro, Dolly Parton, and Andy Williams, or groups like Sha Na Na, The Johnny Mann Singers, and The Golddiggers. Wait Till Your Father Gets Home (1972) was a Hanna-Barbera cartoon series attempting to ape the All in the Family-style sitcoms; Skippy the Bush Kangaroo (1969), an Australian children's series, or Gentle Ben (a decade later, the decidedly not-for-children Australian Prisoner: Cell Block H would have a brief American syndicated run); and a Canadian sketch-comedy series began appearing on U.S. television stations in 1977—Second City Television, which would eventually find a home, for two seasons, on NBC, as SCTV Network 90 (and on premium cable channel Cinemax by 1983).
The Universal/Paramount-produced package of original programming, Operation Prime Time, began appearing on ad hoc quasi-networks of (almost by necessity) non-network stations in the U.S. in 1978, with a mini-series adaptation of John Jakes' The Bastard. From the later 1960s into the late 1970s, Westinghouse also found considerable success with The Mike Douglas Show, a variety/talk show hosted by a singer with an easygoing interview style, which aired in the afternoons in most markets; similar programs soon followed featuring Merv Griffin, who had been the host of CBS' most sustained late-night answer to The Tonight Show Starring Johnny Carson previously, and another network veteran, Dinah Shore. Also notable was the growing success of audience-participation talk shows, particularly that of the innovator of the format, Phil Donahue.
First-run syndication in the 1970s also made it possible for some shows that were no longer wanted by television networks to remain on the air. In 1971, ABC canceled The Lawrence Welk Show, which went on to produce new episodes in syndication for another 11 years, and currently continues to much success in weekend reruns (with new segments featuring Welk cast members inserted within the episodes) distributed to PBS stations by the Oklahoma Educational Television Authority. Also in 1971, CBS dropped Lassie and Hee Haw, the latter show's run ending as part of the network's cancellation of all of its rural-oriented shows (known then as "rural purge", which also resulted in the cancellations of The Beverly Hillbillies and Green Acres). Lassie entered first-run syndication for two years, while Hee Haw continued to produce new episodes until 1992.
The 1980s are also notable for the court show genre being introduced into syndication. It began with The People's Court, an American program featuring an arbitrator handling small claims disputes in a simulated courtroom set. The People's Court was the first of all arbitration-base reality programs, which later exploded in popularity beginning in the late 1990s. The original series ran from 1981 to 1993, with the revival airing from 1997 to 2023. Both versions ran in first-run syndication.
==== First-run syndicated comedy ====
Throughout the mid-to-late 1980s into the early 1990s, sitcoms continued to enter first-run syndication after being canceled by the networks, the most successful of which were Mama's Family and Charles in Charge. Other sitcoms during this time to enter first-run syndication after network cancellation included Silver Spoons, Punky Brewster, Webster, It's a Living, Too Close for Comfort, 9 to 5, What's Happening!!, and WKRP in Cincinnati. Many of these sitcoms produced new shows in syndication mainly to have enough episodes for a profitable run in reruns. Other sitcoms, such as Small Wonder, Out of This World, The Munsters Today, and Harry and the Hendersons (as well as more action-adventure oriented series like Superboy and My Secret Identity) enjoyed success in syndication throughout their entire run.
==== Dramatic first-run syndicated programs ====
The broadcast networks aired many action-adventure programs from the 1950s to the 1980s. By the late 1980s, however, increasing production costs made them less attractive to the networks. Studios found that reruns of one-hour dramas did not sell as well as sitcoms, so they were unable to fully recoup the shows' costs using the traditional deficit financing model. When NBC canceled the television series adaptation of Fame after only two seasons, the producers made special arrangements with LBS Communications, which resulted in MGM reviving the series for first-run syndication in the fall of 1983, where it continued for four more seasons, with the last first-run episode airing in the U.S. on May 18, 1987.
Star Trek: The Next Generation debuted in 1987, and became the most-watched syndicated show throughout its seven-year run. Its great success caused many others to debut. Friday the 13th: The Series (a horror series which shared its title with the successful movie franchise) also debuted in 1987. The next syndicated shows that debuted in 1988 were War of the Worlds and Freddy's Nightmares. Baywatch, which debuted in 1989 on NBC and was canceled after one season also became one of the most watched syndicated shows throughout its ten-year-run, garnering a worldwide audience.
By 1994, there were more than 20 one-hour syndicated shows. Star Trek: Deep Space Nine and Renegade were also syndicated. Hercules: The Legendary Journeys and its spin-off series Xena: Warrior Princess were also popular, often tying Deep Space Nine at 5% to 6% of the Nielsen-monitored audience. Forever Knight drew devoted "cult" audiences (3% rating). Psi Factor and Poltergeist: The Legacy attempted to draw on the audience for the Fox series The X-Files (as did the short-lived spinoff Baywatch Nights). Among the other series were Relic Hunter, V.I.P., High Tide, She Spies, and Once a Thief.
Babylon 5 began life in 1993 on the Prime Time Entertainment Network (PTEN), moved into syndicated distribution when its network was displaced by WB/UPN-affiliated stations, and eventually ended its final season on TNT (1998). In 1997 Earth: Final Conflict, based on ideas from Gene Roddenberry, premiered in syndication. Three years later, a second Gene Roddenberry series, Andromeda also premiered in syndication. As emerging networks WB and UPN signed contracts with formerly-independent stations, and the syndication market shrunk, Andromeda season 5 moved to the Syfy Channel (2004).
There was not another first-run syndicated drama (or a first-run scripted series in syndication) until 2008, when Disney-ABC Domestic Television and ABC Studios teamed up with Sam Raimi to launch a new first-run syndicated series, Legend of the Seeker, based on Terry Goodkind's Sword of Truth novel series. Another gap in first-run scripted series in syndication followed for four years after Legend of the Seeker was canceled in 2009, until Trifecta Entertainment & Media (a company that mainly distributes programs for off-network syndication) began producing SAF3 (pronounced "safe") in 2013.
==== Animated series ====
During the late 1970s and 1980s, independent stations signed on in mid-sized and many small markets. The market for made-for-television cartoons grew as a result to include a branch for such stations. It usually had a greater artistic freedom, and looser standards (not mandated by a network). The older Bugs Bunny and Popeye cartoons made way for first-run syndicated cartoons such as He-Man and the Masters of the Universe, Inspector Gadget, Heathcliff, ThunderCats, My Little Pony, The Transformers, G.I. Joe, Voltron, Teenage Mutant Ninja Turtles, and reruns of Scooby-Doo, Garfield and Friends, and The Pink Panther, among many others.
Syndication was also important for the nascent anime community in the United States, with imports like Speed Racer and Star Blazers (a localized edit of Space Battleship Yamato) helping to grow interest in Japanese animation. This led to the establishment of companies dedicated to importing and translating anime such as Streamline Pictures and Viz Media towards the end of the 1980s.
In 1987, The Walt Disney Company tried its luck at syndication; DuckTales premiered that September and would eventually last for 100 episodes. The success of DuckTales paved the way for a second series two years later, Chip 'n Dale: Rescue Rangers. The following year, the two shows aired together under the umbrella block The Disney Afternoon. In the fall of 1990, Disney added another hour to The Disney Afternoon; the block continued in syndication, running additional first-run animated series until 1999.
These cartoons initially competed with the ones that were nationally televised on the broadcast networks. In the 1980s, national broadcast networks only aired cartoons on Saturday mornings, not competing with the weekday and Sunday syndication blocks aired by local independent stations; however, by the 1990s, Fox and then The WB launched their own weekday afternoon children's program blocks. By the end of the 1990s, both syndication distributors and broadcast networks ended up losing most of their children's market to the rise of cable television channels aimed at that audience such as Nickelodeon and Cartoon Network, which provided appealing children's entertainment throughout the week at nearly all hours.
Syndication remains a method of choice for distributing children's programming, although this has gradually shifted to only produce programs to satisfy the federally mandated "regulations on children's television programming in the United States" (E/I) rule imposed in the late 1990s as part of an amendment to the Children's Television Act of 1990 that requires stations to air three hours of educational children's programs every week, regardless of the station's format. Syndication is generally a less expensive option for a local station than to attempt to produce its own locally originated E/I programming; not all networks provide their own E/I programs, so stations that are affiliated with networks that do not carry children's program blocks acquire E/I programs off the syndication market to fulfill the requirements.
==== News programming and late-night talk shows ====
Also in the 1980s, news programming of various sorts began to be offered widely to stations. Independent Network News, which was produced by WPIX in New York City, was a half-hour nightly program that ran from 1980 to 1990 on independent stations (in some markets, INN was paired with a locally produced primetime newscast); CNN would offer a simulcast of programming from its sister network Headline News (now HLN) to broadcast stations later, as did its rival All News Channel, although both were used mainly to fill overnight time periods and were effectively discontinued in syndication when All News Channel folded in 2002 and HLN launched a "Headline Prime" talk show block in 2006. In 2019, NewsNet began offering a similar service to its affiliates. Entertainment Tonight began its long and continuing run as a "soft" news daily strip, with a number of imitations following (among which have included such entertainment news shows as TMZ on TV, Extra and ET's own spin-off The Insider); and "tabloid" television, in the wake of ABC's 20/20 and, more immediately, 20th Television's A Current Affair, would become a syndication staple with such series as Hard Copy and Real TV.
Another area where network dominance was challenged by syndicated programming in the 1980s was with late-night talk shows; The Arsenio Hall Show was the only very successful one (it would be canceled after five years in 1994 due to ratings declines spurred by many CBS affiliates pushing the show to later timeslots following the debut of the Late Show with David Letterman, and was later revived in 2013), but similar programs were attempted such as Alan Thicke's earlier short-lived Thicke of the Night, Lauren Hutton's innovatively shot Lauren Hutton and..., and talk shows hosted by Dennis Miller, Whoopi Goldberg, David Brenner and Keenen Ivory Wayans; Magic Johnson's The Magic Hour was seen as a massive flop, similar to Thicke of the Night. The popularity of syndicated talk shows fell dramatically in the mid-1990s as network and cable offerings expanded in the wake of Johnny Carson's retirement.
==== Reality and live-action children's shows ====
Long before their popularity on network television from the 2000s onward, reality competition shows in one form or another, such as Star Search and American Gladiators, enjoyed popularity in syndication as early as the mid-1980s. Since the now-defunct networks UPN and The WB began offering their affiliates additional nights of prime time programming in the late 1990s, there have been fewer first-run scripted series in syndication, at least, in the U.S.; much as with the closing of windows that provided opportunity for Ziv in the 1950s and various producers in the early 1970s. The more expensive dramatic projects are less attractive to syndicators (particularly when they might be sold, with somewhat less risk, to cable channels); "reality" series such as Cheaters and Maximum Exposure and several dating series began to be more common in the early 2000s. Some of the more low-key programs in this category were designed to appeal to children, such as Beakman's World, Disney's Sing Me A Story with Belle, Animal Rescue and Jack Hanna's Animal Adventures. They were able to get significant clearance because of stricter Federal Communications Commission (FCC) enforcement of rules on children's television programming.
==== Game shows ====
Several game shows are currently syndicated; historically, the most popular have been Wheel of Fortune and the current version of Jeopardy!, both created by television personality Merv Griffin, respectively premiering in 1983 and 1984. The shows have been No. 1 and No. 2 or No. 1 to No. 3 in the syndication ratings consistently since at least the late 1980s. In fact, according to the Guinness Book of World Records, Wheel is the most popular syndicated television program both within and outside the United States. Family Feud, created by Mark Goodson and Bill Todman, ended its first syndication run in 1985. Three years later, a revival of the program featuring Ray Combs as host became a moderate hit and continued for seven seasons, its last year featuring the return of original host Richard Dawson in a failed attempt to save the series. A third revival hit the airwaves in 1999 and has gone through four hosts. The first three hosts (Louie Anderson, Richard Karn and John O'Hurley) struggled in their respective runs and only lasted three to four years. The current run of the program, hosted by Steve Harvey, has been a major ratings success; on the week of June 12, 2015, for the first time ever, Family Feud was the highest-rated syndicated program in terms of average household ratings.
While the current version of The Price Is Right (another Goodson-Todman game show) has enjoyed tremendous success on the CBS daytime schedule since its inception in 1972 under hosts Bob Barker and Drew Carey, it has also produced three spinoffs, two of which failed after one season. The most successful syndicated edition was the 1972–80 weekly version that was initially hosted by Dennis James, but in 1977, daytime host Bob Barker also hosted the nighttime version for the final three seasons. For the 1985–86 season, Tom Kennedy hosted a daily syndicated version, and in 1994–95, Doug Davidson emceed his own daily syndicated version, titled The New Price Is Right. Unlike the daytime series, which expanded to its current one-hour length in 1975, the syndicated versions of Price were 30 minutes long. A Hollywood Squares revival also thrived beginning in 1998 under host Tom Bergeron, running six seasons until its 2004 cancellation. By far the most successful entry into the market in the 2000s has been the daily version of Who Wants to Be a Millionaire, which premiered in September 2002 and was canceled in May 2019 after 17 seasons in syndication (and a total run of 20 seasons dating back to the show's premiere in August 1999).
Because game shows are very inexpensive to produce, with many episodes completed each day of production, successful ones are very profitable; for example, in 1988 Jeopardy! cost an estimated $5 million to produce but earned almost $50 million in revenue. New game show concepts (that is, not based on an existing or pre-existing format) are rarely tried and usually unsuccessful in syndication; somewhat of an exception to this was Street Smarts, which lasted from 2001 to 2006 (despite the series airing in late night slots in many markets). Between 2003 and 2007, no new game shows debuted in syndication, marking four consecutive seasons where no new shows with that genre debuted, a syndication first. That streak ended with the fall 2007 debuts of Temptation and Merv Griffin's Crosswords, bringing the daytime tally to six game shows; both ended production after one year, though Crosswords aired in reruns in some cities during the 2008–09 season before those reruns moved exclusively to cable.
More new shows were added for the 2008–09 fall season, including a daytime run of Deal or No Deal (which featured certain elements that differed from the show's franchised format, most notably with prospective players instead of models holding briefcases that held the monetary amounts) and an adaptation of the popular board game Trivial Pursuit. While Deal or No Deal caught on and was renewed for the 2009–2010 season, Trivial Pursuit: America Plays suffered low ratings throughout its run and was canceled.
For the 2009–2010 season, the Fox game show Are You Smarter than a 5th Grader? moved to syndication with a new, less expensive format. Don't Forget the Lyrics! followed for the 2010–2011 season. Deal, suffering from falling ratings, was canceled in February 2010, with the final episodes airing in late May of that same year; it would later be revived by CNBC in 2018. 5th Grader and Don't Forget the Lyrics! were canceled the following year for the same reason (although 5th Grader would later be revived by Fox and Nickelodeon on two different occasions). Reruns of the popular Discovery Channel show Cash Cab began airing in syndication in January 2011. Reruns of the GSN dating game show Baggage first aired in syndication as a test run in early 2011 on stations owned by the Sinclair Broadcast Group, which preceded its full launch into other markets in fall 2012; although it was removed from syndication after one season.
The 2014–15 season saw the introduction of Celebrity Name Game, hosted by former The Late Late Show host Craig Ferguson; the series was renewed for a second season in January 2015, while Ferguson would also win a Daytime Emmy Award for Daytime Emmy Award for Outstanding Game Show Host for his work on the program. In January 2016, Fox owned-and-operated stations began a test run of South of Wilshire—a game show produced by TMZ. The 2017 summer season includes the game show iWitness created by TV judge Judith Sheindlin. 2021 saw the debut of a revival of You Bet Your Life that reunited host Jay Leno and sidekick Kevin Eubanks from their time on The Tonight Show; it ran two seasons, before Leno left during the 2023 Hollywood labor disputes. 2022 saw the debut of a televised edition of the hit board game Pictionary, and 2023 saw the debut of two new games, Person, Place or Thing and Who the Bleep Is That. Who the Bleep Is That was cancelled in January 2024, while Pictionary and Person, Place or Thing were both cancelled in January 2025.
==== Stripped talk shows ====
The dominant form of first-run syndication in the U.S. for the last three decades has been the "stripping" (or "strip") talk show, such as Donahue, Oprah, The Tyra Banks Show, and Jerry Springer. Strip programming is a technique used for scheduling television and radio programming to ensure consistency and coherency. Strip programming is used to deliver consistent content to targeted audiences. Broadcasters know or predict the times at which certain demographics will be listening to or watching their programs and play them at that time.
As with game shows, talk shows are inexpensive to produce and very profitable if successful. They have a disadvantage in that their costs can be higher than some other formats due to the high volume of episodes needed. In many markets, a stripped show will be seen twice daily, usually with different episodes (one being a more recent episode and the other being an episode from a previous season). Sometimes, station groups with more than one station in a market, or a "duopoly", will run one episode of a strip on one of their stations in the morning, and the other available episode on another of their stations that night.
Meanwhile, the popularity of some of the audience-participation talk shows continues to encourage new participants, some of whom, such as Morton Downey Jr. and Rosie O'Donnell, have brief periods of impressive ratings and influence; others, such as Oprah Winfrey and Maury Povich, have a sustained run. A notable scheduling decision was made by KRON-TV in San Francisco: a 2000 dispute with NBC led to that station's disaffiliation from that network after 52 years, and since all the other larger networks were already represented in San Francisco, KRON decided to become one of the largest commercial independent stations by market size on the VHF band in the U.S., and soon tried running Dr. Phil, a popular new stripped series hosted by Winfrey-associate Dr. Phil McGraw, in primetime, with impressive ratings results.
With a general decline in first-run production in the 2020s, syndicators and stations have turned to reruns of stripped talk shows to fill time slots, with observers noting that conflict-driven tabloid shows tend to draw higher ratings in reruns than non-tabloid shows.
=== 2000s ===
First-run syndicated shows in the United States include talk shows (e.g., The Dr. Oz Show, Dr. Phil, The Real, The Doctors, The Ellen DeGeneres Show & The Kelly Clarkson Show); tabloid/newsmagazine shows (e.g., TMZ Live); crime/law enforcement shows (e.g., Crime Watch Daily); game shows (e.g., Hollywood Squares, Funny You Should Ask, Family Feud, Jeopardy! and Wheel of Fortune); court shows (e.g., Judge Judy, Judge Mathis, Judge Jerry, Judge Faith, Protection Court, Hot Bench, America's Court with Judge Ross, and The People's Court); and sitcoms (e.g., The First Family).
== Influence on television schedules ==
The emergence of barter syndication in the 1980s caused the number of independent stations to grow from fewer than 100 in 1980 to 328 as of 1986, as they did not need cash for programming. With the loosening of FCC regulations and the creation of new additional broadcast networks (such as The CW and MyNetworkTV), most of these independents have joined one or another of these or smaller (religious or low-budget) networks.
In other cases, like those of KCAL-TV in Los Angeles, KMCI-TV in Lawrence-Kansas City and WMLW-TV in Racine-Milwaukee, those independent stations are used to complement their network-affiliated sister station (respectively in the mentioned cases, KCBS-TV, KSHB-TV and WDJT-TV) by allowing a duopoly control of more syndicated programming than would be possible on one station (and to spread it throughout the schedule of the two stations, often several times a day), or to air news programming in times unavailable on the larger network station, along with fulfilling network and syndicated programming commitments, which allows popular or network programming to be moved to the independent stations due to breaking news or sports commitments without the traditional inconvenience of a late night or weekend airing of the pre-empted show. A duopoly of a network-affiliated and independent station also allows a network station to move a low-rated syndicated program to their sister independent station to stem revenue losses.
== Off-network syndication ==
Off-network syndication occurs when a network television series is syndicated in packages containing some or all episodes, and sold to as many television stations and markets as possible to be used in local programming timeslots. In this manner, sitcoms are preferred and more successful because they are less serialized, and can be run non-sequentially, which is more beneficial and less costly for the station. In the United States, local stations now rarely broadcast reruns of primetime dramas (or simply air them primarily on weekends); instead, they usually air on basic cable channels, which may air each episode 30 to 60 times.
Syndication rights typically last for six consecutive showings of a series within three to five years; if a program continues to perform well enough in broadcast or cable syndication during the initial cycle, television stations or cable networks can opt to renew an off-network program for an additional cycle.
Syndication has been known to spur the popularity of a series that only experienced moderate success during its network run. The best known example of this is the original Star Trek series, which ran for three seasons on NBC from 1966 to 1969, gaining only modest ratings, but became a worldwide phenomenon after it entered off-network syndication. Its success in syndication led to the Star Trek film series, Star Trek: The Next Generation, and the later versions in the franchise.: 91–92
It is common for long-running series to have early seasons syndicated while the series itself is still in first-run network production. To differentiate between new and rebroadcast content, until the 1980s it was not uncommon for series to be syndicated under a different title than that used in their original broadcast run. Examples include Bonanza (which was syndicated as Ponderosa), Gunsmoke (as Marshal Dillon, a title still used to differentiate reruns from the early, half-hour episodes of the show from the later one-hour episodes), Emergency! (as Emergency One), Ironside (as The Raymond Burr Show), Hawaii Five-O (as McGarrett), M*A*S*H (as M*A*S*H 4077th), Marcus Welby, M.D. (as Robert Young, Family Doctor), CHiPs (as CHiPs Patrol), Happy Days (as Happy Days Again), and The Andy Griffith Show (as Andy of Mayberry).
Syndication of older episodes can also increase exposure for a television show that is still airing first-run network episodes. In the case of the CBS sitcom The Big Bang Theory, its syndication, particularly on TBS, is one of the reasons attributed for a rise in first-run ratings for its sixth season. The sixth-season episode "The Bakersfield Expedition", for example, was the first episode of that series to attract 20 million viewers.
=== Strip/daily syndication ===
Off-network syndication can take several forms. The most common form is known as strip syndication or daily syndication, when episodes of a television series are shown daily five times a week in the same time slot. In the 1960s and 1970s, independent stations with no news departments began viewing strip syndication as a necessary means of obtaining effective counterprogramming to the local news programs airing on network affiliates. Typically, this means that enough episodes must exist (88 episodes, or four seasons, is the usual minimum, though many syndicators prefer a fully rounded 100 episodes) to allow for continual strip syndication to take place over the course of several months, without episodes being repeated. However, there are exceptions, such as the 65-episode block (common in children's programming), which allows for a 13-week cycle of daily showings, so there will only be four repeats in a year.
In some cases, more than one episode is shown daily. Half-hour sitcoms are sometimes syndicated in groups of two or four episodes, taking up one or two hours of broadcast time. If a series is not strip syndicated, it may be aired once a week, instead of five times a week. This allows shows with fewer episodes to last long in syndication, but it also may mean viewers will tire of waiting a week for the next episode of a show they have already seen and stop watching. More often, hour-long dramas in their first several runs in syndication are offered weekly; sitcoms are more likely to get stripped. In recent years, there has been something of a trend toward showing two consecutive episodes of a program on Saturday and Sunday nights after prime time (generally following the local news). This pattern has been particularly prominent for shows which are still in production but have run long enough to have many previous episodes available.
As with commercial stations, not all the airtime nor all the perceived audience are met by the productions offered U.S. public-broadcasting stations by PBS; additionally, there are some independent public television stations in the U.S. which take no programming from that (somewhat) decentralized network. As a result, there are several syndicators of programming for the non-profit stations, several of which are descendants of the regional station groups which combined some, not all, of their functions into the creation of PBS in 1969. American Public Television (APT) is the largest of these, nearly matched by the National Educational Telecommunications Association (NETA, a merger of Southern Educational Communications Association and the Pacific Mountain Network). The now defunct Continental Program Marketing was another of the syndicator-descendants (of the Northeastern, Southeastern, and Rocky Mountain educational networks, respectively) of the pre-PBS era. Among the other notable organizations in the U.S. are Westlink Satellite Operations (based at Albuquerque's KNME) and Executive Program Services.
Off-network syndication in its various forms, including Internet, international and traditional direct-to-station sales, constitute roughly half of an individual television program's overall revenue stream, with the other half taken up by advertising.
== Monetary rates ==
In 1993, Universal Television became one of the first studios to cash in on the cable trend, first selling repeats of Major Dad to USA Network in 1993 for $600,000 per episode, the first time a network program was exclusively sold to a cable network for its first run rights. Later it sold reruns of Law & Order to A&E for about $155,000 an episode; in 1996, the studio got $275,000 from USA Network for repeats of New York Undercover, a far less successful show. Law & Order drew A&E's highest daytime ratings – one million viewers per episode.
Universal sold reruns of Xena: Warrior Princess and Hercules: The Legendary Journeys to USA Network for $300,000 each. And even long-forgotten shows can find new life: Paramount Network bought The Dukes of Hazzard from Warner Bros. in 1997 for well over $10 million. USA Network paid $750,000 for the rights to Walker, Texas Ranger; while USA's reruns of the show drew an average of 2.3 million viewers – outstanding by cable standards – Perth says the show will need "an enormous number of airings to have any sort of profitability."
=== Dramatic reruns: rerun prices ===
Sources: Industry sources and Paul Kagan Associates, Inc. Per episode
Not all programs in syndication are sold for a fee. Less popular programming may be distributed by barter, in which the syndicator, instead of selling the show to a station, offers the show for free, with the caveat that the station give up its advertising time on other shows to the syndicator's advertisers. Barter syndication, in addition to the cost advantage, is popular because of its flexibility; a station can typically pick up a barter syndicated program for only a few weeks or months, without the long-term financial commitment of a traditional syndicated series, allowing the station to plug the show into its lineup to fill a hole in the schedule.
== Types of deals ==
Cash deals are when a distributor offers a syndicated program to the highest bidder. A cash plus deal is when the distributor retains advertising space to offset some of the cost for the program. The station gets the program for a little less in exchange for some ad space for the producer.
Barter deals are usually for new untested shows or older shows. In this type of deal, distributors get a fraction of the advertisement revenue in exchange for their program. For example, in a 7/5 deal the producer gets seven minutes of advertising time, leaving five minutes for the station to insert local as well as national advertisements.
== Radio syndication ==
Radio syndication generally works the same way as television syndication, except that radio stations usually are not organized into strict affiliate-only networks. Radio networks generally are only distributors of radio shows, and individual stations (though often owned by large conglomerates) decide which shows to carry from a wide variety of networks and independent radio providers. As a result, radio networks such as Westwood One or Premiere Networks, despite their influence in broadcasting, are not as recognized among the general public as television networks like CBS or ABC (many of these distributors ally themselves with television networks; Westwood One, for instance, is allied with NBC News, while Premiere is allied with Fox). Some examples of widely syndicated commercial broadcasting music programs include weekly countdowns like Rick Dees' Weekly Top 40, the American Top 40, American Country Countdown with Kix Brooks, Canada's Top 20 Countdown, the Canadian Hit 30 Countdown and the nightly program, Delilah, heard on many U.S. stations.
Syndication is particularly popular in talk radio. While syndicated music shows (with the exception of some evening and overnight shows such as Delilah mentioned above) tend to air once a week and are mostly recorded, most popular talk radio programs are syndicated daily and are broadcast live. Also, with relatively few 24-hour live talk radio networks (though this, in recent times, has been changing), most radio stations are free to assemble their own lineup of talk show hosts as they so choose. Examples of syndicated talk programs are Premiere Networks' The Bob & Tom Show, Dial Global's The Jim Bohannon Show, and the self-syndicated The Dave Ramsey Show (more recently, talk networks such as Talk Radio Network have been marketing and packaging all-day lineups, marking a departure from the syndication model; as such, popular shows such as Cumulus Media Networks' The Savage Nation and Premiere's The Rush Limbaugh Show now air as part of a broader network lineup in many markets, particularly on Premiere owned-and-operated stations, though they continue to be syndicated to non-network stations as well). Talk syndication tends to be more prevalent because voice tracking, a practice used by many music stations to have disc jockeys host multiple supposedly local shows at once, is not feasible with live talk radio.
National Public Radio, Public Radio International, and American Public Media all sell programming to local member stations in the U.S., most of which are subsidized through the Corporation for Public Broadcasting but operated by private nonprofit organizations, universities, state or local governments. This is in contrast to centralized public radio networks in other countries (such as Canada's CBC, Australia's ABC and the United Kingdom's BBC) that own and operate all of their stations as arms of the national government and run them as a strict network (from 1948 to 2013, the United States had a strict anti-propaganda law, the Smith–Mundt Act, that prohibited broadcasting government-owned networks such as Voice of America to American audiences. The law was mostly repealed in 2013, but distribution of VOA or other federally produced radio programming is still rare). Two independently produced, non-commercial syndicated programs, heard on hundreds of community radio and indie radio stations, are Alternative Radio and Democracy Now!. Some (in fact, most) radio programs are also offered on a barter system usually at no charge to the radio station. The system is used for live programming or preproduced programs and include a mixture of ad time sold by the program producer as well as time set aside for the radio station to sell.
=== History ===
Before radio networks matured in the United States, some early radio shows were reproduced on transcription disks and mailed to individual stations. An example of syndication using this method was RadiOzark Enterprises, Inc. based in Springfield, Missouri, co-owned with KWTO. The Assembly of God, with national headquarters in Springfield, sponsored a half-hour program on the station called Sermons in Song. RadiOzark began transcribing the show for other stations in the 1940s, and eventually 200 stations carried the program. The company later produced country music programs starring among others, Smiley Burnette, George Morgan, Bill Ring and Tennessee Ernie Ford (260 15-minute episodes of The Tennessee Ernie Show were distributed), and more than 1,200 U.S. and Canadian stations aired the programs. Many syndicated radio programs were distributed through the U.S. mail or another delivery service, although the medium changed as technology developed, going from transcription disks to phonograph records, tape recordings, cassette tapes and eventually CDs. Many smaller weekend programs still use this method to this day, though with the rise of the Internet, many stations have since opted to distribute programs via CD-quality MP3s through FTP downloads.
It was not until the advent of communications satellite in the 1980s that live syndication became popular (though it could be transmitted through network lines, it was not particularly common because of cost, network congestion and quality issues). Since then, most syndicated radio programs are distributed using satellite subcarrier audio technology. Shortly after satellite networks such as RKO, Transtar, and SMN began, the Fairness Doctrine was repealed, which is credited with helping Rush Limbaugh become the first national talk radio superstar. At the same time, the FCC began issuing more FM broadcasting licenses to suburban and rural areas in the late 1980s, which allowed more room for music stations on the FM dial; radio formats such as country music that were traditionally AM fixtures even after most pop and rock music moved to FM were now moving to FM as well, leaving much more room for talk formats on the AM dial. As the 1990s went on, Laura Schlessinger and Howard Stern began their national shows, rising to become national icons. The Telecommunications Act of 1996, which led to significant concentration of media ownership, facilitated the rapid deployment of both existing and new syndicated programs in the late 1990s, putting syndication on par with, and eventually surpassing, the network radio format.
After the September 11 attacks, syndicated talk radio saw a notably rapid rise in popularity, as networks rushed new national shows into syndication to meet the demand for discussion of national issues. Many of these, such as Laura Ingraham, Bill O'Reilly, Sean Hannity and Glenn Beck, were mostly supportive of the actions of the Republican-led government; a few others, such as Alex Jones, were openly critical of the government's actions and motives. After the Democrats took control in the late 2000s, the gap between the two styles narrowed due to the mutual opposition of both camps to the government's actions, which allowed Jones greater clearance on stations.
In contrast to conservative talk radio, which has predominantly been driven by syndication, progressive talk radio has almost always been a network-driven model. The incompatibility of conservative and progressive ideologies and the lack of syndicated progressive hosts required solutions that could produce all-day programming to individual stations. It was not until Air America Radio launched in 2004 that progressive talk would become viable; though it failed several years later, Dial Global now carries a network slate that is carried on most progressive talk stations. Sports radio is likewise mostly a network phenomenon, partially because the irregular nature of sports pre-emptions makes having a full-time network to be able to cut into and join in progress at any time highly convenient. Syndicated radio is not as popular in other parts of the world. Canada has a few independently syndicated shows, but the bulk of syndicated content there comes from the United States, and the sum total of syndicated programming is far less than most American stations, as Canadian stations rely more heavily on local content. Most other countries still follow the network radio model.
== International syndication ==
Syndication also applies to international markets. Same language countries often syndicate programs to each other – such as programs from the United Kingdom being syndicated to Australia and vice versa. Another example would be programs from the United Kingdom, Mexico, Brazil, and Argentina being syndicated to local television stations in the United States, and programs from the United States being syndicated elsewhere in the world. One of the best-known internationally syndicated television series has been The Muppet Show, which was produced by Grade's British ITV franchise company ATV at Elstree Studios in Hertfordshire, and was shown around the world, including the United States, where it aired in syndication (including the owned-and-operated stations of CBS), and Canada, where CBC Television aired the show. The 1970s was a time when many British comedies, including The Benny Hill Show and Monty Python's Flying Circus were syndicated to the United States and worldwide. Many soaps and long-running series are also successfully syndicated around the globe.
The television show CSI: Crime Scene Investigation earned $1.6 million per episode in its first cycle in cable syndication. There were many different versions of the show making it an international success. It was already popular in the U.S., so becoming a success internationally as well as within the U.S. made syndication sensible. Whether a series is produced in the U.S. or not is based on the economic value and potential viability of its sales internationally with the possibility of syndication.
Economic factors that influence production outside the U.S. play a major role in deciding if a television show will be syndicated, internally and internationally. International syndication has sustained a growing of prosperity and monetary value amongst the distributors who sell to them. Due to a rise in competition, syndicators have upheld high standards for different countries to buy the rights to distribute shows. During the 1990s poor ratings were common amongst syndicated shows, but distributors still made it possible for international competition to happen and buy U.S. shows. Colombian, Brazilian, Mexican and Venezuelan telenovelas are programmed throughout the Portuguese and Spanish-speaking world, and in many parts of India, Philippines, China and Europe, while Turkish television drama is broadcast in the Balkans, some other European countries, Western and Central Asia and North Africa.
=== American-style syndication internationally ===
Because of the structural differences discussed above, there are presently very few areas where a true American-style syndication model operates, whereby programs are sold on a per-area basis (within a single country) to local or regional stations with differing (or no) network affiliations. Canada was historically one of the few exceptions. Until the mid-1990s, television stations in Canada, like those in the U.S., were typically run as separate local operations, with a small number of moderately sized ownership groups such as Baton, Canwest, WIC, and CHUM. Those stations that were affiliated with a national network, i.e. CBC or CTV, did not always receive a full schedule of programming from that network.
At this time, it was not uncommon for American syndicators to treat Canada as an extension of their domestic syndication operations, for both their first-run and off-network offerings. This is still the case for American radio programs; Canadian radio networks are not assembled as rigidly into networks (except for the CBC's radio division). However, an alternate form of first-run syndication was performed by some domestic broadcasters: as the Canadian rights to American primetime series were often acquired by individual station groups (as opposed to full-fledged national networks), they would in turn resell local rights for those programs to stations in areas where they did not operate. A few of Canada's independent stations, most notably CHCH-TV and CITY-TV, also resyndicated their own locally produced programs to other television stations. Unlike in the United States, however, few Canadian programs were ever created solely for syndication without officially belonging to at least one specific station or network; those that did exist were intended primarily to be syndicated into the American system, and even those were typically distributed in Canada as "network" programs rather than being sold to individual stations.
Since the late 1990s, as most stations have been consolidated into national networks consisting almost entirely of owned-and-operated stations and with full-day network schedules, both types of syndication have largely disappeared from the Canadian broadcast landscape. Programs that are sold in syndication in the U.S. are now generally sold to Canadian media groups to air across all their properties, with per-market sales now being very rare. For example, American shows that air in syndication in the United States, such as Live with Kelly and Ryan or The Ellen DeGeneres Show, air in Canada as core parts of the CTV Television Network schedule. The Oprah Winfrey Show appears to have been the last significant holdout to this model, having aired primarily on CTV stations, but in some markets airing instead on a Global station, and even some CBC affiliates.
One syndication service remains in Canada, Yes TV, which serves the few remaining independent stations in the country with mostly American programs (Judge Judy, Wheel of Fortune and Jeopardy! are currently syndicated in Canada through Yes TV). These independent stations can also secure deals with American syndicators; CHCH, for example, has a direct deal with 20th Television to carry some of that company's classic sitcoms, including those from the MTM Enterprises library. They were also, in 1986, largely involved in production of the final incarnation of Split Second game show, which was syndicated in U.S. by Viacom.
== Regional syndication ==
There are three key reasons why a radio station will decide to pick up a syndicated show – the program is unique and has difficult to replicate content, has a decent ratings track record or offers a celebrity host. New developing radio programs are generally able to claim one of these attributes, but not all three. Regional syndication attempts to replace these benchmark attributes with other benefits that are generally recognized by the industry as also being important. Given the financial downturn within the industry, the need for quality cost effective locally relevant programming is greater than ever before. Programs that offer regionally specific content while providing the economic benefits of syndication can be especially appealing to potential affiliates. Regional syndication can also be more attractive to area advertisers who share a common regional trading area versus assembling a radio network of stations that hopscotch across the United States.
== See also ==
100 episodes
Direct-to-video
First run (filmmaking)
Flagship (broadcasting)
Print syndication
Rerun
Syndication exclusivity
Video on demand
Web syndication
== References ==
=== Sources ===
"The Museum of Broadcast Communications". Archived from the original on October 9, 2009. Retrieved October 8, 2004.
Television Obscurities – The Syndicated Season: 1987–1988
C21 Media – daily news about the TV business
Radio-Info.com Discussion Boards > National Television Topics > Syndication TV (archived 25 June 2011)
Uso del Feed para sindicación – Web de Mangotropia (archived 25 March 2016)
|
https://en.wikipedia.org/wiki/Broadcast_syndication
|
DIBOL or Digital's Business Oriented Language is a general-purpose, procedural, imperative programming language that was designed for use in Management Information Systems (MIS) software development. It was developed from 1970 to 1993.
DIBOL has a syntax similar to FORTRAN and BASIC, along with BCD arithmetic. It shares the COBOL program structure of separate data and procedure divisions. Unlike Fortran's numeric labels (for GOTO), DIBOL's were alphanumeric; the language supported a counterpart to computed goto.
== History ==
DIBOL was originally marketed by Digital Equipment Corporation (DEC) in 1970.
The original version, DIBOL-8, was produced for PDP-8 systems running COS-300. The PDP-8-like DECmate II, supports the COS-310 Commercial Operating System, featuring DIBOL.
DIBOL-11 was developed for the PDP-11 running COS-350 operating system. It also ran on RSX-11, RT-11, and from 1978 on RSTS/E. DIBOL-32 runs on VMS systems, although it can also be used on other systems through emulators.
ANSI Standards were released in 1983, 1988 and 1992 (ANSI X3.165-1992). The 1992 standard was revised in 2002.
DIBOL compilers were developed by several other companies, including DBL from DISC (later Synergex), Softbol from Omtool, and Unibol from Software Ireland, Ltd. Development of DIBOL effectively ceased after 1993, when an agreement between DEC and DISC replaced DIBOL with DBL on OpenVMS, Digital UNIX, and SCO Unix.
== See also ==
Timeline of programming languages
== References ==
== Reading ==
American National Standards Institute; Computer and Business Equipment Manufacturers Association (CBEMA) (1988). American National Standard for Information Systems- Programming Language, DIBOL. New York, NY: American National Standards Institute. OCLC 23056850. {{cite book}}: |author2= has generic name (help)
American National Standards Institute; Computer and Business Equipment Manufacturers Association (CBEMA) (1992). American National Standard for Information Systems- Programming Language, DIBOL. New York, NY: American National Standards Institute. OCLC 27058852. {{cite book}}: |author2= has generic name (help)
|
https://en.wikipedia.org/wiki/DIBOL
|
Max (formerly HBO Max) is an over-the-top subscription service owned and operated by Warner Bros. Discovery and run by Warner Bros. Entertainment. It distributes a number of original shows, including original series, specials, miniseries, and documentaries and films. The movies and television shows produced for Max are dubbed "Max Originals", and had this name prior to the rebranding of HBO Max to Max on May 23, 2023. HBO Max was an expanded library of programming compared to the former HBO Now, which only carried HBO programming. Max Originals are specifically made for audiences outside of the traditional baseline HBO brand.
== Original programming ==
=== Drama ===
=== Comedy ===
=== Kids & family ===
=== Animation ===
==== Adult animation ====
==== Kids & family ====
=== Non-English language scripted ===
=== Unscripted ===
==== Docuseries ====
==== Reality ====
==== Variety ====
=== Co-productions ===
These are productions that Max co-produced and aired shortly after the show's initial premiere on its parent network.
=== Continuations ===
These shows have been picked up by Max for additional seasons after having aired previous seasons on another network.
=== Specials ===
These programs are one-time original events or supplementary content related to television shows.
=== Regional original programming ===
These shows are originals because HBO Max commissioned or acquired them and had their premiere on the service, but they are not available worldwide.
== Original podcasts ==
=== Scripted ===
=== Unscripted ===
== Upcoming original programming ==
These shows have had their original production or additional seasons commissioned by Max.
=== Drama ===
=== Non-English language scripted ===
=== Unscripted ===
==== Docuseries ====
==== Reality ====
=== Continuations ===
These shows have been picked up by Max for additional seasons after having aired previous seasons on another network.
=== In development ===
== Notes ==
== References ==
|
https://en.wikipedia.org/wiki/List_of_Max_original_programming
|
Stations in Canada's CBC Radio One network each produce some local programming in addition to the network schedule.
The amount of local programming may vary from station to station. For instance, some stations in smaller markets may produce their own morning show but air an afternoon show from another station. Some stations in major markets also preempt some regular network programming in favour of an extended local schedule.
Some regional programming is also produced which is shared by all stations in a province. This most commonly applies to daily noon-hour shows, weekend morning shows and a Saturday afternoon arts and culture magazine.
== Content ==
Local programs on CBC Radio One feature news and human interest content local to the region they serve. Each program also includes both national and local news headline segments. Some general content segments, such as business news reports, science news reports and entertainment reviews, air across the network on all local programs.
Some local segments from the various morning and afternoon programs are also aired on the national network program The Story from Here.
At the top of each hour during the morning and afternoon programs, national newscasts – World Report in the mornings and The World This Hour in the afternoons – air for the first ten minutes. A shorter local newscast typically airs at the half-hour mark.
On statutory holidays, nearly all local programming is preempted in favour of network-wide special programming. In heavily populated provinces like Ontario, the various local morning shows within often rotate broadcasting for the entire province. On Christmas Day, the entire daytime broadcasting schedule, and most of the evening is preempted for holiday music programming except for news programming such as World Report and Your World Tonight.
== Weekday programming ==
Local morning shows air from 5:30 am or 6 am local time, depending on the station, to 8:30 am. They are followed by a local news update, and then The Current at 8:37 am. The sole exception is Qulliq, the program from Nunavut, which begins at 6:30 am ET and airs until 9:30 am ET. As of the 2015-16 television season, the 6:00 a.m. hour of these programs outside of CBC North air on local CBC television stations.
Local afternoon shows on CBC Radio One air from 4 pm to 6 pm local time, except in Halifax, Ottawa, Toronto, Winnipeg, Calgary, Edmonton, Vancouver and Victoria, where they start at 3 pm. Rebroadcasters outside of those cities do not air the first hour of the extended afternoon shows; they stay with regional or conventional network programming and then rejoin their host station's afternoon show at 4 pm.
In addition to the standard local programming blocks, the stations in Nunavut, the Northwest Territories, and northern Quebec also preempt much of the network's afternoon schedule to produce additional local programming in aboriginal languages. See CBC North for further information. (Pre-6 am morning show start times are listed in brackets in the table)
== Weekend programming ==
Each province and territory also has a regional weekend morning show, which airs provincewide Saturday and Sunday mornings from 6 to 9 am, and most also have a regional arts and culture magazine which airs on Saturday afternoons scheduled around the live nationwide call-in show, Just Asking, depending on the local time zone. Stations in the Atlantic provinces air an additional regional arts and culture program on Sunday afternoons at 4 pm. AT, due in part to a hole in the schedule created by the fact that Cross Country Checkup airs live across Canada at 5 pm. AT. CBI in Sydney airs the long running Island Echoes, a weekly cultural program on Saturday evenings at 8 p.m AT.
In parts of Western Canada, however, distinct Saturday afternoon arts and culture magazines are no longer aired; the stations air a repeat broadcast of the national network program Unreserved.
== References ==
|
https://en.wikipedia.org/wiki/CBC_Radio_One_local_programming
|
This is a list of programs formerly broadcast by the now-defunct children's television channel Qubo in the United States, a children's network which existed from January 8, 2007, until February 28, 2021.
Also detailed are Qubo-branded children's programming blocks which were carried by Ion Television and its subnetwork Ion Life/Ion Plus, NBC, and Telemundo. The Qubo blocks ended on the Ion networks on February 26, 2021, and on NBC and Telemundo on July 1, 2012.
== Qubo Channel ==
=== Former programming ===
==== Original programming ====
==== Acquired programming ====
===== NBCUniversal =====
===== Corus Entertainment =====
===== Scholastic Entertainment =====
===== 9 Story Media Group =====
===== WildBrain =====
===== Splash Entertainment =====
===== Bellum Entertainment Group =====
===== Other companies =====
==== Programming from Nick Jr. ====
==== Programming from Discovery Kids ====
==== Programming from PBS Kids ====
==== Interstitial programming ====
==== Blocks ====
=== Scrapped programming ===
==== Acquired programming ====
===== Cookie Jar/WildBrain library =====
== Qubo-branded blocks ==
=== NBC ===
==== Original programming ====
==== Acquired programming ====
==== Short-form programming ====
=== Telemundo ===
==== Original programming ====
All programming utilized the Spanish-language dub.
==== Acquired programming ====
==== Short-form programming ====
=== Ion Television ===
==== Former programming ====
==== Original programming ====
==== Acquired programming ====
==== Short-form programming ====
=== Ion Life/Plus ===
==== Acquired programming ====
==== Short-form programming ====
== References ==
|
https://en.wikipedia.org/wiki/List_of_programs_broadcast_by_Qubo
|
Liberty BASIC (LB) is a commercial computer programming language and integrated development environment (IDE). It has an interpreter, developed in Smalltalk, which recognizes its own dialect of the BASIC programming language. It runs on 16- and 32-bit Windows and OS/2.
== Background ==
Liberty BASIC was written by Carl "Gunner" Gundel and published in its first release by his company, Shoptalk Systems, in 1991. It has progressed steadily since then. The last published update to the software, version 4.5.1, was in June 2018.
Though Liberty BASIC has its share of limitations in its design for advanced programming, it provides an introductory integrated development environment, IDE, for moderate to advanced users of Windows and OS/2. Dynamic-link libraries (DLLs) are available. In its current version, it runs only on Microsoft Windows, and under Wine on Linux. Alpha testing of Liberty BASIC v5.0 is underway with versions that run on Microsoft Windows, Mac OS X, Linux and on the Raspberry Pi as well.
Liberty BASIC does not compile to native code. Instead it compiles the code written in the IDE to an encrypted file with the extension TKN. This file is then executed by an EXE file that carries the same file name, although this may change with the release of version 5.
== Features ==
A visual development tool called FreeForm, written in Liberty BASIC and greatly extended by the Liberty BASIC community over the years
Source level debugger
calling of DLLs and application programming interfaces (APIs)
Color graphics capability
Can create games with sprite animation, sound, music, and joystick control
An add-on package called Assist with many new features, such as a code formatter, source code versioning, a performance profiler, an easy-to-use code difference browser, and an improved package and deployment system
=== Distinguishing features ===
Liberty BASIC allows for procedural programming using a default "main window" that displays formatted text and accepts user input. It also supports event-driven programming based on a graphical user interface, using several types of windows that may contain the standard controls such as buttons, menus, textboxes, etc.
A central idea in creating Liberty BASIC was to model the handling of windows after the syntax for file handling. For example, (from the Liberty BASIC Help File):
"The OPEN command opens communication with a device, which can be a disk file, a window, a dynamic-link library or a serial communications port."
Once a “device” is open, data and also commands to control that device can be “printed” to it. For each type of device there is a set of commands which can be sent to it in this way. In the more recent versions of LB the word "print" may be dropped from the "print" statement, making the syntax even simpler.
Simplicity has been at the heart of Liberty BASIC from the beginning. This makes it easier to learn but at some cost, perhaps, in limiting functionality. Only two data types are supported in LB v4.03 — numeric and string. No type declarations are required; any variable with a $ sign at the end of its name is a string variable, otherwise it is numeric. (The plan for LB v5 is to support other types and user defined types as well as these.) For the purpose of making calls to an API or third-party DLLs there is a STRUCT and the additional types necessary for the DLL. The only other data structure supported is the ARRAY. Arrays of one or two dimensions are supported. LB v5 may support arrays of user-defined types.
== Notable programs written in Liberty BASIC ==
FreeForm, a GUI editor for creating GUI formats
== Example code ==
Here are some examples of the language:
"Hello, World!" program:
Program to display a pop-up message box with the words "Hello, World!" on it:
Program to display an input box:
Running another application:
Printing multiplication table of 5 on form:
== Alternative implementations ==
The GNU/Liberty Basic Compiler Collection (GLBCC), by Anthony Liguori, is a set of tools to compile Liberty Basic programs, runs on Windows and Linux systems, but the project has not been updated since 2001.
In 2012 an alternative Windows implementation of Liberty BASIC, LB Booster (LBB), became available. Although substantially compatible with the Liberty BASIC 4 language syntax, LBB was developed entirely independently by Richard Russell and is written in BBC BASIC.
LBB offers (typically) increased execution speed, smaller self-contained executables and some additional capabilities. However LBB is not 100% compatible with LB4 and while many programs will run without modification, some may need to be adapted, or may even be unsuitable for running under LBB.
Liberty Basic does not provide for data declarations. Instead any new data name is treated as a new declaration. Some regard this as a benefit, others see it as a debugging issue for imperfect typers. In 2019 Peter J. D. Matthews devised a method for adding declarations and checking for undeclared data - without changing the code seen by the LB interpreter. In 2023 this system was ported to GitHub in public repository "LBPrePass" for anyone to use. This repository also contains program documentation. The program is written in Liberty Basic 4.5.1 and is intended to analyse 4.5.1 code.
== References ==
== External links ==
www.libertybasic.com — official site
Carl Gundel's blog
Liberty BASIC (in French)
Liberty BASIC on Rosetta Code
GNU/Liberty Basic Compiler Collection (GLBCC)
LB Booster
|
https://en.wikipedia.org/wiki/Liberty_BASIC
|
Multi-objective optimization or Pareto optimization (also known as multi-objective programming, vector optimization, multicriteria optimization, or multiattribute optimization) is an area of multiple-criteria decision making that is concerned with mathematical optimization problems involving more than one objective function to be optimized simultaneously. Multi-objective is a type of vector optimization that has been applied in many fields of science, including engineering, economics and logistics where optimal decisions need to be taken in the presence of trade-offs between two or more conflicting objectives. Minimizing cost while maximizing comfort while buying a car, and maximizing performance whilst minimizing fuel consumption and emission of pollutants of a vehicle are examples of multi-objective optimization problems involving two and three objectives, respectively. In practical problems, there can be more than three objectives.
For a multi-objective optimization problem, it is not guaranteed that a single solution simultaneously optimizes each objective. The objective functions are said to be conflicting. A solution is called nondominated, Pareto optimal, Pareto efficient or noninferior, if none of the objective functions can be improved in value without degrading some of the other objective values. Without additional subjective preference information, there may exist a (possibly infinite) number of Pareto optimal solutions, all of which are considered equally good. Researchers study multi-objective optimization problems from different viewpoints and, thus, there exist different solution philosophies and goals when setting and solving them. The goal may be to find a representative set of Pareto optimal solutions, and/or quantify the trade-offs in satisfying the different objectives, and/or finding a single solution that satisfies the subjective preferences of a human decision maker (DM).
Bicriteria optimization denotes the special case in which there are two objective functions.
There is a direct relationship between multitask optimization and multi-objective optimization.
== Introduction ==
A multi-objective optimization problem is an optimization problem that involves multiple objective functions. In mathematical terms, a multi-objective optimization problem can be formulated as
min
x
∈
X
(
f
1
(
x
)
,
f
2
(
x
)
,
…
,
f
k
(
x
)
)
{\displaystyle \min _{x\in X}(f_{1}(x),f_{2}(x),\ldots ,f_{k}(x))}
where the integer
k
≥
2
{\displaystyle k\geq 2}
is the number of objectives and the set
X
{\displaystyle X}
is the feasible set of decision vectors, which is typically
X
⊆
R
n
{\displaystyle X\subseteq \mathbb {R} ^{n}}
but it depends on the
n
{\displaystyle n}
-dimensional application domain. The feasible set is typically defined by some constraint functions. In addition, the vector-valued objective function is often defined as
f
:
X
→
R
k
x
↦
(
f
1
(
x
)
⋮
f
k
(
x
)
)
{\displaystyle {\begin{aligned}f:X&\to \mathbb {R} ^{k}\\x&\mapsto {\begin{pmatrix}f_{1}(x)\\\vdots \\f_{k}(x)\end{pmatrix}}\end{aligned}}}
If some objective function is to be maximized, it is equivalent to minimize its negative or its inverse. We denote
Y
⊆
R
k
{\displaystyle Y\subseteq \mathbb {R} ^{k}}
the image of
X
{\displaystyle X}
;
x
∗
∈
X
{\displaystyle x^{*}\in X}
a feasible solution or feasible decision; and
z
∗
=
f
(
x
∗
)
∈
R
k
{\displaystyle z^{*}=f(x^{*})\in \mathbb {R} ^{k}}
an objective vector or an outcome.
In multi-objective optimization, there does not typically exist a feasible solution that minimizes all objective functions simultaneously. Therefore, attention is paid to Pareto optimal solutions; that is, solutions that cannot be improved in any of the objectives without degrading at least one of the other objectives. In mathematical terms, a feasible solution
x
1
∈
X
{\displaystyle x_{1}\in X}
is said to (Pareto) dominate another solution
x
2
∈
X
{\displaystyle x_{2}\in X}
, if
∀
i
∈
{
1
,
…
,
k
}
,
f
i
(
x
1
)
≤
f
i
(
x
2
)
{\displaystyle \forall i\in \{1,\dots ,k\},f_{i}(x_{1})\leq f_{i}(x_{2})}
, and
∃
i
∈
{
1
,
…
,
k
}
,
f
i
(
x
1
)
<
f
i
(
x
2
)
{\displaystyle \exists i\in \{1,\dots ,k\},f_{i}(x_{1})<f_{i}(x_{2})}
.
A solution
x
∗
∈
X
{\displaystyle x^{*}\in X}
(and the corresponding outcome
f
(
x
∗
)
{\displaystyle f(x^{*})}
) is called Pareto optimal if there does not exist another solution that dominates it. The set of Pareto optimal outcomes, denoted
X
∗
{\displaystyle X^{*}}
, is often called the Pareto front, Pareto frontier, or Pareto boundary.
The Pareto front of a multi-objective optimization problem is bounded by a so-called nadir objective vector
z
n
a
d
i
r
{\displaystyle z^{nadir}}
and an ideal objective vector
z
i
d
e
a
l
{\displaystyle z^{ideal}}
, if these are finite. The nadir objective vector is defined as
z
n
a
d
i
r
=
(
sup
x
∗
∈
X
∗
f
1
(
x
∗
)
⋮
sup
x
∗
∈
X
∗
f
k
(
x
∗
)
)
{\displaystyle z^{nadir}={\begin{pmatrix}\sup _{x^{*}\in X^{*}}f_{1}(x^{*})\\\vdots \\\sup _{x^{*}\in X^{*}}f_{k}(x^{*})\end{pmatrix}}}
and the ideal objective vector as
z
i
d
e
a
l
=
(
inf
x
∗
∈
X
∗
f
1
(
x
∗
)
⋮
inf
x
∗
∈
X
∗
f
k
(
x
∗
)
)
{\displaystyle z^{ideal}={\begin{pmatrix}\inf _{x^{*}\in X^{*}}f_{1}(x^{*})\\\vdots \\\inf _{x^{*}\in X^{*}}f_{k}(x^{*})\end{pmatrix}}}
In other words, the components of the nadir and ideal objective vectors define the upper and lower bounds of the objective function of Pareto optimal solutions. In practice, the nadir objective vector can only be approximated as, typically, the whole Pareto optimal set is unknown. In addition, a utopian objective vector
z
u
t
o
p
{\displaystyle z^{utop}}
, such that
z
i
u
t
o
p
=
z
i
i
d
e
a
l
−
ϵ
,
∀
i
∈
{
1
,
…
,
k
}
{\displaystyle z_{i}^{utop}=z_{i}^{ideal}-\epsilon ,\forall i\in \{1,\dots ,k\}}
where
ϵ
>
0
{\displaystyle \epsilon >0}
is a small constant, is often defined because of numerical reasons.
== Examples of applications ==
=== Economics ===
In economics, many problems involve multiple objectives along with constraints on what combinations of those objectives are attainable. For example, consumer's demand for various goods is determined by the process of maximization of the utilities derived from those goods, subject to a constraint based on how much income is available to spend on those goods and on the prices of those goods. This constraint allows more of one good to be purchased only at the sacrifice of consuming less of another good; therefore, the various objectives (more consumption of each good is preferred) are in conflict with each other. A common method for analyzing such a problem is to use a graph of indifference curves, representing preferences, and a budget constraint, representing the trade-offs that the consumer is faced with.
Another example involves the production possibilities frontier, which specifies what combinations of various types of goods can be produced by a society with certain amounts of various resources. The frontier specifies the trade-offs that the society is faced with — if the society is fully utilizing its resources, more of one good can be produced only at the expense of producing less of another good. A society must then use some process to choose among the possibilities on the frontier.
Macroeconomic policy-making is a context requiring multi-objective optimization. Typically a central bank must choose a stance for monetary policy that balances competing objectives — low inflation, low unemployment, low balance of trade deficit, etc. To do this, the central bank uses a model of the economy that quantitatively describes the various causal linkages in the economy; it simulates the model repeatedly under various possible stances of monetary policy, in order to obtain a menu of possible predicted outcomes for the various variables of interest. Then in principle it can use an aggregate objective function to rate the alternative sets of predicted outcomes, although in practice central banks use a non-quantitative, judgement-based, process for ranking the alternatives and making the policy choice.
=== Finance ===
In finance, a common problem is to choose a portfolio when there are two conflicting objectives — the desire to have the expected value of portfolio returns be as high as possible, and the desire to have risk, often measured by the standard deviation of portfolio returns, be as low as possible. This problem is often represented by a graph in which the efficient frontier shows the best combinations of risk and expected return that are available, and in which indifference curves show the investor's preferences for various risk-expected return combinations. The problem of optimizing a function of the expected value (first moment) and the standard deviation (square root of the second central moment) of portfolio return is called a two-moment decision model.
=== Optimal control ===
In engineering and economics, many problems involve multiple objectives which are not describable as the-more-the-better or the-less-the-better; instead, there is an ideal target value for each objective, and the desire is to get as close as possible to the desired value of each objective. For example, energy systems typically have a trade-off between performance and cost or one might want to adjust a rocket's fuel usage and orientation so that it arrives both at a specified place and at a specified time; or one might want to conduct open market operations so that both the inflation rate and the unemployment rate are as close as possible to their desired values.
Often such problems are subject to linear equality constraints that prevent all objectives from being simultaneously perfectly met, especially when the number of controllable variables is less than the number of objectives and when the presence of random shocks generates uncertainty. Commonly a multi-objective quadratic objective function is used, with the cost associated with an objective rising quadratically with the distance of the objective from its ideal value. Since these problems typically involve adjusting the controlled variables at various points in time and/or evaluating the objectives at various points in time, intertemporal optimization techniques are employed.
=== Optimal design ===
Product and process design can be largely improved using modern modeling, simulation, and optimization techniques. The key question in optimal design is measuring what is good or desirable about a design. Before looking for optimal designs, it is important to identify characteristics that contribute the most to the overall value of the design. A good design typically involves multiple criteria/objectives such as capital cost/investment, operating cost, profit, quality and/or product recovery, efficiency, process safety, operation time, etc. Therefore, in practical applications, the performance of process and product design is often measured with respect to multiple objectives. These objectives are typically conflicting, i.e., achieving the optimal value for one objective requires some compromise on one or more objectives.
For example, when designing a paper mill, one can seek to decrease the amount of capital invested in a paper mill and enhance the quality of paper simultaneously. If the design of a paper mill is defined by large storage volumes and paper quality is defined by quality parameters, then the problem of optimal design of a paper mill can include objectives such as i) minimization of expected variation of those quality parameters from their nominal values, ii) minimization of the expected time of breaks and iii) minimization of the investment cost of storage volumes. Here, the maximum volume of towers is a design variable. This example of optimal design of a paper mill is a simplification of the model used in. Multi-objective design optimization has also been implemented in engineering systems in the circumstances such as control cabinet layout optimization, airfoil shape optimization using scientific workflows, design of nano-CMOS, system on chip design, design of solar-powered irrigation systems, optimization of sand mould systems, engine design, optimal sensor deployment and optimal controller design.
=== Process optimization ===
Multi-objective optimization has been increasingly employed in chemical engineering and manufacturing. In 2009, Fiandaca and Fraga used the multi-objective genetic algorithm (MOGA) to optimize the pressure swing adsorption process (cyclic separation process). The design problem involved the dual maximization of nitrogen recovery and nitrogen purity. The results approximated the Pareto frontier well with acceptable trade-offs between the objectives.
In 2010, Sendín et al. solved a multi-objective problem for the thermal processing of food. They tackled two case studies (bi-objective and triple-objective problems) with nonlinear dynamic models. They used a hybrid approach consisting of the weighted Tchebycheff and the Normal Boundary Intersection approach. The novel hybrid approach was able to construct a Pareto optimal set for the thermal processing of foods.
In 2013, Ganesan et al. carried out the multi-objective optimization of the combined carbon dioxide reforming and partial oxidation of methane. The objective functions were methane conversion, carbon monoxide selectivity, and hydrogen to carbon monoxide ratio. Ganesan used the Normal Boundary Intersection (NBI) method in conjunction with two swarm-based techniques (Gravitational Search Algorithm (GSA) and Particle Swarm Optimization (PSO)) to tackle the problem. Applications involving chemical extraction and bioethanol production processes have posed similar multi-objective problems.
In 2013, Abakarov et al. proposed an alternative technique to solve multi-objective optimization problems arising in food engineering. The Aggregating Functions Approach, the Adaptive Random Search Algorithm, and the Penalty Functions Approach were used to compute the initial set of the non-dominated or Pareto-optimal solutions. The Analytic Hierarchy Process and Tabular Method were used simultaneously for choosing the best alternative among the computed subset of non-dominated solutions for osmotic dehydration processes.
In 2018, Pearce et al. formulated task allocation to human and robotic workers as a multi-objective optimization problem, considering production time and the ergonomic impact on the human worker as the two objectives considered in the formulation. Their approach used a Mixed-Integer Linear Program to solve the optimization problem for a weighted sum of the two objectives to calculate a set of Pareto optimal solutions. Applying the approach to several manufacturing tasks showed improvements in at least one objective in most tasks and in both objectives in some of the processes.
=== Radio resource management ===
The purpose of radio resource management is to satisfy the data rates that are requested by the users of a cellular network. The main resources are time intervals, frequency blocks, and transmit powers. Each user has its own objective function that, for example, can represent some combination of the data rate, latency, and energy efficiency. These objectives are conflicting since the frequency resources are very scarce, thus there is a need for tight spatial frequency reuse which causes immense inter-user interference if not properly controlled. Multi-user MIMO techniques are nowadays used to reduce the interference by adaptive precoding. The network operator would like to both bring great coverage and high data rates, thus the operator would like to find a Pareto optimal solution that balance the total network data throughput and the user fairness in an appropriate subjective manner.
Radio resource management is often solved by scalarization; that is, selection of a network utility function that tries to balance throughput and user fairness. The choice of utility function has a large impact on the computational complexity of the resulting single-objective optimization problem. For example, the common utility of weighted sum rate gives an NP-hard problem with a complexity that scales exponentially with the number of users, while the weighted max-min fairness utility results in a quasi-convex optimization problem with only a polynomial scaling with the number of users.
=== Electric power systems ===
Reconfiguration, by exchanging the functional links between the elements of the system, represents one of the most important measures which can improve the operational performance of a distribution system. The problem of optimization through the reconfiguration of a power distribution system, in terms of its definition, is a historical single objective problem with constraints. Since 1975, when Merlin and Back introduced the idea of distribution system reconfiguration for active power loss reduction, until nowadays, a lot of researchers have proposed diverse methods and algorithms to solve the reconfiguration problem as a single objective problem. Some authors have proposed Pareto optimality based approaches (including active power losses and reliability indices as objectives). For this purpose, different artificial intelligence based methods have been used: microgenetic, branch exchange, particle swarm optimization and non-dominated sorting genetic algorithm.
=== Inspection of infrastructure ===
Autonomous inspection of infrastructure has the potential to reduce costs, risks and environmental impacts, as well as ensuring better periodic maintenance of inspected assets. Typically, planning such missions has been viewed as a single-objective optimization problem, where one aims to minimize the energy or time spent in inspecting an entire target structure. For complex, real-world structures, however, covering 100% of an inspection target is not feasible, and generating an inspection plan may be better viewed as a multiobjective optimization problem, where one aims to both maximize inspection coverage and minimize time and costs. A recent study has indicated that multiobjective inspection planning indeed has the potential to outperform traditional methods on complex structures
== Solution ==
As multiple Pareto optimal solutions for multi-objective optimization problems usually exist, what it means to solve such a problem is not as straightforward as it is for a conventional single-objective optimization problem. Therefore, different researchers have defined the term "solving a multi-objective optimization problem" in various ways. This section summarizes some of them and the contexts in which they are used. Many methods convert the original problem with multiple objectives into a single-objective optimization problem. This is called a scalarized problem. If the Pareto optimality of the single-objective solutions obtained can be guaranteed, the scalarization is characterized as done neatly.
Solving a multi-objective optimization problem is sometimes understood as approximating or computing all or a representative set of Pareto optimal solutions.
When decision making is emphasized, the objective of solving a multi-objective optimization problem is referred to as supporting a decision maker in finding the most preferred Pareto optimal solution according to their subjective preferences. The underlying assumption is that one solution to the problem must be identified to be implemented in practice. Here, a human decision maker (DM) plays an important role. The DM is expected to be an expert in the problem domain.
The most preferred results can be found using different philosophies. Multi-objective optimization methods can be divided into four classes.
In so-called no-preference methods, no DM is expected to be available, but a neutral compromise solution is identified without preference information. The other classes are so-called a priori, a posteriori, and interactive methods, and they all involve preference information from the DM in different ways.
In a priori methods, preference information is first asked from the DM, and then a solution best satisfying these preferences is found.
In a posteriori methods, a representative set of Pareto optimal solutions is first found, and then the DM must choose one of them.
In interactive methods, the decision maker is allowed to search for the most preferred solution iteratively. In each iteration of the interactive method, the DM is shown Pareto optimal solution(s) and describes how the solution(s) could be improved. The information given by the DM is then taken into account while generating new Pareto optimal solution(s) for the DM to study in the next iteration. In this way, the DM learns about the feasibility of their wishes and can concentrate on solutions that are interesting to them. The DM may stop the search whenever they want to.
More information and examples of different methods in the four classes are given in the following sections.
== No-preference methods ==
When a decision maker does not explicitly articulate any preference information, the multi-objective optimization method can be classified as a no-preference method. A well-known example is the method of global criterion, in which a scalarized problem of the form
min
‖
f
(
x
)
−
z
i
d
e
a
l
‖
s.t.
x
∈
X
{\displaystyle {\begin{aligned}\min &\|f(x)-z^{ideal}\|\\{\text{s.t. }}&x\in X\end{aligned}}}
is solved. In the above problem,
‖
⋅
‖
{\displaystyle \|\cdot \|}
can be any
L
p
{\displaystyle L_{p}}
norm, with common choices including
L
1
{\displaystyle L_{1}}
,
L
2
{\displaystyle L_{2}}
, and
L
∞
{\displaystyle L_{\infty }}
. The method of global criterion is sensitive to the scaling of the objective functions. Thus, it is recommended that the objectives be normalized into a uniform, dimensionless scale.
== A priori methods ==
A priori methods require that sufficient preference information is expressed before the solution process. Well-known examples of a priori methods include the utility function method, lexicographic method, and goal programming.
=== Utility function method ===
The utility function method assumes the decision maker's utility function is available. A mapping
u
:
Y
→
R
{\displaystyle u\colon Y\rightarrow \mathbb {R} }
is a utility function if for all
y
1
,
y
2
∈
Y
{\displaystyle \mathbf {y} ^{1},\mathbf {y} ^{2}\in Y}
it holds that
u
(
y
1
)
>
u
(
y
2
)
{\displaystyle u(\mathbf {y} ^{1})>u(\mathbf {y} ^{2})}
if the decision maker prefers
y
1
{\displaystyle \mathbf {y} ^{1}}
to
y
2
{\displaystyle \mathbf {y} ^{2}}
, and
u
(
y
1
)
=
u
(
y
2
)
{\displaystyle u(\mathbf {y} ^{1})=u(\mathbf {y} ^{2})}
if the decision maker is indifferent between
y
1
{\displaystyle \mathbf {y} ^{1}}
and
y
2
{\displaystyle \mathbf {y} ^{2}}
. The utility function specifies an ordering of the decision vectors (recall that vectors can be ordered in many different ways). Once
u
{\displaystyle u}
is obtained, it suffices to solve
max
u
(
f
(
x
)
)
subject to
x
∈
X
,
{\displaystyle \max \;u(\mathbf {f} (\mathbf {x} )){\text{ subject to }}\mathbf {x} \in X,}
but in practice, it is very difficult to construct a utility function that would accurately represent the decision maker's preferences, particularly since the Pareto front is unknown before the optimization begins.
=== Lexicographic method ===
The lexicographic method assumes that the objectives can be ranked in the order of importance. We assume that the objective functions are in the order of importance so that
f
1
{\displaystyle f_{1}}
is the most important and
f
k
{\displaystyle f_{k}}
the least important to the decision maker. Subject to this assumption, various methods can be used to attain the lexicographically optimal solution. Note that a goal or target value is not specified for any objective here, which makes it different from the Lexicographic Goal Programming method.
=== Scalarizing ===
Scalarizing a multi-objective optimization problem is an a priori method, which means formulating a single-objective optimization problem such that optimal solutions to the single-objective optimization problem are Pareto optimal solutions to the multi-objective optimization problem. In addition, it is often required that every Pareto optimal solution can be reached with some parameters of the scalarization. With different parameters for the scalarization, different Pareto optimal solutions are produced. A general formulation for a scalarization of a multi-objective optimization problem is
min
g
(
f
1
(
x
)
,
…
,
f
k
(
x
)
,
θ
)
s.t.
x
∈
X
θ
{\displaystyle {\begin{array}{ll}\min &g(f_{1}(x),\ldots ,f_{k}(x),\theta )\\{\text{s.t.}}&x\in X_{\theta }\end{array}}}
where
θ
{\displaystyle \theta }
is a vector parameter, the set
X
θ
⊆
X
{\displaystyle X_{\theta }\subseteq X}
is a set depending on the parameter
θ
{\displaystyle \theta }
, and
g
:
R
k
+
1
→
R
{\displaystyle g:\mathbb {R} ^{k+1}\rightarrow \mathbb {R} }
is a function.
Very well-known examples are:
linear scalarization
min
x
∈
X
∑
i
=
1
k
w
i
f
i
(
x
)
{\displaystyle \min _{x\in X}\sum _{i=1}^{k}w_{i}f_{i}(x)}
where the weights of the objectives
w
i
>
0
{\displaystyle w_{i}>0}
are the parameters of the scalarization.
ϵ
{\displaystyle \epsilon }
-constraint method (see, e.g.)
min
f
j
(
x
)
s.t.
x
∈
X
f
i
(
x
)
≤
ϵ
i
for
i
∈
{
1
,
…
,
k
}
∖
{
j
}
{\displaystyle {\begin{array}{ll}\min &f_{j}(x)\\{\text{s.t.}}&x\in X\\&f_{i}(x)\leq \epsilon _{i}{\text{ for }}i\in \{1,\ldots ,k\}\setminus \{j\}\end{array}}}
where upper bounds
ϵ
j
{\displaystyle \epsilon _{j}}
are parameters as above and
f
j
{\displaystyle f_{j}}
is the objective to be minimized.
Somewhat more advanced examples are the following:
achievement scalarizing problems of Wierzbicki
One example of the achievement scalarizing problems can be formulated as
min
max
i
=
1
,
…
,
k
[
f
i
(
x
)
−
z
¯
i
z
i
n
a
d
i
r
−
z
i
u
t
o
p
]
+
ρ
∑
i
=
1
k
f
i
(
x
)
z
i
n
a
d
i
r
−
z
i
u
t
o
p
s.t.
x
∈
S
{\displaystyle {\begin{aligned}\min &\max _{i=1,\ldots ,k}\left[{\frac {f_{i}(x)-{\bar {z}}_{i}}{z_{i}^{nadir}-z_{i}^{utop}}}\right]+\rho \sum _{i=1}^{k}{\frac {f_{i}(x)}{z_{i}^{nadir}-z_{i}^{utop}}}\\{\text{s.t. }}&x\in S\end{aligned}}}
where the term
ρ
∑
i
=
1
k
f
i
(
x
)
z
i
n
a
d
i
r
−
z
i
u
t
o
p
{\displaystyle \rho \sum _{i=1}^{k}{\frac {f_{i}(x)}{z_{i}^{nadir}-z_{i}^{utop}}}}
is called the augmentation term,
ρ
>
0
{\displaystyle \rho >0}
is a small constant, and
z
n
a
d
i
r
{\displaystyle z^{nadir}}
and
z
u
t
o
p
{\displaystyle z^{utop}}
are the nadir and utopian vectors, respectively. In the above problem, the parameter is the so-called reference point
z
¯
{\displaystyle {\bar {z}}}
representing objective function values preferred by the decision maker.
Sen's multi-objective programming
max
∑
j
=
1
r
Z
j
W
j
−
∑
j
=
r
+
1
s
Z
j
W
r
+
1
s.t.
A
X
=
b
X
≥
0
{\displaystyle {\begin{array}{ll}\max &{\frac {\sum _{j=1}^{r}Z_{j}}{W_{j}}}-{\frac {\sum _{j=r+1}^{s}Z_{j}}{W_{r+1}}}\\{\text{s.t. }}&AX=b\\&X\geq 0\end{array}}}
where
W
j
{\displaystyle W_{j}}
is individual optima (absolute) for objectives of maximization
r
{\displaystyle r}
and minimization
r
+
1
{\displaystyle r+1}
to
s
{\displaystyle s}
.
hypervolume/Chebyshev scalarization
min
x
∈
X
max
i
f
i
(
x
)
w
i
{\displaystyle \min _{x\in X}\max _{i}{\frac {f_{i}(x)}{w_{i}}}}
where the weights of the objectives
w
i
>
0
{\displaystyle w_{i}>0}
are the parameters of the scalarization. If the parameters/weights are drawn uniformly in the positive orthant, it is shown that this scalarization provably converges to the Pareto front, even when the front is non-convex.
For example, portfolio optimization is often conducted in terms of mean-variance analysis. In this context, the efficient set is a subset of the portfolios parametrized by the portfolio mean return
μ
P
{\displaystyle \mu _{P}}
in the problem of choosing portfolio shares to minimize the portfolio's variance of return
σ
P
{\displaystyle \sigma _{P}}
subject to a given value of
μ
P
{\displaystyle \mu _{P}}
; see Mutual fund separation theorem for details. Alternatively, the efficient set can be specified by choosing the portfolio shares to maximize the function
μ
P
−
b
σ
P
{\displaystyle \mu _{P}-b\sigma _{P}}
; the set of efficient portfolios consists of the solutions as
b
{\displaystyle b}
ranges from zero to infinity.
Some of the above scalarizations involve invoking the minimax principle, where always the worst of the different objectives is optimized.
== A posteriori methods ==
A posteriori methods aim at producing all the Pareto optimal solutions or a representative subset of the Pareto optimal solutions. Most a posteriori methods fall into either one of the following three classes:
Mathematical programming-based a posteriori methods where an algorithm is repeated and each run of the algorithm produces one Pareto optimal solution;
Evolutionary algorithms where one run of the algorithm produces a set of Pareto optimal solutions;
Deep learning methods where a model is first trained on a subset of solutions and then queried to provide other solutions on the Pareto front.
=== Mathematical programming ===
Well-known examples of mathematical programming-based a posteriori methods are the Normal Boundary Intersection (NBI), Modified Normal Boundary Intersection (NBIm), Normal Constraint (NC), Successive Pareto Optimization (SPO), and Directed Search Domain (DSD) methods, which solve the multi-objective optimization problem by constructing several scalarizations. The solution to each scalarization yields a Pareto optimal solution, whether locally or globally. The scalarizations of the NBI, NBIm, NC, and DSD methods are constructed to obtain evenly distributed Pareto points that give a good approximation of the real set of Pareto points.
=== Evolutionary algorithms ===
Evolutionary algorithms are popular approaches to generating Pareto optimal solutions to a multi-objective optimization problem. Most evolutionary multi-objective optimization (EMO) algorithms apply Pareto-based ranking schemes. Evolutionary algorithms such as the Non-dominated Sorting Genetic Algorithm-II (NSGA-II), its extended version NSGA-III, Strength Pareto Evolutionary Algorithm 2 (SPEA-2) and multiobjective differential evolution variants have become standard approaches, although some schemes based on particle swarm optimization and simulated annealing are significant. The main advantage of evolutionary algorithms, when applied to solve multi-objective optimization problems, is the fact that they typically generate sets of solutions, allowing computation of an approximation of the entire Pareto front. The main disadvantage of evolutionary algorithms is their lower speed and the Pareto optimality of the solutions cannot be guaranteed; it is only known that none of the generated solutions is dominated by another.
Another paradigm for multi-objective optimization based on novelty using evolutionary algorithms was recently improved upon. This paradigm searches for novel solutions in objective space (i.e., novelty search on objective space) in addition to the search for non-dominated solutions. Novelty search is like stepping stones guiding the search to previously unexplored places. It is especially useful in overcoming bias and plateaus as well as guiding the search in many-objective optimization problems.
=== Deep learning methods ===
Deep learning conditional methods are new approaches to generating several Pareto optimal solutions. The idea is to use the generalization capacity of deep neural networks to learn a model of the entire Pareto front from a limited number of example trade-offs along that front, a task called Pareto Front Learning. Several approaches address this setup, including using hypernetworks and using Stein variational gradient descent.
=== List of methods ===
Commonly known a posteriori methods are listed below:
ε-constraint method
Pareto-Hypernetworks
Multi-objective Branch-and-Bound
Normal Boundary Intersection (NBI)
Modified Normal Boundary Intersection (NBIm)
Normal Constraint (NC)
Successive Pareto Optimization (SPO)
Directed Search Domain (DSD)
NSGA-II
PGEN (Pareto surface generation for convex multi-objective instances)
IOSO (Indirect Optimization on the basis of Self-Organization)
SMS-EMOA (S-metric selection evolutionary multi-objective algorithm)
Approximation-Guided Evolution (first algorithm to directly implement and optimize the formal concept of approximation from theoretical computer science)
Reactive Search Optimization (using machine learning for adapting strategies and objectives), implemented in LIONsolver
Benson's algorithm for multi-objective linear programs and for multi-objective convex programs
Multi-objective particle swarm optimization
Subpopulation Algorithm based on Novelty
MOEA/D (Multi-Objective Evolutionary Algorithm based on Decomposition)
== Interactive methods ==
In interactive methods of optimizing multiple objective problems, the solution process is iterative and the decision maker continuously interacts with the method when searching for the most preferred solution (see e.g., Miettinen 1999, Miettinen 2008). In other words, the decision maker is expected to express preferences at each iteration to get Pareto optimal solutions that are of interest to the decision maker and learn what kind of solutions are attainable.
The following steps are commonly present in interactive methods of optimization:
initialize (e.g., calculate ideal and approximated nadir objective vectors and show them to the decision maker)
generate a Pareto optimal starting point (by using e.g., some no-preference method or solution given by the decision maker)
ask for preference information from the decision maker (e.g., aspiration levels or number of new solutions to be generated)
generate new Pareto optimal solution(s) according to the preferences and show it/them and possibly some other information about the problem to the decision maker
if several solutions were generated, ask the decision maker to select the best solution so far
stop (if the decision maker wants to; otherwise, go to step 3).
The above aspiration levels refer to desirable objective function values forming a reference point. Instead of mathematical convergence, often used as a stopping criterion in mathematical optimization methods, psychological convergence is often emphasized in interactive methods. Generally speaking, a method is terminated when the decision maker is confident that he/she has found the most preferred solution available.
=== Types of preference information ===
There are different interactive methods involving different types of preference information. Three types can be identified based on
trade-off information,
reference points, and
classification of objective functions.
On the other hand, a fourth type of generating a small sample of solutions is included in: An example of the interactive method utilizing trade-off information is the Zionts-Wallenius method, where the decision maker is shown several objective trade-offs at each iteration, and (s)he is expected to say whether (s)he likes, dislikes, or is indifferent with respect to each trade-off. In reference point-based methods (see e.g.,), the decision maker is expected at each iteration to specify a reference point consisting of desired values for each objective and a corresponding Pareto optimal solution(s) is then computed and shown to them for analysis. In classification-based interactive methods, the decision maker is assumed to give preferences in the form of classifying objectives at the current Pareto optimal solution into different classes, indicating how the values of the objectives should be changed to get a more preferred solution. Then, the classification information is considered when new (more preferred) Pareto optimal solution(s) are computed. In the satisficing trade-off method (STOM), three classes are used: objectives whose values 1) should be improved, 2) can be relaxed, and 3) are acceptable as such. In the NIMBUS method, two additional classes are also used: objectives whose values 4) should be improved until a given bound and 5) can be relaxed until a given bound.
== Hybrid methods ==
Different hybrid methods exist, but here we consider hybridizing MCDM (multi-criteria decision-making) and EMO (evolutionary multi-objective optimization). A hybrid algorithm in multi-objective optimization combines algorithms/approaches from these two fields (see e.g.,). Hybrid algorithms of EMO and MCDM are mainly used to overcome shortcomings by utilizing strengths. Several types of hybrid algorithms have been proposed in the literature, e.g., incorporating MCDM approaches into EMO algorithms as a local search operator, leading a DM to the most preferred solution(s), etc. A local search operator is mainly used to enhance the rate of convergence of EMO algorithms.
The roots for hybrid multi-objective optimization can be traced to the first Dagstuhl seminar organized in November 2004 (see here). Here, some of the best minds in EMO (Professor Kalyanmoy Deb, Professor Jürgen Branke, etc.) and MCDM (Professor Kaisa Miettinen, Professor Ralph E. Steuer, etc.) realized the potential in combining ideas and approaches of MCDM and EMO fields to prepare hybrids of them. Subsequently, many more Dagstuhl seminars have been arranged to foster collaboration. Recently, hybrid multi-objective optimization has become an important theme in several international conferences in the area of EMO and MCDM (see e.g.,).
== Visualization of the Pareto front ==
Visualization of the Pareto front is one of the a posteriori preference techniques of multi-objective optimization. The a posteriori preference techniques provide an important class of multi-objective optimization techniques. Usually, the a posteriori preference techniques include four steps: (1) computer approximates the Pareto front, i.e., the Pareto optimal set in the objective space; (2) the decision maker studies the Pareto front approximation; (3) the decision maker identifies the preferred point at the Pareto front; (4) computer provides the Pareto optimal decision, whose output coincides with the objective point identified by the decision maker. From the point of view of the decision maker, the second step of the a posteriori preference techniques is the most complicated. There are two main approaches to informing the decision maker. First, a number of points of the Pareto front can be provided in the form of a list (interesting discussion and references are given in) or using heatmaps.
=== Visualization in bi-objective problems: tradeoff curve ===
In the case of bi-objective problems, informing the decision maker concerning the Pareto front is usually carried out by its visualization: the Pareto front, often named the tradeoff curve in this case, can be drawn at the objective plane. The tradeoff curve gives full information on objective values and on objective tradeoffs, which inform how improving one objective is related to deteriorating the second one while moving along the tradeoff curve. The decision maker takes this information into account while specifying the preferred Pareto optimal objective point. The idea to approximate and visualize the Pareto front was introduced for linear bi-objective decision problems by S. Gass and T. Saaty. This idea was developed and applied in environmental problems by J.L. Cohon. A review of methods for approximating the Pareto front for various decision problems with a small number of objectives (mainly, two) is provided in.
=== Visualization in high-order multi-objective optimization problems ===
There are two generic ideas for visualizing the Pareto front in high-order multi-objective decision problems (problems with more than two objectives). One of them, which is applicable in the case of a relatively small number of objective points that represent the Pareto front, is based on using the visualization techniques developed in statistics (various diagrams, etc.; see the corresponding subsection below). The second idea proposes the display of bi-objective cross-sections (slices) of the Pareto front. It was introduced by W.S. Meisel in 1973 who argued that such slices inform the decision maker on objective tradeoffs. The figures that display a series of bi-objective slices of the Pareto front for three-objective problems are known as the decision maps. They give a clear picture of tradeoffs between the three criteria. The disadvantages of such an approach are related to the following two facts. First, the computational procedures for constructing the Pareto front's bi-objective slices are unstable since the Pareto front is usually not stable. Secondly, it is applicable in the case of only three objectives. In the 1980s, the idea of W.S. Meisel was implemented in a different form—in the form of the Interactive Decision Maps (IDM) technique. More recently, N. Wesner proposed using a combination of a Venn diagram and multiple scatterplots of the objective space to explore the Pareto frontier and select optimal solutions.
== See also ==
Concurrent programming
Decision-making software
Goal programming
Interactive Decision Maps
Multiple-criteria decision-making
Multi-objective linear programming
Multi-disciplinary design optimization
Pareto efficiency
Utility function
Vector optimization
== References ==
== External links ==
Emmerich, M.T.M., Deutz, A.H. A tutorial on multiobjective optimization: fundamentals and evolutionary methods. Nat Comput 17, 585–609 (2018). https://doi.org/10.1007/s11047-018-9685-y
International Society on Multiple Criteria Decision Making
Evolutionary Multiobjective Optimization, The Wolfram Demonstrations Project
A Tutorial on Multiobjective Optimization and Genetic Algorithms, Scilab Professional Partner
Tomoiagă, Bogdan; Chindriş, Mircea; Sumper, Andreas; Sudria-Andreu, Antoni; Villafafila-Robles, Roberto. 2013. "Pareto Optimal Reconfiguration of Power Distribution Systems Using a Genetic Algorithm Based on NSGA-II." Energies 6, no. 3: 1439-1455.
List of References on Evolutionary Multiobjective Optimization
|
https://en.wikipedia.org/wiki/Multi-objective_optimization
|
In computer science, stream processing (also known as event stream processing, data stream processing, or distributed stream processing) is a programming paradigm which views streams, or sequences of events in time, as the central input and output objects of computation. Stream processing encompasses dataflow programming, reactive programming, and distributed data processing. Stream processing systems aim to expose parallel processing for data streams and rely on streaming algorithms for efficient implementation. The software stack for these systems includes components such as programming models and query languages, for expressing computation; stream management systems, for distribution and scheduling; and hardware components for acceleration including floating-point units, graphics processing units, and field-programmable gate arrays.
The stream processing paradigm simplifies parallel software and hardware by restricting the parallel computation that can be performed. Given a sequence of data (a stream), a series of operations (kernel functions) is applied to each element in the stream. Kernel functions are usually pipelined, and optimal local on-chip memory reuse is attempted, in order to minimize the loss in bandwidth, associated with external memory interaction. Uniform streaming, where one kernel function is applied to all elements in the stream, is typical. Since the kernel and stream abstractions expose data dependencies, compiler tools can fully automate and optimize on-chip management tasks. Stream processing hardware can use scoreboarding, for example, to initiate a direct memory access (DMA) when dependencies become known. The elimination of manual DMA management reduces software complexity, and an associated elimination for hardware cached I/O, reduces the data area expanse that has to be involved with service by specialized computational units such as arithmetic logic units.
During the 1980s stream processing was explored within dataflow programming. An example is the language SISAL (Streams and Iteration in a Single Assignment Language).
== Applications ==
Stream processing is essentially a compromise, driven by a data-centric model that works very well for traditional DSP or GPU-type applications (such as image, video and digital signal processing) but less so for general purpose processing with more randomized data access (such as databases). By sacrificing some flexibility in the model, the implications allow easier, faster and more efficient execution. Depending on the context, processor design may be tuned for maximum efficiency or a trade-off for flexibility.
Stream processing is especially suitable for applications that exhibit three application characteristics:
Compute intensity, the number of arithmetic operations per I/O or global memory reference. In many signal processing applications today it is well over 50:1 and increasing with algorithmic complexity.
Data parallelism exists in a kernel if the same function is applied to all records of an input stream and a number of records can be processed simultaneously without waiting for results from previous records.
Data locality is a specific type of temporal locality common in signal and media processing applications where data is produced once, read once or twice later in the application, and never read again. Intermediate streams passed between kernels as well as intermediate data within kernel functions can capture this locality directly using the stream processing programming model.
Examples of records within streams include:
In graphics, each record might be the vertex, normal, and color information for a triangle;
In image processing, each record might be a single pixel from an image;
In a video encoder, each record may be 256 pixels forming a macroblock of data; or
In wireless signal processing, each record could be a sequence of samples received from an antenna.
For each record we can only read from the input, perform operations on it, and write to the output. It is permissible to have multiple inputs and multiple outputs, but never a piece of memory that is both readable and writable.
== Code examples ==
By way of illustration, the following code fragments demonstrate detection of patterns within event streams. The first is an example of processing a data stream using a continuous SQL query (a query that executes forever processing arriving data based on timestamps and window duration). This code fragment illustrates a JOIN of two data streams, one for stock orders, and one for the resulting stock trades. The query outputs a stream of all Orders matched by a Trade within one second of the Order being placed. The output stream is sorted by timestamp, in this case, the timestamp from the Orders stream.
Another sample code fragment detects weddings among a flow of external "events" such as church bells ringing, the appearance of a man in a tuxedo or morning suit, a woman in a flowing white gown and rice flying through the air. A "complex" or "composite" event is what one infers from the individual simple events: a wedding is happening.
== Comparison to prior parallel paradigms ==
Basic computers started from a sequential execution paradigm. Traditional CPUs are SISD based, which means they conceptually perform only one operation at a time.
As the computing needs of the world evolved, the amount of data to be managed increased very quickly. It was obvious that the sequential programming model could not cope with the increased need for processing power. Various efforts have been spent on finding alternative ways to perform massive amounts of computations but the only solution was to exploit some level of parallel execution. The result of those efforts was SIMD, a programming paradigm which allowed applying one instruction to multiple instances of (different) data. Most of the time, SIMD was being used in a SWAR environment. By using more complicated structures, one could also have MIMD parallelism.
Although those two paradigms were efficient, real-world implementations were plagued with limitations from memory alignment problems to synchronization issues and limited parallelism. Only few SIMD processors survived as stand-alone components; most were embedded in standard CPUs.
Consider a simple program adding up two arrays containing 100 4-component vectors (i.e. 400 numbers in total).
=== Conventional, sequential paradigm ===
This is the sequential paradigm that is most familiar. Variations do exist (such as inner loops, structures and such), but they ultimately boil down to that construct.
=== Parallel SIMD paradigm, packed registers (SWAR) ===
This is actually oversimplified. It assumes the instruction vector_sum works. Although this is what happens with instruction intrinsics, much information is actually not taken into account here such as the number of vector components and their data format. This is done for clarity.
You can see however, this method reduces the number of decoded instructions from numElements * componentsPerElement to numElements. The number of jump instructions is also decreased, as the loop is run fewer times. These gains result from the parallel execution of the four mathematical operations.
What happened however is that the packed SIMD register holds a certain amount of data so it's not possible to get more parallelism. The speed up is somewhat limited by the assumption we made of performing four parallel operations (please note this is common for both AltiVec and SSE).
=== Parallel stream paradigm (SIMD/MIMD) ===
In this paradigm, the whole dataset is defined, rather than each component block being defined separately. Describing the set of data is assumed to be in the first two rows. After that, the result is inferred from the sources and kernel. For simplicity, there's a 1:1 mapping between input and output data but this does not need to be. Applied kernels can also be much more complex.
An implementation of this paradigm can "unroll" a loop internally. This allows throughput to scale with chip complexity, easily utilizing hundreds of ALUs. The elimination of complex data patterns makes much of this extra power available.
While stream processing is a branch of SIMD/MIMD processing, they must not be confused. Although SIMD implementations can often work in a "streaming" manner, their performance is not comparable: the model envisions a very different usage pattern which allows far greater performance by itself.
It has been noted that when applied on generic processors such as standard CPU, only a 1.5x speedup can be reached. By contrast, ad-hoc stream processors easily reach over 10x performance, mainly attributed to the more efficient memory access and higher levels of parallel processing.
Although there are various degrees of flexibility allowed by the model, stream processors usually impose some limitations on the kernel or stream size. For example, consumer hardware often lacks the ability to perform high-precision math, lacks complex indirection chains or presents lower limits on the number of instructions which can be executed.
== Research ==
Stanford University stream processing projects included the Stanford Real-Time Programmable Shading Project started in 1999.
A prototype called Imagine was developed in 2002.
A project called Merrimac ran until about 2004.
AT&T also researched stream-enhanced processors as graphics processing units rapidly evolved in both speed and functionality.[1] Since these early days, dozens of stream processing languages have been developed, as well as specialized hardware.
=== Programming model notes ===
The most immediate challenge in the realm of parallel processing does not lie as much in the type of hardware architecture used, but in how easy it will be to program the system in question in a real-world environment with acceptable performance. Machines like Imagine use a straightforward single-threaded model with automated dependencies, memory allocation and DMA scheduling. This in itself is a result of the research at MIT and Stanford in finding an optimal layering of tasks between programmer, tools and hardware. Programmers beat tools in mapping algorithms to parallel hardware, and tools beat programmers in figuring out smartest memory allocation schemes, etc. Of particular concern are MIMD designs such as Cell, for which the programmer needs to deal with application partitioning across multiple cores and deal with process synchronization and load balancing.
A drawback of SIMD programming was the issue of array-of-structures (AoS) and structure-of-arrays (SoA). Programmers often create representations of enitities in memory, for example, the location of an particle in 3D space, the colour of the ball and its size as below:
When multiple of these structures exist in memory they are placed end to end creating an arrays in an array of structures (AoS) topology. This means that should some algorithim be applied to the location of each particle in turn it must skip over memory locations containing the other attributes. If these attributes are not needed this results in wasteful usage of the CPU cache. Additionally, a SIMD instruction will typically expect the data it will operate on to be contiguous in memory, the elements may also need to be aligned. By moving the memory location of the data out of the structure data can be better organised for efficient access in a stream and for SIMD instructions to operate one. A structure of arrays (SoA), as shown below, can allow this.
Instead of holding the data in the structure, it holds only pointers (memory locations) for the data. Shortcomings are that if an multiple attributes to of an object are to be operated on they might now be distant in memory and so result in a cache miss. The aligning and any needed padding lead to increased memory usage. Overall, memory management may be more complicated if structures are added and removed for example.
For stream processors, the usage of structures is encouraged. From an application point of view, all the attributes can be defined with some flexibility.
Taking GPUs as reference, there is a set of attributes (at least 16) available. For each attribute, the application can state the number of components and the format of the components (but only primitive data types are supported for now). The various attributes are then attached to a memory block, possibly defining a stride between 'consecutive' elements of the same attributes, effectively allowing interleaved data.
When the GPU begins the stream processing, it will gather all the various attributes in a single set of parameters (usually this looks like a structure or a "magic global variable"), performs the operations and scatters the results to some memory area for later processing (or retrieving).
More modern stream processing frameworks provide a FIFO like interface to structure data as a literal stream. This abstraction
provides a means to specify data dependencies implicitly while enabling the runtime/hardware to take full advantage of that
knowledge for efficient computation. One of the simplest and most efficient stream processing modalities to date for C++,
is RaftLib, which enables linking independent compute kernels together as a data flow graph using C++ stream operators. As an example:
=== Models of computation for stream processing ===
Apart from specifying streaming applications in high-level languages, models of computation (MoCs) also have been widely used as dataflow models and process-based models.
=== Generic processor architecture ===
Historically, CPUs began implementing various tiers of memory access optimizations because of the ever-increasing performance when compared to relatively slow growing external memory bandwidth. As this gap widened, big amounts of die area were dedicated to hiding memory latencies. Since fetching information and opcodes to those few ALUs is expensive, very little die area is dedicated to actual mathematical machinery (as a rough estimation, consider it to be less than 10%).
A similar architecture exists on stream processors but thanks to the new programming model, the amount of transistors dedicated to management is actually very little.
Beginning from a whole system point of view, stream processors usually exist in a controlled environment. GPUs do exist on an add-in board (this seems to also apply to Imagine). CPUs continue do the job of managing system resources, running applications, and such.
The stream processor is usually equipped with a fast, efficient, proprietary memory bus (crossbar switches are now common, multi-buses have been employed in the past). The exact amount of memory lanes is dependent on the market range. As this is written, there are still 64-bit wide interconnections around (entry-level). Most mid-range models use a fast 128-bit crossbar switch matrix (4 or 2 segments), while high-end models deploy huge amounts of memory (actually up to 512 MB) with a slightly slower crossbar that is 256 bits wide. By contrast, standard processors from Intel Pentium to some Athlon 64 have only a single 64-bit wide data bus.
Memory access patterns are much more predictable. While arrays do exist, their dimension is fixed at kernel invocation. The thing which most closely matches a multiple pointer indirection is an indirection chain, which is however guaranteed to finally read or write from a specific memory area (inside a stream).
Because of the SIMD nature of the stream processor's execution units (ALUs clusters), read/write operations are expected to happen in bulk, so memories are optimized for high bandwidth rather than low latency (this is a difference from Rambus and DDR SDRAM, for example). This also allows for efficient memory bus negotiations.
Most (90%) of a stream processor's work is done on-chip, requiring only 1% of the global data to be stored to memory. This is where knowing the kernel temporaries and dependencies pays.
Internally, a stream processor features some clever communication and management circuits but what's interesting is the Stream Register File (SRF). This is conceptually a large cache in which stream data is stored to be transferred to external memory in bulks. As a cache-like software-controlled structure to the various ALUs, the SRF is shared between all the various ALU clusters. The key concept and innovation here done with Stanford's Imagine chip is that the compiler is able to automate and allocate memory in an optimal way, fully transparent to the programmer. The dependencies between kernel functions and data is known through the programming model which enables the compiler to perform flow analysis and optimally pack the SRFs. Commonly, this cache and DMA management can take up the majority of a project's schedule, something the stream processor (or at least Imagine) totally automates. Tests done at Stanford showed that the compiler did an as well or better job at scheduling memory than if you hand tuned the thing with much effort.
There is proof; there can be a lot of clusters because inter-cluster communication is assumed to be rare. Internally however, each cluster can efficiently exploit a much lower amount of ALUs because intra-cluster communication is common and thus needs to be highly efficient.
To keep those ALUs fetched with data, each ALU is equipped with local register files (LRFs), which are basically its usable registers.
This three-tiered data access pattern, makes it easy to keep temporary data away from slow memories, thus making the silicon implementation highly efficient and power-saving.
=== Hardware-in-the-loop issues ===
Although an order of magnitude speedup can be reasonably expected (even from mainstream GPUs when computing in a streaming manner), not all applications benefit from this. Communication latencies are actually the biggest problem. Although PCI Express improved this with full-duplex communications, getting a GPU (and possibly a generic stream processor) to work will possibly take long amounts of time. This means it's usually counter-productive to use them for small datasets. Because changing the kernel is a rather expensive operation the stream architecture also incurs penalties for small streams, a behaviour referred to as the short stream effect.
Pipelining is a very widespread and heavily used practice on stream processors, with GPUs featuring pipelines exceeding 200 stages. The cost for switching settings is dependent on the setting being modified but it is now considered to always be expensive. To avoid those problems at various levels of the pipeline, many techniques have been deployed such as "über shaders" and "texture atlases". Those techniques are game-oriented because of the nature of GPUs, but the concepts are interesting for generic stream processing as well.
== Examples ==
The Blitter in the Commodore Amiga is an early (circa 1985) graphics processor capable of combining three source streams of 16 component bit vectors in 256 ways to produce an output stream consisting of 16 component bit vectors. Total input stream bandwidth is up to 42 million bits per second. Output stream bandwidth is up to 28 million bits per second.
Imagine, headed by Professor William Dally of Stanford University, is a flexible architecture intended to be both fast and energy efficient. The project, originally conceived in 1996, included architecture, software tools, a VLSI implementation and a development board, was funded by DARPA, Intel and Texas Instruments.
Another Stanford project, called Merrimac, is aimed at developing a stream-based supercomputer. Merrimac intends to use a stream architecture and advanced interconnection networks to provide more performance per unit cost than cluster-based scientific computers built from the same technology.
The Storm-1 family from Stream Processors, Inc, a commercial spin-off of Stanford's Imagine project, was announced during a feature presentation at ISSCC 2007. The family contains four members ranging from 30 GOPS to 220 16-bit GOPS (billions of operations per second), all fabricated at TSMC in a 130 nanometer process. The devices target the high end of the DSP market including video conferencing, multifunction printers and digital video surveillance equipment.
GPUs are widespread, consumer-grade stream processors[2] designed mainly by AMD and Nvidia. Various generations to be noted from a stream processing point of view:
Pre-R2xx/NV2x: no explicit support for stream processing. Kernel operations were hidden in the API and provided too little flexibility for general use.
R2xx/NV2x: kernel stream operations became explicitly under the programmer's control but only for vertex processing (fragments were still using old paradigms). No branching support severely hampered flexibility but some types of algorithms could be run (notably, low-precision fluid simulation).
R3xx/NV4x: flexible branching support although some limitations still exist on the number of operations to be executed and strict recursion depth, as well as array manipulation.
R8xx: Supports append/consume buffers and atomic operations. This generation is the state of the art.
AMD FireStream brand name for product line targeting HPC
Nvidia Tesla brand name for product line targeting HPC
The Cell processor from STI, an alliance of Sony Computer Entertainment, Toshiba Corporation, and IBM, is a hardware architecture that can function like a stream processor with appropriate software support. It consists of a controlling processor, the PPE (Power Processing Element, an IBM PowerPC) and a set of SIMD coprocessors, called SPEs (Synergistic Processing Elements), each with independent program counters and instruction memory, in effect a MIMD machine. In the native programming model all DMA and program scheduling is left up to the programmer. The hardware provides a fast ring bus among the processors for local communication. Because the local memory for instructions and data is limited the only programs that can exploit this architecture effectively either require a tiny memory footprint or adhere to a stream programming model. With a suitable algorithm the performance of the Cell can rival that of pure stream processors, however this nearly always requires a complete redesign of algorithms and software.
== Stream programming libraries and languages ==
Most programming languages for stream processors start with Java, C or C++ and add extensions which provide specific instructions to allow application developers to tag kernels and/or streams. This also applies to most shading languages, which can be considered stream programming languages to a certain degree.
Non-commercial examples of stream programming languages include:
Ateji PX Free Edition, enables a simple expression of stream programming, the actor model, and the MapReduce algorithm on JVM
Auto-Pipe, from the Stream Based Supercomputing Lab at Washington University in St. Louis, an application development environment for streaming applications that allows authoring of applications for heterogeneous systems (CPU, GPGPU, FPGA). Applications can be developed in any combination of C, C++, and Java for the CPU. Verilog or VHDL for FPGAs. Cuda is currently used for Nvidia GPGPUs. Auto-Pipe also handles coordination of TCP connections between multiple machines.
ACOTES programming model: language from Polytechnic University of Catalonia based on OpenMP
BeepBeep, a simple and lightweight Java-based event stream processing library from the Formal Computer Science Lab at Université du Québec à Chicoutimi
Brook language from Stanford
CAL Actor Language: a high-level programming language for writing (dataflow) actors, which are stateful operators that transform input streams of data objects (tokens) into output streams.
Cal2Many a code generation framework from Halmstad University, Sweden. It takes CAL code as input and generates different target specific languages including sequential C, Chisel, parallel C targeting Epiphany architecture, ajava & astruct targeting Ambric architecture, etc..
DUP language from Technical University of Munich and University of Denver
HSTREAM: a directive-based language extension for heterogeneous stream computing
RaftLib - open source C++ stream processing template library originally from the Stream Based Supercomputing Lab at Washington University in St. Louis
Rimmel.js a JavaScript library enabling streams-based UI development by treating all HTML nodes and attributes as reactive sources and sinks)
SPar - C++ domain-specific language for expressing stream parallelism from the Application Modelling Group (GMAP) at Pontifical Catholic University of Rio Grande do Sul
Sh library from the University of Waterloo
Shallows, an open source project
S-Net coordination language from the University of Hertfordshire, which provides separation of coordination and algorithmic programming
StreamIt from MIT
Siddhi from WSO2
WaveScript functional stream processing, also from MIT.
Functional reactive programming could be considered stream processing in a broad sense.
Commercial implementations are either general purpose or tied to specific hardware by a vendor. Examples of general purpose languages include:
AccelerEyes' Jacket, a commercialization of a GPU engine for MATLAB
Ateji PX Java extension that enables a simple expression of stream programming, the Actor model, and the MapReduce algorithm
Embiot, a lightweight embedded streaming analytics agent from Telchemy
Floodgate, a stream processor provided with the Gamebryo game engine for PlayStation 3, Xbox360, Wii, and PC
OpenHMPP, a "directive" vision of Many-Core programming
PeakStream, a spinout of the Brook project (acquired by Google in June 2007)
IBM Spade - Stream Processing Application Declarative Engine (B. Gedik, et al. SPADE: the system S declarative stream processing engine. ACM SIGMOD 2008.)
RapidMind, a commercialization of Sh (acquired by Intel in August 2009)
TStreams, Hewlett-Packard Cambridge Research Lab
Vendor-specific languages include:
Brook+ (AMD hardware optimized implementation of Brook) from AMD/ATI
CUDA (Compute Unified Device Architecture) from Nvidia
Intel Ct - C for Throughput Computing
StreamC from Stream Processors, Inc, a commercialization of the Imagine work at Stanford
Event-Based Processing
Apama - a combined complex event and stream processing engine by Software AG
Wallaroo
WSO2 stream processor by WSO2
Apache NiFi
Batch file-based processing (emulates some of actual stream processing, but much lower performance in general)
Apache Kafka
Apache Storm
Apache Apex
Apache Spark
Continuous operator stream processing
Apache Flink
Walmartlabs Mupd8
Eclipse Streamsheets - spreadsheet for stream processing
Stream processing services:
Amazon Web Services - Kinesis
Google Cloud - Dataflow
Microsoft Azure - Stream analytics
Datastreams - Data streaming analytics platform
IBM streams
IBM streaming analytics
Eventador SQLStreamBuilder
== See also ==
== References ==
|
https://en.wikipedia.org/wiki/Stream_processing
|
Red is a programming language designed to overcome the limitations of the programming language Rebol. Red was introduced in 2011 by Nenad Rakočević, and is both an imperative and functional programming language. Its syntax and general usage overlaps that of the interpreted Rebol language.
The implementation choices of Red intend to create a full stack programming language: Red can be used for extremely high-level programming (DSLs and GUIs) as well as low-level programming (operating systems and device drivers). Key to the approach is that the language has two parts: Red/System and Red.
Red/System is similar to C, but packaged into a Rebol lexical structure – for example, one would write if x > y [print "Hello"] instead of if (x > y) {printf("Hello\n");}.
Red is a homoiconic language, which is capable of meta-programming with Rebol-like semantics. Red's runtime library is written in Red/System, and uses a hybrid approach: it compiles what it can deduce statically and uses an embedded interpreter otherwise. The project roadmap includes a just-in-time compiler for cases in between, but this has not yet been implemented.
Red seeks to remain independent of any other toolchain; it does its own code generation. It is therefore possible to cross-compile Red programs from any platform it supports to any other, via a command-line switch. Both Red and Red/System are distributed as open-source software under the modified BSD license. The runtime library is distributed under the more permissive Boost Software License.
As of version 0.6.4 Red includes a garbage collector "the Simple GC".
== Introduction ==
Red was introduced in the Netherlands in February 2011 at the Rebol & Boron conference by its author Nenad Rakočević. In September 2011, the Red programming language was presented to a larger audience during the Software Freedom Day 2011. Rakočević is a long-time Rebol developer known as the creator of the Cheyenne HTTP server.
== Features ==
Red's syntax and semantics are very close to those of Rebol. Like Rebol, it strongly supports metaprogramming and domain-specific languages (DSLs) and is therefore a highly efficient tool for dialecting (creating embedded DSLs). Red includes a dialect called Red/System, a C-level language which provides system programming facilities. Red is easy to integrate with other tools and languages as a DLL (libRed) and very lightweight (around 1 MB). It is also able to cross-compile to various platforms (see Cross Compilation section below) and create packages for platforms that require them (e.g., .APK on Android). Red also includes a fully reactive cross-platform GUI system based on an underlying reactive dataflow engine, a 2D drawing dialect comparable to SVG, compile-time and runtime macro support, and more than 40 standard datatypes.
== Goals ==
The following is the list of Red's Goals as presented on the Software Freedom Day 2011:
Simplicity ("An IDE should not be necessary to write code.")
Compactness ("Being highly expressive maximizes productivity.")
Speed ("If too slow, it cannot be general-purpose enough.")
Be "Green", Have a Small Footprint ("Because resources are not limitless.")
Ubiquity ("Spread everywhere.")
Portability, Write once run everywhere ("That's the least expected from a programming language.")
Flexibility ("Not best but good fit for any task!")
== Commercial applications ==
The following commercial applications are currently developed on Red:
DiaGrammar — Live coded diagramming
SmartXML — XML parsing tool.
== Development ==
Red's development is planned to be done in two phases:
Initial phase: Red and Red/System compilers written in Rebol 2
Bootstrap phase: Red and Red/System compilers complemented by a Red JIT-compiler, all written in Red
== Cross compilation ==
Red currently supports the following cross-compilation targets:
MS-DOS: Windows, x86, console (and GUI) applications
Windows: Windows, x86, GUI applications
Linux: Linux, x86
Linux-ARM: Linux, ARMv5, armel (soft-float)
Raspberry Pi: Linux, ARMv5, armhf (hard-float)
FreeBSD: x86
Darwin: OS X Intel, console (and GUI) applications
Android: Android, ARMv5
Android-x86: Android, x86
(Note: Presently, Red applications are 32-bit, but it is planned to switch to 64-bit in the future.)
== Hello World! ==
The "Hello, World!" program in Red:
== Factorial example ==
IMPORTANT: These are intended as syntax examples. Until Red has 64-bit support, the integer example will overflow a 32-bit integer very quickly. Changing that to `float!` will go farther, but these are merely to show the syntax of the language.
The following is a factorial example in Red:
The following is the same factorial example in Red/System (in this very simple case, the source code is very similar to Red's version):
== See also ==
Comparison of programming languages
History of programming languages
List of programming languages
List of programming languages by type
== References ==
== Further reading ==
Balbaert, Ivo (May 2018). Learn Red - Fundamentals of Red. Packt Publishing. ISBN 978-1789130706.
== External links ==
Official website
Latest builds from official website
Red on GitHub
Redprogramming.com
Helpin' Red Archived 2021-09-28 at the Wayback Machine
|
https://en.wikipedia.org/wiki/Red_(programming_language)
|
In mathematical optimization, fractional programming is a generalization of linear-fractional programming. The objective function in a fractional program is a ratio of two functions that are in general nonlinear. The ratio to be optimized often describes some kind of efficiency of a system.
== Definition ==
Let
f
,
g
,
h
j
,
j
=
1
,
…
,
m
{\displaystyle f,g,h_{j},j=1,\ldots ,m}
be real-valued functions defined on a set
S
0
⊂
R
n
{\displaystyle \mathbf {S} _{0}\subset \mathbb {R} ^{n}}
. Let
S
=
{
x
∈
S
0
:
h
j
(
x
)
≤
0
,
j
=
1
,
…
,
m
}
{\displaystyle \mathbf {S} =\{{\boldsymbol {x}}\in \mathbf {S} _{0}:h_{j}({\boldsymbol {x}})\leq 0,j=1,\ldots ,m\}}
. The nonlinear program
maximize
x
∈
S
f
(
x
)
g
(
x
)
,
{\displaystyle {\underset {{\boldsymbol {x}}\in \mathbf {S} }{\text{maximize}}}\quad {\frac {f({\boldsymbol {x}})}{g({\boldsymbol {x}})}},}
where
g
(
x
)
>
0
{\displaystyle g({\boldsymbol {x}})>0}
on
S
{\displaystyle \mathbf {S} }
, is called a fractional program.
== Concave fractional programs ==
A fractional program in which f is nonnegative and concave, g is positive and convex, and S is a convex set is called a concave fractional program. If g is affine, f does not have to be restricted in sign. The linear fractional program is a special case of a concave fractional program where all functions
f
,
g
,
h
j
,
j
=
1
,
…
,
m
{\displaystyle f,g,h_{j},j=1,\ldots ,m}
are affine.
=== Properties ===
The function
q
(
x
)
=
f
(
x
)
/
g
(
x
)
{\displaystyle q({\boldsymbol {x}})=f({\boldsymbol {x}})/g({\boldsymbol {x}})}
is semistrictly quasiconcave on S. If f and g are differentiable, then q is pseudoconcave. In a linear fractional program, the objective function is pseudolinear.
=== Transformation to a concave program ===
By the transformation
y
=
x
g
(
x
)
;
t
=
1
g
(
x
)
{\displaystyle {\boldsymbol {y}}={\frac {\boldsymbol {x}}{g({\boldsymbol {x}})}};t={\frac {1}{g({\boldsymbol {x}})}}}
, any concave fractional program can be transformed to the equivalent parameter-free concave program
maximize
y
t
∈
S
0
t
f
(
y
t
)
subject to
t
g
(
y
t
)
≤
1
,
t
≥
0.
{\displaystyle {\begin{aligned}{\underset {{\frac {\boldsymbol {y}}{t}}\in \mathbf {S} _{0}}{\text{maximize}}}\quad &tf\left({\frac {\boldsymbol {y}}{t}}\right)\\{\text{subject to}}\quad &tg\left({\frac {\boldsymbol {y}}{t}}\right)\leq 1,\\&t\geq 0.\end{aligned}}}
If g is affine, the first constraint is changed to
t
g
(
y
t
)
=
1
{\displaystyle tg({\frac {\boldsymbol {y}}{t}})=1}
and the assumption that g is positive may be dropped. Also, it simplifies to
g
(
y
)
=
1
{\displaystyle g({\boldsymbol {y}})=1}
.
=== Duality ===
The Lagrangian dual of the equivalent concave program is
minimize
u
sup
x
∈
S
0
f
(
x
)
−
u
T
h
(
x
)
g
(
x
)
subject to
u
i
≥
0
,
i
=
1
,
…
,
m
.
{\displaystyle {\begin{aligned}{\underset {\boldsymbol {u}}{\text{minimize}}}\quad &{\underset {{\boldsymbol {x}}\in \mathbf {S} _{0}}{\operatorname {sup} }}{\frac {f({\boldsymbol {x}})-{\boldsymbol {u}}^{T}{\boldsymbol {h}}({\boldsymbol {x}})}{g({\boldsymbol {x}})}}\\{\text{subject to}}\quad &u_{i}\geq 0,\quad i=1,\dots ,m.\end{aligned}}}
== Notes ==
== References ==
Avriel, Mordecai; Diewert, Walter E.; Schaible, Siegfried; Zang, Israel (1988). Generalized Concavity. Plenum Press.
Schaible, Siegfried (1983). "Fractional programming". Zeitschrift für Operations Research. 27: 39–54. doi:10.1007/bf01916898. S2CID 28766871.
|
https://en.wikipedia.org/wiki/Fractional_programming
|
CBS Broadcasting Inc. (CBS) is an American commercial broadcasting television network that launched in 1941. It is owned by the CBS Entertainment Group division of Paramount Global and is one of the "Big Four" television networks. Below is a list of programs currently broadcast on the network.
== Current programming ==
=== Drama ===
=== Comedy ===
=== Unscripted ===
==== Docuseries ====
==== Game shows ====
==== Reality ====
==== Variety ====
=== Soap operas ===
=== Co-productions ===
=== Awards shows ===
=== News programming ===
=== Film presentations ===
CBS Sunday Movie (1989–2006, 2007–2015; 2020)
=== Saturday mornings ===
=== Specials ===
The Story of Santa Claus (1996)
Robbie the Reindeer in Hooves of Fire (2002)
=== Sports programming ===
NFL on CBS (1956)
AFC games (and inter-conference games when the AFC team is the road team)
The AFC Championship Game
The Super Bowl (every four years)
The NFL Today (1961)
PGA Tour on CBS (1970)
Masters Tournament (shared with ESPN)
PGA Championship (shared with ESPN)
PGA Tour (shared with NBC Sports)
College Basketball on CBS (1981)
Select weekend regular season games
CBS Sports Classic
Missouri Valley Conference men's basketball tournament championship
Mountain West Conference men's basketball tournament championship
Atlantic 10 men's basketball tournament championship
Big Ten Conference men's basketball tournament semifinals and Championship
Big Ten Conference women's basketball tournament Championship
College Football (1996)
Big Ten Conference Football, including:
Saturday Game of the Week
The Big Ten Championship Game (in 2024 and 2028)
The Sun Bowl
The Army-Navy Game
NCAA March Madness (2011)
Selection Sunday
NCAA Division I men's basketball tournament (shared with TNT Sports)
Final Four and National Championship Game (in odd-numbered years)
Big3 (2019)
Formula E (2021–present)
New York City ePrix, as well as 1 additional race
UEFA Champions League (2021)
WNBA on CBS (2019)
== Upcoming programming ==
=== Drama ===
=== Comedy ===
=== Unscripted ===
==== Docuseries ====
==== Reality ====
=== In development ===
==== Drama ====
==== Comedy ====
==== Reality ====
== Notes ==
== References ==
|
https://en.wikipedia.org/wiki/List_of_programs_broadcast_by_CBS
|
In computing, just-in-time (JIT) compilation (also dynamic translation or run-time compilations) is compilation (of computer code) during execution of a program (at run time) rather than before execution. This may consist of source code translation but is more commonly bytecode translation to machine code, which is then executed directly. A system implementing a JIT compiler typically continuously analyses the code being executed and identifies parts of the code where the speedup gained from compilation or recompilation would outweigh the overhead of compiling that code.
JIT compilation is a combination of the two traditional approaches to translation to machine code—ahead-of-time compilation (AOT), and interpretation—and combines some advantages and drawbacks of both. Roughly, JIT compilation combines the speed of compiled code with the flexibility of interpretation, with the overhead of an interpreter and the additional overhead of compiling and linking (not just interpreting). JIT compilation is a form of dynamic compilation, and allows adaptive optimization such as dynamic recompilation and microarchitecture-specific speedups. Interpretation and JIT compilation are particularly suited for dynamic programming languages, as the runtime system can handle late-bound data types and enforce security guarantees.
== History ==
The earliest published JIT compiler is generally attributed to work on LISP by John McCarthy in 1960. In his seminal paper Recursive functions of symbolic expressions and their computation by machine, Part I, he mentions functions that are translated during runtime, thereby sparing the need to save the compiler output to punch cards (although this would be more accurately known as a "Compile and go system"). Another early example was by Ken Thompson, who in 1968 gave one of the first applications of regular expressions, here for pattern matching in the text editor QED. For speed, Thompson implemented regular expression matching by JITing to IBM 7094 code on the Compatible Time-Sharing System. An influential technique for deriving compiled code from interpretation was pioneered by James G. Mitchell in 1970, which he implemented for the experimental language LC².
Smalltalk (c. 1983) pioneered new aspects of JIT compilations. For example, translation to machine code was done on demand, and the result was cached for later use. When memory became scarce, the system would delete some of this code and regenerate it when it was needed again. Sun's Self language improved these techniques extensively and was at one point the fastest Smalltalk system in the world, achieving up to half the speed of optimized C but with a fully object-oriented language.
Self was abandoned by Sun, but the research went into the Java language. The term "Just-in-time compilation" was borrowed from the manufacturing term "Just in time" and popularized by Java, with James Gosling using the term from 1993. Currently JITing is used by most implementations of the Java Virtual Machine, as HotSpot builds on, and extensively uses, this research base.
The HP project Dynamo was an experimental JIT compiler where the "bytecode" format and the machine code format were the same; the system optimized PA-8000 machine code. Counterintuitively, this resulted in speed ups, in some cases of 30% since doing this permitted optimizations at the machine code level, for example, inlining code for better cache usage and optimizations of calls to dynamic libraries and many other run-time optimizations which conventional compilers are not able to attempt.
In November 2020, PHP 8.0 introduced a JIT compiler. In October 2024, CPython introduced an experimental JIT compiler.
== Design ==
In a bytecode-compiled system, source code is translated to an intermediate representation known as bytecode. Bytecode is not the machine code for any particular computer, and may be portable among computer architectures. The bytecode may then be interpreted by, or run on a virtual machine. The JIT compiler reads the bytecodes in many sections (or in full, rarely) and compiles them dynamically into machine code so the program can run faster. This can be done per-file, per-function or even on any arbitrary code fragment; the code can be compiled when it is about to be executed (hence the name "just-in-time"), and then cached and reused later without needing to be recompiled.
By contrast, a traditional interpreted virtual machine will simply interpret the bytecode, generally with much lower performance. Some interpreters even interpret source code, without the step of first compiling to bytecode, with even worse performance. Statically-compiled code or native code is compiled prior to deployment. A dynamic compilation environment is one in which the compiler can be used during execution. A common goal of using JIT techniques is to reach or surpass the performance of static compilation, while maintaining the advantages of bytecode interpretation: Much of the "heavy lifting" of parsing the original source code and performing basic optimization is often handled at compile time, prior to deployment: compilation from bytecode to machine code is much faster than compiling from source. The deployed bytecode is portable, unlike native code. Since the runtime has control over the compilation, like interpreted bytecode, it can run in a secure sandbox. Compilers from bytecode to machine code are easier to write, because the portable bytecode compiler has already done much of the work.
JIT code generally offers far better performance than interpreters. In addition, it can in some cases offer better performance than static compilation, as many optimizations are only feasible at run-time:
The compilation can be optimized to the targeted CPU and the operating system model where the application runs. For example, JIT can choose SSE2 vector CPU instructions when it detects that the CPU supports them. To obtain this level of optimization specificity with a static compiler, one must either compile a binary for each intended platform/architecture, or else include multiple versions of portions of the code within a single binary.
The system is able to collect statistics about how the program is actually running in the environment it is in, and it can rearrange and recompile for optimum performance. However, some static compilers can also take profile information as input.
The system can do global code optimizations (e.g. inlining of library functions) without losing the advantages of dynamic linking and without the overheads inherent to static compilers and linkers. Specifically, when doing global inline substitutions, a static compilation process may need run-time checks and ensure that a virtual call would occur if the actual class of the object overrides the inlined method, and boundary condition checks on array accesses may need to be processed within loops. With just-in-time compilation in many cases this processing can be moved out of loops, often giving large increases of speed.
Although this is possible with statically compiled garbage collected languages, a bytecode system can more easily rearrange executed code for better cache utilization.
Because a JIT must render and execute a native binary image at runtime, true machine-code JITs necessitate platforms that allow for data to be executed at runtime, making using such JITs on a Harvard architecture-based machine impossible; the same can be said for certain operating systems and virtual machines as well. However, a special type of "JIT" may potentially not target the physical machine's CPU architecture, but rather an optimized VM bytecode where limitations on raw machine code prevail, especially where that bytecode's VM eventually leverages a JIT to native code.
== Performance ==
JIT causes a slight to noticeable delay in the initial execution of an application, due to the time taken to load and compile the input code. Sometimes this delay is called "startup time delay" or "warm-up time". In general, the more optimization JIT performs, the better the code it will generate, but the initial delay will also increase. A JIT compiler therefore has to make a trade-off between the compilation time and the quality of the code it hopes to generate. Startup time can include increased IO-bound operations in addition to JIT compilation: for example, the rt.jar class data file for the Java Virtual Machine (JVM) is 40 MB and the JVM must seek a lot of data in this contextually huge file.
One possible optimization, used by Sun's HotSpot Java Virtual Machine, is to combine interpretation and JIT compilation. The application code is initially interpreted, but the JVM monitors which sequences of bytecode are frequently executed and translates them to machine code for direct execution on the hardware. For bytecode which is executed only a few times, this saves the compilation time and reduces the initial latency; for frequently executed bytecode, JIT compilation is used to run at high speed, after an initial phase of slow interpretation. Additionally, since a program spends most time executing a minority of its code, the reduced compilation time is significant. Finally, during the initial code interpretation, execution statistics can be collected before compilation, which helps to perform better optimization.
The correct tradeoff can vary due to circumstances. For example, Sun's Java Virtual Machine has two major modes—client and server. In client mode, minimal compilation and optimization is performed, to reduce startup time. In server mode, extensive compilation and optimization is performed, to maximize performance once the application is running by sacrificing startup time. Other Java just-in-time compilers have used a runtime measurement of the number of times a method has executed combined with the bytecode size of a method as a heuristic to decide when to compile. Still another uses the number of times executed combined with the detection of loops. In general, it is much harder to accurately predict which methods to optimize in short-running applications than in long-running ones.
Native Image Generator (Ngen) by Microsoft is another approach at reducing the initial delay. Ngen pre-compiles (or "pre-JITs") bytecode in a Common Intermediate Language image into machine native code. As a result, no runtime compilation is needed. .NET Framework 2.0 shipped with Visual Studio 2005 runs Ngen on all of the Microsoft library DLLs right after the installation. Pre-jitting provides a way to improve the startup time. However, the quality of code it generates might not be as good as the one that is JITed, for the same reasons why code compiled statically, without profile-guided optimization, cannot be as good as JIT compiled code in the extreme case: the lack of profiling data to drive, for instance, inline caching.
There also exist Java implementations that combine an AOT (ahead-of-time) compiler with either a JIT compiler (Excelsior JET) or interpreter (GNU Compiler for Java).
JIT compilation may not reliably achieve its goal, namely entering a steady state of improved performance after a short initial warmup period. Across eight different virtual machines, Barrett et al. (2017) measured six widely-used microbenchmarks which are commonly used by virtual machine implementors as optimisation targets, running them repeatedly within a single process execution. On Linux, they found that 8.7% to 9.6% of process executions failed to reach a steady state of performance, 16.7% to 17.9% entered a steady state of reduced performance after a warmup period, and 56.5% pairings of a specific virtual machine running a specific benchmark failed to consistently see a steady-state non-degradation of performance across multiple executions (i.e., at least one execution failed to reach a steady state or saw reduced performance in the steady state). Even where an improved steady-state was reached, it sometimes took many hundreds of iterations. Traini et al. (2022) instead focused on the HotSpot virtual machine but with a much wider array of benchmarks, finding that 10.9% of process executions failed to reach a steady state of performance, and 43.5% of benchmarks did not consistently attain a steady state across multiple executions.
== Security ==
JIT compilation fundamentally uses executable data, and thus poses security challenges and possible exploits.
Implementation of JIT compilation consists of compiling source code or byte code to machine code and executing it. This is generally done directly in memory: the JIT compiler outputs the machine code directly into memory and immediately executes it, rather than outputting it to disk and then invoking the code as a separate program, as in usual ahead of time compilation. In modern architectures this runs into a problem due to executable space protection: arbitrary memory cannot be executed, as otherwise there is a potential security hole. Thus memory must be marked as executable; for security reasons this should be done after the code has been written to memory, and marked read-only, as writable/executable memory is a security hole (see W^X). For instance Firefox's JIT compiler for Javascript introduced this protection in a release version with Firefox 46.
JIT spraying is a class of computer security exploits that use JIT compilation for heap spraying: the resulting memory is then executable, which allows an exploit if execution can be moved into the heap.
== Uses ==
JIT compilation can be applied to some programs, or can be used for certain capacities, particularly dynamic capacities such as regular expressions. For example, a text editor may compile a regular expression provided at runtime to machine code to allow faster matching: this cannot be done ahead of time, as the pattern is only provided at runtime. Several modern runtime environments rely on JIT compilation for high-speed code execution, including most implementations of Java, together with Microsoft's .NET. Similarly, many regular-expression libraries feature JIT compilation of regular expressions, either to bytecode or to machine code. JIT compilation is also used in some emulators, in order to translate machine code from one CPU architecture to another.
A common implementation of JIT compilation is to first have AOT compilation to bytecode (virtual machine code), known as bytecode compilation, and then have JIT compilation to machine code (dynamic compilation), rather than interpretation of the bytecode. This improves the runtime performance compared to interpretation, at the cost of lag due to compilation. JIT compilers translate continuously, as with interpreters, but caching of compiled code minimizes lag on future execution of the same code during a given run. Since only part of the program is compiled, there is significantly less lag than if the entire program were compiled prior to execution.
== See also ==
Binary translation
Common Language Runtime
Copy-and-patch
Dynamic compilation
GNU lightning
LLVM
OVPsim
Self-modifying code
Tracing just-in-time compilation
Transmeta Crusoe
== Notes ==
== References ==
== Bibliography ==
Barrett, Ed; Bolz-Tereick, Carl Friedrich; Killick, Rebecca; Mount, Sarah; Tratt, Laurence (12 October 2017). "Virtual machine warmup blows hot and cold". Proceedings of the ACM on Programming Languages. 1: 1–27. arXiv:1602.00602. doi:10.1145/3133876. S2CID 1036324.
Traini, Luca; Cortellessa, Vittorio; Di Pompeo, Daniele; Tucci, Michele (30 September 2022). "Towards effective assessment of steady state performance in Java software: Are we there yet?". Empirical Software Engineering. 28. arXiv:2209.15369. doi:10.1007/s10664-022-10247-x. S2CID 252668652.
Aycock, J. (June 2003). "A brief history of just-in-time". ACM Computing Surveys. 35 (2): 97–113. CiteSeerX 10.1.1.97.3985. doi:10.1145/857076.857077. S2CID 15345671.
Thompson, K. (1968). "Programming Techniques: Regular expression search algorithm". Communications of the ACM. 11 (6): 419–422. doi:10.1145/363347.363387. S2CID 21260384.
== External links ==
Free Online Dictionary of Computing entry
Mozilla Nanojit Archived 2012-05-09 at the Wayback Machine: A small, cross-platform C++ library that emits machine code. It is used as the JIT for the Mozilla Tamarin and SpiderMonkey Javascript engines.
Profiling Runtime Generated and Interpreted Code using the VTune Performance Analyzer
|
https://en.wikipedia.org/wiki/Just-in-time_compilation
|
In computer science, a preprocessor (or precompiler) is a program that processes its input data to produce output that is used as input in another program. The output is said to be a preprocessed form of the input data, which is often used by some subsequent programs like compilers. The amount and kind of processing done depends on the nature of the preprocessor; some preprocessors are only capable of performing relatively simple textual substitutions and macro expansions, while others have the power of full-fledged programming languages.
A common example from computer programming is the processing performed on source code before the next step of compilation.
In some computer languages (e.g., C and PL/I) there is a phase of translation known as preprocessing. It can also include macro processing, file inclusion and language extensions.
== Lexical preprocessors ==
Lexical preprocessors are the lowest-level of preprocessors as they only require lexical analysis, that is, they operate on the source text, prior to any parsing, by performing simple substitution of tokenized character sequences for other tokenized character sequences, according to user-defined rules. They typically perform macro substitution, textual inclusion of other files, and conditional compilation or inclusion.
=== C preprocessor ===
The most common example of this is the C preprocessor, which takes lines beginning with '#' as directives.
The C preprocessor does not expect its input to use the syntax of the C language.
Some languages take a different approach and use built-in language features to achieve similar things. For example:
Instead of macros, some languages use aggressive inlining and templates.
Instead of includes, some languages use compile-time imports that rely on type information in the object code.
Some languages use if-then-else and dead code elimination to achieve conditional compilation.
=== Other lexical preprocessors ===
Other lexical preprocessors include the general-purpose m4, most commonly used in cross-platform build systems such as autoconf, and GEMA, an open source macro processor which operates on patterns of context.
== Syntactic preprocessors ==
Syntactic preprocessors were introduced with the Lisp family of languages. Their role is to transform syntax trees according to a number of user-defined rules. For some programming languages, the rules are written in the same language as the program (compile-time reflection). This is the case with Lisp and OCaml. Some other languages rely on a fully external language to define the transformations, such as the XSLT preprocessor for XML, or its statically typed counterpart CDuce.
Syntactic preprocessors are typically used to customize the syntax of a language, extend a language by adding new primitives, or embed a domain-specific programming language (DSL) inside a general purpose language.
=== Customizing syntax ===
A good example of syntax customization is the existence of two different syntaxes in the Objective Caml programming language. Programs may be written indifferently using the "normal syntax" or the "revised syntax", and may be pretty-printed with either syntax on demand.
Similarly, a number of programs written in OCaml customize the syntax of the language by the addition of new operators.
=== Extending a language ===
The best examples of language extension through macros are found in the Lisp family of languages. While the languages, by themselves, are simple dynamically typed functional cores, the standard distributions of Scheme or Common Lisp permit imperative or object-oriented programming, as well as static typing. Almost all of these features are implemented by syntactic preprocessing, although it bears noting that the "macro expansion" phase of compilation is handled by the compiler in Lisp. This can still be considered a form of preprocessing, since it takes place before other phases of compilation.
=== Specializing a language ===
One of the unusual features of the Lisp family of languages is the possibility of using macros to create an internal DSL. Typically, in a large Lisp-based project, a module may be written in a variety of such minilanguages, one perhaps using a SQL-based dialect of Lisp, another written in a dialect specialized for GUIs or pretty-printing, etc. Common Lisp's standard library contains an example of this level of syntactic abstraction in the form of the LOOP macro, which implements an Algol-like minilanguage to describe complex iteration, while still enabling the use of standard Lisp operators.
The MetaOCaml preprocessor/language provides similar features for external DSLs. This preprocessor takes the description of the semantics of a language (i.e. an interpreter) and, by combining compile-time interpretation and code generation, turns that definition into a compiler to the OCaml programming language—and from that language, either to bytecode or to native code.
== General purpose preprocessor ==
Most preprocessors are specific to a particular data processing task (e.g., compiling the C language). A preprocessor may be promoted as being general purpose, meaning that it is not aimed at a specific usage or programming language, and is intended to be used for a wide variety of text processing tasks.
M4 is probably the most well known example of such a general purpose preprocessor, although the C preprocessor is sometimes used in a non-C specific role. Examples:
using C preprocessor for JavaScript preprocessing.
using C preprocessor for devicetree processing within the Linux kernel.
using M4 (see on-article example) or C preprocessor as a template engine, to HTML generation.
imake, a make interface using the C preprocessor, written for the X Window System but now deprecated in favour of automake.
grompp, a preprocessor for simulation input files for GROMACS (a fast, free, open-source code for some problems in computational chemistry) which calls the system C preprocessor (or other preprocessor as determined by the simulation input file) to parse the topology, using mostly the #define and #include mechanisms to determine the effective topology at grompp run time.
== See also ==
Directive (programming) – Language construct that specifies how a compiler should process its input
Metaprogramming – Programming paradigm
Macros – Rule for substituting a set input with a set output
Source-to-source compiler, also known as Transpiler – Translator of computer source code
Sass (stylesheet language) – Stylesheet languagePages displaying short descriptions of redirect targets
Stylus (stylesheet language) – Stylesheet preprocessor languagePages displaying short descriptions of redirect targets
Less (stylesheet language) – Dynamic stylesheet languagePages displaying short descriptions of redirect targets
Snippet (programming) – Small region of re-usable source code, machine code, or text
Template engine – Software designed to combine templates with a data model to produce result documents
The C preprocessor – Text processor used with C and C++ and other programming tools
The OCaml preprocessor-pretty-printer – Programming software system
The PL/I preprocessor
The Windows software trace preprocessor
General-purpose macro processor – Macro processor that is not tied to or integrated with a particular language or piece of software.
== References ==
== External links ==
DSL Design in Lisp
Programming from the bottom up
The Generic PreProcessor
Gema, the General Purpose Macro Processor
The PIKT piktc text, script, and configuration file preprocessor
pyexpander, a python based general purpose macro processor
minimac, a minimalist macro processor
Java Comment Preprocessor
|
https://en.wikipedia.org/wiki/Preprocessor
|
Application software is any computer program that is intended for end-user use – not operating, administering or programming the computer. An application (app, application program, software application) is any program that can be categorized as application software. Common types of applications include word processor, media player and accounting software.
The term application software refers to all applications collectively and can be used to differentiate from system and utility software.
Applications may be bundled with the computer and its system software or published separately. Applications may be proprietary or open-source.
The short term app (coined in 1981 or earlier) became popular with the 2008 introduction of the iOS App Store, to refer to applications for mobile devices such as smartphones and tablets. Later, with introduction of the Mac App Store (in 2010) and Windows Store (in 2011), the term was extended in popular use to include desktop applications.
== Terminology ==
The delineation between system software such as operating systems and application software is not exact and is occasionally the object of controversy. For example, one of the key questions in the United States v. Microsoft Corp. antitrust trial was whether Microsoft's Internet Explorer web browser was part of its Windows operating system or a separate piece of application software. As another example, the GNU/Linux naming controversy is, in part, due to disagreement about the relationship between the Linux kernel and the operating systems built over this kernel. In some types of embedded systems, the application software and the operating system software may be indistinguishable by the user, as in the case of software used to control a VCR, DVD player, or microwave oven. The above definitions may exclude some applications that may exist on some computers in large organizations. For an alternative definition of an app: see Application Portfolio Management.
When used as an adjective, application is not restricted to mean: of or on application software. For example, concepts such as application programming interface (API), application server, application virtualization, application lifecycle management and portable application apply to all computer programs alike, not just application software.
=== Killer app ===
Sometimes a new and popular application arises that only runs on one platform that results in increasing the desirability of that platform. This is called a killer application or killer app, coined in the late 1980s. For example, VisiCalc was the first modern spreadsheet software for the Apple II and helped sell the then-new personal computers into offices. For the BlackBerry, it was its email software.
=== Platform specific naming ===
Some applications are available for multiple platforms while others only work on one and are thus called, for example, a geography application for Microsoft Windows, or an Android application for education, or a Linux game.
== Classification ==
There are many different and alternative ways to classify application software.
From the legal point of view, application software is mainly classified with a black-box approach, about the rights of its end-users or subscribers (with eventual intermediate and tiered subscription levels).
Software applications are also classified with respect to the programming language in which the source code is written or executed, and concerning their purpose and outputs.
=== By property and use rights ===
Application software is usually distinguished into two main classes: closed source vs open source software applications, and free or proprietary software applications.
Proprietary software is placed under the exclusive copyright, and a software license grants limited usage rights. The open-closed principle states that software may be "open only for extension, but not for modification". Such applications can only get add-ons from third parties.
Free and open-source software (FOSS) shall be run, distributed, sold, or extended for any purpose, and -being open- shall be modified or reversed in the same way.
FOSS software applications released under a free license may be perpetual and also royalty-free. Perhaps, the owner, the holder or third-party enforcer of any right (copyright, trademark, patent, or ius in re aliena) are entitled to add exceptions, limitations, time decays or expiring dates to the license terms of use.
Public-domain software is a type of FOSS which is royalty-free and - openly or reservedly- can be run, distributed, modified, reversed, republished, or created in derivative works without any copyright attribution and therefore revocation. It can even be sold, but without transferring the public domain property to other single subjects. Public-domain SW can be released under a (un)licensing legal statement, which enforces those terms and conditions for an indefinite duration (for a lifetime, or forever).
=== By coding language ===
Since the development and near-universal adoption of the web, an important distinction that has emerged, has been between web applications — written with HTML, JavaScript and other web-native technologies and typically requiring one to be online and running a web browser — and the more traditional native applications written in whatever languages are available for one's particular type of computer. There has been a contentious debate in the computing community regarding web applications replacing native applications for many purposes, especially on mobile devices such as smartphones and tablets. Web apps have indeed greatly increased in popularity for some uses, but the advantages of applications make them unlikely to disappear soon, if ever. Furthermore, the two can be complementary, and even integrated.
=== By purpose and output ===
Application software can also be seen as being either horizontal or vertical. Horizontal applications are more popular and widespread, because they are general purpose, for example word processors or databases. Vertical applications are niche products, designed for a particular type of industry or business, or department within an organization. Integrated suites of software will try to handle every specific aspect possible of, for example, manufacturing or banking worker, accounting, or customer service.
There are many types of application software:
An application suite consists of multiple applications bundled together. They usually have related functions, features, and user interfaces, and may be able to interact with each other, e.g. open each other's files. Business applications often come in suites, e.g. Microsoft Office, LibreOffice and iWork, which bundle together a word processor, a spreadsheet, etc.; but suites exist for other purposes, e.g. graphics or music.
Enterprise software addresses the needs of an entire organization's processes and data flows, across several departments, often in a large distributed environment. Examples include enterprise resource planning systems, customer relationship management (CRM) systems, data replication engines, and supply chain management software. Departmental Software is a sub-type of enterprise software with a focus on smaller organizations or groups within a large organization. (Examples include travel expense management and IT Helpdesk.)
Enterprise infrastructure software provides common capabilities needed to support enterprise software systems. (Examples include databases, email servers, and systems for managing networks and security.)
Application platform as a service (aPaaS) is a cloud computing service that offers development and deployment environments for application services.
Information worker software lets users create and manage information, often for individual projects within a department, in contrast to enterprise management. Examples include time management, resource management, analytical, collaborative and documentation tools. Word processors, spreadsheets, email and blog clients, personal information systems, and individual media editors may aid in multiple information worker tasks.
Content access software is used primarily to access content without editing, but may include software that allows for content editing. Such software addresses the needs of individuals and groups to consume digital entertainment and published digital content. (Examples include media players, web browsers, and help browsers.)
Educational software is related to content access software, but has the content or features adapted for use by educators or students. For example, it may deliver evaluations (tests), track progress through material, or include collaborative capabilities.
Simulation software simulates physical or abstract systems for either research, training, or entertainment purposes.
Media development software generates print and electronic media for others to consume, most often in a commercial or educational setting. This includes graphic-art software, desktop publishing software, multimedia development software, HTML editors, digital-animation editors, digital audio and video composition, and many others.
Product engineering software is used in developing hardware and software products. This includes computer-aided design (CAD), computer-aided engineering (CAE), computer language editing and compiling tools, integrated development environments, and application programmer interfaces.
Entertainment Software can refer to video games, screen savers, programs to display motion pictures or play recorded music, and other forms of entertainment which can be experienced through the use of a computing device.
=== By platform ===
Applications can also be classified by computing platforms such as a desktop application for a particular operating system, delivery network such as in cloud computing and Web 2.0 applications, or delivery devices such as mobile apps for mobile devices.
The operating system itself can be considered application software when performing simple calculating, measuring, rendering, and word processing tasks not used to control hardware via a command-line interface or graphical user interface. This does not include application software bundled within operating systems such as a software calculator or text editor.
=== Information worker software ===
Accounting software
Data management
Contact manager
Spreadsheet
Database software
Documentation
Document automation
Word processor
Desktop publishing software
Diagramming software
Presentation software
Email
Blog software
Enterprise resource planning
Financial software
Banking software
Clearing systems
Financial accounting software
Financial software
Field service management
Workforce management software
Project management software
Calendaring software
Employee scheduling software
Workflow software
Reservation systems
=== Entertainment software ===
Screen savers
Video games
Arcade video games
Console games
Mobile games
Personal computer games
Software art
Demo
64K intro
=== Educational software ===
Classroom management
Reference software
Sales readiness software
Survey management
Encyclopedia software
=== Enterprise infrastructure software ===
Artificial Intelligence for IT Operations (AIOps)
Business workflow software
Database management system (DBMS)
Digital asset management (DAM) software
Document management software
Geographic information system (GIS)
=== Simulation software ===
Computer simulators
Scientific simulators
Social simulators
Battlefield simulators
Emergency simulators
Vehicle simulators
Flight simulators
Driving simulators
Simulation games
Vehicle simulation games
=== Media development software ===
3D computer graphics software
Animation software
Graphic art software
Raster graphics editor
Vector graphics editor
Image organizer
Video editing software
Audio editing software
Digital audio workstation
Music sequencer
Scorewriter
HTML editor
Game development tool
=== Product engineering software ===
Hardware engineering
Computer-aided engineering
Computer-aided design (CAD)
Computer-aided manufacturing (CAM)
Finite element analysis
=== Software engineering ===
Compiler software
Integrated development environment
Compiler
Linker
Debugger
Version control
Game development tool
License manager
== See also ==
Software development – Creation and maintenance of software
Mobile app – Software application designed to run on mobile devices
Web application – Application that uses a web browser as a client
Server application – Computer to access a central resource or service on a networkPages displaying short descriptions of redirect targets
Super-app – Mobile application that provides multiple services including financial transactions
== References ==
== External links ==
Learning materials related to Application software at Wikiversity
|
https://en.wikipedia.org/wiki/Application_software
|
The Art of Computer Programming (TAOCP) is a comprehensive multi-volume monograph written by the computer scientist Donald Knuth presenting programming algorithms and their analysis. As of 2025 it consists of published volumes 1, 2, 3, 4A, and 4B, with more expected to be released in the future. The Volumes 1–5 are intended to represent the central core of computer programming for sequential machines; the subjects of Volumes 6 and 7 are important but more specialized.
When Knuth began the project in 1962, he originally conceived of it as a single book with twelve chapters. The first three volumes of what was then expected to be a seven-volume set were published in 1968, 1969, and 1973. Work began in earnest on Volume 4 in 1973, but was suspended in 1977 for work on typesetting prompted by the second edition of Volume 2. Writing of the final copy of Volume 4A began in longhand in 2001, and the first online pre-fascicle, 2A, appeared later in 2001. The first published installment of Volume 4 appeared in paperback as Fascicle 2 in 2005. The hardback Volume 4A, combining Volume 4, Fascicles 0–4, was published in 2011. Volume 4, Fascicle 6 ("Satisfiability") was released in December 2015; Volume 4, Fascicle 5 ("Mathematical Preliminaries Redux; Backtracking; Dancing Links") was released in November 2019.
Volume 4B consists of material evolved from Fascicles 5 and 6. The manuscript was sent to the publisher on August 1, 2022, and the volume was published in September 2022. Fascicle 7 ("Constraint Satisfaction"), planned for Volume 4C, was the subject of Knuth's talk on August 3, 2022 and was published on February 5, 2025.
== History ==
After winning a Westinghouse Talent Search scholarship, Knuth enrolled at the Case Institute of Technology (now Case Western Reserve University), where his performance was so outstanding that the faculty voted to award him a master of science upon his completion of the bachelor's degree. During his summer vacations, Knuth was hired by the Burroughs Corporation to write compilers, earning more in his summer months than full professors did for an entire year. Such exploits made Knuth a topic of discussion among the mathematics department, which included Richard S. Varga.
In January 1962, when he was a graduate student in the mathematics department at Caltech, Knuth was approached by Addison-Wesley to write a book about compiler design, and he proposed a larger scope. He came up with a list of twelve chapter titles the same day. In the summer of 1962 he worked on a FORTRAN compiler for UNIVAC, considering that he had "sold my soul to the devil" to develop a FORTRAN compiler: 15 after ALGOL developments with Burroughs. He remained as a consultant to Burroughs over the period 1960 to 1968 while writing Volume 1 "Fundamental Algorithms".
During this time, he also developed a mathematical analysis of linear probing, which convinced him to present the material with a quantitative approach. After receiving his Ph.D. in June 1963, he began working on his manuscript, of which he finished his first draft in June 1965, at 3000 hand-written pages. He had assumed that about five hand-written pages would translate into one printed page, but his publisher said instead that about 1+1⁄2 hand-written pages translated to one printed page. This meant he had approximately 2000 printed pages of material, which closely matches the size of the first three published volumes.
The first volume of "The Art of Computer Programming", "Fundamental Algorithms", took five years to complete between 1963 and 1968 while working at both Caltech and Burroughs.
Knuth's dedication in Volume 1 reads:
This series of books is affectionately dedicatedto the Type 650 computer once installed atCase Institute of Technology,in remembrance of many pleasant evenings.
In the preface, he thanks first his wife Jill, then Burroughs for the use of B220 and B5500 computers in testing most of the programs, and Caltech, the National Science Foundation, and the Office of Naval Research.: xii
Section 2.5 of "Fundamental Algorithms" is on Dynamic Storage Allocation. Parts of this are used in the Burroughs approach to memory management. Knuth claims credit for “The “boundary-tag” method, introduced in Section 2.5, was designed by the author in 1962 for use in a control program for the B5000 computer.”: 460
Knuth received support from Richard S. Varga, who was the scientific adviser to the publisher. Varga was visiting Olga Taussky-Todd and John Todd at Caltech. With Varga's enthusiastic endorsement, the publisher accepted Knuth's expanded plans. In its expanded version, the book would be published in seven volumes, each with just one or two chapters. Due to the growth in Chapter 7, which was fewer than 100 pages of the 1965 manuscript, per Vol. 4A p. vi, the plan for Volume 4 has since expanded to include Volumes 4A, 4B, 4C, 4D, and possibly more.
In 1976, Knuth prepared a second edition of Volume 2, requiring it to be typeset again, but the style of type used in the first edition (called hot type) was no longer available. In 1977, he decided to spend some time creating something more suitable. Eight years later, he returned with TEX, which is currently used for all volumes.
Another characteristic of the volumes is the variation in the difficulty of the exercises including a numerical rating varying from 0 to 50, where 0 is trivial, and 50 is an open question in contemporary research.
== Bounty for finding errors ==
The offer of a so-called Knuth reward check worth "one hexadecimal dollar" (100HEX base 16 cents, in decimal, is $2.56) for any errors found, and the correction of these errors in subsequent printings, has contributed to the highly polished and still-authoritative nature of the work, long after its first publication.
== Assembly language in the book ==
All examples in the books use a hypothetical language called "MIX assembly language" (MIXAL), which runs on "a mythical computer called MIX". Currently, the MIX computer is being replaced by the MMIX computer, which is a RISC version. The conversion from MIX to MMIX was a large ongoing project for which Knuth solicited volunteers for help. Software such as GNU MDK exists to provide emulation of the MIX architecture. Knuth considers the use of assembly language necessary for the speed and memory usage of algorithms to be judged.
MIX was much like any computer then in existence, but nicer. The name ‘MIX’ is 1009 in Roman numerals and this is given by a formula involving series numbers of several computers of the time: (360 + 650 + 709 + U3 + SS80 + 1107 + 1604 + G2- + B220 + S2000 + 920 + 601 + H800 + PDP-4 + 11)/16 = 1009 or MIX. The name MMIX is 2009 in Roman numerals and Knuth claims MMIX is even nicer than MIX.
== Critical response ==
Knuth was awarded the 1974 Turing Award "for his major contributions to the analysis of algorithms […], and in particular for his contributions to the 'art of computer programming' through his well-known books in a continuous series by this title." American Scientist has included this work among "100 or so Books that shaped a Century of Science", referring to the twentieth century. Covers of the third edition of Volume 1 quote Bill Gates as saying, "If you think you're a really good programmer… read (Knuth's) Art of Computer Programming… You should definitely send me a résumé if you can read the whole thing." The New York Times referred to it as "the profession's defining treatise".
== Volumes ==
=== Completed ===
Volume 1 – Fundamental algorithms
Chapter 1 – Basic concepts
Chapter 2 – Information structures
Volume 2 – Seminumerical algorithms
Chapter 3 – Random numbers
Chapter 4 – Arithmetic
Volume 3 – Sorting and searching
Chapter 5 – Sorting
Chapter 6 – Searching
Volume 4A – Combinatorial algorithms
Chapter 7 – Combinatorial searching (part 1)
Volume 4B – Combinatorial algorithms
Chapter 7 – Combinatorial searching (part 2)
=== Planned ===
Volume 4C, 4D, ... Combinatorial algorithms (chapters 7 & 8 released in several subvolumes)
Chapter 7 – Combinatorial searching (continued)
Chapter 8 – Recursion
Volume 5 – Syntactic algorithms
Chapter 9 – Lexical scanning (also includes string search and data compression)
Chapter 10 – Parsing techniques
Volume 6 – The Theory of context-free languages
Chapter 11 – Mathematical linguistics
Volume 7 – Compiler techniques
Chapter 12 – Programming language translation
== Chapter outlines ==
=== Completed ===
==== Volume 1 – Fundamental algorithms ====
Chapter 1 – Basic concepts
1.1. Algorithms
1.2. Mathematical preliminaries
1.2.1. Mathematical induction
1.2.2. Numbers, powers, and logarithms
1.2.3. Sums and products
1.2.4. Integer functions and elementary number theory
1.2.5. Permutations and factorials
1.2.6. Binomial coefficients
1.2.7. Harmonic numbers
1.2.8. Fibonacci numbers
1.2.9. Generating functions
1.2.10. Analysis of an algorithm
1.2.11. Asymptotic representations
1.2.11.1. The O-notation
1.2.11.2. Euler's summation formula
1.2.11.3. Some asymptotic calculations
1.3 MIX (Updated with MMIX in Volume 1 fascicle 1)
1.3.1. Description of MIX
1.3.2. The MIX assembly language
1.3.3. Applications to permutations
1.4. Some fundamental programming techniques
1.4.1. Subroutines
1.4.2. Coroutines
1.4.3. Interpretive routines
1.4.3.1. A MIX simulator
1.4.3.2. Trace routines
1.4.4. Input and output
1.4.5. History and bibliography
Chapter 2 – Information structures
2.1. Introduction
2.2. Linear lists
2.2.1. Stacks, queues, and deques
2.2.2. Sequential allocation
2.2.3. Linked allocation (topological sorting)
2.2.4. Circular lists
2.2.5. Doubly linked lists
2.2.6. Arrays and orthogonal lists
2.3. Trees
2.3.1. Traversing binary trees
2.3.2. Binary tree representation of trees
2.3.3. Other representations of trees
2.3.4. Basic mathematical properties of trees
2.3.4.1. Free trees
2.3.4.2. Oriented trees
2.3.4.3. The "infinity lemma"
2.3.4.4. Enumeration of trees
2.3.4.5. Path length
2.3.4.6. History and bibliography
2.3.5. Lists and garbage collection
2.4. Multilinked structures
2.5. Dynamic storage allocation
2.6. History and bibliography
==== Volume 2 – Seminumerical algorithms ====
Chapter 3 – Random numbers
3.1. Introduction
3.2. Generating uniform random numbers
3.2.1. The linear congruential method
3.2.1.1. Choice of modulus
3.2.1.2. Choice of multiplier
3.2.1.3. Potency
3.2.2. Other methods
3.3. Statistical tests
3.3.1. General test procedures for studying random data
3.3.2. Empirical tests
3.3.3. Theoretical tests
3.3.4. The spectral test
3.4. Other types of random quantities
3.4.1. Numerical distributions
3.4.2. Random sampling and shuffling
3.5. What Is a random sequence?
3.6. Summary
Chapter 4 – Arithmetic
4.1. Positional number systems
4.2. Floating point arithmetic
4.2.1. Single-precision calculations
4.2.2. Accuracy of floating point arithmetic
4.2.3. Double-precision calculations
4.2.4. Distribution of floating point numbers
4.3. Multiple precision arithmetic
4.3.1. The classical algorithms
4.3.2. Modular arithmetic
4.3.3. How fast can we multiply?
4.4. Radix conversion
4.5. Rational arithmetic
4.5.1. Fractions
4.5.2. The greatest common divisor
4.5.3. Analysis of Euclid's algorithm
4.5.4. Factoring into primes
4.6. Polynomial arithmetic
4.6.1. Division of polynomials
4.6.2. Factorization of polynomials
4.6.3. Evaluation of powers (addition-chain exponentiation)
4.6.4. Evaluation of polynomials
4.7. Manipulation of power series
==== Volume 3 – Sorting and searching ====
Chapter 5 – Sorting
5.1. Combinatorial properties of permutations
5.1.1. Inversions
5.1.2. Permutations of a multiset
5.1.3. Runs
5.1.4. Tableaux and involutions
5.2. Internal sorting
5.2.1. Sorting by insertion
5.2.2. Sorting by exchanging
5.2.3. Sorting by selection
5.2.4. Sorting by merging
5.2.5. Sorting by distribution
5.3. Optimum sorting
5.3.1. Minimum-comparison sorting
5.3.2. Minimum-comparison merging
5.3.3. Minimum-comparison selection
5.3.4. Networks for sorting
5.4. External sorting
5.4.1. Multiway merging and replacement selection
5.4.2. The polyphase merge
5.4.3. The cascade merge
5.4.4. Reading tape backwards
5.4.5. The oscillating sort
5.4.6. Practical considerations for tape merging
5.4.7. External radix sorting
5.4.8. Two-tape sorting
5.4.9. Disks and drums
5.5. Summary, history, and bibliography
Chapter 6 – Searching
6.1. Sequential searching
6.2. Searching by comparison of keys
6.2.1. Searching an ordered table
6.2.2. Binary tree searching
6.2.3. Balanced trees
6.2.4. Multiway trees
6.3. Digital searching
6.4. Hashing
6.5. Retrieval on secondary keys
==== Volume 4A – Combinatorial algorithms, Part 1 ====
Chapter 7 – Combinatorial searching
7.1. Zeros and ones
7.1.1. Boolean basics
7.1.2. Boolean evaluation
7.1.3. Bitwise tricks and techniques
7.1.4. Binary decision diagrams
7.2. Generating all possibilities
7.2.1. Generating basic combinatorial patterns
7.2.1.1. Generating all n-tuples
7.2.1.2. Generating all permutations
7.2.1.3. Generating all combinations
7.2.1.4. Generating all integer partitions
7.2.1.5. Generating all set partitions
7.2.1.6. Generating all trees
7.2.1.7. History and further references
==== Volume 4B – Combinatorial algorithms, Part 2 ====
Chapter 7 – Combinatorial searching (continued)
7.2. Generating all possibilities (continued)
7.2.2. Backtrack programming
7.2.2.1. Dancing links (includes discussion of exact cover)
7.2.2.2. Satisfiability
=== Planned ===
==== Volumes 4C, 4D, 4E, 4F – Combinatorial algorithms ====
Chapter 7 – Combinatorial searching (continued)
7.2. Generating all possibilities (continued)
7.2.2. Backtrack programming (continued)
7.2.2.3. Constraint satisfaction (released as Pre-Fascicle 7A)
7.2.2.4. Hamiltonian paths and cycles
7.2.2.5. Cliques
7.2.2.6. Covers (vertex cover, set cover problem, exact cover, clique cover)
7.2.2.7. Squares
7.2.2.8. A potpourri of puzzles (includes perfect digital invariant)
7.2.2.9. Estimating backtrack costs (chapter 6 of "Selected Papers on Analysis of Algorithms", and Fascicle 5, pp. 44−47, under the heading "Running time estimates")
7.2.3. Generating inequivalent patterns (includes discussion of Pólya enumeration theorem) (see "Techniques for Isomorph Rejection", chapter 4 of "Classification Algorithms for Codes and Designs" by Kaski and Östergård)
7.3. Shortest paths
7.4. Graph algorithms
7.4.1. Components and traversal
7.4.1.1. Union-find algorithms
7.4.1.2. Depth-first search
7.4.1.3. Vertex and edge connectivity
7.4.2. Special classes of graphs
7.4.3. Expander graphs
7.4.4. Random graphs
7.5. Graphs and optimization
7.5.1. Bipartite matching (including maximum-cardinality matching, stable marriage problem, mariages stables)
7.5.2. The assignment problem
7.5.3. Network flows
7.5.4. Optimum subtrees
7.5.5. Optimum matching
7.5.6. Optimum orderings
7.6. Independence theory
7.6.1. Independence structures
7.6.2. Efficient matroid algorithms
7.7. Discrete dynamic programming (see also transfer-matrix method)
7.8. Branch-and-bound techniques
7.9. Herculean tasks (aka NP-hard problems)
7.10. Near-optimization
Chapter 8 – Recursion (chapter 22 of "Selected Papers on Analysis of Algorithms")
==== Volume 5 – Syntactic algorithms ====
Chapter 9 – Lexical scanning (includes also string search and data compression)
Chapter 10 – Parsing techniques
==== Volume 6 – The theory of context-free languages ====
Chapter 11 – Mathematical linguistics
==== Volume 7 – Compiler techniques ====
Chapter 12 – Programming language translation
== English editions ==
=== Current editions ===
These are the current editions in order by volume number:
The Art of Computer Programming, Volumes 1-4B Boxed Set. (Reading, Massachusetts: Addison-Wesley, 2023), 3904pp. ISBN 978-0-13-793510-9, 0-13-793510-2
Volume 1: Fundamental Algorithms. Third Edition (Reading, Massachusetts: Addison-Wesley, 1997), xx+650pp. ISBN 978-0-201-89683-1, 0-201-89683-4. Errata: [1] (from 2011-01-08), [2] (from 2022, 49th printing). Addenda: [3] (2011).
Volume 2: Seminumerical Algorithms. Third Edition (Reading, Massachusetts: Addison-Wesley, 1997), xiv+762pp. ISBN 978-0-201-89684-8, 0-201-89684-2. Errata: [4] (from 2011-01-08), [5] (from 2022, 45th printing). Addenda: [6] (2011).
Volume 3: Sorting and Searching. Second Edition (Reading, Massachusetts: Addison-Wesley, 1998), xiv+780pp.+foldout. ISBN 978-0-201-89685-5, 0-201-89685-0. Errata: [7] (from 2011-01-08), [8] (from 2022, 45th printing). Addenda: [9] (2011).
Volume 4A: Combinatorial Algorithms, Part 1. First Edition (Upper Saddle River, New Jersey: Addison-Wesley, 2011, 24th printing), xv+883pp. ISBN 978-0-201-03804-0, 0-201-03804-8. Errata: [10] (from 2011), [11] (from 2022, 20th printing).
Volume 4B: Combinatorial Algorithms, Part 2. First Edition (Upper Saddle River, New Jersey: Addison-Wesley, 2023, 2nd printing), xviii+714pp. ISBN 978-0-201-03806-4, 0-201-03806-4. Errata: [12] (from 2023, 1st printing).
Volume 1, Fascicle 1: MMIX – A RISC Computer for the New Millennium. (Addison-Wesley, 2005-02-14), 144pp. ISBN 0-201-85392-2. Errata: [13] (from 2005, 1st printing) (will be in the fourth edition of volume 1)
The MMIX Supplement by Martin Ruckert. (Addison-Wesley), 193pp. ISBN 0-13-399231-4. A conversion of the MIX problems/programs in volumes 1, 2 & 3 to MMIX.
Volume 4, Fascicle 7: Constraint Satisfaction. (Addison-Wesley, 2025-02-05), xiv+281pp. ISBN 978-0-13-532824-8.
=== Previous editions ===
==== Complete volumes ====
These volumes were superseded by newer editions and are in order by date.
Volume 1: Fundamental Algorithms. First edition, 1968, xxi+634pp, ISBN 0-201-03801-3.
Volume 2: Seminumerical Algorithms. First edition, 1969, xi+624pp, ISBN 0-201-03802-1.
Volume 3: Sorting and Searching. First edition, 1973, xi+723pp+foldout, ISBN 0-201-03803-X. Errata: [14].
Volume 1: Fundamental Algorithms. Second edition, 1973, xxi+634pp, ISBN 0-201-03809-9. Errata: [15].
Volume 2: Seminumerical Algorithms. Second edition, 1981, xiii+ 688pp, ISBN 0-201-03822-6. Errata: [16].
The Art of Computer Programming, Volumes 1-3 Boxed Set. Second Edition (Reading, Massachusetts: Addison-Wesley, 1998), pp. ISBN 978-0-201-48541-7, 0-201-48541-9
The Art of Computer Programming, Volumes 1-4A Boxed Set. Third Edition (Reading, Massachusetts: Addison-Wesley, 2011), 3168pp. ISBN 978-0-321-75104-1, 0-321-75104-3
==== Fascicles ====
Volume 4, Fascicles 0–4 were revised and published as Volume 4A.
Volume 4, Fascicle 0: Introduction to Combinatorial Algorithms and Boolean Functions. (Addison-Wesley Professional, 2008-04-28) vi+240pp, ISBN 0-321-53496-4. Errata: [17] (2011-01-01).
Volume 4, Fascicle 1: Bitwise Tricks & Techniques; Binary Decision Diagrams. (Addison-Wesley Professional, 2009-03-27) viii+260pp, ISBN 0-321-58050-8. Errata: [18] (2011-01-01).
Volume 4, Fascicle 2: Generating All Tuples and Permutations. (Addison-Wesley, 2005-02-14) v+127pp, ISBN 0-201-85393-0. Errata: [19] (2011-01-01).
Volume 4, Fascicle 3: Generating All Combinations and Partitions. (Addison-Wesley, 2005-07-26) vi+150pp, ISBN 0-201-85394-9. Errata: [20] (2011-01-01).
Volume 4, Fascicle 4: Generating All Trees; History of Combinatorial Generation. (Addison-Wesley, 2006-02-06) vi+120pp, ISBN 0-321-33570-8. Errata: [21] (2011-01-01).
Volume 4, Fascicles 5–6 were revised and published as Volume 4B.
Volume 4, Fascicle 5: Mathematical Preliminaries Redux; Backtracking; Dancing Links. (Addison-Wesley, 2019-11-22) xiii+382pp, ISBN 978-0-13-467179-6. Errata: [22] (2020-03-27)
Volume 4, Fascicle 6: Satisfiability. (Addison-Wesley, 2015-12-08) xiii+310pp, ISBN 978-0-13-439760-3. Errata: [23] (2020-03-26)
==== Pre-fascicles ====
Volume 1
Pre-fascicle 1 was revised and published as Volume 1, fascicle 1.
Volume 4
Pre-fascicles 0A, 0B, and 0C were revised and published as Volume 4, fascicle 0.
Pre-fascicles 1A and 1B were revised and published as Volume 4, fascicle 1.
Pre-fascicles 2A and 2B were revised and published as Volume 4, fascicle 2.
Pre-fascicles 3A and 3B were revised and published as Volume 4, fascicle 3.
Pre-fascicles 4A and 4B were revised and published as Volume 4, fascicle 4.
Pre-fascicles 5A, 5B, and 5C were revised and published as Volume 4, fascicle 5.
Pre-fascicle 6A was revised and published as Volume 4, fascicle 6.
Pre-fascicle 7A was revised and published as Volume 4, fascicle 7.
The remaining pre-fascicles contain draft material that is set to appear in future fascicles and volumes.
Volume 4, Pre-fascicle 8A: Hamiltonian Paths and Cycles
Volume 4, Pre-fascicle 8B: Cliques
Volume 4, Pre-fascicle 9B: A Potpourri of Puzzles
Volume 4, Pre-fascicle 9C: Estimating Backtrack Costs
Volume 4, Pre-fascicle 12A: Components and Traversal (PDF Version)
Volume 4, Pre-fascicle 14A: Bipartite Matching
Volume 4, Pre-fascicle 16A: Introduction to Recursion
== See also ==
Introduction to Algorithms
== References ==
Notes
Citations
Sources
== External links ==
Overview of topics (Knuth's personal homepage)
Announcement of Volume 1 of 'The Art of Computer Programming'
Oral history interview with Donald E. Knuth at Charles Babbage Institute, University of Minnesota, Minneapolis, 2001. Knuth discusses software patenting, structured programming, collaboration and his development of TeX. The oral history discusses the writing of The Art of Computer Programming.
"Robert W Floyd, In Memoriam", by Donald E. Knuth, 2003 - (on the influence of Bob Floyd)
TAoCP and its Influence of Computer Science (Softpanorama)
|
https://en.wikipedia.org/wiki/The_Art_of_Computer_Programming
|
In the context of hardware and software systems, formal verification is the act of proving or disproving the correctness of a system with respect to a certain formal specification or property, using formal methods of mathematics.
Formal verification is a key incentive for formal specification of systems, and is at the core of formal methods.
It represents an important dimension of analysis and verification in electronic design automation and is one approach to software verification. The use of formal verification enables the highest Evaluation Assurance Level (EAL7) in the framework of common criteria for computer security certification.
Formal verification can be helpful in proving the correctness of systems such as: cryptographic protocols, combinational circuits, digital circuits with internal memory, and software expressed as source code in a programming language. Prominent examples of verified software systems include the CompCert verified C compiler and the seL4 high-assurance operating system kernel.
The verification of these systems is done by ensuring the existence of a formal proof of a mathematical model of the system. Examples of mathematical objects used to model systems are: finite-state machines, labelled transition systems, Horn clauses, Petri nets, vector addition systems, timed automata, hybrid automata, process algebra, formal semantics of programming languages such as operational semantics, denotational semantics, axiomatic semantics and Hoare logic.
== Approaches ==
=== Model checking ===
Model checking involves a systematic and exhaustive exploration of the mathematical model. Such exploration is possible for finite models, but also for some infinite models, where infinite sets of states can be effectively represented finitely by using abstraction or taking advantage of symmetry. Usually, this consists of exploring all states and transitions in the model, by using smart and domain-specific abstraction techniques to consider whole groups of states in a single operation and reduce computing time. Implementation techniques include state space enumeration, symbolic state space enumeration, abstract interpretation, symbolic simulation, abstraction refinement. The properties to be verified are often described in temporal logics, such as linear temporal logic (LTL), Property Specification Language (PSL), SystemVerilog Assertions (SVA), or computational tree logic (CTL). The great advantage of model checking is that it is often fully automatic; its primary disadvantage is that it does not in general scale to large systems; symbolic models are typically limited to a few hundred bits of state, while explicit state enumeration requires the state space being explored to be relatively small.
=== Deductive verification ===
Another approach is deductive verification. It consists of generating from the system and its specifications (and possibly other annotations) a collection of mathematical proof obligations, the truth of which imply conformance of the system to its specification, and discharging these obligations using either proof assistants (interactive theorem provers) (such as HOL, ACL2, Isabelle, Rocq (previously known as Coq) or PVS), or automatic theorem provers, including in particular satisfiability modulo theories (SMT) solvers. This approach has the disadvantage that it may require the user to understand in detail why the system works correctly, and to convey this information to the verification system, either in the form of a sequence of theorems to be proved or in the form of specifications (invariants, preconditions, postconditions) of system components (e.g. functions or procedures) and perhaps subcomponents (such as loops or data structures).
=== Application to software ===
Formal verification of software programs involves proving that a program satisfies a formal specification of its behavior. Subareas of formal verification include deductive verification (see above), abstract interpretation, automated theorem proving, type systems, and lightweight formal methods. A promising type-based verification approach is dependently typed programming, in which the types of functions include (at least part of) those functions' specifications, and type-checking the code establishes its correctness against those specifications. Fully featured dependently typed languages support deductive verification as a special case.
Another complementary approach is program derivation, in which efficient code is produced from functional specifications by a series of correctness-preserving steps. An example of this approach is the Bird–Meertens formalism, and this approach can be seen as another form of program synthesis.
These techniques can be sound, meaning that the verified properties can be logically deduced from the semantics, or unsound, meaning that there is no such guarantee. A sound technique yields a result only once it has covered the entire space of possibilities. An example of an unsound technique is one that covers only a subset of the possibilities, for instance only integers up to a certain number, and give a "good-enough" result. Techniques can also be decidable, meaning that their algorithmic implementations are guaranteed to terminate with an answer, or undecidable, meaning that they may never terminate. By bounding the scope of possibilities, unsound techniques that are decidable might be able to be constructed when no decidable sound techniques are available.
== Verification and validation ==
Verification is one aspect of testing a product's fitness for purpose. Validation is the complementary aspect. Often one refers to the overall checking process as V & V.
Validation: "Are we trying to make the right thing?", i.e., is the product specified to the user's actual needs?
Verification: "Have we made what we were trying to make?", i.e., does the product conform to the specifications?
The verification process consists of static/structural and dynamic/behavioral aspects. E.g., for a software product one can inspect the source code (static) and run against specific test cases (dynamic). Validation usually can be done only dynamically, i.e., the product is tested by putting it through typical and atypical usages ("Does it satisfactorily meet all use cases?").
== Automated program repair ==
Program repair is performed with respect to an oracle, encompassing the desired functionality of the program which is used for validation of the generated fix. A simple example is a test-suite—the input/output pairs specify the functionality of the program. A variety of techniques are employed, most notably using satisfiability modulo theories (SMT) solvers, and genetic programming, using evolutionary computing to generate and evaluate possible candidates for fixes. The former method is deterministic, while the latter is randomized.
Program repair combines techniques from formal verification and program synthesis. Fault-localization techniques in formal verification are used to compute program points which might be possible bug-locations, which can be targeted by the synthesis modules. Repair systems often focus on a small pre-defined class of bugs in order to reduce the search space. Industrial use is limited owing to the computational cost of existing techniques.
== Industry use ==
The growth in complexity of designs increases the importance of formal verification techniques in the hardware industry. At present, formal verification is used by most or all leading hardware companies, but its use in the software industry is still languishing. This could be attributed to the greater need in the hardware industry, where errors have greater commercial significance. Because of the potential subtle interactions between components, it is increasingly difficult to exercise a realistic set of possibilities by simulation. Important aspects of hardware design are amenable to automated proof methods, making formal verification easier to introduce and more productive.
As of 2011, several operating systems have been formally verified:
NICTA's Secure Embedded L4 microkernel, sold commercially as seL4 by OK Labs; OSEK/VDX based real-time operating system ORIENTAIS by East China Normal University; Green Hills Software's Integrity operating system; and SYSGO's PikeOS.
In 2016, a team led by Zhong Shao at Yale developed a formally verified operating system kernel called CertiKOS.
As of 2017, formal verification has been applied to the design of large computer networks through a mathematical model of the network, and as part of a new network technology category, intent-based networking. Network software vendors that offer formal verification solutions include Cisco Forward Networks and Veriflow Systems.
The SPARK programming language provides a toolset which enables software development with formal verification and is used in several high-integrity systems.
The CompCert C compiler is a formally verified C compiler implementing the majority of ISO C.
== See also ==
Automated theorem proving
Model checking
List of model checking tools
Formal equivalence checking
Proof checker
Property Specification Language
Static code analysis
Temporal logic in finite-state verification
Post-silicon validation
Intelligent verification
Runtime verification
Software verification
Hardware verification
== References ==
|
https://en.wikipedia.org/wiki/Formal_verification
|
Probabilistic logic programming is a programming paradigm that combines logic programming with probabilities.
Most approaches to probabilistic logic programming are based on the distribution semantics, which splits a program into a set of probabilistic facts and a logic program. It defines a probability distribution on interpretations of the Herbrand universe of the program.
== Languages ==
Most approaches to probabilistic logic programming are based on the distribution semantics, which underlies many languages such as Probabilistic Horn Abduction, PRISM, Independent Choice Logic , probabilistic Datalog, Logic Programs with Annotated Disjunctions, ProbLog, P-log, and CP-logic. While the number of languages is large, many share a common approach so that there are transformations with linear complexity that can translate one language into another.
== Semantics ==
Under the distribution semantics, a probabilistic logic program is interpreted as a set of independent probabilistic facts (ground atomic formulas annotated with a probability) and a logic program which can use the probabilistic facts in the bodies of its clauses. The probability of any assignment of truth values to the groundings of the formulas associated with probabilistic facts is given by the product of their probabilities; this is equivalent to assuming the choices of probabilistic facts to be independent random variables.
=== Stratified programs ===
If for any choice of truth values for the probabilistic facts, the resulting logic program is stratified, it has a unique minimal Herbrand model which can be seen as the unique interpretation associated with that choice of truth values.
Important subclasses of stratified programs are positive programs, which do not use negation, but may be recursive, and acyclic programs, which may use negation but have no recursive dependencies.
=== Answer set programs ===
The stable model semantics underlying answer set programming gives meaning to unstratified programs by allocating potentially more than one answer set to every truth value assignment of the probabilistic facts. This raises the question of how to distribute the probability mass across the answer sets.
The probabilistic logic programming language P-Log resolves this by dividing the probability mass equally between the answer sets, following the principle of indifference.
Alternatively, probabilistic answer set programming under the credal semantics allocates a credal set to every query. Its lower probability bound is defined by only considering those truth value assignments of the probabilistic facts for which the query is true in every answer set of the resulting program (cautious reasoning); its upper probability bound is defined by considering those assignments for which the query is true in some answer set (brave reasoning).
== Inference ==
Under the distribution semantics, a probabilistic logic program defines a probability distribution over interpretations of its predicates on its Herbrand universe. The probability of a ground query is then obtained from the joint distribution of the query and the worlds: it is the sum of the probability of the worlds where the query is true.
The problem of computing the probability of queries is called (marginal) inference. Solving it by computing all the worlds and then identifying those that entail the query is impractical as the number of possible worlds is exponential in the number of ground probabilistic facts. In fact, already for acyclic programs and atomic queries, computing the conditional probability of a query given a conjunction of atoms as evidence is #P-complete.
=== Exact inference ===
Usually, exact inference is performed by resorting to knowledge compilation: according to this, a propositional theory and a query are compiled into a “target language”, which is then used to answer queries in polynomial time. The compilation becomes the main computational bottleneck, but considerable effort has been devoted to the development of efficient compilers. The compilation methods differ in the compactness of the target language and the class of queries and transformations that they support in polynomial time.
=== Approximate inference ===
Since the cost of inference may be very high, approximate algorithms have been developed. They either compute subsets of possibly incomplete explanations or use random sampling. In the first approach, a subset of the explanations provides a lower bound and the set of partially expanded explanations provides an upper bound. In the second approach, the truth of the query is repeatedly checked in an ordinary logic program sampled from the probabilistic program. The probability of the query is then given by the fraction of the successes.
== Learning ==
Probabilistic inductive logic programming aims to learn probabilistic logic programs from data. This includes parameter learning, which estimates the probability annotations of a program while the clauses themselves are given by the user, and structure learning, in which the clauses themselves are induced by the probabilistic inductive logic programming system.
Common approaches to parameter learning are based on expectation–maximization or gradient descent, while structure learning can be performed by searching the space of possible clauses under a variety of heuristics.
== See also ==
Inductive logic programming
Probabilistic database
Probabilistic programming
ProbLog
Statistical relational learning
== References ==
As of 3 February 2024, this article is derived in whole or in part from Riguzzi, Fabrizio; Bellodi, Elena; Zese, Riccardo (2014). "A History of Probabilistic Inductive Logic Programming". Frontiers in Robotics and AI. 1. doi:10.3389/frobt.2014.00006. The copyright holder has licensed the content in a manner that permits reuse under CC BY-SA 3.0 and GFDL. All relevant terms must be followed.
|
https://en.wikipedia.org/wiki/Probabilistic_logic_programming
|
In computer science and operations research, a genetic algorithm (GA) is a metaheuristic inspired by the process of natural selection that belongs to the larger class of evolutionary algorithms (EA). Genetic algorithms are commonly used to generate high-quality solutions to optimization and search problems via biologically inspired operators such as selection, crossover, and mutation. Some examples of GA applications include optimizing decision trees for better performance, solving sudoku puzzles, hyperparameter optimization, and causal inference.
== Methodology ==
=== Optimization problems ===
In a genetic algorithm, a population of candidate solutions (called individuals, creatures, organisms, or phenotypes) to an optimization problem is evolved toward better solutions. Each candidate solution has a set of properties (its chromosomes or genotype) which can be mutated and altered; traditionally, solutions are represented in binary as strings of 0s and 1s, but other encodings are also possible.
The evolution usually starts from a population of randomly generated individuals, and is an iterative process, with the population in each iteration called a generation. In each generation, the fitness of every individual in the population is evaluated; the fitness is usually the value of the objective function in the optimization problem being solved. The more fit individuals are stochastically selected from the current population, and each individual's genome is modified (recombined and possibly randomly mutated) to form a new generation. The new generation of candidate solutions is then used in the next iteration of the algorithm. Commonly, the algorithm terminates when either a maximum number of generations has been produced, or a satisfactory fitness level has been reached for the population.
A typical genetic algorithm requires:
a genetic representation of the solution domain,
a fitness function to evaluate the solution domain.
A standard representation of each candidate solution is as an array of bits (also called bit set or bit string). Arrays of other types and structures can be used in essentially the same way. The main property that makes these genetic representations convenient is that their parts are easily aligned due to their fixed size, which facilitates simple crossover operations. Variable length representations may also be used, but crossover implementation is more complex in this case. Tree-like representations are explored in genetic programming and graph-form representations are explored in evolutionary programming; a mix of both linear chromosomes and trees is explored in gene expression programming.
Once the genetic representation and the fitness function are defined, a GA proceeds to initialize a population of solutions and then to improve it through repetitive application of the mutation, crossover, inversion and selection operators.
==== Initialization ====
The population size depends on the nature of the problem, but typically contains hundreds or thousands of possible solutions. Often, the initial population is generated randomly, allowing the entire range of possible solutions (the search space). Occasionally, the solutions may be "seeded" in areas where optimal solutions are likely to be found or the distribution of the sampling probability tuned to focus in those areas of greater interest.
==== Selection ====
During each successive generation, a portion of the existing population is selected to reproduce for a new generation. Individual solutions are selected through a fitness-based process, where fitter solutions (as measured by a fitness function) are typically more likely to be selected. Certain selection methods rate the fitness of each solution and preferentially select the best solutions. Other methods rate only a random sample of the population, as the former process may be very time-consuming.
The fitness function is defined over the genetic representation and measures the quality of the represented solution. The fitness function is always problem-dependent. For instance, in the knapsack problem one wants to maximize the total value of objects that can be put in a knapsack of some fixed capacity. A representation of a solution might be an array of bits, where each bit represents a different object, and the value of the bit (0 or 1) represents whether or not the object is in the knapsack. Not every such representation is valid, as the size of objects may exceed the capacity of the knapsack. The fitness of the solution is the sum of values of all objects in the knapsack if the representation is valid, or 0 otherwise.
In some problems, it is hard or even impossible to define the fitness expression; in these cases, a simulation may be used to determine the fitness function value of a phenotype (e.g. computational fluid dynamics is used to determine the air resistance of a vehicle whose shape is encoded as the phenotype), or even interactive genetic algorithms are used.
==== Genetic operators ====
The next step is to generate a second generation population of solutions from those selected, through a combination of genetic operators: crossover (also called recombination), and mutation.
For each new solution to be produced, a pair of "parent" solutions is selected for breeding from the pool selected previously. By producing a "child" solution using the above methods of crossover and mutation, a new solution is created which typically shares many of the characteristics of its "parents". New parents are selected for each new child, and the process continues until a new population of solutions of appropriate size is generated.
Although reproduction methods that are based on the use of two parents are more "biology inspired", some research suggests that more than two "parents" generate higher quality chromosomes.
These processes ultimately result in the next generation population of chromosomes that is different from the initial generation. Generally, the average fitness will have increased by this procedure for the population, since only the best organisms from the first generation are selected for breeding, along with a small proportion of less fit solutions. These less fit solutions ensure genetic diversity within the genetic pool of the parents and therefore ensure the genetic diversity of the subsequent generation of children.
Opinion is divided over the importance of crossover versus mutation. There are many references in Fogel (2006) that support the importance of mutation-based search.
Although crossover and mutation are known as the main genetic operators, it is possible to use other operators such as regrouping, colonization-extinction, or migration in genetic algorithms.
It is worth tuning parameters such as the mutation probability, crossover probability and population size to find reasonable settings for the problem's complexity class being worked on. A very small mutation rate may lead to genetic drift (which is non-ergodic in nature). A recombination rate that is too high may lead to premature convergence of the genetic algorithm. A mutation rate that is too high may lead to loss of good solutions, unless elitist selection is employed. An adequate population size ensures sufficient genetic diversity for the problem at hand, but can lead to a waste of computational resources if set to a value larger than required.
==== Heuristics ====
In addition to the main operators above, other heuristics may be employed to make the calculation faster or more robust. The speciation heuristic penalizes crossover between candidate solutions that are too similar; this encourages population diversity and helps prevent premature convergence to a less optimal solution.
==== Termination ====
This generational process is repeated until a termination condition has been reached. Common terminating conditions are:
A solution is found that satisfies minimum criteria
Fixed number of generations reached
Allocated budget (computation time/money) reached
The highest ranking solution's fitness is reaching or has reached a plateau such that successive iterations no longer produce better results
Manual inspection
Combinations of the above
== The building block hypothesis ==
Genetic algorithms are simple to implement, but their behavior is difficult to understand. In particular, it is difficult to understand why these algorithms frequently succeed at generating solutions of high fitness when applied to practical problems. The building block hypothesis (BBH) consists of:
A description of a heuristic that performs adaptation by identifying and recombining "building blocks", i.e. low order, low defining-length schemata with above average fitness.
A hypothesis that a genetic algorithm performs adaptation by implicitly and efficiently implementing this heuristic.
Goldberg describes the heuristic as follows:
"Short, low order, and highly fit schemata are sampled, recombined [crossed over], and resampled to form strings of potentially higher fitness. In a way, by working with these particular schemata [the building blocks], we have reduced the complexity of our problem; instead of building high-performance strings by trying every conceivable combination, we construct better and better strings from the best partial solutions of past samplings.
"Because highly fit schemata of low defining length and low order play such an important role in the action of genetic algorithms, we have already given them a special name: building blocks. Just as a child creates magnificent fortresses through the arrangement of simple blocks of wood, so does a genetic algorithm seek near optimal performance through the juxtaposition of short, low-order, high-performance schemata, or building blocks."
Despite the lack of consensus regarding the validity of the building-block hypothesis, it has been consistently evaluated and used as reference throughout the years. Many estimation of distribution algorithms, for example, have been proposed in an attempt to provide an environment in which the hypothesis would hold. Although good results have been reported for some classes of problems, skepticism concerning the generality and/or practicality of the building-block hypothesis as an explanation for GAs' efficiency still remains. Indeed, there is a reasonable amount of work that attempts to understand its limitations from the perspective of estimation of distribution algorithms.
== Limitations ==
The practical use of a genetic algorithm has limitations, especially as compared to alternative optimization algorithms:
Repeated fitness function evaluation for complex problems is often the most prohibitive and limiting segment of artificial evolutionary algorithms. Finding the optimal solution to complex high-dimensional, multimodal problems often requires very expensive fitness function evaluations. In real world problems such as structural optimization problems, a single function evaluation may require several hours to several days of complete simulation. Typical optimization methods cannot deal with such types of problem. In this case, it may be necessary to forgo an exact evaluation and use an approximated fitness that is computationally efficient. It is apparent that amalgamation of approximate models may be one of the most promising approaches to convincingly use GA to solve complex real life problems.
Genetic algorithms do not scale well with complexity. That is, where the number of elements which are exposed to mutation is large there is often an exponential increase in search space size. This makes it extremely difficult to use the technique on problems such as designing an engine, a house or a plane . In order to make such problems tractable to evolutionary search, they must be broken down into the simplest representation possible. Hence we typically see evolutionary algorithms encoding designs for fan blades instead of engines, building shapes instead of detailed construction plans, and airfoils instead of whole aircraft designs. The second problem of complexity is the issue of how to protect parts that have evolved to represent good solutions from further destructive mutation, particularly when their fitness assessment requires them to combine well with other parts.
The "better" solution is only in comparison to other solutions. As a result, the stopping criterion is not clear in every problem.
In many problems, GAs have a tendency to converge towards local optima or even arbitrary points rather than the global optimum of the problem. This means that it does not "know how" to sacrifice short-term fitness to gain longer-term fitness. The likelihood of this occurring depends on the shape of the fitness landscape: certain problems may provide an easy ascent towards a global optimum, others may make it easier for the function to find the local optima. This problem may be alleviated by using a different fitness function, increasing the rate of mutation, or by using selection techniques that maintain a diverse population of solutions, although the No Free Lunch theorem proves that there is no general solution to this problem. A common technique to maintain diversity is to impose a "niche penalty", wherein, any group of individuals of sufficient similarity (niche radius) have a penalty added, which will reduce the representation of that group in subsequent generations, permitting other (less similar) individuals to be maintained in the population. This trick, however, may not be effective, depending on the landscape of the problem. Another possible technique would be to simply replace part of the population with randomly generated individuals, when most of the population is too similar to each other. Diversity is important in genetic algorithms (and genetic programming) because crossing over a homogeneous population does not yield new solutions. In evolution strategies and evolutionary programming, diversity is not essential because of a greater reliance on mutation.
Operating on dynamic data sets is difficult, as genomes begin to converge early on towards solutions which may no longer be valid for later data. Several methods have been proposed to remedy this by increasing genetic diversity somehow and preventing early convergence, either by increasing the probability of mutation when the solution quality drops (called triggered hypermutation), or by occasionally introducing entirely new, randomly generated elements into the gene pool (called random immigrants). Again, evolution strategies and evolutionary programming can be implemented with a so-called "comma strategy" in which parents are not maintained and new parents are selected only from offspring. This can be more effective on dynamic problems.
GAs cannot effectively solve problems in which the only fitness measure is a binary pass/fail outcome (like decision problems), as there is no way to converge on the solution (no hill to climb). In these cases, a random search may find a solution as quickly as a GA. However, if the situation allows the success/failure trial to be repeated giving (possibly) different results, then the ratio of successes to failures provides a suitable fitness measure.
For specific optimization problems and problem instances, other optimization algorithms may be more efficient than genetic algorithms in terms of speed of convergence. Alternative and complementary algorithms include evolution strategies, evolutionary programming, simulated annealing, Gaussian adaptation, hill climbing, and swarm intelligence (e.g.: ant colony optimization, particle swarm optimization) and methods based on integer linear programming. The suitability of genetic algorithms is dependent on the amount of knowledge of the problem; well known problems often have better, more specialized approaches.
== Variants ==
=== Chromosome representation ===
The simplest algorithm represents each chromosome as a bit string. Typically, numeric parameters can be represented by integers, though it is possible to use floating point representations. The floating point representation is natural to evolution strategies and evolutionary programming. The notion of real-valued genetic algorithms has been offered but is really a misnomer because it does not really represent the building block theory that was proposed by John Henry Holland in the 1970s. This theory is not without support though, based on theoretical and experimental results (see below). The basic algorithm performs crossover and mutation at the bit level. Other variants treat the chromosome as a list of numbers which are indexes into an instruction table, nodes in a linked list, hashes, objects, or any other imaginable data structure. Crossover and mutation are performed so as to respect data element boundaries. For most data types, specific variation operators can be designed. Different chromosomal data types seem to work better or worse for different specific problem domains.
When bit-string representations of integers are used, Gray coding is often employed. In this way, small changes in the integer can be readily affected through mutations or crossovers. This has been found to help prevent premature convergence at so-called Hamming walls, in which too many simultaneous mutations (or crossover events) must occur in order to change the chromosome to a better solution.
Other approaches involve using arrays of real-valued numbers instead of bit strings to represent chromosomes. Results from the theory of schemata suggest that in general the smaller the alphabet, the better the performance, but it was initially surprising to researchers that good results were obtained from using real-valued chromosomes. This was explained as the set of real values in a finite population of chromosomes as forming a virtual alphabet (when selection and recombination are dominant) with a much lower cardinality than would be expected from a floating point representation.
An expansion of the Genetic Algorithm accessible problem domain can be obtained through more complex encoding of the solution pools by concatenating several types of heterogenously encoded genes into one chromosome. This particular approach allows for solving optimization problems that require vastly disparate definition domains for the problem parameters. For instance, in problems of cascaded controller tuning, the internal loop controller structure can belong to a conventional regulator of three parameters, whereas the external loop could implement a linguistic controller (such as a fuzzy system) which has an inherently different description. This particular form of encoding requires a specialized crossover mechanism that recombines the chromosome by section, and it is a useful tool for the modelling and simulation of complex adaptive systems, especially evolution processes.
Another important expansion of the Genetic Algorithm (GA) accessible solution space was driven by the need to make representations amenable to variable levels of knowledge about the solution states. Variable-length representations were inspired by the observation that, in nature, evolution tends to progress from simpler organisms to more complex ones—suggesting an underlying rationale for embracing flexible structures. A second, more pragmatic motivation was that most real-world engineering and knowledge-based problems do not naturally conform to rigid knowledge structures.
These early innovations in variable-length representations laid essential groundwork for the development of Genetic programming, which further extended the classical GA paradigm. Such representations required enhancements to the simplistic genetic operators used for fixed-length chromosomes, enabling the emergence of more sophisticated and adaptive GA models.
=== Elitism ===
A practical variant of the general process of constructing a new population is to allow the best organism(s) from the current generation to carry over to the next, unaltered. This strategy is known as elitist selection and guarantees that the solution quality obtained by the GA will not decrease from one generation to the next.
=== Parallel implementations ===
Parallel implementations of genetic algorithms come in two flavors. Coarse-grained parallel genetic algorithms assume a population on each of the computer nodes and migration of individuals among the nodes. Fine-grained parallel genetic algorithms assume an individual on each processor node which acts with neighboring individuals for selection and reproduction.
Other variants, like genetic algorithms for online optimization problems, introduce time-dependence or noise in the fitness function.
=== Adaptive GAs ===
Genetic algorithms with adaptive parameters (adaptive genetic algorithms, AGAs) is another significant and promising variant of genetic algorithms. The probabilities of crossover (pc) and mutation (pm) greatly determine the degree of solution accuracy and the convergence speed that genetic algorithms can obtain. Researchers have analyzed GA convergence analytically.
Instead of using fixed values of pc and pm, AGAs utilize the population information in each generation and adaptively adjust the pc and pm in order to maintain the population diversity as well as to sustain the convergence capacity. In AGA (adaptive genetic algorithm), the adjustment of pc and pm depends on the fitness values of the solutions. There are more examples of AGA variants: Successive zooming method is an early example of improving convergence. In CAGA (clustering-based adaptive genetic algorithm), through the use of clustering analysis to judge the optimization states of the population, the adjustment of pc and pm depends on these optimization states. Recent approaches use more abstract variables for deciding pc and pm. Examples are dominance & co-dominance principles and LIGA (levelized interpolative genetic algorithm), which combines a flexible GA with modified A* search to tackle search space anisotropicity.
It can be quite effective to combine GA with other optimization methods. A GA tends to be quite good at finding generally good global solutions, but quite inefficient at finding the last few mutations to find the absolute optimum. Other techniques (such as simple hill climbing) are quite efficient at finding absolute optimum in a limited region. Alternating GA and hill climbing can improve the efficiency of GA while overcoming the lack of robustness of hill climbing.
This means that the rules of genetic variation may have a different meaning in the natural case. For instance – provided that steps are stored in consecutive order – crossing over may sum a number of steps from maternal DNA adding a number of steps from paternal DNA and so on. This is like adding vectors that more probably may follow a ridge in the phenotypic landscape. Thus, the efficiency of the process may be increased by many orders of magnitude. Moreover, the inversion operator has the opportunity to place steps in consecutive order or any other suitable order in favour of survival or efficiency.
A variation, where the population as a whole is evolved rather than its individual members, is known as gene pool recombination.
A number of variations have been developed to attempt to improve performance of GAs on problems with a high degree of fitness epistasis, i.e. where the fitness of a solution consists of interacting subsets of its variables. Such algorithms aim to learn (before exploiting) these beneficial phenotypic interactions. As such, they are aligned with the Building Block Hypothesis in adaptively reducing disruptive recombination. Prominent examples of this approach include the mGA, GEMGA and LLGA.
== Problem domains ==
Problems which appear to be particularly appropriate for solution by genetic algorithms include timetabling and scheduling problems, and many scheduling software packages are based on GAs. GAs have also been applied to engineering. Genetic algorithms are often applied as an approach to solve global optimization problems.
As a general rule of thumb genetic algorithms might be useful in problem domains that have a complex fitness landscape as mixing, i.e., mutation in combination with crossover, is designed to move the population away from local optima that a traditional hill climbing algorithm might get stuck in. Observe that commonly used crossover operators cannot change any uniform population. Mutation alone can provide ergodicity of the overall genetic algorithm process (seen as a Markov chain).
Examples of problems solved by genetic algorithms include: mirrors designed to funnel sunlight to a solar collector, antennae designed to pick up radio signals in space, walking methods for computer figures, optimal design of aerodynamic bodies in complex flowfields
In his Algorithm Design Manual, Skiena advises against genetic algorithms for any task:
[I]t is quite unnatural to model applications in terms of genetic operators like mutation and crossover on bit strings. The pseudobiology adds another level of complexity between you and your problem. Second, genetic algorithms take a very long time on nontrivial problems. [...] [T]he analogy with evolution—where significant progress require [sic] millions of years—can be quite appropriate.
[...]
I have never encountered any problem where genetic algorithms seemed to me the right way to attack it. Further, I have never seen any computational results reported using genetic algorithms that have favorably impressed me. Stick to simulated annealing for your heuristic search voodoo needs.
== History ==
In 1950, Alan Turing proposed a "learning machine" which would parallel the principles of evolution. Computer simulation of evolution started as early as in 1954 with the work of Nils Aall Barricelli, who was using the computer at the Institute for Advanced Study in Princeton, New Jersey. His 1954 publication was not widely noticed. Starting in 1957, the Australian quantitative geneticist Alex Fraser published a series of papers on simulation of artificial selection of organisms with multiple loci controlling a measurable trait. From these beginnings, computer simulation of evolution by biologists became more common in the early 1960s, and the methods were described in books by Fraser and Burnell (1970) and Crosby (1973). Fraser's simulations included all of the essential elements of modern genetic algorithms. In addition, Hans-Joachim Bremermann published a series of papers in the 1960s that also adopted a population of solution to optimization problems, undergoing recombination, mutation, and selection. Bremermann's research also included the elements of modern genetic algorithms. Other noteworthy early pioneers include Richard Friedberg, George Friedman, and Michael Conrad. Many early papers are reprinted by Fogel (1998).
Although Barricelli, in work he reported in 1963, had simulated the evolution of ability to play a simple game, artificial evolution only became a widely recognized optimization method as a result of the work of Ingo Rechenberg and Hans-Paul Schwefel in the 1960s and early 1970s – Rechenberg's group was able to solve complex engineering problems through evolution strategies. Another approach was the evolutionary programming technique of Lawrence J. Fogel, which was proposed for generating artificial intelligence. Evolutionary programming originally used finite state machines for predicting environments, and used variation and selection to optimize the predictive logics. Genetic algorithms in particular became popular through the work of John Holland in the early 1970s, and particularly his book Adaptation in Natural and Artificial Systems (1975). His work originated with studies of cellular automata, conducted by Holland and his students at the University of Michigan. Holland introduced a formalized framework for predicting the quality of the next generation, known as Holland's Schema Theorem. Research in GAs remained largely theoretical until the mid-1980s, when The First International Conference on Genetic Algorithms was held in Pittsburgh, Pennsylvania.
=== Commercial products ===
In the late 1980s, General Electric started selling the world's first genetic algorithm product, a mainframe-based toolkit designed for industrial processes.
In 1989, Axcelis, Inc. released Evolver, the world's first commercial GA product for desktop computers. The New York Times technology writer John Markoff wrote about Evolver in 1990, and it remained the only interactive commercial genetic algorithm until 1995. Evolver was sold to Palisade in 1997, translated into several languages, and is currently in its 6th version. Since the 1990s, MATLAB has built in three derivative-free optimization heuristic algorithms (simulated annealing, particle swarm optimization, genetic algorithm) and two direct search algorithms (simplex search, pattern search).
== Related techniques ==
=== Parent fields ===
Genetic algorithms are a sub-field:
Evolutionary algorithms
Evolutionary computing
Metaheuristics
Stochastic optimization
Optimization
=== Related fields ===
==== Evolutionary algorithms ====
Evolutionary algorithms is a sub-field of evolutionary computing.
Evolution strategies (ES, see Rechenberg, 1994) evolve individuals by means of mutation and intermediate or discrete recombination. ES algorithms are designed particularly to solve problems in the real-value domain. They use self-adaptation to adjust control parameters of the search. De-randomization of self-adaptation has led to the contemporary Covariance Matrix Adaptation Evolution Strategy (CMA-ES).
Evolutionary programming (EP) involves populations of solutions with primarily mutation and selection and arbitrary representations. They use self-adaptation to adjust parameters, and can include other variation operations such as combining information from multiple parents.
Estimation of Distribution Algorithm (EDA) substitutes traditional reproduction operators by model-guided operators. Such models are learned from the population by employing machine learning techniques and represented as Probabilistic Graphical Models, from which new solutions can be sampled or generated from guided-crossover.
Genetic programming (GP) is a related technique popularized by John Koza in which computer programs, rather than function parameters, are optimized. Genetic programming often uses tree-based internal data structures to represent the computer programs for adaptation instead of the list structures typical of genetic algorithms. There are many variants of Genetic Programming, including Cartesian genetic programming, Gene expression programming, grammatical evolution, Linear genetic programming, Multi expression programming etc.
Grouping genetic algorithm (GGA) is an evolution of the GA where the focus is shifted from individual items, like in classical GAs, to groups or subset of items. The idea behind this GA evolution proposed by Emanuel Falkenauer is that solving some complex problems, a.k.a. clustering or partitioning problems where a set of items must be split into disjoint group of items in an optimal way, would better be achieved by making characteristics of the groups of items equivalent to genes. These kind of problems include bin packing, line balancing, clustering with respect to a distance measure, equal piles, etc., on which classic GAs proved to perform poorly. Making genes equivalent to groups implies chromosomes that are in general of variable length, and special genetic operators that manipulate whole groups of items. For bin packing in particular, a GGA hybridized with the Dominance Criterion of Martello and Toth, is arguably the best technique to date.
Interactive evolutionary algorithms are evolutionary algorithms that use human evaluation. They are usually applied to domains where it is hard to design a computational fitness function, for example, evolving images, music, artistic designs and forms to fit users' aesthetic preference.
==== Swarm intelligence ====
Swarm intelligence is a sub-field of evolutionary computing.
Ant colony optimization (ACO) uses many ants (or agents) equipped with a pheromone model to traverse the solution space and find locally productive areas.
Although considered an Estimation of distribution algorithm, Particle swarm optimization (PSO) is a computational method for multi-parameter optimization which also uses population-based approach. A population (swarm) of candidate solutions (particles) moves in the search space, and the movement of the particles is influenced both by their own best known position and swarm's global best known position. Like genetic algorithms, the PSO method depends on information sharing among population members. In some problems the PSO is often more computationally efficient than the GAs, especially in unconstrained problems with continuous variables.
==== Other evolutionary computing algorithms ====
Evolutionary computation is a sub-field of the metaheuristic methods.
Memetic algorithm (MA), often called hybrid genetic algorithm among others, is a population-based method in which solutions are also subject to local improvement phases. The idea of memetic algorithms comes from memes, which unlike genes, can adapt themselves. In some problem areas they are shown to be more efficient than traditional evolutionary algorithms.
Bacteriologic algorithms (BA) inspired by evolutionary ecology and, more particularly, bacteriologic adaptation. Evolutionary ecology is the study of living organisms in the context of their environment, with the aim of discovering how they adapt. Its basic concept is that in a heterogeneous environment, there is not one individual that fits the whole environment. So, one needs to reason at the population level. It is also believed BAs could be successfully applied to complex positioning problems (antennas for cell phones, urban planning, and so on) or data mining.
Cultural algorithm (CA) consists of the population component almost identical to that of the genetic algorithm and, in addition, a knowledge component called the belief space.
Differential evolution (DE) inspired by migration of superorganisms.
Gaussian adaptation (normal or natural adaptation, abbreviated NA to avoid confusion with GA) is intended for the maximisation of manufacturing yield of signal processing systems. It may also be used for ordinary parametric optimisation. It relies on a certain theorem valid for all regions of acceptability and all Gaussian distributions. The efficiency of NA relies on information theory and a certain theorem of efficiency. Its efficiency is defined as information divided by the work needed to get the information. Because NA maximises mean fitness rather than the fitness of the individual, the landscape is smoothed such that valleys between peaks may disappear. Therefore it has a certain "ambition" to avoid local peaks in the fitness landscape. NA is also good at climbing sharp crests by adaptation of the moment matrix, because NA may maximise the disorder (average information) of the Gaussian simultaneously keeping the mean fitness constant.
==== Other metaheuristic methods ====
Metaheuristic methods broadly fall within stochastic optimisation methods.
Simulated annealing (SA) is a related global optimization technique that traverses the search space by testing random mutations on an individual solution. A mutation that increases fitness is always accepted. A mutation that lowers fitness is accepted probabilistically based on the difference in fitness and a decreasing temperature parameter. In SA parlance, one speaks of seeking the lowest energy instead of the maximum fitness. SA can also be used within a standard GA algorithm by starting with a relatively high rate of mutation and decreasing it over time along a given schedule.
Tabu search (TS) is similar to simulated annealing in that both traverse the solution space by testing mutations of an individual solution. While simulated annealing generates only one mutated solution, tabu search generates many mutated solutions and moves to the solution with the lowest energy of those generated. In order to prevent cycling and encourage greater movement through the solution space, a tabu list is maintained of partial or complete solutions. It is forbidden to move to a solution that contains elements of the tabu list, which is updated as the solution traverses the solution space.
Extremal optimization (EO) Unlike GAs, which work with a population of candidate solutions, EO evolves a single solution and makes local modifications to the worst components. This requires that a suitable representation be selected which permits individual solution components to be assigned a quality measure ("fitness"). The governing principle behind this algorithm is that of emergent improvement through selectively removing low-quality components and replacing them with a randomly selected component. This is decidedly at odds with a GA that selects good solutions in an attempt to make better solutions.
==== Other stochastic optimisation methods ====
The cross-entropy (CE) method generates candidate solutions via a parameterized probability distribution. The parameters are updated via cross-entropy minimization, so as to generate better samples in the next iteration.
Reactive search optimization (RSO) advocates the integration of sub-symbolic machine learning techniques into search heuristics for solving complex optimization problems. The word reactive hints at a ready response to events during the search through an internal online feedback loop for the self-tuning of critical parameters. Methodologies of interest for Reactive Search include machine learning and statistics, in particular reinforcement learning, active or query learning, neural networks, and metaheuristics.
== See also ==
Genetic programming
List of genetic algorithm applications
Genetic algorithms in signal processing (a.k.a. particle filters)
Propagation of schema
Universal Darwinism
Metaheuristics
Learning classifier system
Rule-based machine learning
== References ==
== Bibliography ==
== External links ==
=== Resources ===
[1] Provides a list of resources in the genetic algorithms field
An Overview of the History and Flavors of Evolutionary Algorithms
=== Tutorials ===
Genetic Algorithms - Computer programs that "evolve" in ways that resemble natural selection can solve complex problems even their creators do not fully understand An excellent introduction to GA by John Holland and with an application to the Prisoner's Dilemma
An online interactive Genetic Algorithm tutorial for a reader to practise or learn how a GA works: Learn step by step or watch global convergence in batch, change the population size, crossover rates/bounds, mutation rates/bounds and selection mechanisms, and add constraints.
A Genetic Algorithm Tutorial by Darrell Whitley Computer Science Department Colorado State University An excellent tutorial with much theory
"Essentials of Metaheuristics", 2009 (225 p). Free open text by Sean Luke.
Global Optimization Algorithms – Theory and Application Archived 11 September 2008 at the Wayback Machine
Genetic Algorithms in Python Tutorial with the intuition behind GAs and Python implementation.
Genetic Algorithms evolves to solve the prisoner's dilemma. Written by Robert Axelrod.
|
https://en.wikipedia.org/wiki/Genetic_algorithm
|
Coroutines are computer program components that allow execution to be suspended and resumed, generalizing subroutines for cooperative multitasking. Coroutines are well-suited for implementing familiar program components such as cooperative tasks, exceptions, event loops, iterators, infinite lists and pipes.
They have been described as "functions whose execution you can pause".
Melvin Conway coined the term coroutine in 1958 when he applied it to the construction of an assembly program. The first published explanation of the coroutine appeared later, in 1963.
== Definition and types ==
There is no single precise definition of coroutine. In 1980 Christopher D. Marlin summarized two widely-acknowledged fundamental characteristics of a coroutine:
the values of data local to a coroutine persist between successive calls;
the execution of a coroutine is suspended as control leaves it, only to carry on where it left off when control re-enters the coroutine at some later stage.
Besides that, a coroutine implementation has 3 features:
the control-transfer mechanism. Asymmetric coroutines usually provide keywords like yield and resume. Programmers cannot freely choose which frame to yield to. The runtime only yields to the nearest caller of the current coroutine. On the other hand, in symmetric coroutines, programmers must specify a yield destination.
whether coroutines are provided in the language as first-class objects, which can be freely manipulated by the programmer, or as constrained constructs;
whether a coroutine is able to suspend its execution from within nested function calls. Such a coroutine is a stackful coroutine. One to the contrary is called stackless coroutines, where unless marked as coroutine, a regular function can't use the keyword yield.
The paper "Revisiting Coroutines" published in 2009 proposed term full coroutine to denote one that supports first-class coroutine and is stackful. Full Coroutines deserve their own name in that they have the same expressive power as one-shot continuations and delimited continuations. Full coroutines are either symmetric or asymmetric. Importantly, whether a coroutine is symmetric or asymmetric has no bearing on how expressive it can be as they are equally as expressive, though full coroutines are more expressive than non-full coroutines. While their expressive power is the same, asymmetrical coroutines more closely resemble routine based control structures in the sense that control is always passed back to the invoker, which programmers may find more familiar.
== Comparison with ==
=== Subroutines ===
Subroutines are special cases of coroutines. When subroutines are invoked, execution begins at the start, and once a subroutine exits, it is finished; an instance of a subroutine only returns once, and does not hold state between invocations. By contrast, coroutines can exit by calling other coroutines, which may later return to the point where they were invoked in the original coroutine; from the coroutine's point of view, it is not exiting but calling another coroutine. Thus, a coroutine instance holds state, and varies between invocations; there can be multiple instances of a given coroutine at once. The difference between calling another coroutine by means of "yielding" to it and simply calling another routine (which then, also, would return to the original point), is that the relationship between two coroutines which yield to each other is not that of caller-callee, but instead symmetric.
Any subroutine can be translated to a coroutine which does not call yield.
Here is a simple example of how coroutines can be useful. Suppose you have a consumer-producer relationship where one routine creates items and adds them to a queue and another removes items from the queue and uses them. For reasons of efficiency, you want to add and remove several items at once. The code might look like this:
var q := new queue
coroutine produce
loop
while q is not full
create some new items
add the items to q
yield to consume
coroutine consume
loop
while q is not empty
remove some items from q
use the items
yield to produce
call produce
The queue is then completely filled or emptied before yielding control to the other coroutine using the yield command. The further coroutines calls are starting right after the yield, in the outer coroutine loop.
Although this example is often used as an introduction to multithreading, two threads are not needed for this: the yield statement can be implemented by a jump directly from one routine into the other.
=== Threads ===
Coroutines are very similar to threads. However, coroutines are cooperatively multitasked, whereas threads are typically preemptively multitasked. Coroutines provide concurrency, because they allow tasks to be performed out of order or in a changeable order, without changing the overall outcome, but they do not provide parallelism, because they do not execute multiple tasks simultaneously. The advantages of coroutines over threads are that they may be used in a hard-realtime context (switching between coroutines need not involve any system calls or any blocking calls whatsoever), there is no need for synchronization primitives such as mutexes, semaphores, etc. in order to guard critical sections, and there is no need for support from the operating system.
It is possible to implement coroutines using preemptively-scheduled threads, in a way that will be transparent to the calling code, but some of the advantages (particularly the suitability for hard-realtime operation and relative cheapness of switching between them) will be lost.
=== Generators ===
Generators, also known as semicoroutines, are a subset of coroutines. Specifically, while both can yield multiple times, suspending their execution and allowing re-entry at multiple entry points, they differ in coroutines' ability to control where execution continues immediately after they yield, while generators cannot, instead transferring control back to the generator's caller. That is, since generators are primarily used to simplify the writing of iterators, the yield statement in a generator does not specify a coroutine to jump to, but rather passes a value back to a parent routine.
However, it is still possible to implement coroutines on top of a generator facility, with the aid of a top-level dispatcher routine (a trampoline, essentially) that passes control explicitly to child generators identified by tokens passed back from the generators:
var q := new queue
generator produce
loop
while q is not full
create some new items
add the items to q
yield
generator consume
loop
while q is not empty
remove some items from q
use the items
yield
subroutine dispatcher
var d := new dictionary(generator → iterator)
d[produce] := start consume
d[consume] := start produce
var current := produce
loop
call current
current := next d[current]
call dispatcher
A number of implementations of coroutines for languages with generator support but no native coroutines (e.g. Python before 2.5) use this or a similar model.
=== Mutual recursion ===
Using coroutines for state machines or concurrency is similar to using mutual recursion with tail calls, as in both cases the control changes to a different one of a set of routines. However, coroutines are more flexible and generally more efficient. Since coroutines yield rather than return, and then resume execution rather than restarting from the beginning, they are able to hold state, both variables (as in a closure) and execution point, and yields are not limited to being in tail position; mutually recursive subroutines must either use shared variables or pass state as parameters. Further, each mutually recursive call of a subroutine requires a new stack frame (unless tail call elimination is implemented), while passing control between coroutines uses the existing contexts and can be implemented simply by a jump.
== Common uses ==
Coroutines are useful to implement the following:
State machines within a single subroutine, where the state is determined by the current entry/exit point of the procedure; this can result in more readable code compared to use of goto, and may also be implemented via mutual recursion with tail calls.
Actor model of concurrency, for instance in video games. Each actor has its own procedures (this again logically separates the code), but they voluntarily give up control to central scheduler, which executes them sequentially (this is a form of cooperative multitasking).
Generators, and these are useful for streams – particularly input/output – and for generic traversal of data structures.
Communicating sequential processes where each sub-process is a coroutine. Channel inputs/outputs and blocking operations yield coroutines and a scheduler unblocks them on completion events. Alternatively, each sub-process may be the parent of the one following it in the data pipeline (or preceding it, in which case the pattern can be expressed as nested generators).
Reverse communication, commonly used in mathematical software, wherein a procedure such as a solver, integral evaluator, ... needs the using process to make a computation, such as evaluating an equation or integrand.
== Native support ==
Coroutines originated as an assembly language method, but are supported in some high-level programming languages.
Since continuations can be used to implement coroutines, programming languages that support them can also quite easily support coroutines.
== Implementations ==
As of 2003, many of the most popular programming languages, including C and its derivatives, do not have built-in support for coroutines within the language or their standard libraries. This is, in large part, due to the limitations of stack-based subroutine implementation. An exception is the C++ library Boost.Context, part of boost libraries, which supports context swapping on ARM, MIPS, PowerPC, SPARC and x86 on POSIX, Mac OS X and Windows. Coroutines can be built upon Boost.Context.
In situations where a coroutine would be the natural implementation of a mechanism, but is not available, the typical response is to use a closure – a subroutine with state variables (static variables, often boolean flags) to maintain an internal state between calls, and to transfer control to the correct point. Conditionals within the code result in the execution of different code paths on successive calls, based on the values of the state variables. Another typical response is to implement an explicit state machine in the form of a large and complex switch statement or via a goto statement, particularly a computed goto. Such implementations are considered difficult to understand and maintain, and a motivation for coroutine support.
Threads, and to a lesser extent fibers, are an alternative to coroutines in mainstream programming environments today. Threads provide facilities for managing the real-time cooperative interaction of simultaneously executing pieces of code. Threads are widely available in environments that support C (and are supported natively in many other modern languages), are familiar to many programmers, and are usually well-implemented, well-documented and well-supported. However, as they solve a large and difficult problem they include many powerful and complex facilities and have a correspondingly difficult learning curve. As such, when a coroutine is all that is needed, using a thread can be overkill.
One important difference between threads and coroutines is that threads are typically preemptively scheduled while coroutines are not. Because threads can be rescheduled at any instant and can execute concurrently, programs using threads must be careful about locking. In contrast, because coroutines can only be rescheduled at specific points in the program and do not execute concurrently, programs using coroutines can often avoid locking entirely. This property is also cited as a benefit of event-driven or asynchronous programming.
Since fibers are cooperatively scheduled, they provide an ideal base for implementing coroutines above. However, system support for fibers is often lacking compared to that for threads.
=== C ===
In order to implement general-purpose coroutines, a second call stack must be obtained, which is a feature not directly supported by the C language. A reliable (albeit platform-specific) way to achieve this is to use a small amount of inline assembly to explicitly manipulate the stack pointer during initial creation of the coroutine. This is the approach recommended by Tom Duff in a discussion on its relative merits vs. the method used by Protothreads. On platforms which provide the POSIX sigaltstack system call, a second call stack can be obtained by calling a springboard function from within a signal handler to achieve the same goal in portable C, at the cost of some extra complexity. C libraries complying to POSIX or the Single Unix Specification (SUSv3) provided such routines as getcontext, setcontext, makecontext and swapcontext, but these functions were declared obsolete in POSIX 1.2008.
Once a second call stack has been obtained with one of the methods listed above, the setjmp and longjmp functions in the standard C library can then be used to implement the switches between coroutines. These functions save and restore, respectively, the stack pointer, program counter, callee-saved registers, and any other internal state as required by the ABI, such that returning to a coroutine after having yielded restores all the state that would be restored upon returning from a function call. Minimalist implementations, which do not piggyback off the setjmp and longjmp functions, may achieve the same result via a small block of inline assembly which swaps merely the stack pointer and program counter, and clobbers all other registers. This can be significantly faster, as setjmp and longjmp must conservatively store all registers which may be in use according to the ABI, whereas the clobber method allows the compiler to store (by spilling to the stack) only what it knows is actually in use.
Due to the lack of direct language support, many authors have written their own libraries for coroutines which hide the above details. Russ Cox's libtask library is a good example of this genre. It uses the context functions if they are provided by the native C library; otherwise it provides its own implementations for ARM, PowerPC, Sparc, and x86. Other notable implementations include libpcl, coro, lthread, libCoroutine, libconcurrency, libcoro, ribs2, libdill., libaco, and libco.
In addition to the general approach above, several attempts have been made to approximate coroutines in C with combinations of subroutines and macros. Simon Tatham's contribution, based on Duff's device, is a notable example of the genre, and is the basis for Protothreads and similar implementations. In addition to Duff's objections, Tatham's own comments provide a frank evaluation of the limitations of this approach: "As far as I know, this is the worst piece of C hackery ever seen in serious production code." The main shortcomings of this approximation are that, in not maintaining a separate stack frame for each coroutine, local variables are not preserved across yields from the function, it is not possible to have multiple entries to the function, and control can only be yielded from the top-level routine.
=== C++ ===
C++20 introduced standardized coroutines as stackless functions that can be suspended in the middle of execution and resumed at a later point. The suspended state of a coroutine is stored on the heap. Implementation of this standard is ongoing, with the G++ and MSVC compilers currently fully supporting standard coroutines in recent versions.
concurrencpp - a C++20 library which provides third-party support for C++20 coroutines, in the form of awaitable-tasks and executors that run them.
Boost.Coroutine - created by Oliver Kowalke, is the official released portable coroutine library of boost since version 1.53. The library relies on Boost.Context and supports ARM, MIPS, PowerPC, SPARC and X86 on POSIX, Mac OS X and Windows.
Boost.Coroutine2 - also created by Oliver Kowalke, is a modernized portable coroutine library since boost version 1.59. It takes advantage of C++11 features, but removes the support for symmetric coroutines.
Mordor - In 2010, Mozy open sourced a C++ library implementing coroutines, with an emphasis on using them to abstract asynchronous I/O into a more familiar sequential model.
CO2 - stackless coroutine based on C++ preprocessor tricks, providing await/yield emulation.
ScummVM - The ScummVM project implements a light-weight version of stackless coroutines based on Simon Tatham's article.
tonbit::coroutine - C++11 single .h asymmetric coroutine implementation via ucontext / fiber
Coroutines landed in Clang in May 2017, with libc++ implementation ongoing.
elle by Docker
oatpp-coroutines - stackless coroutines with scheduling designed for high-concurrency level I/O operations. Used in the 5-million WebSocket connections experiment by Oat++. Part of the Oat++ web framework.
=== C# ===
C# 2.0 added semi-coroutine (generator) functionality through the iterator pattern and yield keyword. C# 5.0 includes await syntax support. In addition:
The MindTouch Dream REST framework provides an implementation of coroutines based on the C# 2.0 iterator pattern.
The Caliburn (Archived 2013-01-19 at archive.today) screen patterns framework for WPF uses C# 2.0 iterators to ease UI programming, particularly in asynchronous scenarios.
The Power Threading Library (Archived 2010-03-24 at the Wayback Machine) by Jeffrey Richter implements an AsyncEnumerator that provides simplified Asynchronous Programming Model using iterator-based coroutines.
The Unity game engine implements coroutines.
The Servelat Pieces project by Yevhen Bobrov provides transparent asynchrony for Silverlight WCF services and ability to asynchronously call any synchronous method. The implementation is based on Caliburn's Coroutines iterator and C# iterator blocks.
StreamThreads is an open-source, light-weight C# co-routine library based on iterator extension methods. It supports error handling and return values.
=== Clojure ===
Cloroutine is a third-party library providing support for stackless coroutines in Clojure. It's implemented as a macro, statically splitting an arbitrary code block on arbitrary var calls and emitting the coroutine as a stateful function.
=== D ===
D implements coroutines as its standard library class Fiber A generator makes it trivial to expose a fiber function as an input range, making any fiber compatible with existing range algorithms.
=== Go ===
Go has a built-in concept of "goroutines", which are lightweight, independent processes managed by the Go runtime. A new goroutine can be started using the "go" keyword. Each goroutine has a variable-size stack which can be expanded as needed. Goroutines generally communicate using Go's built-in channels. However, goroutines are not coroutines (for instance, local data does not persist between successive calls).
=== Java ===
There are several implementations for coroutines in Java. Despite the constraints imposed by Java's abstractions, the JVM does not preclude the possibility. There are four general methods used, but two break bytecode portability among standards-compliant JVMs.
Modified JVMs. It is possible to build a patched JVM to support coroutines more natively. The Da Vinci JVM has had patches created.
Modified bytecode. Coroutine functionality is possible by rewriting regular Java bytecode, either on the fly or at compile time. Toolkits include Javaflow, Java Coroutines, and Coroutines.
Platform-specific JNI mechanisms. These use JNI methods implemented in the OS or C libraries to provide the functionality to the JVM.
Thread abstractions. Coroutine libraries which are implemented using threads may be heavyweight, though performance will vary based on the JVM's thread implementation.
=== JavaScript ===
Since ECMAScript 2015, JavaScript has support for generators, which are a special case of coroutines.
=== Kotlin ===
Kotlin implements coroutines as part of a first-party library.
=== Lua ===
Lua has supported first-class stackful asymmetric coroutines since version 5.0 (2003), in the standard library coroutine.
=== Modula-2 ===
Modula-2 as defined by Wirth implements coroutines as part of the standard SYSTEM library.
The procedure NEWPROCESS() fills in a context given a code block and space for a stack as parameters, and the procedure TRANSFER() transfers control to a coroutine given the coroutine's context as its parameter.
=== Mono ===
The Mono Common Language Runtime has support for continuations, from which coroutines can be built.
=== .NET Framework ===
During the development of the .NET Framework 2.0, Microsoft extended the design of the Common Language Runtime (CLR) hosting APIs to handle fiber-based scheduling with an eye towards its use in fiber-mode for SQL server. Before release, support for the task switching hook ICLRTask::SwitchOut was removed due to time constraints. Consequently, the use of the fiber API to switch tasks is currently not a viable option in the .NET Framework.
=== OCaml ===
OCaml supports coroutines through its Thread module. These coroutines provide concurrency without parallelism, and are scheduled preemptively on a single operating system thread. Since OCaml 5.0, green threads are also available; provided by different modules.
=== Perl ===
Coro
Coroutines are natively implemented in all Raku backends.
=== PHP ===
Fibers native since PHP 8.1
Amphp
Open Swoole
Coroutine implemented in a way that resembles Python functions, and some Go, many examples showing there code converted with same number of lines and behavior.
=== Python ===
Python 2.5 implements better support for coroutine-like functionality, based on extended generators (PEP 342)
Python 3.3 improves this ability, by supporting delegating to a subgenerator (PEP 380)
Python 3.4 introduces a comprehensive asynchronous I/O framework as standardized in PEP 3156, which includes coroutines that leverage subgenerator delegation
Python 3.5 introduces explicit support for coroutines with async/await syntax (PEP 0492).
Since Python 3.7, async/await have become reserved keywords.
Eventlet
Greenlet
gevent
stackless python
=== Racket ===
Racket provides native continuations, with a trivial implementation of coroutines provided in the official package catalog. Implementation by S. De Gabrielle
=== Ruby ===
Ruby 1.9 supports coroutines natively which are implemented as fibers, which are semi-coroutines.
An implementation by Marc De Scheemaecker
Ruby 2.5 and higher supports coroutines natively which are implemented as fibers
An implementation by Thomas W Branson
=== Scheme ===
Since Scheme provides full support for continuations, implementing coroutines is nearly trivial, requiring only that a queue of continuations be maintained.
=== Smalltalk ===
Since, in most Smalltalk environments, the execution stack is a first-class citizen, coroutines can be implemented without additional library or VM support.
=== Tool Command Language (Tcl) ===
Since version 8.6, the Tool Command Language supports coroutines in the core language.
=== Vala ===
Vala implements native support for coroutines. They are designed to be used with a Gtk Main Loop, but can be used alone if care is taken to ensure that the end callback will never have to be called before doing, at least, one yield.
=== Assembly languages ===
Machine-dependent assembly languages often provide direct methods for coroutine execution. For example, in MACRO-11, the assembly language of the PDP-11 family of minicomputers, the "classic" coroutine switch is effected by the instruction "JSR PC,@(SP)+", which jumps to the address popped from the stack and pushes the current (i.e that of the next) instruction address onto the stack. On VAXen (in VAX MACRO) the comparable instruction is "JSB @(SP)+". Even on a Motorola 6809 there is the instruction "JSR [,S++]"; note the "++", as 2 bytes (of address) are popped from the stack. This instruction is much used in the (standard) 'monitor' Assist 09.
== See also ==
Async/await
Pipeline, a kind of coroutine used for communicating between programs
Protothreads, a stackless lightweight thread implementation using a coroutine like mechanism
== References ==
== Further reading ==
Ana Lucia de Moura; Roberto Ierusalimschy (2004). "Revisiting Coroutines". ACM Transactions on Programming Languages and Systems. 31 (2): 1–31. CiteSeerX 10.1.1.58.4017. doi:10.1145/1462166.1462167. S2CID 9918449.
== External links ==
Simon Tatham's C oriented comprehensive introduction to coroutines
Softpanorama coroutine page – contains extensive assembler coroutines links
|
https://en.wikipedia.org/wiki/Coroutine
|
Memory management (also dynamic memory management, dynamic storage allocation, or dynamic memory allocation) is a form of resource management applied to computer memory. The essential requirement of memory management is to provide ways to dynamically allocate portions of memory to programs at their request, and free it for reuse when no longer needed. This is critical to any advanced computer system where more than a single process might be underway at any time.
Several methods have been devised that increase the effectiveness of memory management. Virtual memory systems separate the memory addresses used by a process from actual physical addresses, allowing separation of processes and increasing the size of the virtual address space beyond the available amount of RAM using paging or swapping to secondary storage. The quality of the virtual memory manager can have an extensive effect on overall system performance. The system allows a computer to appear as if it may have more memory available than physically present, thereby allowing multiple processes to share it.
In some operating systems, e.g. Burroughs/Unisys MCP, and OS/360 and successors, memory is managed by the operating system. In other operating systems, e.g. Unix-like operating systems, memory is managed at the application level.
Memory management within an address space is generally categorized as either manual memory management or automatic memory management.
== Manual memory management ==
The task of fulfilling an allocation request consists of locating a block of unused memory of sufficient size. Memory requests are satisfied by allocating portions from a large pool of memory called the heap or free store. At any given time, some parts of the heap are in use, while some are "free" (unused) and thus available for future allocations.
In the C language, the function which allocates memory from the heap is called malloc and the function which takes previously allocated memory and marks it as "free" (to be used by future allocations) is called free.
Several issues complicate the implementation, such as external fragmentation, which arises when there are many small gaps between allocated memory blocks, which invalidates their use for an allocation request. The allocator's metadata can also inflate the size of (individually) small allocations. This is often managed by chunking. The memory management system must track outstanding allocations to ensure that they do not overlap and that no memory is ever "lost" (i.e. that there are no "memory leaks").
=== Efficiency ===
The specific dynamic memory allocation algorithm implemented can impact performance significantly. A study conducted in 1994 by Digital Equipment Corporation illustrates the overheads involved for a variety of allocators. The lowest average instruction path length required to allocate a single memory slot was 52 (as measured with an instruction level profiler on a variety of software).
=== Implementations ===
Since the precise location of the allocation is not known in advance, the memory is accessed indirectly, usually through a pointer reference. The specific algorithm used to organize the memory area and allocate and deallocate chunks is interlinked with the kernel, and may use any of the following methods:
==== Fixed-size blocks allocation ====
Fixed-size blocks allocation, also called memory pool allocation, uses a free list of fixed-size blocks of memory (often all of the same size). This works well for simple embedded systems where no large objects need to be allocated but suffers from fragmentation especially with long memory addresses. However, due to the significantly reduced overhead, this method can substantially improve performance for objects that need frequent allocation and deallocation, and so it is often used in video games.
==== Buddy blocks ====
In this system, memory is allocated into several pools of memory instead of just one, where each pool represents blocks of memory of a certain power of two in size, or blocks of some other convenient size progression. All blocks of a particular size are kept in a sorted linked list or tree and all new blocks that are formed during allocation are added to their respective memory pools for later use. If a smaller size is requested than is available, the smallest available size is selected and split. One of the resulting parts is selected, and the process repeats until the request is complete. When a block is allocated, the allocator will start with the smallest sufficiently large block to avoid needlessly breaking blocks. When a block is freed, it is compared to its buddy. If they are both free, they are combined and placed in the correspondingly larger-sized buddy-block list.
==== Slab allocation ====
This memory allocation mechanism preallocates memory chunks suitable to fit objects of a certain type or size. These chunks are called caches and the allocator only has to keep track of a list of free cache slots. Constructing an object will use any one of the free cache slots and destructing an object will add a slot back to the free cache slot list. This technique alleviates memory fragmentation and is efficient as there is no need to search for a suitable portion of memory, as any open slot will suffice.
==== Stack allocation ====
Many Unix-like systems as well as Microsoft Windows implement a function called alloca for dynamically allocating stack memory in a way similar to the heap-based malloc. A compiler typically translates it to inlined instructions manipulating the stack pointer. Although there is no need of manually freeing memory allocated this way as it is automatically freed when the function that called alloca returns, there exists a risk of overflow. And since alloca is an ad hoc expansion seen in many systems but never in POSIX or the C standard, its behavior in case of a stack overflow is undefined.
A safer version of alloca called _malloca, which reports errors, exists on Microsoft Windows. It requires the use of _freea. gnulib provides an equivalent interface, albeit instead of throwing an SEH exception on overflow, it delegates to malloc when an overlarge size is detected. A similar feature can be emulated using manual accounting and size-checking, such as in the uses of alloca_account in glibc.
== Automated memory management ==
The proper management of memory in an application is a difficult problem, and several different strategies for handling memory management have been devised.
=== Automatic management of call stack variables ===
In many programming language implementations, the runtime environment for the program automatically allocates memory in the call stack for non-static local variables of a subroutine, called automatic variables, when the subroutine is called, and automatically releases that memory when the subroutine is exited. Special declarations may allow local variables to retain values between invocations of the procedure, or may allow local variables to be accessed by other subroutines. The automatic allocation of local variables makes recursion possible, to a depth limited by available memory.
=== Garbage collection ===
Garbage collection is a strategy for automatically detecting memory allocated to objects that are no longer usable in a program, and returning that allocated memory to a pool of free memory locations. This method is in contrast to "manual" memory management where a programmer explicitly codes memory requests and memory releases in the program. While automatic garbage collection has the advantages of reducing programmer workload and preventing certain kinds of memory allocation bugs, garbage collection does require memory resources of its own, and can compete with the application program for processor time.
=== Reference counting ===
Reference counting is a strategy for detecting that memory is no longer usable by a program by maintaining a counter for how many independent pointers point to the memory. Whenever a new pointer points to a piece of memory, the programmer is supposed to increase the counter. When the pointer changes where it points, or when the pointer is no longer pointing to any area or has itself been freed, the counter should decrease. When the counter drops to zero, the memory should be considered unused and freed. Some reference counting systems require programmer involvement and some are implemented automatically by the compiler. A disadvantage of reference counting is that circular references can develop which cause a memory leak to occur. This can be mitigated by either adding the concept of a "weak reference" (a reference that does not participate in reference counting, but is notified when the area it is pointing to is no longer valid) or by combining reference counting and garbage collection together.
=== Memory pools ===
A memory pool is a technique of automatically deallocating memory based on the state of the application, such as the lifecycle of a request or transaction. The idea is that many applications execute large chunks of code which may generate memory allocations, but that there is a point in execution where all of those chunks are known to be no longer valid. For example, in a web service, after each request the web service no longer needs any of the memory allocated during the execution of the request. Therefore, rather than keeping track of whether or not memory is currently being referenced, the memory is allocated according to the request or lifecycle stage with which it is associated. When that request or stage has passed, all associated memory is deallocated simultaneously.
== Systems with virtual memory ==
Virtual memory is a method of decoupling the memory organization from the physical hardware. The applications operate on memory via virtual addresses. Each attempt by the application to access a particular virtual memory address results in the virtual memory address being translated to an actual physical address. In this way the addition of virtual memory enables granular control over memory systems and methods of access.
In virtual memory systems the operating system limits how a process can access the memory. This feature, called memory protection, can be used to disallow a process to read or write to memory that is not allocated to it, preventing malicious or malfunctioning code in one program from interfering with the operation of another.
Even though the memory allocated for specific processes is normally isolated, processes sometimes need to be able to share information. Shared memory is one of the fastest techniques for inter-process communication.
Memory is usually classified by access rate into primary storage and secondary storage. Memory management systems, among other operations, also handle the moving of information between these two levels of memory.
== Memory management in Burroughs/Unisys MCP systems ==
An operating system manages various resources in the computing system. The memory subsystem is the system element for managing memory. The memory subsystem combines the hardware memory resource and the MCP OS software that manages the resource.
The memory subsystem manages the physical memory and the virtual memory of the system (both part of the hardware resource). The virtual memory extends physical memory by using extra space on a peripheral device, usually disk. The memory subsystem is responsible for moving code and data between main and virtual memory in a process known as overlaying. Burroughs was the first commercial implementation of virtual memory (although developed at Manchester University for the Ferranti Atlas computer) and integrated virtual memory with the system design of the B5000 from the start (in 1961) needing no external memory management unit (MMU).: 48
The memory subsystem is responsible for mapping logical requests for memory blocks to physical portions of memory (segments) which are found in the list of free segments. Each allocated block is managed by means of a segment descriptor, a special control word containing relevant metadata about the segment including address, length, machine type, and the p-bit or ‘presence’ bit which indicates whether the block is in main memory or needs to be loaded from the address given in the descriptor.
Descriptors are essential in providing memory safety and security so that operations cannot overflow or underflow the referenced block (commonly known as buffer overflow). Descriptors themselves are protected control words that cannot be manipulated except for specific elements of the MCP OS (enabled by the UNSAFE block directive in NEWP).
Donald Knuth describes a similar system in Section 2.5 ‘Dynamic Storage Allocation’ of ‘Fundamental Algorithms’.
== Memory management in OS/360 and successors ==
IBM System/360 does not support virtual memory. Memory isolation of jobs is optionally accomplished using protection keys, assigning storage for each job a different key, 0 for the supervisor or 1–15. Memory management in OS/360 is a supervisor function. Storage is requested using the GETMAIN macro and freed using the FREEMAIN macro, which result in a call to the supervisor (SVC) to perform the operation.
In OS/360 the details vary depending on how the system is generated, e.g., for PCP, MFT, MVT.
In OS/360 MVT, suballocation within a job's region or the shared System Queue Area (SQA) is based on subpools, areas a multiple of 2 KB in size—the size of an area protected by a protection key. Subpools are numbered 0–255. Within a region subpools are assigned either the job's storage protection or the supervisor's key, key 0. Subpools 0–127 receive the job's key. Initially only subpool zero is created, and all user storage requests are satisfied from subpool 0, unless another is specified in the memory request. Subpools 250–255 are created by memory requests by the supervisor on behalf of the job. Most of these are assigned key 0, although a few get the key of the job. Subpool numbers are also relevant in MFT, although the details are much simpler. MFT uses fixed partitions redefinable by the operator instead of dynamic regions and PCP has only a single partition.
Each subpool is mapped by a list of control blocks identifying allocated and free memory blocks within the subpool. Memory is allocated by finding a free area of sufficient size, or by allocating additional blocks in the subpool, up to the region size of the job. It is possible to free all or part of an allocated memory area.
The details for OS/VS1 are similar to those for MFT and for MVT; the details for OS/VS2 are similar to those for MVT, except that the page size is 4 KiB. For both OS/VS1 and OS/VS2 the shared System Queue Area (SQA) is nonpageable.
In MVS the address space includes an additional pageable shared area, the Common Storage Area (CSA), and two additional private areas, the nonpageable local system queue area (LSQA) and the pageable System Work area (SWA). Also, the storage keys 0–7 are all reserved for use by privileged code.
== See also ==
Dynamic array
Out of memory
Heap pollution
== Notes ==
== References ==
== Bibliography ==
Donald Knuth. Fundamental Algorithms, Third Edition. Addison-Wesley, 1997. ISBN 0-201-89683-4. Section 2.5: Dynamic Storage Allocation, pp. 435–456.
Simple Memory Allocation AlgorithmsArchived 5 March 2016 at the Wayback Machine (originally published on OSDEV Community)
Wilson, P. R.; Johnstone, M. S.; Neely, M.; Boles, D. (1995). "Dynamic storage allocation: A survey and critical review" (PDF). Memory Management. Lecture Notes in Computer Science. Vol. 986. pp. 1–116. CiteSeerX 10.1.1.47.275. doi:10.1007/3-540-60368-9_19. ISBN 978-3-540-60368-9.
Berger, E. D.; Zorn, B. G.; McKinley, K. S. (June 2001). "Composing High-Performance Memory Allocators" (PDF). Proceedings of the ACM SIGPLAN 2001 conference on Programming language design and implementation. PLDI '01. pp. 114–124. CiteSeerX 10.1.1.1.2112. doi:10.1145/378795.378821. ISBN 1-58113-414-2. S2CID 7501376.
Berger, E. D.; Zorn, B. G.; McKinley, K. S. (November 2002). "Reconsidering Custom Memory Allocation" (PDF). Proceedings of the 17th ACM SIGPLAN conference on Object-oriented programming, systems, languages, and applications. OOPSLA '02. pp. 1–12. CiteSeerX 10.1.1.119.5298. doi:10.1145/582419.582421. ISBN 1-58113-471-1. S2CID 481812.
OS360Sup
OS Release 21 IBM System/360 Operating System Supervisor Services and Macro Instructions (PDF). IBM Systems Reference Library (Eighth ed.). IBM. September 1974. GC28-6646-7.
OSVS1Dig
OS/VS1 Programmer's Reference Digest Release 6 (PDF). Systems (Sixth ed.). IBM. September 15, 1976. GC24-5091-5 with TNLs.
== External links ==
"Generic Memory Manager" C++ library
Sample bit-mapped arena memory allocator in C
TLSF: a constant time allocator for real-time systems
Slides on Dynamic memory allocation
Inside A Storage Allocator
The Memory Management Reference
The Memory Management Reference, Beginner's Guide Allocation
Linux Memory Management
Memory Management For System Programmers
VMem - general malloc/free replacement. Fast thread safe C++ allocator
Operating System Memory Management
|
https://en.wikipedia.org/wiki/Memory_management
|
Multitier programming (or tierless programming) is a programming paradigm for distributed software, which typically follows a multitier architecture, physically separating different functional aspects of the software into different tiers (e.g., the client, the server and the database in a Web application). Multitier programming allows functionalities that span multiple of such tiers to be developed in a single compilation unit using a single programming language. Without multitier programming, tiers are developed using different languages, e.g., JavaScript for the Web client, PHP for the Web server and SQL for the database. Multitier programming is often integrated into general-purpose languages by extending them with support for distribution.
Concepts from multitier programming were pioneered by the Hop and Links languages
and have found industrial adoption in solutions such as Ocsigen, Opa, WebSharper, Meteor or GWT.
Multitier programming provides a global view on the distributed system. This aspect has been shown similar to other programming paradigms such as choreographic programming, macroprogramming, and aggregate computing.
== Context ==
The code of the different tiers can be executed in a distributed manner on different networked computers. For instance, in a three-tier architecture, a system is divided into three main layers – typically the presentation, business, and data tiers. This approach has the benefit that by dividing a system into layers, the functionality implemented in one of the layers can be changed independently of the other layers. On the other hand, this architectural decision scatters a cross-cutting functionality belonging to several tiers over several compilation units.
In multitier programming, the different tiers are implemented using a single programming language. Different compilation backends take into account the destination tier (e.g., Java for a server and JavaScript for a web browser). Consequently, a functionality that is spread over tiers can be implemented in a single compilation unit of a multitier program.
== Example ==
At their core, multitier languages allow developers to define for different pieces of code the tiers to which the code belongs. The language features that enable this definition are quite diverse between different multitier languages, ranging from staging to annotations to types. The following example shows an Echo client–server application that illustrates different approaches. In the example, the client sends a message to the server and the server returns the same message to the client, where it is appended to a list of received messages.
=== Echo application in Hop.js ===
Hop uses staging to embed code that is to be run on the client into a server-side program: Using the ~{…} notation, the code for the onload (Line 4) and onclick (Line 10) handlers is not immediately executed but the server generates the code for later execution on the client. On the other hand, the ${…} notation escapes one level of program generation. The expressions hop.port (Line 5), event.data (Line 6) and input (Line 9 and 10) are evaluated by the outer server program and the values to which they evaluate are injected into the generated client program. Hop supports full stage programming, i.e., ~{…} expressions can be arbitrarily nested such that not only server-side programs can generate client-side programs but also client-side programs are able to generate other client-side programs.
HTML can be embedded directly in Hop code. HTML generated on the server (Line 2–14) is passed to the client. HTML generated on the client can be added to the page using the standard DOM API (Line 6). Hop supports bidirectional communication between a running server and a running client instance through its standard library. The client connects to the WebSocket server through the standard HTML5 API (Line 5) and sends the current input value (Line 10). The server opens a WebSocket server (Line 17) that returns the value back to the client (Line 20). So-called services, which are executed on the server and produce a value that is returned to the client that invoked the service. For example, the echo service (Line 1) produces the HTML page served to the web client of the Echo application. Thus, the code in a service block is executed on the server.
=== Echo application in Links ===
Links uses annotations on functions to specify whether they run on the client or on the server (Line 1 and 5). Upon request from the client, the server executes the main function (Line 18), which constructs the code that is sent to the client. Links allows embedding XML code (Line 7–15). XML attributes with the l: prefix are treated specially. The l:name attribute (Line 10) declares an identifier to which the value of the input field is bound. The identifier can be used elsewhere (Line 9). The code to be executed for the l:onsubmit handler (Line 9) is not immediately executed but compiled to JavaScript for client-side execution. Curly braces indicate Links code embedded into XML. The l:onsubmit handler sends the current input value item to the server by calling echo. The item is returned by the server and appended to the list of received items using standard DOM APIs. The call to the server (Line 9) does not block the client. Instead, the continuation on the client is invoked when the result of the call is available. Client–server interaction is based on resumption passing style: Using continuation passing style transformation and defunctionalization, remote calls are implemented by passing the name of a function for the continuation and the data needed to continue the computation.
=== Echo application in ScalaLoci ===
ScalaLoci is a language that targets generic distributed systems rather than the Web only, i.e., it is not restricted to a client–server architecture. To this end, ScalaLoci supports peer types to encode the different tiers at the type level. Placement types are used to assign locations to data and computations. ScalaLoci supports multitier reactives – language abstractions for reactive programming that are placed on specific locations – for composing data flows cross different peers.
The application first defines an input field (Line 11) using the ScalaTags library. The value of this field is used in the click event handler of a button (Line 15) to fire the message event with the current value of the input field. The value is then propagated to the server (Line 6) and back to the client (Line 9). On the client, the value of the event are accumulated using the list function and mapped to an HTML list (Line 10). This list is then used in the HTML (Line 16) to display the previous inputs.
== List of multitier programming languages ==
Hop/Hop.js
Links
Ur/Web
Eliom/Ocsigen
ScalaLoci
StiP.js
Scala Multi-Tier FRP
Opa
AmbientTalk/R
ML5
WebSharper
Haste
Fun
Koka
Multi-Tier Calculus
Swift
Volta
GWT
Meteor
J-Orchestra
Hiphop
Distributed Orc
Jif/split
Fission
SIF
WebDSL
Acute
Mobl
High-Level Abstractions for Web Programming
== References ==
|
https://en.wikipedia.org/wiki/Multitier_programming
|
The Xojo programming environment and programming language is developed and commercially marketed by Xojo, Inc. of Austin, Texas for software development targeting macOS, Microsoft Windows, Linux, iOS, Android, the Web and Raspberry Pi. Xojo uses a proprietary object-oriented language.
== History ==
In 1996, FYI Software, founded by Geoff Perlman, bought CrossBasic, which had been marketed by its author Andrew Barry as a shareware product. CrossBasic got its name from its ability to compile the same programming code for the classic Mac OS and the Java virtual machine (although the integrated development environment was Mac only). A public beta was released in April 1996. The CrossBasic name was trademarked by another company, so the product was renamed REALbasic.
Prior to version 2, the Java target was dropped and later replaced with a Windows target and database support. The option to compile for Linux was added in 2005 and the integrated development environment (IDE) was ported to Windows and as a free public beta for Linux platforms. The new IDE employed a redesigned user interface.
In 2004, REAL software announced the "Made with REALbasic Showcase" program to highlight applications created with the product. In 2009, a migration assistant was launched to help move code from Visual Basic. In 2010, to combat the perception that it was similar to the original BASIC, it was renamed Real Studio.
The company announced Real Studio Web Edition, allowing developers to compile web applications without the knowledge of multiple web technologies.
On June 4, 2013 the company officially changed their name to Xojo, Inc. and Real Studio was renamed Xojo. Also on this date they released Xojo 2013 Release 1 which included an all-new user interface, full support for Cocoa on OS X, improved support for web applications, all new documentation and a new Introduction to Programming Using Xojo textbook that was designed for beginners to learn the fundamentals of object oriented programming. Xojo, Inc. calls it "the spiritual successor to Visual BASIC".
The Xojo IDE is currently available for Microsoft Windows, macOS, 32-bit x86 Linux, and can compile 32-bit and 64-bit applications for Windows (Windows XP and higher), macOS (running on Intel or Apple silicon Macs using the Cocoa frameworks), x86 Linux, iOS, Android, the web, and Raspberry Pi. Xojo is self-hosted: the Xojo IDE is built with the current release of Xojo. The 2015r3 release includes 64-bit support for Desktop, Web and Console targets as well as a new platform, Raspberry Pi.
Xojo added many new features in 2018 and 2019, including support for macOS and iOS light/dark modes, a GraphicsPath for drawing Bézier curves, and a new DateTime class.
In 2020, Xojo introduced a new web framework, which is a ground-up re-write that adds modern-looking new controls, support for Bootstrap themes, two layout modes and more. The new web framework takes advantage of all that modern web browsers have to offer, providing a more robust foundation to build responsive web apps.
Xojo has ranked among the top 100 most popular programming languages as published by TIOBE, a company which rates the quality of software.
== Timeline ==
=== 1990s ===
In 1996, Geoff Perlman founds the company that is now Xojo in Austin, Texas.
CrossBasic is acquired in 1997.
In 1998, REALbasic 1.0 released and introduced at MacWorld Expo. This first release made it easy for anyone, not just developers, to create apps for the Mac System 7 running on a 680x0 or PowerPC processor.
Windows support was added in 1999 with the release of REALbasic 2.0, making it a true cross-platform development tool.
=== 2000s ===
Support for Mac OS X is added to REALbasic in 2001.
In 2002, the first Windows IDE of REALbasic is announced.
In September 2005, REALbasic is updated to include support for building Linux apps. REALbasic now compiles for three desktop platforms from a single code base.
Continuing to keep up with the rapidly changing needs of developers and hobbyists, Intel-based Mac support is added in 2006.
=== 2010s ===
Expanding beyond desktop platforms, support for building web applications is added in 2010.
REALbasic becomes Xojo in 2013.
Xojo Cloud, Xojo's one-click deployment service for Xojo web apps, is launched in early 2014.
In December 2014, Xojo iOS, Xojo's first mobile platform, is released.
After much interest from the community, Xojo Pi is released, letting users build applications for Raspberry Pi with Xojo in 2015.
Support for macOS Mojave Dark Mode for the Xojo IDE and compiled apps was added in Xojo 2018 Release 3.
In 2019, Xojo Pi licenses are for free for building both console and desktop apps.
Xojo introduces new API in Xojo 2019 Release 2, which includes new classes and updated method and property names for better consistency across platforms.
In December 2019, Xojo formed the MVP program to facilitate community communication and serve as an informal advisory committee.
=== 2020s ===
Xojo announced the 2020 Xojo Design Award winners during a video keynote on March 25, 2020.
On July 15, 2020, Xojo released an update for Xojo to run on macOS Big Sur as well as Apple silicon.
Xojo released their new web framework on August 26, 2020 for developing web apps with Xojo.
Xojo shipped 2020 Release 2 on November 24, 2020 with support for building native applications for Apple silicon (M1), making it the first cross-platform development tool to do so.
Xojo 2021 Release 1 added support for the Xojo IDE and XojoScript to run native on M1 Macs.
Xojo shipped 2021 Release 3 on November 18, 2021 that brings back cross-compilation from Windows and Linux to macOS. This release also introduces Dark Mode support for Windows.
On November 18, 2021, Xojo announces that their Android framework is in public pre-release testing.
Xojo released support for building applications for Windows ARM with Xojo 2022 Release 2, available on July 25, 2022.
At their Xojo Developer Conference in London, Xojo announced that their support for Android will be shipping in the next release of Xojo, 2023r2 and, as it is a new platform, it will be marked as beta.
On August 9, 2023 Xojo shipped 2023 Release 2, which added the ability to build mobile applications for Android. It also added Dark Mode support for web applications and a DesktopXAMLContainer control to access modern looking Windows user interface controls.
On March 26, 2024 Xojo shipped 2024 Release 1, which added the ability to build Linux desktop and console apps from Linux, macOS, or Windows, for free. Xojo 2024r1 also upgraded all Xojo Lite licenses to include the text project file format for better compatibility with version control systems, making it much easier to share and contribute to open-source projects.
== Editions of IDE ==
The Xojo IDE is free to use for learning and development. Compiling or deploying applications with Xojo requires a license. Multiple license levels are available for purchase, enabling Desktop, Web, iOS and Android. Building applications for Linux Desktop and Console, including for Raspberry Pi, is free.
Licenses can be purchased a la carte, in any combination required, and include 1 year of access to new releases. Xojo Pro, a bundle offered by Xojo, includes the ability to compile for Desktop, iOS, Android, Web and Console, along with technical support, access to consulting leads, and a license that will work on three machines. Xojo also has a Pro Plus license that includes everything in Xojo Pro, plus additional support benefits and can be installed on up to six devices (for a single user).
The default database used with Xojo is SQLite.
Unlike most programming environments, project source code is not stored in plain text files by default, but in a proprietary, single-file format. However, source code can be saved to a plain-text format for use with version control systems and can be exported to XML format as well.
== Xojo Cloud ==
On March 11, 2014, Xojo launched Xojo Cloud, their cloud hosting service for Xojo web applications.
In July 2014, Xojo Cloud added the ability to transfer files to the server using a client other than the Xojo IDE.
In March 2015, Xojo added MySQL and Postgres databases to Xojo Cloud. In addition, they also enabled the creation of SSH Tunnels for a direct connection to databases using a third party management tool.
In 2018, Release 1, Xojo added server stats for Xojo Cloud.
A new Xojo Cloud control panel was introduced in August 2020; it is built using the new Xojo web framework. Other recent updates to Xojo Cloud include the ability to point domains at individual applications.
== Example code ==
The Xojo programming language looks similar to Visual Basic.
The following code snippet placed in the Open event of a Window displays a message box saying "Hello, World!" as the window loads:
This code populates a ListBox with the values from an array:
== See also ==
Visual Basic
Gambas
Lazarus (IDE)
Comparison of programming languages
== References ==
== External links ==
Xojo, Inc., makers of Xojo
|
https://en.wikipedia.org/wiki/Xojo
|
In computer programming, an operator is a programming language construct that provides functionality that may not be possible to define as a user-defined function (i.e. sizeof in C) or has syntax different than a function (i.e. infix addition as in a+b). Like other programming language concepts, operator has a generally accepted, although debatable meaning among practitioners while at the same time each language gives it specific meaning in that context, and therefore the meaning varies by language.
Some operators are represented with symbols – characters typically not allowed for a function identifier – to allow for presentation that is more familiar looking than typical function syntax. For example, a function that tests for greater-than could be named gt, but many languages provide an infix symbolic operator so that code looks more familiar. For example, this:
if gt(x, y) then return
Can be:
if x > y then return
Some languages allow a language-defined operator to be overridden with user-defined behavior and some allow for user-defined operator symbols.
Operators may also differ semantically from functions. For example, short-circuit Boolean operations evaluate later arguments only if earlier ones are not false.
== Differences from functions ==
=== Syntax ===
Many operators differ syntactically from user-defined functions. In most languages, a function is prefix notation with fixed precedence level and associativity and often with compulsory parentheses (e.g. Func(a) or (Func a) in Lisp). In contrast, many operators are infix notation and involve different use of delimiters such as parentheses.
In general, an operator may be prefix, infix, postfix, matchfix, circumfix or bifix, and the syntax of an expression involving an operator depends on its arity (number of operands), precedence, and (if applicable), associativity. Most programming languages support binary operators and a few unary operators, with a few supporting more operands, such as the ?: operator in C, which is ternary. There are prefix unary operators, such as unary minus -x, and postfix unary operators, such as post-increment x++; and binary operations are infix, such as x + y or x = y. Infix operations of higher arity require additional symbols, such as the ternary operator ?: in C, written as a ? b : c – indeed, since this is the only common example, it is often referred to as the ternary operator. Prefix and postfix operations can support any desired arity, however, such as 1 2 3 4 +.
=== Semantics ===
The semantics of an operator may significantly differ from that of a normal function. For reference, addition is evaluated like a normal function. For example, x + y can be equivalent to a function add(x, y) in that the arguments are evaluated and then the functional behavior is applied. However, assignment is different. For example, given a = b the target a is not evaluated. Instead its value is replaced with the value of b. The scope resolution and element access operators (as in Foo::Bar and a.b, respectively, in the case of e.g. C++) operate on identifier names; not values.
In C, for instance, the array indexing operator can be used for both read access as well as assignment. In the following example, the increment operator reads the element value of an array and then assigns the element value.
The C++ << operator allows for fluent syntax by supporting a sequence of operators that affect a single argument. For example:
== ad hoc polymorphic ==
Some languages provide operators that are ad hoc polymorphic – inherently overloaded. For example, in Java the + operator sums numbers or concatenates strings.
== Customization ==
Some languages support user-defined overloading (such as C++ and Fortran). An operator, defined by the language, can be overloaded to behave differently based on the type of input.
Some languages (e.g. C, C++ and PHP) define a fixed set of operators, while others (e.g. Prolog, Seed7, F#, OCaml, Haskell) allow for user-defined operators. Some programming languages restrict operator symbols to special characters like + or := while others allow names like div (e.g. Pascal), and even arbitrary names (e.g. Fortran where an upto 31 character long operator name is enclosed between dots).
Most languages do not support user-defined operators since the feature significantly complicates parsing. Introducing a new operator changes the arity and precedence lexical specification of the language, which affects phrase-level lexical analysis. Custom operators, particularly via runtime definition, often make correct static analysis of a program impossible, since the syntax of the language may be Turing-complete, so even constructing the syntax tree may require solving the halting problem, which is impossible. This occurs for Perl, for example, and some dialects of Lisp.
If a language does allow for defining new operators, the mechanics of doing so may involve meta-programming – specifying the operator in a separate language.
== Operand coercion ==
Some languages implicitly convert (aka coerce) operands to be compatible with each other. For example, Perl coercion rules cause 12 + "3.14" to evaluate to 15.14. The string literal "3.14" is converted to the numeric value 3.14 before addition is applied. Further, 3.14 is treated as floating point so the result is floating point even though 12 is an integer literal. JavaScript follows different rules so that the same expression evaluates to "123.14" since 12 is converted to a string which is then concatenated with the second operand.
In general, a programmer must be aware of the specific rules regarding operand coercion in order to avoid unexpected and incorrect behavior.
== Examples ==
Mathematical operators
Arithmetic: such as addition, a + b
Relational: such as greater than, a > b
Logic: such as a AND b or a && b
Assignment: such as a = b or a := b
Three-way comparison (aka spaceship): x <=> y
Program structure operators
Record or object field access: such as a.b
Scope resolution: such as a::b or a.b
Conditional operators
Ternary conditional: condition ? a : b
Elvis: x ?: y
Null coalesing: x ?? y
Notable C and C++ operators
Address-of operator: &x
Dereference: *p
Comma: e, f
Compound operators
Compound assignment (aka augmented assignment) in C/C++: +=, -=, *=, /=, %=, <<=, >>=, &=, ^=, |=
Fused: such as cis x = cos x + i sin x
== Operator features in programming languages ==
The following table shows the operator features in several programming languages:
== See also ==
Operators in C and C++
== References ==
|
https://en.wikipedia.org/wiki/Operator_(computer_programming)
|
Programming languages are used for controlling the behavior of a machine (often a computer). Like natural languages, programming languages follow rules for syntax and semantics.
There are thousands of programming languages and new ones are created every year. Few languages ever become sufficiently popular that they are used by more than a few people, but professional programmers may use dozens of languages in a career.
Most programming languages are not standardized by an international (or national) standard, even widely used ones, such as Perl or Standard ML (despite the name). Notable standardized programming languages include ALGOL, C, C++, JavaScript (under the name ECMAScript), Smalltalk, Prolog, Common Lisp, Scheme (IEEE standard), ISLISP, Ada, Fortran, COBOL, SQL, and XQuery.
== General comparison ==
The following table compares general and technical information for a selection of commonly used programming languages. See the individual languages' articles for further information.
== Type systems ==
== Failsafe I/O and system calls ==
Most programming languages will print an error message or throw an exception if an input/output operation or other system call (e.g., chmod, kill) fails, unless the programmer has explicitly arranged for different handling of these events. Thus, these languages fail safely in this regard.
Some (mostly older) languages require that programmers explicitly add checks for these kinds of errors. Psychologically, different cognitive biases (e.g., optimism bias) may affect novices and experts alike and lead them to skip these checks. This can lead to erroneous behavior.
Failsafe I/O is a feature of 1C:Enterprise, Ada (exceptions), ALGOL (exceptions or return value depending on function), Ballerina, C#, Common Lisp ("conditions and restarts" system), Curry, D (throwing on failure), Erlang, Fortran, Go (unless result explicitly ignored), Gosu, Harbour, Haskell, ISLISP, Java, Julia, Kotlin, LabVIEW, Mathematica, Objective-C (exceptions), OCaml (exceptions), OpenLisp, PHP, Python, Raku, Rebol, Rexx (with optional signal on... trap handling), Ring, Ruby, Rust (unless result explicitly ignored), Scala, Smalltalk, Standard ML , Swift ≥ 2.0 (exceptions), Tcl, Visual Basic, Visual Basic .NET, Visual Prolog, Wolfram Language, Xojo, XPath/XQuery (exceptions), and Zeek.
No Failsafe I/O:
AutoHotkey (global ErrorLevel must be explicitly checked), C, COBOL, Eiffel (it actually depends on the library and it is not defined by the language), GLBasic (will generally cause program to crash), RPG, Lua (some functions do not warn or throw exceptions), and Perl.
Some I/O checking is built in C++ (STL iostreams throw on failure but C APIs like stdio or POSIX do not) and Object Pascal, in Bash it is optional.
== Expressiveness ==
The literature on programming languages contains an abundance of informal claims about their relative expressive power, but there is no framework for formalizing such statements nor for deriving interesting consequences. This table provides two measures of expressiveness from two different sources. An additional measure of expressiveness, in GZip bytes, can be found on the Computer Language Benchmarks Game.
== Benchmarks ==
Benchmarks are designed to mimic a particular type of workload on a component or system. The computer programs used for compiling some of the benchmark data in this section may not have been fully optimized, and the relevance of the data is disputed. The most accurate benchmarks are those that are customized to your particular situation. Other people's benchmark data may have some value to others, but proper interpretation brings many challenges. The Computer Language Benchmarks Game site warns against over-generalizing from benchmark data, but contains a large number of micro-benchmarks of reader-contributed code snippets, with an interface that generates various charts and tables comparing specific programming languages and types of tests.
== Timeline of specific language comparisons ==
1974 – Comparative Notes on Algol 68 and PL/I – S. H. Valentine – November 1974
1976 – Evaluation of ALGOL 68, JOVIAL J3B, Pascal, Simula 67, and TACPOL Versus TINMAN – Requirements for a Common High Order Programming Language.
1977 – A comparison of PASCAL and ALGOL 68 – Andrew S. Tanenbaum – June 1977.
1993 – Five Little Languages and How They Grew – BLISS, Pascal, ALGOL 68, BCPL & C – Dennis M. Ritchie – April 1993.
2009 – On Go – oh, go on – How well will Google's Go stand up against Brand X programming language? – David Given – November 2009
== See also ==
Comparison of programming languages (basic instructions)
Comparison of programming languages (syntax)
Comparison of integrated development environments
Comparison of multi-paradigm programming languages
TIOBE index
== References ==
== Further reading ==
Cezzar, Ruknet (1995). A Guide to Programming Languages: Overview and Comparison. Artech House. ISBN 978-0-89006-812-0.
|
https://en.wikipedia.org/wiki/Comparison_of_programming_languages
|
In computing, a namespace is a set of signs (names) that are used to identify and refer to objects of various kinds. A namespace ensures that all of a given set of objects have unique names so that they can be easily identified.
Namespaces are commonly structured as hierarchies to allow reuse of names in different contexts. As an analogy, consider a system of naming of people where each person has a given name, as well as a family name shared with their relatives. If the first names of family members are unique only within each family, then each person can be uniquely identified by the combination of first name and family name; there is only one Jane Doe, though there may be many Janes. Within the namespace of the Doe family, just "Jane" suffices to unambiguously designate this person, while within the "global" namespace of all people, the full name must be used.
Prominent examples for namespaces include file systems, which assign names to files.
Some programming languages organize their variables and subroutines in namespaces.
Computer networks and distributed systems assign names to resources, such as computers, printers, websites, and remote files. Operating systems can partition kernel resources by isolated namespaces to support virtualization containers.
Similarly, hierarchical file systems organize files in directories. Each directory is a separate namespace, so that the directories "letters" and "invoices" may both contain a file "to_jane".
In computer programming, namespaces are typically employed for the purpose of grouping symbols and identifiers around a particular functionality and to avoid name collisions between multiple identifiers that share the same name.
In networking, the Domain Name System organizes websites (and other resources) into hierarchical namespaces.
== Name conflicts ==
Element names are defined by the developer. This often results in a conflict when trying to mix XML documents from different XML applications.
This XML carries HTML table information:
This XML carries information about a table (i.e. a piece of furniture):
If these XML fragments were added together, there would be a name conflict. Both contain a <table>...</table> element, but the elements have different content and meaning.
An XML parser will not know how to handle these differences.
=== Solution via prefix ===
Name conflicts in XML can easily be avoided using a name prefix.
The following XML distinguishes between information about the HTML table and furniture by prefixing "h" and "f" at the beginning of the elements.
== Naming system ==
A name in a namespace consists of a namespace name and a local name. The namespace name is usually applied as a prefix to the local name.
In augmented Backus–Naur form:
When local names are used by themselves, name resolution is used to decide which (if any) particular name is alluded to by some particular local name.
=== Examples ===
=== Delegation ===
Delegation of responsibilities between parties is important in real-world applications, such as the structure of the World Wide Web. Namespaces allow delegation of identifier assignment to multiple name issuing organisations whilst retaining global uniqueness. A central Registration authority registers the assigned namespace names allocated. Each namespace name is allocated to an organisation which is subsequently responsible for the assignment of names in their allocated namespace. This organisation may be a name issuing organisation that assign the names themselves, or another Registration authority which further delegates parts of their namespace to different organisations.
=== Hierarchy ===
A naming scheme that allows subdelegation of namespaces to third parties is a hierarchical namespace.
A hierarchy is recursive if the syntax for the namespace names is the same for each subdelegation. An example of a recursive hierarchy is the Domain name system.
An example of a non-recursive hierarchy are Uniform Resource Name representing an Internet Assigned Numbers Authority (IANA) number.
=== Namespace versus scope ===
A namespace name may provide context (scope in computer science) to a name, and the terms are sometimes used interchangeably. However, the context of a name may also be provided by other factors, such as the location where it occurs or the syntax of the name.
== In programming languages ==
For many programming languages, namespace is a context for their identifiers. In an operating system, an example of namespace is a directory. Each name in a directory uniquely identifies one file or subdirectory.
As a rule, names in a namespace cannot have more than one meaning; that is, different meanings cannot share the same name in the same namespace. A namespace is also called a context, because the same name in different namespaces can have different meanings, each one appropriate for its namespace.
Following are other characteristics of namespaces:
Names in the namespace can represent objects as well as concepts, be the namespace a natural or ethnic language, a constructed language, the technical terminology of a profession, a dialect, a sociolect, or an artificial language (e.g., a programming language).
In the Java programming language, identifiers that appear in namespaces have a short (local) name and a unique long "qualified" name for use outside the namespace.
Some compilers (for languages such as C++) combine namespaces and names for internal use in the compiler in a process called name mangling.
As well as its abstract language technical usage as described above, some languages have a specific keyword used for explicit namespace control, amongst other uses. Below is an example of a namespace in C++:
=== Computer-science considerations ===
A namespace in computer science (sometimes also called a name scope) is an abstract container or environment created to hold a logical grouping of unique identifiers or symbols (i.e. names). An identifier defined in a namespace is associated only with that namespace. The same identifier can be independently defined in multiple namespaces. That is, an identifier defined in one namespace may or may not have the same meaning as the same identifier defined in another namespace. Languages that support namespaces specify the rules that determine to which namespace an identifier (not its definition) belongs.
This concept can be illustrated with an analogy. Imagine that two companies, X and Y, each assign ID numbers to their employees. X should not have two employees with the same ID number, and likewise for Y; but it is not a problem for the same ID number to be used at both companies. For example, if Bill works for company X and Jane works for company Y, then it is not a problem for each of them to be employee #123. In this analogy, the ID number is the identifier, and the company serves as the namespace. It does not cause problems for the same identifier to identify a different person in each namespace.
In large computer programs or documents it is common to have hundreds or thousands of identifiers. Namespaces (or a similar technique, see Emulating namespaces) provide a mechanism for hiding local identifiers. They provide a means of grouping logically related identifiers into corresponding namespaces, thereby making the system more modular.
Data storage devices and many modern programming languages support namespaces. Storage devices use directories (or folders) as namespaces. This allows two files with the same name to be stored on the device so long as they are stored in different directories. In some programming languages (e.g. C++, Python), the identifiers naming namespaces are themselves associated with an enclosing namespace. Thus, in these languages namespaces can nest, forming a namespace tree. At the root of this tree is the unnamed global namespace.
==== Use in common languages ====
===== C =====
It is possible to use anonymous structs as namespaces in C since C99.
===== C++ =====
In C++, a namespace is defined with a namespace block.
Within this block, identifiers can be used exactly as they are declared. Outside of this block, the namespace specifier must be prefixed. For example, outside of namespace abc, bar must be written abc::bar to be accessed. C++ includes another construct that makes this verbosity unnecessary. By adding the line
to a piece of code, the prefix abc:: is no longer needed.
Identifiers that are not explicitly declared within a namespace are considered to be in the global namespace.
These identifiers can be used exactly as they are declared, or, since the global namespace is unnamed, the namespace specifier :: can be prefixed. For example, foo can also be written ::foo.
Namespace resolution in C++ is hierarchical. This means that within the hypothetical namespace food::soup, the identifier chicken refers to food::soup::chicken. If food::soup::chicken doesn't exist, it then refers to food::chicken. If neither food::soup::chicken nor food::chicken exist, chicken refers to ::chicken, an identifier in the global namespace.
Namespaces in C++ are most often used to avoid naming collisions. Although namespaces are used extensively in recent C++ code, most older code does not use this facility because it did not exist in early versions of the language. For example, the entire C++ Standard Library is defined within namespace std, but before standardization many components were originally in the global namespace. A programmer can insert the using directive to bypass namespace resolution requirements and obtain backwards compatibility with older code that expects all identifiers to be in the global namespace. However the use of the using directive for reasons other than backwards compatibility (e.g., convenience) is considered to be against good code practices.
===== Java =====
In Java, the idea of a namespace is embodied in Java packages. All code belongs to a package, although that package need not be explicitly named. Code from other packages is accessed by prefixing the package name before the appropriate identifier, for example class String in package java.lang can be referred to as java.lang.String (this is known as the fully qualified class name). Like C++, Java offers a construct that makes it unnecessary to type the package name (import). However, certain features (such as reflection) require the programmer to use the fully qualified name.
Unlike C++, namespaces in Java are not hierarchical as far as the syntax of the language is concerned. However, packages are named in a hierarchical manner. For example, all packages beginning with java are a part of the Java platform—the package java.lang contains classes core to the language, and java.lang.reflect contains core classes specifically relating to reflection.
In Java (and Ada, C#, and others), namespaces/packages express semantic categories of code. For example, in C#, namespace System contains code provided by the system (the .NET Framework). How specific these categories are and how deep the hierarchies go differ from language to language.
Function and class scopes can be viewed as implicit namespaces that are inextricably linked with visibility, accessibility, and object lifetime.
===== C# =====
Namespaces are heavily used in C# language. All .NET Framework classes are organized in namespaces, to be used more clearly and to avoid chaos. Furthermore, custom namespaces are extensively used by programmers, both to organize their work and to avoid naming collisions.
When referencing a class, one should specify either its fully qualified name, which means namespace followed by the class name:
or add a using statement. This eliminates the need to mention the complete name of all classes in that namespace.
In the above examples, System is a namespace, and Console and Convert are classes defined within System.
===== Python =====
In Python, namespaces are defined by the individual modules, and since modules can be contained in hierarchical packages, then namespaces are hierarchical too.
In general when a module is imported then the names defined in the module are defined via that module's namespace, and are accessed in from the calling modules by using the fully qualified name.
The from ... import ... statement can be used to insert the relevant names directly into the calling module's namespace, and those names can be accessed from the calling module without the qualified name:
Since this directly imports names (without qualification) it can overwrite existing names with no warnings.
A special form of the statement is from ... import * which imports all names defined in the named package directly in the calling module's namespace. Use of this form of import, although supported within the language, is generally discouraged as it pollutes the namespace of the calling module and will cause already defined names to be overwritten in the case of name clashes.
Python also supports import x as y as a way of providing an alias or alternative name for use by the calling module:
===== XML namespace =====
In XML, the XML namespace specification enables the names of elements and attributes in an XML document to be unique, similar to the role of namespaces in programming languages. Using XML namespaces, XML documents may contain element or attribute names from more than one XML vocabulary.
===== PHP =====
Namespaces were introduced into PHP from version 5.3 onwards. Naming collision of classes, functions and variables can be avoided.
In PHP, a namespace is defined with a namespace block.
We can reference a PHP namespace with the following different ways:
=== Emulating namespaces ===
In programming languages lacking language support for namespaces, namespaces can be emulated to some extent by using an identifier naming convention. For example, C libraries such as libpng often use a fixed prefix for all functions and variables that are part of their exposed interface. Libpng exposes identifiers such as:
png_create_write_struct
png_get_signature
png_read_row
png_set_invalid
This naming convention provides reasonable assurance that the identifiers are unique and can therefore be used in larger programs without naming collisions. Likewise, many packages originally written in Fortran (e.g., BLAS, LAPACK) reserve the first few letters of a function's name to indicate the group to which the function belongs.
This technique has several drawbacks:
It doesn't scale well to nested namespaces; identifiers become excessively long since all uses of the identifiers must be fully namespace-qualified;
Individuals or organizations may use inconsistent naming conventions, potentially introducing unwanted obfuscation;
Compound or "query-based" operations on groups of identifiers, based on the namespaces in which they are declared, are rendered unwieldy or unfeasible;
In languages with restricted identifier length, the use of prefixes limits the number of characters that can be used to identify what the function does; this is a particular problem for packages originally written in FORTRAN 77, which offered only 6 characters per identifier; for example, the name of the BLAS function DGEMM indicates that it operates on double-precision floating-point numbers (D) and general matrices (GE), with only the last two characters (MM) showing what it actually does: matrix–matrix multiplication.
It also has a few advantages:
No special software tools are required to locate names in source-code files; a simple program like grep suffices;
There are no namespace-related name conflicts;
There is no need for name mangling, and thus no potential incompatibility problems.
== See also ==
11-digit delivery point ZIP code
Binomial nomenclature (genus-species in biology)
Chemical nomenclature
Dewey Decimal Classification
Digital object identifier
Domain Name System
Fourth wall
Identity (object-oriented programming)
Library of Congress Classification
Star catalogues and astronomical naming conventions
Violation of abstraction level
XML namespace
Argument-dependent name lookup
== References ==
|
https://en.wikipedia.org/wiki/Namespace
|
Impromptu is a Mac OS X programming environment for live coding. Impromptu is built around the Scheme language, which is a member of the Lisp family of languages. The source code of its core has been opened as the Extempore project.
== Description ==
The environment allows to make changes to a program at runtime, so variables and functions may be redefined and the changes take effect immediately. A programmer can also create and schedule code for future execution, as well as data events such as notes and graphics objects. Once an event is scheduled, execution continues. Looping is performed by using an idiom called "temporal recursion" which works by having a function asynchronously schedule a future call to itself as its final action.
The library allows communicating with Audio Units for audio synthesis, and with graphics layers such as QuickTime, Quartz, Core Image, OpenGL for video composition. Code written in Objective-C can be called from the editor, and also Objective-C frameworks can perform calls to the Scheme interpreter.
Impromptu's Scheme interpreter was initially built from the TinyScheme 1.35 baseline, but it has been substantially modified since to better suit the live coding context. A real-time garbage collector, and Objective-C integration were added. Also, a new statically typed language called the Extempore Language has been integrated to the system. This language is syntactically Scheme-like, but semantically closer to C, and is designed for real-time sound synthesis and other computationally heavy tasks. It provides type inference and is compiled to machine language by LLVM.
== Sample performance ==
A Study in Keith is a live coding performance in Impromptu by Andrew Sorensen. The first two minutes (1:56) are silent, while the performer writes the program that will produce the introduction of the piece. From then on, he modifies the code on the fly to evolve the composition.
== Extempore ==
The core of Impromptu has been released as Extempore under a BSD style licence. It runs under both Linux and Mac OS X. It includes the Scheme interpreter, the Extempore Language compiler and the scheduler. The bindings to Apple libraries are absent, but the environment can interface with dynamic libraries.
== See also ==
Csound
Comparison of audio synthesis environments
SuperCollider
Processing (programming language)
OpenFrameworks
ChucK
List of music software
Max (software)
Pure Data
== References ==
=== Academic papers ===
Sorensen, A (2010) "A Distributed Memory For Networked Livecoding Performance Archived 2021-02-26 at the Wayback Machine" International Computer Music Conference 2010, New York
Sorensen, A & Brown, A (2008) "A Computational Model For The Generation Of Orchestral Music In The Germanic Symphonic Tradition: A progress report" paper presented to the Australasian Computer Music Conference 2008, Sydney
Sorensen, A & Brown, A (2007) "aa-cell in Practice: An Approach to Musical Live Coding" paper presented to the International Computer Music Conference 2007, Copenhagen
Sorensen, A. (2005) "Impromptu: An interactive programming environment for composition and performance" a paper presented to the Australasian Computer Music Conference 2005, Brisbane: ACMA, pp. 149–153. (Note: Impromptu version discussed is obsolete)
Sorensen, A. "ICR - Impromptu Compiler Runtime"
Thor Magnusson, "Confessions of a Live Coder", Proceedings of International Computer Music Conference, 2011.
=== Other sources ===
Peter Kirn, "Thought and Performance, Live Coding Music, Explained to Anyone - Really", Create Digital Music, 2011
Mitchell Whitelaw, "From Scratch - A Conversation with Andrew Sorensen", 2007
== External links ==
Official website
|
https://en.wikipedia.org/wiki/Impromptu_(programming_environment)
|
Client is a computer that gets information from another computer called server in the context of client–server model of computer networks. The server is often (but not always) on another computer system, in which case the client accesses the service by way of a network.
A client is a program that, as part of its operation, relies on sending a request to another program or a computer hardware or software that accesses a service made available by a server (which may or may not be located on another computer). For example, web browsers are clients that connect to web servers and retrieve web pages for display. Email clients retrieve email from mail servers. Online chat uses a variety of clients, which vary on the chat protocol being used. Multiplayer video games or online video games may run as a client on each computer. The term "client" may also be applied to computers or devices that run the client software or users that use the client software.
A client is part of a client–server model, which is still used today. Clients and servers may be computer programs run on the same machine and connect via inter-process communication techniques. Combined with Internet sockets, programs may connect to a service operating on a possibly remote system through the Internet protocol suite. Servers wait for potential clients to initiate connections that they may accept.
The term was first applied to devices that were not capable of running their own stand-alone programs, but could interact with remote computers via a network. These computer terminals were clients of the time-sharing mainframe computer.
== Types ==
In one classification, client computers and devices are either thick clients, thin clients, or diskless nodes.
=== Thick ===
A thick client, also known as a rich client or fat client, is a client that performs the bulk of any data processing operations itself, and does not necessarily rely on the server. The personal computer is a common example of a fat client, because of its relatively large set of features and capabilities and its light reliance upon a server. For example, a computer running an art program (such as Krita or Sketchup) that ultimately shares the result of its work on a network is a thick client. A computer that runs almost entirely as a standalone machine save to send or receive files via a network is by a standard called a workstation.
=== Thin ===
A thin client is a minimal sort of client. Thin clients use the resources of the host computer. A thin client generally only presents processed data provided by an application server, which performs the bulk of any required data processing. A device using web application (such as Office Web Apps) is a thin client.
=== Diskless node ===
A diskless node is a mixture of the above two client models. Similar to a fat client, it processes locally, but relies on the server for storing persistent data. This approach offers features from both the fat client (multimedia support, high performance) and the thin client (high manageability, flexibility). A device running an online version of the video game Diablo III is an example of diskless node.
== References ==
|
https://en.wikipedia.org/wiki/Client_(computing)
|
The CW Network, LLC (commonly referred to as The CW or simply CW) is an American commercial broadcast television network which is controlled by Nexstar Media Group through a 75% ownership interest. The network's name is derived from the first letters of the names of its two founding co-owners CBS Corporation and Warner Bros. Nexstar acquired a 75% controlling stake in the network on October 3, 2022, with Paramount Global and Warner Bros. Discovery (CBS Entertainment Group and Warner Bros. Television's respective parent companies) each retaining a 12.5% ownership stake.
The CW debuted on September 18, 2006 as the successor to UPN and the WB, which had respectively shut down on September 15 and 17 of that year. The CW's first two nights of programming – on September 18, 2006 and September 19, 2006 – consisted of reruns and launch-related specials. The CW marked its formal launch date on September 20, 2006, with the two-hour premiere of the seventh cycle of America's Next Top Model. The network's programming lineup is intended to appeal mainly to viewers between the ages of 18 and 34, although from 2008 to 2011 the network shifted its programming to appeal to women in that demographic. As of August 2017, the network's audience was evenly split between men and women.
The CW runs programming seven days a week: airing nightly in prime time along with a Saturday morning live-action educational programming block produced by Hearst Media Production Group called One Magnificent Morning.
The CW is also available in Canada on pay television providers through stations owned-and-operated by Nexstar and on affiliates owned by others that are located within proximity to the Canada–United States border (whose broadcasts of CW shows are subject to simultaneous substitution laws imposed by the Canadian Radio-television and Telecommunications Commission, if a Canadian network holds the broadcast rights); it’s also available through two Nexstar-controlled stations that are classified in the United States as superstations – New York City-based de facto flagship WPIX and Los Angeles-based secondary flagship KTLA.
Additionally, the network is available in northern Mexico through affiliates located near the Mexico–U.S. border (such as KFMB-DT2—San Diego/Tijuana, KECY-DT3 in El Centro, California, KVIA-DT2 in El Paso, and KCWT-CD with simulcast network KMBH-LD2 in McAllen/Brownsville, Texas) on pay television providers. In both Canada and Mexico, some free-to-air CW affiliate signals originating from the U.S. are receivable over-the-air in border areas depending on the station's signal coverage.
In Central America, Venezuela, Colombia, Peru, Ecuador and the Caribbean, many subscription providers carry either select U.S.-based The CW-affiliated stations or the main network feed from The CW O&Os WPIX in New York City, WDCW in Washington, D.C., WPHL-TV in Philadelphia, KTLA in Los Angeles, KRON-TV in San Francisco, KIAH in Houston or WGN-TV in Chicago.
== History ==
=== 1993–2006: Predecessors and formation ===
In April 1993, the Federal Communications Commission (FCC) ended the fin-syn rules that prohibited television networks from owning the rerun rights to programs they broadcast. Fearing that the networks would stop buying programs from independent studios, Warner Bros. Television and Paramount Television each decided to start their own networks.
The WB and UPN both launched within one week of each other in January 1995, just as the Fox Broadcasting Company had started to secure a foothold with American television audiences. The two networks launched to limited fanfare and generally mediocre to poor results. However, over the subsequent 11+1⁄2 seasons, both were able to air several series that became quite popular (such as Buffy the Vampire Slayer, Star Trek: Voyager, The Sentinel, 7th Heaven, Dawson's Creek, Charmed, Smallville, Everwood, Gilmore Girls, Reba, The Steve Harvey Show, and America's Next Top Model).
Although their simultaneous starts and competition for affiliate stations caused the two networks to appear as rivals, by 1999, they had differing strategies: The WB targeted young women, and UPN young men. Towards the end of their first decade on the air, the WB and UPN were in decline, unable to reach the audience share or have the effect that Fox had gained within its first decade, much less than that of the Big Three networks (ABC, CBS, and NBC). In the eleven years that UPN and the WB were in operation, the two networks lost a combined $2 billion. Chris-Craft Industries, Viacom, and Time Warner officials had discussed a possible merger of UPN and the WB as early as September 1995, only eight months after their respective launches; however, discussions ultimately broke down over issues on how to combine Chris-Craft and Tribune Broadcasting's station interests in the proposal to merge the networks, since the two companies' station portfolios overlapped with one another in several major markets. By 2003, however, Time Warner became mired in several debt problems. The company had already been responsible for shutting down Warner Bros.' in-house animation department and for selling off major portions of the conglomerate, such as the 2004 sale of Warner Bros. Records and the rest of Warner Music Group to an investor group led by Edgar Bronfman Jr. and Thomas H. Lee Partners.
Executives from CBS and Warner Bros. announced on January 24, 2006 that they would respectively shut down UPN and the WB; they would combine resources to form a new broadcast network, to be known as The CW Television Network. They confirmed that the network would – at the outset – feature programming from both of its predecessors-to-be as well as new content developed specifically for the new network. Warners and CBS expected to produce inexpensive shows for the network, which they could sell outside the US. Then CBS chairman Les Moonves explained that the name of the new network was formed from the first letters of CBS and Warner Bros, joking, "We couldn't call it the WC for obvious reasons." Although some executives reportedly disliked the new name, Moonves stated in March 2006 that there was "zero chance" the name would change, citing research claiming 48 percent of the target demographic were already aware of the "CW" name.
In May 2006, The CW announced that it would pick up a combined thirteen programs from its two predecessors to air as part of the network's inaugural fall schedule: seven series held over from the WB (7th Heaven, Beauty and the Geek, Gilmore Girls, One Tree Hill, Reba, Smallville and Supernatural) and six held over from UPN (America's Next Top Model, Veronica Mars, Everybody Hates Chris, Girlfriends, All of Us and WWE SmackDown!). Upon the network's launch, the CW chose to use the scheduling model utilized by the WB due in part to the fact that it had a more extensive base programming schedule than UPN, allowing for a larger total of weekly programming hours for the new network to fill. (The WB carried 30 hours of programming each week because it had a children's program block and a daytime lineup that UPN did not offer; UPN was primarily a prime time-only network with 10 weekly hours of network programming at the time of the network's shutdown.)
=== 2006–2011: Launch and early struggles ===
Like both UPN and the WB, The CW targets its programming towards younger audiences. CBS and Time Warner hoped that combining their networks' schedules and affiliate lineups would strengthen The CW into a fifth "major" broadcast network. One week before the network's official launch, on September 11, 2006, a new, full version of the network website was launched, the website began to feature more in-depth information about The CW's shows.
The CW launched with a premiere special / launch party from the CBS Paramount-produced Entertainment Tonight at Warner Bros. Studios in Burbank, California on September 18, 2006, after a repeat of the tenth-season finale of 7th Heaven; the same schedule was repeated on September 19, 2006, with the sixth-season finale of Gilmore Girls. The network continued to air season finales from the previous season through the remainder of the first week, except for America's Next Top Model and WWE SmackDown!, which respectively began their new seasons on September 20, 2006, and September 22, 2006, with two-hour premieres. When Top Model made its network premiere on September 20, 2006, The CW scored a 3.4 rating/5 share (with hourly ratings of 3.1/5 and 3.6/6, The CW placed fifth overall) in the Nielsen household ratings. It scored a 2.6 rating among adults 18–49, finishing fourth in that age demographic and beating the 2.2 rating earned by Fox on that night. The network's second week consisted of season and series premieres for all of its other series from September 25, 2006, to October 1, 2006, with the exception of Veronica Mars, which debuted its third season on October 3, 2006.
Despite having several of the most popular programs carried over from UPN and the WB as part of its schedule, The CW – even though it experienced some success with newer programs that launched in subsequent seasons which became modest hits – largely struggled to gain an audience foothold throughout its first five years on the air. Because of declining viewership for the network during the 2007–08 season and effects from the Writers Guild of America strike, the network announced on March 4, 2008, that it would eliminate its comedy department (dismissing executive vice president of comedy Kim Fleary and senior vice president of comedy Steve Veisel), while also combining its drama and current programming departments into a single scripted programming unit. The corporate restructuring resulted in the layoffs of approximately 25 to 30 employees. It also included the elimination of certain positions, other newly opened positions being left unfilled, and layoffs from the Kids' WB unit, as the block was set to be replaced by the CW4Kids.
On May 9, 2008, The CW announced that it would lease its Sunday lineup (then running from 5:00 p.m. to 10:00 p.m. Eastern and Pacific Time) to production company Media Rights Capital (MRC). As Sundays have historically been a low-rated night for the network during its first two seasons on the air (due to stiff competition from CBS, ABC, and Fox's strong Sunday lineups, and complicated further by NBC's acquisition of Sunday Night Football in September 2006, shortly before The CW debuted), the move allowed The CW to concentrate on its Monday through Friday prime time schedule, while giving MRC the right to develop and schedule programs of its own choosing and reap advertising revenue generated by the lineup. The Sunday series that were scheduled – two reality series (4Real and In Harm's Way) and two scripted series (romantic dramedy Valentine and drama Easy Money) – performed poorly in the ratings (averaging only 1.04 million viewers), prompting the CW to scrap its agreement with MRC and program Sunday nights on its own starting on November 30, 2008. With no first-run programming available to run on Sundays as a backup, the network added reruns of The Drew Carey Show and Jericho, and movies to replace the MRC-produced programs.
One of the shows carried over to the network from UPN, WWE SmackDown, ended its run on The CW after the September 26, 2008, episode due to negotiations ending between the WWE and The CW on renewing the program. Representatives for The CW later confirmed that it had chosen not to continue carrying SmackDown because the network had redefined its target audience as exclusively females 18 to 34 years old, whereas SmackDown targeted a predominantly male audience. Following SmackDown's move to MyNetworkTV that same season, the Fox-owned network (which launched the same month as The CW's debut, albeit two weeks earlier, on September 5, 2006) began beating The CW in the Friday ratings every week from that program's debut on the network, though The CW continued to beat MyNetworkTV overall.
The CW generally struggled in the Nielsen ratings from its inception, primarily placing fifth in all statistics tabulated by Nielsen (total audience viewership and demographic ratings). On several occasions, The CW was even outrated by the Spanish language network Univision. This led to speculation within the industry (including a May 16, 2008, article in The Wall Street Journal) that CBS, Time Warner or both companies might abandon the venture if ratings did not improve. However, The CW's fortunes were buoyed in the 2008–09 and 2009–10 television seasons thanks to increased ratings among females in the 18–34 demographic and the buzz that some of its newer series (such as Gossip Girl, 90210 and The Vampire Diaries) had generated with audiences. Executives with CBS Corporation and Time Warner also emphasized their commitment to the network.
On May 5, 2009, The CW announced that it would give the five hours of network time on Sundays back to its affiliated stations that fall, effectively becoming a weeknight-only network in prime time, in addition to The CW Daytime and The CW4Kids blocks (the latter block, airing on Saturday mornings, would remain the only weekend programming supplied by the network). This change meant the Sunday late afternoon repeat block that The CW inherited from the WB (formerly branded by that network as "EasyView") was discontinued. Subsequently, in mid-May, 65 percent of The CW's affiliates, including those carrying The CW Plus, signed agreements to air the replacement MGM Showcase movie package on Sundays.
=== 2011–2016: New leadership and content shift ===
On April 28, 2011, Mark Pedowitz was appointed by the network to succeed original president of entertainment Dawn Ostroff; Pedowitz was made the network's first president and assumed broader responsibilities in The CW's business operations than Ostroff had. As president of entertainment, Ostroff oversaw entertainment operations while John Maatta, the network's chief operating officer, handled business affairs; both reported to a board composed of CBS and Warner Bros. executives. Maatta began reporting to Pedowitz as a result of the latter's appointment as network president. Pedowitz revealed that the core target demographic of the network would not change, though The CW would attempt to lure new viewers. Pedowitz began looking to bring comedies back to The CW after Ostroff had publicly declared that the difficulty of developing comedies for its target demographic was the reason for their removal from the network following the 2008–09 season (with Everybody Hates Chris, and The Game – a spin-off of Girlfriends – becoming the last comedies to be cancelled). The network also ordered more episodes of its original series and ran them consecutively starting on September 12 through the first week of December without repeats. In July 2012, Pedowitz no longer referred to the target demographic of The CW as women 18–34, but rather that it would now be an "18–34 adult network".
Although the network was still not profitable, CBS and Warner Bros. were very successful in selling their CW shows overseas. In 2011, a $1 billion deal with streaming service Netflix became another way to sell CW shows. The introduction of action-superhero series Arrow, based on DC Comics' Green Arrow, received favorable reviews from critics and became a hit with audiences when it premiered. As evidence of the network's refocusing toward a broader audience, Arrow not only premiered to some of the highest viewership totals in the network's history (the third-highest overall as of 2015, behind the series premieres of The Vampire Diaries and The Flash), but it also gave the network its strongest performance in the demographic of males 18–34 since Smallville ended its run in May 2011. The network also found success with its summer programming in 2013 with the revival of the U.S. version of the improv comedy series Whose Line Is It Anyway?, which later became a year-round staple on the network's schedule. Arrow continued to perform strongly, leading to a spin-off with The Flash, which surpassed The Vampire Diaries as the highest-rated premiere in the network's history and became the most-watched show on the network. Jane the Virgin earned some of the highest critical praise of any series during the 2014–15 television season, and became the first CW series ever to be nominated for, and win, a Golden Globe Award, with lead actress Gina Rodriguez winning the Golden Globe for Best Actress - Television Series Musical or Comedy. Other CW shows like The Flash, The 100, and Nikita would also go on to be nominated for Primetime Emmy Awards categories, and several shows from 2011 to 2019 being nominated for categories in the Teen Choice Awards, Saturn Awards, and others.
Overall, the network ended the 2014–15 season posting its highest average total viewership in a single television season since 2007–08 with 2.15 million viewers, a 12 percent increase in total viewership year-to-year; The CW also posted its highest seasonal demographic ratings among males ages 18–49 with a 0.8 share.
Expanding on the success of the network's Arrowverse franchise, DC's Legends of Tomorrow premiered to high ratings for the network and became the most-watched show on the network's Thursday night block in two years. The 2015–16 season also saw Crazy Ex-Girlfriend become one of the most critically acclaimed shows of the season and the second show on the network to be nominated for, and win, a Golden Globe Award, with actress Rachel Bloom winning a Golden Globe Award for Best Actress - Television Series Musical or Comedy.
=== 2016–2021: Streaming era deals ===
The network's Arrowverse expanded again with Supergirl being moved to the network from CBS for its second season. The debut of Archie Comics-based Riverdale signaled the network's foray into mining their parent studio's library of IP to create new television series based on recognizable properties. This led to another new DC Comics series, Black Lightning, and a rebooted Dynasty. While it met with poor ratings, Dynasty proved lucrative thanks to the Netflix output deal and international syndication, which earned CBS Studios millions of dollars per episode.
Selling CW series like Dynasty to Netflix and overseas markets was so profitable for Warner Bros. and CBS that the network almost stopped cancelling shows, and expanded its broadcast schedule. On February 14, 2018, The CW announced that it would add a 2-hour primetime block on Sunday nights beginning in the fourth quarter of 2018 (it later added a third hour in October 2023), returning the network to Sundays for the first time since the lease to Media Rights Capital ended in 2009, as well as expanding The CW's primetime slate from 10 hours a week to 12. Discussions with CBS and Warner Bros. about the expansion began as early as July 2017; both gave their approval to the move that December, with the network reaching clearance deals with key affiliate partners in early 2018.
On June 12, 2018, AT&T received antitrust approval to acquire Warner Bros. parent Time Warner, with the acquisition closing two days later. Time Warner was renamed WarnerMedia and AT&T became a co-owner of The CW with CBS.
The CW debuted reboots of Charmed, Roswell, and Originals spin-off Legacies during the 2018–19 season. Despite modest ratings, their renewals – along with the renewal of the entire 2018–19 lineup (absent those series already previously announced as ending) – reflected their value to the network's founding co-owners CBS and Warner Bros., which received the windfall of selling them to Netflix and international buyers. This strategy continued with the 2019–20 season debuts of the new Arrowverse series Batwoman, Riverdale spin-off Katy Keene, and Nancy Drew.
On August 13, 2019, CBS and Viacom officially announced their intention to re-merge, with the combined company to be named ViacomCBS. The merger was completed on December 4, 2019, making them officially with AT&T's WarnerMedia co-owners of The CW.
WarnerMedia and ViacomCBS did not renew CW's Netflix deal in 2019, intending to use their shows on the network for their own streaming services. International sales also mostly ended, because both companies wanted to retain rights to their own shows to compete with Netflix outside the United States. WarnerMedia's HBO Max streaming service subsequently acquired exclusive streaming rights to Warner Bros.-produced CW shows. This began with the 2019–20 season, with the Warner Bros.-produced Batwoman and Katy Keene debuting on HBO Max after their current seasons finished airing on The CW. The CBS Studios-produced Nancy Drew was originally announced to be heading to corporate-sibling owned CBS All Access, but appeared on HBO Max instead. The reason for this was amid the rebranding of CBS All Access to Paramount+ and the changes surrounding the ViacomCBS merger, CBS and Warner Bros. made the collective decision to have all CW shows have a singular streaming home on HBO Max.
Beyond being the streaming home of CW programming, HBO Max shares a co-ownership connection with the network which allows for programming partnerships. This began with DC Comics series Stargirl, which The CW shared with DC Universe. DC Universe and The CW co-financed the series, with episodes premiering on DC Universe and airing the next day on The CW. After DC Universe was folded into HBO Max, Stargirl was renewed with a new co-finance deal in which The CW receives first-run airings followed by its launch on HBO Max. Going forward, The CW and HBO Max will continue to collaborate on potentially co-financing new projects, with the model of premiering first on HBO Max and a second run on The CW. "They creatively have to want the show too and believe that the show should go on their platform first for them to work," CW CEO Pedowitz said. "For us its a great model because it's a way to get excellent summer scripted programming and maximize programming across platforms."
On May 13, 2021, The CW announced that it would begin programming Saturday nights on a regular basis beginning in the 2021–22 television season, following approval of the expansion by the network's key affiliate groups. As part of the deal, The CW ceased programming The CW Daytime block and returned the time to its stations. With the addition of Saturday nights, The CW has programming on every night of the week for the first time in the network's history, becoming only the sixth American English-language commercial broadcast network ever and the first since Fox to have offered prime time content on a nightly basis.
=== 2022: Acquisition by Nexstar ===
On January 5, 2022, The Wall Street Journal reported that WarnerMedia and ViacomCBS were exploring a possible sale of either a majority stake or all of The CW, and that Nexstar Media Group, which became The CW's largest affiliate group when it acquired former WB-era network co-owner Tribune Broadcasting in 2019, was considered a leading bidder. Network president and CEO Mark Pedowitz confirmed talks of a potential sale but added that it was "too early to speculate what might happen". Nexstar CEO Perry Sook in Spring 2022 did not confirm the rumored buyout but stated that he would not be surprised if Nexstar owned a broadcast network.
In May 2022, three months before Nexstar made their purchase official, The CW cancelled ten shows, three times the average number per year that The CW had canceled over the previous decade, including one-season shows 4400 and Naomi, and longtime fixtures including Dynasty, Legends of Tomorrow, Roswell, New Mexico, and Legacies. More shows were cancelled or given final season orders in the following months including Nancy Drew, Stargirl, The Flash, and Riverdale.
In late June 2022, The Wall Street Journal indicated a purchase of The CW by Nexstar was close, and on August 15 Nexstar confirmed it had "entered into a definitive agreement" to acquire a 75% majority share in the network; the remaining 25% would be shared equally by Paramount Global (the former ViacomCBS) and Warner Bros. Discovery (the company formed by Discovery, Inc.'s acquisition of WarnerMedia from AT&T). Additionally, Nexstar stated that Mark Pedowitz would remain the chairman and CEO of The CW. Though no monetary terms were announced, Nexstar reportedly would not pay any cash or stock up front, and would absorb approximately $100 million of network debt. The Hollywood Reporter stated that Nexstar retained $54 million based on its cash on hand, accounts receivable, accounts payable and other liabilities. As the sale did not entail the transfer of any FCC broadcast licenses, Nexstar immediately took operational control of the network.
Nexstar, in a conference call that took place the day its purchase was announced, indicated a desire to run The CW cost-consciously. Citing research that indicated the network spends "almost twice" the amount other broadcast networks spend on programming, a partial reason for the May 2022 cancellations, Nexstar stated that it planned to seek shows with smaller production budgets and/or a reasonably-priced acquisition fee, including unscripted fare, syndicated content, and other content that can create profits through broadcast airings. Nexstar also stated that it aimed for The CW to turn a profit by 2025.
In the conference call, Nexstar indicated that it wanted to convert The CW into a network with broad appeal. It cited data indicating that the young audience which The CW focused upon preferred watching its shows through streaming platforms instead of during live broadcasts, while the average audience of a broadcast CW affiliate was approximately 58 years old. Nexstar indicated that it would focus on the older audiences as well and not just the younger demographic. In particular, Nexstar was reported to have been seeking older-skewing dramas, police procedurals, and sitcoms.
Paramount Global and Warner Bros. Discovery would still produce content for The CW as primary content suppliers, though Nexstar noted that the arrangement would be primarily for the 2022–23 broadcast season. It indicated that it "will have the option to extend the partnership" with Paramount and WBD beyond that season. Nexstar stated in September 2022 that it would seek to supplement The CW's content by acquiring projects from studios beyond solely Paramount and WBD. while any The CW content not licensed to other streaming services would continue to appear on its own streaming platform CW Seed.
On October 3, Nexstar officially announced that it had closed the deal to acquire the majority ownership of The CW. Longtime chairman and CEO Mark Pedowitz resigned from his role, with Dennis Miller taking over as the president of The CW. Rick Haskins, The CW's chief branding officer and president of the network's streaming division, as well as chief financial officer Mitch Nedick were let go on the same day. Thirty to forty employees were laid off on November 1, including several executives. Longtime executive Paul Hewitt was replaced with Beth Feldman as the senior vice president of the network's communications unit. On the following day, Brad Schwartz was appointed as the president for the entertainment division, overseeing programming strategy, creative and brand development, and day-to-day operations.
On November 8, Nexstar announced that the carryover programming from the former majority parent companies of The CW, Paramount and WBD, would be minimal by the 2023–24 season.
=== 2023–present: Focus on linear and sports ===
On February 1, 2023, The CW appointed Heather Olander as the head of unscripted programming, a position under which she reports to Schwartz. In a shift away from scripted programming, it also let go of Executive VP for Current Programming Michael Roberts, and Executive VP for Development Gaye Hirsch, among other layoffs on the following day. The CW appointed Chris Spadaccini as the chief marketing officer on February 6, 2023, and Tom Martin as the head of business affairs and general counsel on February 9, 2023. It later appointed Betzy Slenzak as the vice president of unscripted programming on March 30, 2023, and Ashley Hovey as the network's first chief digital officer on April 11, 2023.
On May 18, 2023, The CW unveiled its schedule for the 2023–24 broadcast season, consisting mostly of acquired shows from outside the United States, and unscripted series. Schwartz criticized the previous co-owners of the network, stating that it would no longer exist for benefiting them, and that the shows left over from the previous regimes did not perform well on linear broadcast. He added that in order to achieve profitability, The CW was focusing on acquired shows and co-productions while expanding its audience. He also revealed that the network was in production or negotiations for a total of 72 shows.
On February 25, 2023, CW Sports was launched by acquiring the rights to LIV Golf and soon expanded by acquiring ACC college football and basketball games, Inside the NFL, the NASCAR Xfinity Series, and WWE NXT. In August 2023, Schwartz stated that the network was involved in many upcoming US-produced scripted shows and will focus on getting monetization rights on any scripted content it broadcasts, while producing shows at a profitable price point. He also stated that they were using sports programming for bringing in new and older audiences. Nexstar CEO Perry Sook later stated that, beyond causing the delay of four scripted shows, the 2023 Writers Guild of America and SAG-AFTRA strikes did not have much impact on The CW's fall schedule, adding that they would not affect the network's future progress.
In January 2024, during the 29th Critics' Choice Awards, The CW launched a new brand identity by DixonBaxi—which updated the logo with a bolder appearance, changed the network's main color from green to red-orange, and introduced a new "stage" device used in promos (formed by extending the C lettering from the logo), as well as a new sound trademark of a struck match. Spadaccini explained that the rebranding was intended to help make the network's brand more consistent and optimized for digital platforms, the word "The" was removed from the logo to streamline its appearance (especially in use cases such as "CW Original" or "CW Sports"). Spadaccini said that the network's name and verbal branding would remain "The CW.”
The CW unveiled its fall schedule for the 2024–25 broadcast season in May 2024, with programming consisting of co-produced scripted series, game shows, unscripted series, and an expansion of CW Sports. Three of its four remaining pre-Nexstar scripted series, Superman & Lois, All American: Homecoming, and Walker, would conclude that year, leaving All American as the sole remaining legacy series to continue beyond the 2023-24 season. Miller and Schwartz revealed that the network planned to air its own television films later in 2024, with Miller adding that they planned to do more deals for sports programming. The CW's losses meanwhile declined by $50 million for the first quarter of 2024, compared to the $100 million loss during the quarter when Nexstar acquired it. In June 2024, Schwartz stated that he hoped to have more scripted series on air, but their new financial model necessitated finding production partners. CW Studios was launched in August 2024 after The CW pulled The Librarians: The Next Chapter from their fall schedule and sold the series to TNT. The CW retained a stake in the series through the newly formed studio, providing the network with an in-house production arm.
Miller departed as president of The CW in October 2024, with Brad Schwartz being promoted to fill the role. In November 2024, Nexstar reported that The CW had reduced its operating losses by $119 million year-to-date, exceeding the goal of $100 million for the year. Nexstar executives attributed this to lower cost programming and credited the growing CW Sports portfolio for increasing the network's viewership. The CW underwent a round of layoffs later in the same month to streamline the network's focus on sports and unscripted programming, with Liz Wise Lyall, head of the scripted programming department, and Betsy Slenzak, vice president of the unscripted programming department, exiting.
Michael Perman was appointed as the Senior Vice President of CW Sports in February 2025, overseeing programming and media rights for the division. Nexstar President and COO Mike Biard stated later in the same month that the sports portfolio would account for 40% of the programming of The CW in 2025 and the network would become profitable by 2026. By the end of the fiscal year 2024-25, The CW had reduced its year-over-year losses by $126 million.
== Programming ==
=== Network programming and scheduling ===
As of October 1, 2023, The CW provides 18 hours of regularly scheduled network programming each week, over the course of seven days. The network offers 15 hours of prime time programming to its owned-and-operated and affiliated stations, airing from 8:00 p.m. to 10:00 p.m. Eastern and Pacific Time on Monday through Saturday nights and 7:00 p.m. to 10:00 p.m. (Eastern and Pacific) on Sunday nights. Outside of prime time, a three-hour educational programming block called "One Magnificent Morning" (which airs as part of The CW schedule through a time-lease agreement with Hearst Media Production Group) airs on Saturday mornings from 8:00 a.m. to 11:00 a.m. in all time zones, subject to reschedulings due to local or CW sports broadcasts.
Similar to Fox, along with network forerunners the WB and UPN, The CW uses the "common prime" scheduling practice, avoiding the 10:00 p.m. (Eastern and Pacific) hour broadcast by the "Big Three" networks (NBC, CBS, and ABC). The network, unlike the Big Three, does not air any national newscasts, late-night programming, and, since 2021, daytime programming. It also did not run prime-time programming on Saturday nights and during the primetime access hour on Sundays until the 2021–22 and 2023–24 broadcast seasons respectively. Because of these factors, The CW's affiliates handle the responsibility of programming non-network time periods, with the majority of its stations filling those slots mainly with syndicated programming. However, some of the network's affiliates broadcast their own local news and/or sports programs (either produced by the station itself or through outsourcing agreements with an affiliate of another network), preempting network prime time programming to a specific time period (New York City affiliate WPIX, for instance, preempts CW prime time to the afternoon hours).
The Hearst-produced Saturday morning block, One Magnificent Morning (which is subject to scheduling variances similar to the weekday hour in some markets, such as in Atlanta and San Diego), is designed to be tape delayed and therefore recommended to air in the same time slot in all time zones. However, it is broadcast one hour earlier on affiliates of The CW Plus in the Central, Mountain and Alaska Time Zones. In Guam, CW Plus affiliate KTKB-LD in Hagåtña airs The CW lineup on a one-day tape delay from its initial broadcast because of the time difference between Guam and the continental United States as the island is on the west side of the International Date Line.
Supernatural (which initially aired on the WB) was the final CW series carried over from either of the network's respective predecessors that continued to be broadcast, airing its final episode in November 2020.
The CW formerly aired short segments during commercial breaks within certain episodes of its programs known as "Content Wraps" – a play on the network's name – to advertise one company's product during part or the entirety of a commercial break, a concept since classified under the term of native advertising. The entertainment magazine series CW Now was inspired in part by the success of the Content Wraps as it was intended to be a series with product placement; the program was canceled in 2008, after a single 23-episode season. For the 2006–07 season, The CW reached an agreement with American Eagle Outfitters to incorporate tie-ins with the company's aerie clothing line as part of the Content Wrap concept within the network's Tuesday night schedule, which included subjects in the commercials commenting on plot points in each of the shows. The agreement was cut down to regular advertising in February 2007, after a fan backlash by viewers of both shows and general criticism of the campaign.
=== News programming ===
Prior to Nexstar ownership, the network did not produce national news content. However, on December 6, 2023, The CW simulcast new sister network NewsNation's coverage of the fourth 2024 Republican Party presidential debate. The debate marked the first national news program aired on the network under Nexstar ownership. The partnership drew a combined 4 million viewers.
As part of the company's efforts to expand its linear reach and the success between The CW and NewsNation's airing of one the GOP primary debates, Nexstar began distributing a Sunday morning talk show in a collaboration between The CW, NewsNation and The Hill. CW president of entertainment Brad Schwartz said that the show would have both CW and The Hill branding. It was announced that Chris Stirewalt would anchor a new political Sunday show called The Hill Sunday; the program, which NewsNation launched on March 3, 2024, began airing on The CW on April 7, 2024. The CW also aired NewsNation's 2024 United States presidential election night coverage along with a 2025 town hall with President Donald Trump hosted by Chris Cuomo.
Most of The CW's affiliates do not have autonomous news operations. The network has six affiliates that produce their own local news programming, which were all carry-overs from previous affiliations: WPIX in New York City, WGN in Chicago, and KTLA in Los Angeles started their news departments as independent stations and/or during early affiliations with other networks including DuMont (KTLA) and CBS (WGN); WCCB in Charlotte, North Carolina, started its news operation as a Fox affiliate in 2000, and had also aired local newscasts when it was an ABC affiliate from 1967 to 1978; WISH-TV in Indianapolis (formerly CBS) has been airing local news since 1956, and KRON-TV in San Francisco (formerly NBC and MyNetworkTV) has produced local news since 1957. KTLA has the largest number of weekly hours devoted to local news programming of any CW affiliate, and any broadcast television station in the United States, with 94+3⁄4 hours of scheduled news each week.
Other CW-affiliated stations maintained in-house news operations, but have since disaffiliated from the network or discontinued in-house production. One example of this is WGN-TV in Chicago, who maintains a news department since it launched as a CBS affiliate in 1948; the station transitioned into a news-intensive outlet during its tenures with The WB and The CW, and retained a news-heavy format after disaffiliating from the network for eight years beginning in September 2016. Another one is KCWI-TV in Des Moines, Iowa; the station broadcasts a morning news and talk program, which transitioned from an in-house production to a brand extension during Good Morning America of ABC affiliate WOI-DT's morning newscast on April 11, 2016, as a result of Nexstar's acquisition of KCWI.
News programming on CW affiliates – if the station carries any – is often outsourced to another major network affiliate in the market, especially if they are operated as part of a duopoly or management agreement, such as Nexstar's respective CW-Fox duopolies of KWGN-TV/KDVR in Denver and KPLR-TV/KTVI in St. Louis; and CW affiliate WTVW and ABC affiliate WEHT in Evansville, Indiana (a de facto duopoly formed through Nexstar's 2011 purchase of WEHT and trade of WTVW to partner group Mission Broadcasting). WPHL-TV in Philadelphia began producing its own morning news show on March 9, 2015, while continuing to air a prime time newscast produced by ABC O&O WPVI-TV, which launched on September 15, 2012 (WPHL also ran its own news department as a WB affiliate from 1996 to the end of 2005).
The scheduling of news programming on The CW's affiliates often mirrors that of Fox stations, with morning newscasts designed to compete with the national morning shows on ABC, CBS and NBC in the 7:00 a.m.–9:00 a.m. time slot (in duopolies, these are typically an extension of a sister station's morning newscast) and a prime time newscast within the 10:00 p.m.–11:00 p.m. Eastern/Pacific (9:00 p.m.–10:00 p.m. Central/Mountain) time slot, though some may only air for 35 minutes to match up with network late night schedules. Rarely (but more common on the few major-market CW affiliates with in-house news departments), they may also include midday and/or early evening newscasts, including the network newscast slot of 6:30 p.m. ET/5:30 p.m. CT.
=== Sports programming ===
The CW agreed to a three-year broadcast deal in January 2023 with LIV Golf, a professional golf tour financed by Saudi Arabia's Public Investment Fund, marking the first-ever national sports broadcasting contract for both the network and the tour. On February 14, 2023, the network said their LIV Golf coverage would be available in 100 percent of media markets in the United States, but encountered numerous affiliates that declined carriage of the tour, including all eight owned by Paramount Global. Consequently, LIV coverage in those affected markets aired on Nexstar-owned stations or subchannels, or on other stations via secondary affiliation agreements. Both the network and Nexstar were criticized by the National Press Club for participating in alleged sportswashing by the Saudi government following the assassination of journalist Jamal Khashoggi in 2018.
The CW announced on July 13 that it had acquired the exclusive broadcast rights to 50 Atlantic Coast Conference (ACC) college football and basketball games each season through 2026–27, with Raycom Sports producing the broadcasts.
On July 28, The CW announced it had picked up the media rights to the NASCAR Xfinity Series in a seven-year deal starting in 2025 and going through the 2031 season. The CW will broadcast 33 races annually, along with practice and qualifying events. NASCAR Productions will produce the broadcasts. On April 11, 2024, it was announced that the deal's start was pushed up to September 2024, beginning with the 26th race of the season and regular season finale, the Food City 300.
On November 7, 2023, it was announced that WWE NXT would be moving to The CW from USA Network in a five-year deal that began in October 2024. This marked the first time that WWE programming aired on The CW since 2013, when Saturday Morning Slam aired on the defunct Vortexx children's programming block; The CW aired SmackDown! from the network's launch to 2008.
The CW and Range Sports announced an agreement in January 2024 under which Range Sports would develop content in conjunction with Nexstar and CW Sports, in addition to assisting The CW with talent representation, brand consulting, data and analytics and provide production capabilities for scripted and unscripted programs by utilizing the resources of its parent company Range Media Partners.
The CW in May 2024 gained rights for broadcasting eleven Pac-12 football games featuring Oregon State University and Washington State University football teams for the 2024 season. In April 2025, it gained the rights for broadcasting all thirteen games of the 2025 Pac-12 football season featuring Oregon State University and Washington State University football teams.
In August 2024, The CW acquired rights to air the 2024 Chicago Open Men's and Women's finals from the Association of Volleyball Professionals (AVP). In March 2025, the AVP renewed its agreement with The CW for multi-year rights to broadcast its volleyball matches from across the United States on Saturday nights, from Memorial Day till Labor Day.
In April 2025, The CW and the Professional Bowlers Association (PBA) reached a two-year media rights agreement, which was negotiated in cooperation with the IMG, to broadcast ten PBA events.
Outside of network programming, several CW affiliates have carried telecasts of basketball, football and in some cases, other collegiate sporting events (such as baseball or hockey) that are produced by syndicators, while a few carry games from local teams of major professional sports leagues such as Major League Baseball (the New York Mets on WPIX) and the NBA (the Los Angeles Clippers on KTLA).
=== Children's programming ===
On September 23, 2006, the Kids' WB children's programming block – which originated on The WB in September 1995 and continued to be produced by Warner Bros. – was carried over to The CW as part of its inaugural programming lineup; although the network on which it originated ceased operations, the "Kids' WB" branding was retained for the block.
On October 2, 2007, through a joint decision between corporate parents Warner Bros. and CBS Corporation, The CW announced that it would shut down Kids' WB and lease the programming rights of the Saturday morning timeslots to 4Kids Entertainment (which was producing a competing children's programming block, 4Kids TV, for Fox at the time of the announcement). The CW cited competition from children's cable networks and a challenging advertising marketplace as factors in the decision. Kids' WB ended its nearly thirteen year-old run on May 17, 2008 (though some CW affiliates that delayed the block to Sundays, such as Atlanta affiliate WUPA, aired the block for the last time on May 18).
The following week on May 24, 4Kids Entertainment took over programming of The CW's Saturday morning timeslots, with the debut of a new block called The CW4Kids. The block's lineup initially consisted mostly of programs carried over from Kids' WB and 4Kids TV, before eventually adding first-run 4Kids-produced shows such as Chaotic as well as new seasons of Yu-Gi-Oh! and Teenage Mutant Ninja Turtles. The block was rebranded to Toonzai on August 14, 2010 (though The CW4Kids name was retained as a sub-brand to fulfill branding obligations with the network). Toonzai ended its run on August 18, 2012, after 4Kids Entertainment auctioned off their assets in bankruptcy court.
On July 3, 2012, Saban Brands announced that they had acquired the rights to program The CW's Saturday morning timeslots from 4Kids Entertainment in bankruptcy proceedings. The block was relaunched as Vortexx on August 25, featuring programs produced by Saban Brands such as Power Rangers Lost Galaxy and Digimon Fusion. Vortexx also aired notable third-party programming such as WWE Saturday Morning Slam, which marked the return of WWE programming to the network since WWE Smackdown departed in 2008.
On June 5, 2014, The CW announced an agreement with Litton Entertainment (now known as Hearst Media Production Group) to program a block of live-action series designed to comply with the FCC's educational programming guidelines. Vortexx (which was the last remaining non-educational children's block on the major U.S. broadcast networks) was replaced by One Magnificent Morning on October 4. The block features a mix of wildlife and lifestyle-themed programs, similar to those featured on the Litton-produced blocks aired by ABC and CBS. On January 7, 2016, The CW and Litton announced a five-year renewal for the block, extending it through the 2020–21 broadcast season. Starting with the 2017–18 broadcast season, the block's running time was reduced to three hours. On July 1, 2021, The CW and Litton announced another multi-year extension for the block.
== Stations ==
The CW has 46 stations owned and/or operated by its majority owner Nexstar Media Group, and current and pending affiliation agreements with 221 additional television stations encompassing 50 states, the District of Columbia and three U.S. possessions. Counting only conventional CW affiliates and over-the-air affiliates of The CW Plus, the network has an estimated combined national reach of 100-percent of all households in the United States (or 330,866,316 Americans with at least one television set); this makes The CW the largest U.S. broadcast network by population reach percentage. As of January 2023, three U.S. states (Delaware, New Hampshire, and New Jersey) and three U.S. territories (American Samoa, Puerto Rico and the United States Virgin Islands) do not have their own locally licensed CW affiliates, largely because those areas are either located within the broadcast ranges of stations in nearby states or served by out-of-market stations via cable or satellite. Delaware is served by Philadelphia's WPHL-TV and Salisbury, Maryland affiliate WMDT-DT2, while New Hampshire is served by four CW stations based in three neighboring states (including Boston affiliate WLVI). New Jersey is served by WPHL and New York City affiliate WPIX.
As a newer broadcast network, The CW maintains affiliations with low-power stations (broadcasting either in analog or digital) in a few markets, such as Boise, Idaho (KYUU-LD). In some markets, including both of those mentioned, these stations also maintain digital simulcasts on a subchannel of a co-owned/co-managed full-power television station. The CW also maintains a sizeable number of subchannel-only affiliations, the majority of which are with stations in cities located outside of the 50 largest Nielsen-designated markets and receive the network's programming via The CW Plus; the largest subchannel-only CW affiliate by market size, as of February 1, 2024, is WZTV-DT2 in Nashville, Tennessee.
Nexstar Media Group is the largest operator of CW stations by numerical total, owning or providing services to 41 CW-affiliated stations, and also is the largest in terms of overall market reach, owning or providing services to CW stations (including its largest affiliates in New York and Los Angeles), covering 32 percent of the U.S.
=== Digital multicasting and cable television ===
Unlike the other major networks, The CW distributes its programming in small and certain mid-sized markets throughout the United States (generally those ranked among the bottom 110 Nielsen media markets) through The CW Plus, a separate national feed and programming service that is carried on a mixture of full-power and low-power stations in some markets, and cable-only outlets and digital subchannel affiliations on major network stations in markets that do not have enough commercial stations to support a standalone CW affiliate (several of The CW Plus's digital subchannel outlets originally operated as cable-only affiliates at the network's launch). The programming service offers its own master schedule of syndicated and brokered programming acquired by the network (including some feature films and infomercials) during non-network programming hours, although some CW Plus affiliates may also run local newscasts produced by a major network affiliate.
CW predecessor the WB previously had two cable-only affiliate outlets: WGN America, the national superstation feed of WGN-TV at the time, from January 1995 to October 1999 and network-operated the WB 100+ Station Group (the direct predecessor to The CW Plus), which was formed in September 1998 and had several of its cable-only outlets join The CW Plus at The CW network's launch. Not all of the network's cable-only affiliates were CW Plus outlets; WT05 in Toledo, Ohio offered its own schedule of syndicated programs during non-network hours that was programmed by its then-owner Block Communications, which also operates that market's major cable provider Buckeye CableSystem (WT05 now exists as "CW13", having been converted into a digital subchannel of Gray Television-owned ABC affiliate WTVG in October 2014). Though The CW is the only network with a station group that includes cable-only outlets, it is actually one of only three networks that have had cable-only stations within its affiliate body (ABC formerly had a cable-only affiliate in Winchester, Virginia-based TV3 Winchester until Gray shut the channel down in December 2013).
=== Affiliate issues ===
==== Problems with Time Warner Cable ====
Some Time Warner Cable subscribers around the country were unable to watch CW programming when the network debuted, as stations in several markets were not able to reach carriage deals with the provider to distribute the local affiliates. In markets like Charleston, South Carolina; El Paso, Texas; Honolulu, Hawaii; Palm Springs, California; Beaumont; Waco and Corpus Christi, Texas, where The CW is broadcast on a digital subchannel of one of the market's major network affiliates, there were unsuccessful attempts in getting Time Warner Cable to carry the subchannel affiliates (CW then-co-parent Time Warner had owned Time Warner Cable until it spun off the provider into a separate company in 2009; TWC was later acquired by Charter Communications in 2016).
Some affiliates eventually signed carriage deals with Time Warner Cable, but not all of The CW affiliates received carriage on the provider's basic cable tiers (for example, Syracuse, New York affiliate WSTQ-LP could only be viewed on digital cable channel 266 in the Ithaca market). The largest market without a known affiliate is the Johnstown–Altoona market, whose closest CW station was CBS-owned WPCW (now known as independent station WPKD-TV) in Pittsburgh, which is carried on Charter's Johnstown and Altoona area systems; WPKD-TV was originally targeted to serve that area before it refocused its programming toward the Pittsburgh market in the late 1990s.
On February 2, 2007, Beaumont, Texas CBS station KFDM made its CW-affiliated subchannel available to Time Warner Cable customers in the market on channel 10. On April 20, 2007, ABC affiliate KVIA-TV in El Paso, Texas began broadcasting its CW-affiliated subchannel on Time Warner Cable channel 13. On April 21, 2007, KCWQ-LP made its broadcast debut on channel 5 on Time Warner Cable in the Palm Springs area.
==== Pappas Telecasting bankruptcy ====
One of the network's major affiliate groups, Pappas Telecasting Companies, filed for Chapter 11 bankruptcy for thirteen of its television stations on May 10, 2008. Within the petition, Pappas specifically cited the network's low ratings and lackluster performance as one of many complications that had forced it to make the filing. Several of the stations have since been sold either in business transactions with representatives involved in Pappas's bankruptcy proceedings or via station auction processes as the company winds down operations.
Although Pappas had originally stated that none of its stations would be affected at all by the closing, two stations owned by the company that were formerly affiliated with The CW have ceased operations. On May 29, 2008, Yakima, Washington affiliate KCWK (which served the south-central portion of that state) shut down and the station's offices were closed, leaving that area without locally based CW programming and forcing pay television providers to carry Los Angeles affiliate KTLA in order to provide the network's programming to their subscribers. The situation was resolved in April 2009, when Fisher Communications announced that its CBS affiliates in the area, KIMA-TV and satellite station KEPR-TV, would carry the network through DTT subchannel affiliations.
Subsequently, WLGA in Columbus, Georgia lost its CW affiliation in April 2009 to a subchannel of NBC affiliate WLTZ because of the network's concerns about Pappas' financial state; WLGA ultimately ceased operations in June 2010 as it was unable to compete in the market as an independent station.
==== Tribune's relations with The CW ====
While Tribune Media had solid affiliation deals with The CW on several of its stations, it also maintained a strong affiliation alliance with Fox. But with new management and ownership taking over Tribune in 2008, it was apparent that the company would switch one of its CW-affiliated stations to Fox (at least those in markets without a Fox owned-and-operated station or a former O&O that was acquired by Local TV, which Tribune later acquired in 2013), adding to more questions surrounding The CW's future. In a March 2008 seminar by Tribune's then-chairman and CEO Sam Zell, it was revealed that the company's San Diego outlet KSWB-TV would switch its affiliation from The CW to Fox that August, with KSWB assuming the Fox affiliation from XETV-TV, which had been a Fox charter affiliate since that network's October 1986 inception. XETV (which is licensed to Tijuana, Baja California, Mexico under the ownership of Grupo Televisa but whose U.S. operations are programmed by Bay City Television) was not informed of Zell's deal until it was made public.
After the news broke, XETV planned on suing to prevent the switch because it would violate an affiliation contract that XETV had with Fox that was not set to expire until 2010. However, on July 2, 2008, XETV announced that it would join The CW on August 1 (the same day that KSWB became a Fox affiliate) and rebrand as "San Diego 6". Though twelve of Tribune's thirteen other CW-affiliated stations have remained with the network, all of them began to de-emphasize the network from their branding (e.g., "CW 11") in favor of one with a stronger local identity. On-air branding that excised The CW name began being implemented by the stations in July 2008, either on-air (in the case of KWGN-TV) or through their websites (as part of a redesign for all of the Tribune stations' websites). Some of these stations eventually began reincorporating The CW branding starting in 2011, such as KDAF/Dallas, KIAH/Houston and KRCW-TV/Portland, Oregon.
Tribune Company president and CEO Peter Liguori said in a May 2014 discussion at the MoffettNathanson Media & Communications Summit that he was "not pleased with where The CW is [in regards to its ratings performance]", stating that the network "should not program to [young] people who don't watch [conventional] television". Liguori also stated that he would consider collaborating with the network in regards to improving its programming slate, possibly by incorporating programs from the company's Tribune Studios unit (a production division which launched shortly after Liguori was appointed president of Tribune in November 2013) onto the network, as well as having Tribune play a larger role in the CW's management.
Speaking at Goldman Sachs' 23rd Annual Communacopia Conference in September 2014, Les Moonves acknowledged that Tribune had been looking for more input in how the network is programmed and noted that Liguori is a former programmer (having previously served in executive roles at Fox, FX and Discovery Communications), saying that "[Liguori] would like to participate. He has some good ideas. He's part of our team. Will there be some change in how The CW is structured going forward? I don't know." Moonves went on to reiterate that Tribune is "a very important part of [CBS'] future" (considering that Tribune had recently acquired the CBS affiliation for its Indianapolis station and then-CW affiliate WTTV, following disagreements between CBS and longtime affiliate WISH-TV, which would eventually take over The CW affiliation in January 2015, over reverse compensation demands by the network).
In an October 2014 interview with Broadcasting & Cable, Liguori appeared to reverse course on his previous statements and spoke of Tribune's support of the network. Liguori said in a statement, "We are very encouraged by the recent uptick in The CW['s] ratings and the positive critical response to the new primetime lineup. In particular, [CW CEO Mark Pedowitz] has put in place a programming strategy that will help the network appeal to a wider, more inclusive audience, which is important for our stations across the country. We were glad to support the launch of the new shows through editorial and promotional initiatives, and we look forward to more continued collaboration to build upon this momentum."
In January 2016, The CW and Tribune began negotiations on a new affiliation deal, as the original 10-year agreement signed at the network's inception was approaching its end. Complicating matters was the desire by The CW's then-parent companies, CBS and Warner Bros., to stream the network's programming as a standalone pay OTT service. The impasse in negotiations resulted in a months-long standoff between the two groups.
On May 23, 2016, The CW and Tribune announced they had come to a new affiliation agreement. As part of the deal, Tribune's Chicago flagship WGN-TV would leave the network and revert to being an independent station after nearly 21 years of being affiliated with The CW and its predecessor network, the WB. A major factor in this decision was WGN-TV's large use of local sports programming at the time, which led to many pre-emptions of The CW while WGN-TV had to move as many as 30 games a year to another local station in Chicago. The CW affiliation moved to WPWR-TV, a Fox Television Stations-owned MyNetworkTV station. On September 19, 2019, Tribune Media was acquired by Nexstar Media Group.
==== Roberts Broadcasting bankruptcy ====
Roberts Broadcasting filed for Chapter 11 bankruptcy protection on October 7, 2011; the company cited the loss of the UPN affiliations on its stations in St. Louis (WRBU), Columbia, South Carolina (WZRB) and Jackson, Mississippi (WRBJ-TV) when that network shut down in favor of The CW in 2006, as much of UPN's programming consisted of minority-targeted programs that Roberts felt were compatible with their stations' target audiences (though the stations have since recovered from this setback; additionally, its station in Evansville, Indiana, WAZE-TV, had instead affiliated with the WB prior to 2006, as it was owned by South Central Communications until February 2007). The company had also been hit with lawsuits from Warner Bros. Television, Twentieth Television and CBS Television Distribution over its failure to pay fees for syndicated programming; Roberts eventually settled with Twentieth but lost the Warner Bros. and CBS cases.
On March 24, 2011, the Federal Communications Commission (FCC) canceled WAZE's license for Roberts' failure to construct its digital transmitter facilities. However, the station continued to broadcast via its three-station analog translator network.
On February 20, 2012, Roberts Broadcasting announced that it was exploring the possibility of selling one or all four of its television stations in order to raise enough cash to pay off its creditors. On October 22, 2012, Roberts announced that it had sold WRBJ to the Trinity Broadcasting Network; the deal was approved by a bankruptcy court on January 17, 2013, with TBN officially taking over operational control of WRBJ five months later on May 24 The CW would return to the Jackson market on the second digital subchannel of CBS affiliate WJTV in September 2013. On January 3, 2013, the repeater network of WAZE ceased operations; later that month on January 28, independent station WTVW hurriedly joined The CW, in order to maintain the network in the Evansville area.
On December 2, 2013, Roberts filed to sell WZRB to Radiant Light Ministries, a subsidiary of Tri-State Christian Television, for $2 million. On December 4, Roberts also filed to sell WRBU to TCT for $5.5 million. However, on December 11, the United States bankruptcy court gave initial approval for a plan by Roberts's creditors to instead transfer WRBU, WZRB and the WAZE repeaters to a trust with Ion Media Networks (a creditor in Roberts's chapter 11 bankruptcy proceedings) as its beneficiary, with Roberts' attorney subsequently stating that Ion would purchase the stations for $7.75 million. Roberts had earlier proposed an alternate plan that would have had only the WAZE repeaters be transferred to the trust, which would have allowed the sale of WRBU and WZRB to TCT. The CW affiliation in Columbia moved to WKTC (with MyNetworkTV, which the station had already been affiliated with, being relegated to a secondary affiliation) in March 2014, after temporarily remaining on WZRB after its conversion into an Ion Television O&O the previous month. Ion Media later chose to wind down the ex-WAZE-TV translator network entirely and instead affiliate with Nexstar's WTVW-DT4 (itself a CW affiliate on its main channel) by 2017.
==== Carriage dispute with DirecTV ====
In July 2023, Nexstar implemented a blackout of The CW, along with its affiliates for other major broadcast networks, on DirecTV, DirecTV Stream, and U-verse TV, causing DirecTV to complain to the FCC. In return, Nexstar stated that their streaming agreement with DirecTV had expired in November 2022 and it was illegally streaming content on DirecTV Stream from The CW. In August 2023, Nexstar reached a renewal agreement with Sinclair Broadcast Group for 35 markets, including restoring broadcasting of The CW on DirecTV Stream in 21 markets. Nexstar and DirecTV signed a new multi-year agreement on September 17, 2023, allowing the latter to resume broadcasting and streaming The CW.
==== Paramount's withdrawal and affiliation realignment ====
As part of the sale to Nexstar, Paramount Global's CBS News and Stations subsidiary was granted the right to withdraw its eight affiliates from the network—in Atlanta, Detroit, Philadelphia, Pittsburgh, Sacramento, San Francisco, Seattle and the Tampa Bay area—which was exercised on May 5, 2023, effective September 1, 2023. In some of the affected markets, Nexstar-owned stations were announced as replacements. The remainder of the affected markets were addressed through new affiliation agreements with group owners Hearst Television, Gray Television, The E.W. Scripps Company and Sinclair Broadcast Group, each of which already owned multiple CW affiliates. Nexstar also began reclaiming the network affiliation in other markets where it operated, including Oklahoma City; Billings, Montana; Grand Rapids, Michigan; Panama City, Florida; and Sioux Falls, South Dakota.
The situation of The CW in the Detroit market after the CBS withdrawal was tenuous for several months. Mission Broadcasting, a company that contracts with Nexstar for the operational services of its stations, agreed to purchase WADL from Adell Broadcasting Corporation in a deal that provided for Nexstar to supply many of its operating functions. In addition, WADL became the new CW affiliate in Detroit while the deal was pending. The acquisition stalled at the FCC over objections concerning the relationship between Mission and Nexstar. As a result, Adell Broadcasting removed CW programming from the station on October 30, 2023; the network's programs reappeared on Scripps-owned WMYD on November 13, 2023. The acquisition of WADL by Mission was called off in May 2024, despite the purchase being approved by the FCC a month prior.
On April 19, 2024, Nexstar announced that The CW would not renew its affiliations with the seven E.W. Scripps Company-owned stations—in Norfolk, Lafayette, Detroit, Miami, Tucson, Corpus Christi, and San Luis Obispo—that still carried the network. Nexstar concurrently announced that The CW would move to its own stations in Norfolk and Lafayette effective September 1, 2024; the move would also end WMYD's brief affiliation with the network. On May 1, 2024, it was announced that The CW would move back to its original Chicago station affiliate, WGN-TV (Channel 9), beginning September 1, 2024.
==== Carriage dispute with Optimum ====
On January 10, 2025, Nexstar implemented a blackout of 63 of its local stations and NewsNation on Optimum, with The CW's flagship station WPIX being a major part of the dispute. Nexstar accused Optimum's owner Altice USA of making irrational demands for special terms during contract negotiations, while Altice in return accused it of demanding excessive rates for its programming and forcing it to carry unpopular channels like NewsNation. The two reached a carriage agreement on January 18, allowing Nexstar programming to be restored on Optimum.
== Related services ==
=== Video-on-demand services ===
The CW provides video on demand access for delayed viewing of full episodes of the network's programming through various means, including via its website at CWTV.com and its mobile apps for iOS and Android devices (with programs streamable over Wi-Fi and cellular networks), a traditional VOD service – The CW on Demand – that is available on most traditional cable and IPTV providers, and through content deals with Hulu, iTunes and Netflix.
In January 2007, The CW began streaming full-length episodes of several of its programs on The CWTV.com website. The most recent episodes of the network's shows are usually made available on The CW app and The CW on Demand the day after their original broadcast. Due to restrictions imposed through its deal with the streaming service, streaming of the most recent episode of any CW program on Hulu is restricted until eight days after their initial broadcast, in order to encourage live or same-week (via both DVR and cable on-demand) viewing, with day-after-air streaming on either service limited to subscribers of Hulu's subscription service. The CW previously imposed a three-day delay after an episode's original airdate before making its programs available on its website and through the Hulu subscription service (then known as Hulu Plus). However, changes implemented by the network on March 15, 2012, to reduce copyright infringement of its programming content through illegal streaming and downloading internet platforms resulted in that delay being reduced to eight hours after a program's original airing through both services.
In October 2011, the network entered into digital distribution deals with streaming services Netflix and Hulu. The four-year Netflix agreement allowed its customers to instantly watch more than 700 hours of previous seasons of The CW's then-current scripted series, while Hulu signed a five-year deal, giving the streaming site access to next-day content from four of the five major networks (except for CW sister network CBS). The Netflix deal was estimated to be worth $1 billion, providing a much needed lifeline to the money-losing CW network and solidified its future as a valuable asset for then-co-owners CBS and Warner Bros. The Netflix deal was renewed in 2016, updated to allow the streaming service to provide entire seasons of CW shows a week after their airing. The Hulu deal was discontinued at this time. In 2019, The CW and Netflix opted not to renew the deal. The respective studios of CW shows would instead sell to streaming services individually. Beginning in 2020, WarnerMedia streaming service HBO Max (later rebranded to Max under Warner Bros. Discovery) would be the exclusive streaming home for Warners-produced CW shows.
On October 24, 2012, The CW entered into its first video-on-demand distribution deal with a pay television provider through an agreement with Comcast that allows customers to watch the four most-recent episodes of the network's primetime shows on the cable provider's Xfinity On Demand service, along with next-day episode content. The CW On Demand, which is accessible to subscribers at no additional charge, debuted on Comcast Xfinity systems nationwide on October 25, 2012.
=== High-definition feed ===
The CW's master feed is transmitted in 1080i high definition with 5.1 surround sound. All transmission of the network's programming moved to the format in June 2012, with the network's prime time lineup being presented in HD since March 2012 (when America's Next Top Model became the final CW program to convert to the format), with the exception of certain specials produced prior to that point (such as Grandma Got Run Over by a Reindeer, a holiday special carried over to the network from the WB) and select movie presentations. The network's Saturday morning E/I block, One Magnificent Morning, is also broadcast in HD, with the final SD program, the two-season daytime talk show The Robert Irvine Show converting to the format for its second and final season in September 2017 (and in turn ending U.S. broadcast television's standard definition age).
The network is available in HD on most of its full-power affiliates, while availability of high definition content on subchannel-only or cable-exclusive affiliates varies by market; in some of these cases, the over-the-air signal is available only in standard definition (a 16:9 widescreen feed transmitted in 480i SD is presented on some over-the-air affiliates to meet minimum requirements for presentation), with the station offering an exclusive high definition feed to pay television providers. Some affiliates transmit CW programming in 720p HD due to technical considerations if the network is carried on a digital terrestrial subchannel of a station affiliated with another major network or if a primary feed CW affiliate carries more than one subchannel. Since June 2012, The CW Plus feed is also transmitted in HD, and the network has asked those affiliates to carry it in high definition wherever possible. With CBS beginning to use 16:9 framing for all of their graphics on September 24, 2018, The CW was the last major network that continued to use 4:3 framing for all graphics, before switching to the 16:9 framing for all of their graphics in August 2020.
=== CW Seed ===
CW Seed (originally called CWD or the CW Digital Studio) is a production arm that provided original content created exclusively for digital platforms focused in the areas of animation, game shows, comedy, and digital personalities. Previously existing as a section on The CW's main website, CW Seed was spun-off to a separate domain in 2013 as a streaming platform. The free media app became available on several devices, including Roku and Amazon Fire TV.
CW Seed produced various web series, including Vixen, Freedom Fighters: The Ray, and Constantine: City of Demons. On January 8, 2020, CW Seed acquired U.S. streaming rights to 14 series from BBC Studios. In September 2020, the platform added over 300 hours of programming with additional seasons for existing shows and new series, such as 90210, Lost Girl, Nikita, and XIII: The Conspiracy. The CW Seed app and website were reabsorbed into The CW's in April 2022.
== Footnotes ==
== References ==
== Further reading ==
Lausch, Kayti Adaire (2013), The niche network: gender, genre, and the CW brand, retrieved January 27, 2017
== External links ==
Official website (site only accessible from within the United States)
|
https://en.wikipedia.org/wiki/The_CW
|
Netflix is an American global Internet streaming-on-demand media provider that has distributed a number of original streaming television shows, including original series, specials, miniseries, documentaries and films. Netflix's original productions also include continuations of canceled series from other networks, as well as licensing or co-producing content from international broadcasters for exclusive broadcast in other territories, which is also branded in those regions as Netflix original content. Netflix previously produced content through Red Envelope Entertainment. The company has since increased its original content. All programming is in English unless stated otherwise, is organized by its primary genre or format, and is sorted by premiere date. These shows had their original production commissioned by Netflix, or had additional seasons commissioned by Netflix.
== Drama ==
== Comedy ==
== Kids & family ==
== Animation ==
=== Adult animation ===
=== Anime ===
=== Kids & family ===
== Non-English language scripted ==
These shows are created by Netflix and are spoken entirely or almost entirely in a non-English language. Most have the option of watching with English subtitles and dub.
=== Arabic ===
=== French ===
=== German ===
=== Hindi ===
=== Italian ===
=== Japanese ===
=== Korean ===
=== Mandarin ===
=== Polish ===
=== Spanish ===
=== Thai ===
=== Turkish ===
=== Other ===
== Unscripted ==
=== Docuseries ===
=== Reality ===
=== Variety ===
== Continuations ==
These shows have been picked up by Netflix for additional seasons after having aired previous seasons on another network.
== Specials ==
These are one-time original events or episodic supplementary content related to original series.
=== Episodic ===
== Regional original programming ==
These shows are originals because Netflix commissioned or acquired them and had their premiere on the service, but they are not available in all Netflix territories.
=== Co-productions ===
These shows have been commissioned by Netflix in cooperation with a partner network.
=== Continuations ===
== Upcoming original programming ==
The following projects have all received series orders from Netflix or are in development, but currently have an unknown specific release date at this time.
=== Drama ===
=== Comedy ===
=== Animation ===
==== Adult animation ====
==== Anime ====
==== Kids & family ====
=== Non-English language scripted ===
==== French ====
==== German ====
==== Hindi ====
==== Italian ====
==== Japanese ====
==== Korean ====
==== Mandarin ====
==== Norwegian ====
==== Spanish ====
==== Turkish ====
==== Other ====
=== Unscripted ===
==== Docuseries ====
==== Reality ====
==== Variety ====
=== Co-productions ===
=== Continuations ===
=== Specials ===
==== One-time ====
=== In development ===
== Notes ==
== References ==
== External links ==
Netflix Originals current list on Netflix (based on geolocation)
|
https://en.wikipedia.org/wiki/List_of_Netflix_original_programming
|
MSG Western New York (MSG WNY) is an American regional sports network that is a joint venture between MSG Entertainment and Hockey Western New York LLC. The channel (also on occasion credited as Pegula Sports Network or MSG Buffalo) is a sub-feed of MSG Network, with programming oriented towards the Western New York region, including coverage of the National Hockey League's Buffalo Sabres and the National Football League's Buffalo Bills. It replaced MSG Network on television providers in the Sabres' media market in 2016.
MSG Western New York is available on cable providers throughout Western New York. Most programming is available nationwide on satellite via DirecTV.
== History ==
After the collapse of Empire Sports Network and its parent Adelphia, MSG bought the rights to the Buffalo Sabres in 2006 under a 10-year deal; where telecasts are controlled by the team via the Sabres Hockey Network, including the sale of advertising, and the simulcast of Rick Jeanneret's commentary on both radio and television (although, during the 2015-16 season, the team experimented with having separate commentary teams on radio and television for selected games, which the Buffalo News speculated was in preparation for Jeanneret's eventual retirement), conditions that the Sabres always make as part of their telecast deals going back to the days of Empire. After acquiring the rights, MSG divided its network into three regional broadcast "zones"; Sabres games were available within "Zone 3", which covered Buffalo and Rochester, and "Zone 2", the remainder of the state excluding Buffalo, Rochester, and New York City—which was shared by the Sabres, Devils, Islanders, and Rangers. The exact channel assignment for Sabres games varied by region (some games were carried by FSN New York in Zone 2), but all games were carried on the main MSG Network service within Zone 3.
The Buffalo Sabres' regional television ratings are among the highest in the league; in the 2015-16 season, despite the team's poor overall performance, fan enthusiasm over star prospect Jack Eichel helped the team achieve the highest average regional viewership of all NHL teams for the first time since 2008-09, with a 6.55 share. National telecasts on NBC and NBCSN have also had notably high ratings in Buffalo.
It was speculated that Pegula Sports and Entertainment, which had recently bought the Sabres, Rochester Americans, Buffalo Bandits and Buffalo Bills, was planning to take advantage of the high viewership by establishing a team-owned regional sports network once the Sabres' existing television contract with MSG expired. The Buffalo News's Alan Pergament also acknowledged the impending end of the Sabres and Bills' radio contracts with WGR as a possibility that the group could, potentially, acquire a radio station to serve as a team-owned radio outlet if it is unable to renew its contract with Entercom (Entercom had purchased the Sabres' previous owned-and-operated station, 107.7 WNSA, in 2004, and merged its remaining programming onto WGR). Pegula eventually secured a contract extension with Entercom keeping the Bills and Sabres on WGR through the spring of 2021. However, in regards to television, he felt that it was more likely for Pegula to partner with MSG to form a full-time, Buffalo-specific feed of MSG Network with additional local programming, rather than actually establishing a new, standalone outlet.
On June 20, 2016, Pegula announced that it had entered into a joint venture with MSG to establish a new service known as MSG Western New York. The channel, a sub-feed of MSG Network took over the former MSG Zone 3/Sabres game only channel, replacing the parent channel within the Sabres existing television market—which was also, notably, expanded to include the entirety of Rochester. The arrangement allows Pegula access to MSG's existing distribution and statewide programming, while allowing opt-outs for an expanded slate of local programming dedicated to the Bills and Sabres, which is produced and controlled by Pegula. MSG as part of the agreement pays $19 to $20 million per-year in rights fees to broadcast Sabres games and programming, as well as Buffalo Bills programming; it is nearly double the value of the previous Sabres deal. As with the previous deal, Pegula controls team programming on the network, including advertising sales and production (which is handled through PSE's production wing PicSix Creative), and receives all advertising revenue, while MSG collects the retransmission consent fee. Besides original programming and broadcasts exclusive to MSG WNY, the network also carries selected programming from the main MSG Network channel.
Pegula's executive vice president of media and content Mark Preisler explained that the deal was an alternative to establishing a new regional sports network from scratch, as the company would be able to expand on its relationship with MSG as a long-standing partner by leveraging its infrastructure and distribution, rather than needing to invest in building a network and negotiating carriage with television providers.
The first promos seen for the channel ran during a Bills preseason game against the Indianapolis Colts on August 13, 2016 promoting its Bills programming. The channel debuted on September 10, 2016 at 8:00pm with a Western New York cut in showing the 2016 debut of The Rex Ryan Show and a special behind the scenes feature called Rex and Rob Reunited at 8:30 and 9pm, the daily feed followed on October 3.
On April 4, 2017, news broke that James L. Dolan, controlling owner of MSG, was exploring the sale of his regional sports networks, including his share of MSG Western New York.
On August 28, 2023, Pegula Sports and Entertainment was dissolved, with the Bills and Hockey Western New York LLC (the holding company that owns the Sabres, Americans and Bandits) becoming separate business entities and Terry Pegula assuming Presidency of the Sabres organization.
On August 28, 2024, MSG Networks, along with the YES Network announced a combined streaming app for their teams called the Gotham Sports App. Their television rights are not affected.
== Programming ==
The network carries team programming related to the Buffalo Sabres and Buffalo Bills; the former including all 70 regional Sabres games and the latter including local Bills shows formerly aired by WKBW-TV; preseason telecasts began to be simulcast with WKBW beginning in 2017. In addition, the channel simulcasts The Instigators (formerly known as Sabres Hockey Hotline) and One Bills Live (formerly known as The John Murphy Show) from WGR radio as part of a five-hour weekday block, originating from studios (dubbed the One Buffalo studios) at Highmark Stadium; Murphy's program was moved from the evening to the afternoon and had a co-host added. As an aspect of the overall deal, PSE agreed in principle to extend its radio rights with WGR.
MSG Western New York added a package of five Rochester Americans contests beginning in December 2016, moving the team's television broadcasts to MSG WNY from the moribund Time Warner Cable Sports Channel. Select away playoff games are aired by the channel if the team is playing in a market where the home team has a television partner to simulcast from such as Leafs Nation Network for the Toronto Marlies. On September 7, 2017, it was announced that the channel would begin airing select Monsignor Martin Athletic Association high school football games produced by Pegula as part of a multi-year deal, including a three-game showcase at New Era Field. The high school coverage moved exclusively online for 2018. The remainder of MSG WNY's schedule consists of programming from the main MSG Network schedule, such as New York Knicks basketball. In turn, MSG also has rights to air the Pegula-produced original programming and game converge on its other networks.
In 2018, MSG-produced Bills preseason telecasts moved to the stations of Nexstar Media Group in all media markets outside Buffalo. As the Bills could not break their existing contract with WKBW in Buffalo, the rights in that city did not change until 2021, when Nexstar-owned WIVB-TV would begin carrying the games.
=== Original programming ===
=== Hockey ===
Beyond Blue & Gold — a periodical Sabres magazine show that debuted in 2013
The Instigators — daily talk show co-hosted by Andrew Peters and Craig Rivet with regular contributor Martin Biron; simulcast on WGR (formerly known as Sabres Hockey Hotline, Tuesday through Friday)
Sabres Showdown — short-form penalty shootout knockout tournament featuring Sabres stars, based on the 1970s-era NHL on NBC/Hockey Night in Canada feature of the same name
Sabres Live — daily talk show co-hosted by Martin Biron and Brian Duff; simulcast on WGR
=== Football ===
The Sean McDermott Show — weekly coach's show hosted by John Murphy and head coach Sean McDermott.
Bills All-Access — weekly half-hour newsmagazine
Bills Tonight — weekly postgame show
One Bills Live — daily talk show co-hosted by Chris Brown and Steve Tasker; simulcast on WGR (formerly known as The John Murphy Show)
Top 10 in Bills History — countdown miniseries; debuted June 12, 2017
The Extra Point — Monday radio show simulcast with WGR
Buffalo Bills: Embedded — Documentary series covering the Bills training camp; debuted August 2018, created by MSG WNY for Facebook Watch
== On-air staff ==
=== Current on-air staff ===
==== Football ====
Chris Brown — contributor to Bills All Access, co-host of One Bills Live and high school play-by-play
Ruben Brown — analyst for Bills Tonight
Thad Brown — preseason sideline reporter
Sal Capaccio — host of The Extra Point
Andrew Catalon — Bills preseason play-by-play (rotating)
Cynthia Frelund — Bills sideline reporter
Maddy Glab — host of Bills Tonight
Fred Jackson — analyst for Bills Tonight
Len Jankiewicz — high school color commentary
Rob Stone — Bills preseason play-by-play (rotating)
Steve Tasker — host of Bills All Access, co-host of One Bills Live and Bills preseason color commentator
==== Hockey ====
Martin Biron – Sabres studio analyst, co-host of Sabres Live
Brian Duff – Sabres studio host, co-host of Sabres Live
Dan Dunleavy – Sabres play-by-play announcer
Danny Gare – Sabres fill-in analyst
Rob Ray – Sabres color analyst
Ric Seiling – Amerks color analyst
Don Stevens – Amerks play-by-play announcer
=== Former on-air staff ===
Mike Catalana — various roles
Rick Jeanneret – Sabres play-by-play announcer
Donald Jones – co-host of The John Murphy Show
Brad May – Sabres studio analyst
John Murphy — host of One Bills Live and The Sean McDermott Show
Andrew Peters – co-host of The Instigators
Craig Rivet – co-host of The Instigators
== Carriage ==
=== Cable television ===
Both of the two primary cable providers in Western New York, Spectrum (formerly Time Warner Cable, which covers the vast majority of the state) and Atlantic Broadband (which covers a small portion of Cattaraugus County) have carried the network from its inception.
=== DirecTV ===
On August 10, 2016, the debut night of MSG Western New York it was revealed that DirecTV would not be running the network's full programming schedule. The Sabres noted that MSG made the programming available to DirecTV but the provider was not willing to carry it. This made MSG WNY a part-time channel on DirecTV with the provider continuing to air the channel as a game only service showing Sabres games only. For the 2017 NFL season, DirecTV began showing Bills All Access and irregularly showing the first runs of The Sean McDermott Show and Bills Tonight in addition to the Sabres games that the channel airs. A week later DirecTV began showing The Instigators and The John Murphy Show. DirecTV happens to be the service that Pegula owned properties like 716 Food and Sport, a sports bar and grill in downtown Buffalo use.
=== Dish Network ===
MSG Western New York, like MSG and MSG Sportsnet, is unavailable on Dish Network. As part of an ongoing feud with the family of Charles Dolan (owners of MSG), Dish has not carried any MSG network channel since the last agreement expired on October 1, 2010.
=== Over-the-top services ===
FuboTV added the MSG networks for the fall 2017 season.
MSG launched a standalone over-the-top service MSG+, which includes MSG Western New York within the Sabres' broadcast territory, in 2023. It is slated to be merged into Gotham Sports, a joint venture with MSG and YES Network, some time in 2025.
== See also ==
Sabres Hockey Network
Buffalo Bills Radio Network
Spectrum Sports
MSG Sportsnet
== References ==
|
https://en.wikipedia.org/wiki/MSG_Western_New_York
|
Programming the Universe: A Quantum Computer Scientist Takes On the Cosmos is a 2006 popular science book by Seth Lloyd, professor of mechanical engineering at the Massachusetts Institute of Technology. The book proposes that the Universe is a quantum computer (supercomputer), and advances in the understanding of physics may come from viewing entropy as a phenomenon of information, rather than simply thermodynamics. Lloyd also postulates that the Universe can be fully simulated using a quantum computer; however, in the absence of a theory of quantum gravity, such a simulation is not yet possible. "Particles not only collide, they compute."
== Reaction ==
Reviewer Corey S. Powell of The New York Times writes:
In the space of 221 dense, frequently thrilling and occasionally exasperating pages, ... tackles computer logic, thermodynamics, chaos theory, complexity, quantum mechanics, cosmology, consciousness, sex and the origin of life—throwing in, for good measure, a heartbreaking afterword that repaints the significance of all that has come before. The source of all this intellectual mayhem is the kind of Big Idea so prevalent in popular science books these days. Lloyd, a professor of mechanical engineering at M.I.T., takes as his topic the fundamental workings of the universe..., which he thinks has been horribly misunderstood. Scientists have looked at it as a ragtag collection of particles and fields while failing to see what it is as a majestic whole: an enormous computer.
In an interview with Wired magazine, Lloyd writes:
everything in the universe is made of bits. Not chunks of stuff, but chunks of information—ones and zeros. ... Atoms and electrons are bits. Atomic collisions are "ops." Machine language is the laws of physics. The universe is a quantum computer.
Gilbert Taylor, writing in Booklist of the American Library Association, said that the book:
offers brilliantly clarifying explanations of the "bit," the smallest unit of information; how bits change their state; and how changes-of-state can be registered on atoms via quantum-mechanical qualities such as "spin" and "superposition." Putting readers in the know about quantum computation, Lloyd then informs them that it may well be the answer to physicists' search for a unified theory of everything. Exploring big questions in accessible, comprehensive fashion, Lloyd's work is of vital importance to the general-science audience.
== See also ==
Digital physics
Decoding the Universe, a 2007 book by Charles Seife
Seth Lloyd
Simulation hypothesis
Simulated reality
== References ==
== External links ==
Official website
Ultimate physical limits to computation, Nature, volume 406, pages 1047–1054
|
https://en.wikipedia.org/wiki/Programming_the_Universe
|
Moody Radio is one of the largest Christian radio networks in the United States. Located in downtown Chicago, Moody Radio has 71 owned and operated stations and hundreds of affiliates and outlets that carry all or part of its programming. It is owned by the Moody Bible Institute.
The network airs a variety of programming directed primarily toward a Christian audience. The format features local morning drives, teaching and national talk programming, plus specially selected Christian music.
== History ==
WMBI, the flagship station of Moody Radio, got its start seemingly by accident. A violent storm in October 1925 prevented the talent for WGES scheduled broadcast from performing on the radio. This opened the door for two cornet-playing Moody Bible Institute students, who happened to be on-site and could fill the time slot. Few would have thought this "chance-encounter" would result in a weekly show and less than a year later help to launch WMBI, the first noncommercial educational and religious radio station. Despite changing technology, audiences and formats, the station maintained a familiar presence on the air for over eight decades.
This station was just the beginning of what would come to be known as Moody Radio. In 1958, MBI purchased WCRF in Cleveland, Ohio, and shortly thereafter, WDLM in Moline, Illinois. These purchases were the catalyst for a network that would grow to include 36 stations in the continental U.S. By the end of the 1960s, the network's potential audience had increased to 30 million listeners. In 1982, Moody Radio began a satellite-fed network enabling communications across America.
In 2019, Moody Radio put three of its AM stations up for sale. The company announced that the proceeds from the sale would be put towards furthering the expansion of Moody Radio with added digital and online content in both English and Spanish.
== Programs ==
Moody Radio provides biblical programming 24 hours a day. Some of the most popular and award-winning programs include: Equipped with Chris Brooks, Chris Fabry Live!, In the Market with Janet Parshall, and Open Line with Dr. Michael Rydelnik. From 11pm CT until 5am CT, Music Thru the Night is broadcast. From 1982 until his retirement in 2014, Mike Kellogg hosted the program. It is currently hosted by Bill Maier.
== Owned & operated stations ==
The following stations are owned and operated by Moody Radio.
=== Full-powered stations ===
Notes:
=== Translators ===
== References ==
== External links ==
Moody Radio Official Site
|
https://en.wikipedia.org/wiki/Moody_Radio
|
In programming language theory and type theory, polymorphism is the use of one symbol to represent multiple different types.
In object-oriented programming, polymorphism is the provision of one interface to entities of different data types. The concept is borrowed from a principle in biology where an organism or species can have many different forms or stages.
The most commonly recognized major forms of polymorphism are:
Ad hoc polymorphism: defines a common interface for an arbitrary set of individually specified types.
Parametric polymorphism: not specifying concrete types and instead use abstract symbols that can substitute for any type.
Subtyping (also called subtype polymorphism or inclusion polymorphism): when a name denotes instances of many different classes related by some common superclass.
== History ==
Interest in polymorphic type systems developed significantly in the 1990s, with practical implementations beginning to appear by the end of the decade. Ad hoc polymorphism and parametric polymorphism were originally described in Christopher Strachey's Fundamental Concepts in Programming Languages, where they are listed as "the two main classes" of polymorphism. Ad hoc polymorphism was a feature of ALGOL 68, while parametric polymorphism was the core feature of ML's type system.
In a 1985 paper, Peter Wegner and Luca Cardelli introduced the term inclusion polymorphism to model subtypes and inheritance, citing Simula as the first programming language to implement it.
== Forms ==
=== Ad hoc polymorphism ===
Christopher Strachey chose the term ad hoc polymorphism to refer to polymorphic functions that can be applied to arguments of different types, but that behave differently depending on the type of the argument to which they are applied (also known as function overloading or operator overloading). The term "ad hoc" in this context is not pejorative: instead, it means that this form of polymorphism is not a fundamental feature of the type system. In the Java example below, the add functions seem to work generically over two types (integer and string) when looking at the invocations, but are considered to be two entirely distinct functions by the compiler for all intents and purposes:
In dynamically typed languages the situation can be more complex as the correct function that needs to be invoked might only be determinable at run time.
Implicit type conversion has also been defined as a form of polymorphism, referred to as "coercion polymorphism".
=== Parametric polymorphism ===
Parametric polymorphism allows a function or a data type to be written generically, so that it can handle values uniformly without depending on their type. Parametric polymorphism is a way to make a language more expressive while still maintaining full static type safety.
The concept of parametric polymorphism applies to both data types and functions. A function that can evaluate to or be applied to values of different types is known as a polymorphic function. A data type that can appear to be of a generalized type (e.g., a list with elements of arbitrary type) is designated polymorphic data type like the generalized type from which such specializations are made.
Parametric polymorphism is ubiquitous in functional programming, where it is often simply referred to as "polymorphism". The next example in Haskell shows a parameterized list data type and two parametrically polymorphic functions on them:
Parametric polymorphism is also available in several object-oriented languages. For instance, templates in C++ and D, or under the name generics in C#, Delphi, Java, and Go:
John C. Reynolds (and later Jean-Yves Girard) formally developed this notion of polymorphism as an extension to lambda calculus (called the polymorphic lambda calculus or System F). Any parametrically polymorphic function is necessarily restricted in what it can do, working on the shape of the data instead of its value, leading to the concept of parametricity.
=== Subtyping ===
Some languages employ the idea of subtyping (also called subtype polymorphism or inclusion polymorphism) to restrict the range of types that can be used in a particular case of polymorphism. In these languages, subtyping allows a function to be written to take an object of a certain type T, but also work correctly, if passed an object that belongs to a type S that is a subtype of T (according to the Liskov substitution principle). This type relation is sometimes written S <: T. Conversely, T is said to be a supertype of S, written T :> S. Subtype polymorphism is usually resolved dynamically (see below).
In the following Java example cats and dogs are made subtypes of pets. The procedure letsHear() accepts a pet, but will also work correctly if a subtype is passed to it:
In another example, if Number, Rational, and Integer are types such that Number :> Rational and Number :> Integer (Rational and Integer as subtypes of a type Number that is a supertype of them), a function written to take a Number will work equally well when passed an Integer or Rational as when passed a Number. The actual type of the object can be hidden from clients into a black box, and accessed via object identity. If the Number type is abstract, it may not even be possible to get your hands on an object whose most-derived type is Number (see abstract data type, abstract class). This particular kind of type hierarchy is known, especially in the context of the Scheme language, as a numerical tower, and usually contains many more types.
Object-oriented programming languages offer subtype polymorphism using subclassing (also known as inheritance). In typical implementations, each class contains what is called a virtual table (shortly called vtable) — a table of functions that implement the polymorphic part of the class interface—and each object contains a pointer to the vtable of its class, which is then consulted whenever a polymorphic method is called. This mechanism is an example of:
late binding, because virtual function calls are not bound until the time of invocation;
single dispatch (i.e., single-argument polymorphism), because virtual function calls are bound simply by looking through the vtable provided by the first argument (the this object), so the runtime types of the other arguments are completely irrelevant.
The same goes for most other popular object systems. Some, however, such as Common Lisp Object System, provide multiple dispatch, under which method calls are polymorphic in all arguments.
The interaction between parametric polymorphism and subtyping leads to the concepts of variance and bounded quantification.
=== Row polymorphism ===
Row polymorphism is a similar, but distinct concept from subtyping. It deals with structural types. It allows the usage of all values whose types have certain properties, without losing the remaining type information.
=== Polytypism ===
A related concept is polytypism (or data type genericity). A polytypic function is more general than polymorphic, and in such a function, "though one can provide fixed ad hoc cases for specific data types, an ad hoc combinator is absent".
=== Rank polymorphism ===
Rank polymorphism is one of the defining features of the array programming languages, like APL. The essence of the rank-polymorphic programming model is implicitly treating all operations as aggregate operations, usable on arrays with arbitrarily many dimensions, which is to say that rank polymorphism allows functions to be defined to operate on arrays of any shape and size.
== Implementation aspects ==
=== Static and dynamic polymorphism ===
Polymorphism can be distinguished by when the implementation is selected: statically (at compile time) or dynamically (at run time, typically via a virtual function). This is known respectively as static dispatch and dynamic dispatch, and the corresponding forms of polymorphism are accordingly called static polymorphism and dynamic polymorphism.
Static polymorphism executes faster, because there is no dynamic dispatch overhead, but requires additional compiler support. Further, static polymorphism allows greater static analysis by compilers (notably for optimization), source code analysis tools, and human readers (programmers). Dynamic polymorphism is more flexible but slower—for example, dynamic polymorphism allows duck typing, and a dynamically linked library may operate on objects without knowing their full type.
Static polymorphism typically occurs in ad hoc polymorphism and parametric polymorphism, whereas dynamic polymorphism is usual for subtype polymorphism. However, it is possible to achieve static polymorphism with subtyping through more sophisticated use of template metaprogramming, namely the curiously recurring template pattern.
When polymorphism is exposed via a library, static polymorphism becomes impossible for dynamic libraries as there is no way of knowing what types the parameters are when the shared object is built. While languages like C++ and Rust use monomorphized templates, the Swift programming language makes extensive use of dynamic dispatch to build the application binary interface for these libraries by default. As a result, more code can be shared for a reduced system size at the cost of runtime overhead.
== See also ==
Type class
Virtual inheritance
== References ==
== External links ==
C++ examples of polymorphism
Objects and Polymorphism (Visual Prolog)
Polymorphism on MSDN
Polymorphism Java Documentation on Oracle
|
https://en.wikipedia.org/wiki/Polymorphism_(computer_science)
|
Web development is the work involved in developing a website for the Internet (World Wide Web) or an intranet (a private network). Web development can range from developing a simple single static page of plain text to complex web applications, electronic businesses, and social network services. A more comprehensive list of tasks to which Web development commonly refers, may include Web engineering, Web design, Web content development, client liaison, client-side/server-side scripting, Web server and network security configuration, and e-commerce development.
Among Web professionals, "Web development" usually refers to the main non-design aspects of building Web sites: writing markup and coding. Web development may use content management systems (CMS) to make content changes easier and available with basic technical skills.
For larger organizations and businesses, Web development teams can consist of hundreds of people (Web developers) and follow standard methods like Agile methodologies while developing Web sites. Smaller organizations may only require a single permanent or contracting developer, or secondary assignment to related job positions such as a graphic designer or information systems technician. Web development may be a collaborative effort between departments rather than the domain of a designated department. There are three kinds of Web developer specialization: front-end developer, back-end developer, and full-stack developer. Front-end developers are responsible for behavior and visuals that run in the user browser, while back-end developers deal with the servers. Since the commercialization of the Web, the industry has boomed and has become one of the most used technologies ever.
== Evolution of the World Wide Web and web development ==
=== Origin/ Web 1.0 ===
Tim Berners-Lee created the World Wide Web in 1989 at CERN.
The primary goal in the development of the Web was to fulfill the automated information-sharing needs of academics affiliated with institutions and various global organizations. Consequently, HTML was developed in 1993.
Web 1.0 is described as the first paradigm wherein users could only view material and provide a small amount of information. Core protocols of web 1.0 were HTTP, HTML and URI.
=== Web 2.0 ===
Web 2.0, a term popularised by Dale Dougherty, then vice president of O'Reilly, during a 2004 conference with Media Live, marks a shift in internet usage, emphasizing interactivity.
Web 2.0 introduced increased user engagement and communication. It evolved from the static, read-only nature of Web 1.0 and became an integrated network for engagement and communication. It is often referred to as a user-focused, read-write online network.
In the realm of Web 2.0 environments, users now have access to a platform that encourages sharing activities such as creating music, files, images, and movies. The architecture of Web 2.0 is often considered the "backbone of the internet," using standardized XML (Extensible Markup Language) tags to authorize information flow from independent platforms and online databases.
=== Web 3.0 ===
Web 3.0, considered the third and current version of the web, was introduced in 2014. The concept envisions a complete redesign of the web. Key features include the integration of metadata, precise information delivery, and improved user experiences based on preferences, history, and interests.
Web 3.0 aims to turn the web into a sizable, organized database, providing more functionality than traditional search engines. Users can customize navigation based on their preferences, and the core ideas involve identifying data sources, connecting them for efficiency, and creating user profiles.
This version is sometimes also known as Semantic Web.
=== Evolution of web development technologies ===
The journey of web development technologies began with simple HTML pages in the early days of the internet. Over time, advancements led to the incorporation of CSS for styling and JavaScript for interactivity. This evolution transformed static websites into dynamic and responsive platforms, setting the stage for the complex and feature-rich web applications we have today.
Static HTML Pages (1990s)
Introduction of CSS (late 1990s)
JavaScript and Dynamic HTML (1990s - early 2000s)
AJAX (1998)
Rise of Content management systems (CMS) (mid-2000s)
Mobile web (late 2000s - 2010s)
Single-page applications (SPAs) and front-end frameworks (2010s)
Server-side javaScript (2010s)
Microservices and API-driven development (2010s - present)
Progressive web apps (PWAs) (2010s - present)
JAMstack Architecture (2010s - present)
WebAssembly (Wasm) (2010s - present)
Serverless computing (2010s - present)
AI and machine learning integration (2010s - present)
Web development in future will be driven by advances in browser technology, Web internet infrastructure, protocol standards, software engineering methods, and application trends.
== Web development life cycle ==
The web development life cycle is a method that outlines the stages involved in building websites and web applications. It provides a structured approach, ensuring optimal results throughout the development process.
A typical Web Development process can be divided into 7 steps.
=== Analysis ===
Debra Howcraft and John Carroll proposed a methodology in which web development process can be divided into sequential steps. They mentioned different aspects of analysis.
Phase one involves crafting a web strategy and analyzing how a website can effectively achieve its goals. Keil et al.'s research identifies the primary reasons for software project failures as a lack of top management commitment and misunderstandings of system requirements. To mitigate these risks, Phase One establishes strategic goals and objectives, designing a system to fulfill them. The decision to establish a web presence should ideally align with the organization's corporate information strategy.
The analysis phase can be divided into 3 steps:
Development of a web strategy
Defining objectives
Objective analysis
During this phase, the previously outlined objectives and available resources undergo analysis to determine their feasibility. This analysis is divided into six tasks, as follows:
Technology analysis: Identification of all necessary technological components and tools for constructing, hosting, and supporting the site.
Information analysis: Identification of user-required information, whether static (web page) or dynamic (pulled "live" from a database server).
Skills analysis: Identification of the diverse skill sets necessary to complete the project.
User analysis: Identification of all intended users of the site, a more intricate process due to the varied range of users and technologies they may use.
Cost analysis: Estimation of the development cost for the site or an evaluation of what is achievable within a predefined budget.
Risk analysis: Examination of any major risks associated with site development.
Following this analysis, a more refined set of objectives is documented. Objectives that cannot be presently fulfilled are recorded in a Wish List, constituting part of the Objectives Document. This documentation becomes integral to the iterative process during the subsequent cycle of the methodology.
=== Planning: sitemap and wireframe ===
It is crucial for web developers to be engaged in formulating a plan and determining the optimal architecture and selecting the frameworks. Additionally, developers/consultants play a role in elucidating the total cost of ownership associated with supporting a website, which may surpass the initial development expenses.
Key aspects in this step are:
Sitemap creation
Wireframe creation
Tech stack
=== Design and layout ===
Following the analysis phase, the development process moves on to the design phase, which is guided by the objectives document. Recognizing the incremental growth of websites and the potential lack of good design architecture, the methodology includes iteration to account for changes and additions over the life of the site. The design phase, which is divided into Information Design and Graphic Design, results in a detailed Design Document that details the structure of the website, database data structures, and CGI scripts.*
The following step, design testing, focuses on early, low-cost testing to identify inconsistencies or flaws in the design. This entails comparing the website's design to the goals and objectives outlined in the first three steps. Phases One and Two involve an iterative loop in which objectives in the Objectives Document are revisited to ensure alignment with the design. Any objectives that are removed are added to the Wish List for future consideration.
Key aspects in this step are:
Page layouts
Review
Approval
=== Content creation ===
No matter how visually appealing a website is, good communication with clients is critical. The primary purpose of content production is to create a communication channel through the user interface by delivering relevant information about your firm in an engaging and easily understandable manner. This includes:
Developing appealing calls to action
Making creative headlines
Content formatting for readability
Carrying out line editing
Text updating throughout the site development process.
The stage of content production is critical in establishing the branding and marketing of your website or web application. It serves as a platform for defining the purpose and goals of your online presence through compelling and convincing content.
=== Development ===
During this critical stage, the website is built while keeping its fundamental goal in mind, paying close attention to all graphic components to assure the establishment of a completely working site.
The procedure begins with the development of the main page, which is followed by the production of interior pages. The site's navigational structure is being refined in particular.
During this development phase, key functionality such as the Content Management System, interactive contact forms, and shopping carts are activated.
The coding process includes creating all of the site's software and installing it on the appropriate Web servers. This can range from simple things like posting to a Web server to more complex tasks like establishing database connections.
=== Testing, review and launch ===
In any web project, the testing phase is incredibly intricate and difficult. Because web apps are frequently designed for a diverse and often unknown user base running in a range of technological environments, their complexity exceeds that of traditional Information Systems (IS). To ensure maximum reach and efficacy, the website must be tested in a variety of contexts and technologies. The website moves to the delivery stage after gaining final approval from the designer. To ensure its preparation for launch, the quality assurance team performs rigorous testing for functionality, compatibility, and performance.
Additional testing is carried out, including integration, stress, scalability, load, resolution, and cross-browser compatibility. When the approval is given, the website is pushed to the server via FTP, completing the development process.
Key aspects in this step are:
Test Lost Links
Use code validators
Check browser
=== Maintenance and updating ===
The web development process goes beyond deployment to include a variety of post-deployment tasks.
Websites, in example, are frequently under ongoing maintenance, with new items being uploaded on a daily basis. The maintenance costs increases immensely as the site grows in size. The accuracy of content on a website is critical, demanding continuous monitoring to verify that both information and links, particularly external links, are updated. Adjustments are made in response to user feedback, and regular support and maintenance actions are carried out to maintain the website's long-term effectiveness.
== Traditional development methodologies ==
Debra Howcraft and John Carroll discussed a few traditional web development methodologies in their research paper:
Waterfall: The waterfall methodology comprises a sequence of cascading steps, addressing the development process with minimal iteration between each stage. However, a significant drawback when applying the waterfall methodology to the development of websites (as well as information systems) lies in its rigid structure, lacking iteration beyond adjacent stages. Any methodology used for the development of Web-sites must be flexible enough to cope with change.
Structured Systems Analysis and Design Method (SSADM): Structured Systems Analysis and Design Method (SSADM) is a widely used methodology for systems analysis and design in information systems and software engineering. Although it does not cover the entire lifecycle of a development project, it places a strong emphasis on the stages of analysis and design in the hopes of minimizing later-stage, expensive errors and omissions.
Prototyping: Prototyping is a software development approach in which a preliminary version of a system or application is built to visualize and test its key functionalities. The prototype serves as a tangible representation of the final product, allowing stakeholders, including users and developers, to interact with it and provide feedback.
Rapid Application Development: Rapid Application Development (RAD) is a software development methodology that prioritizes speed and flexibility in the development process. It is designed to produce high-quality systems quickly, primarily through the use of iterative prototyping and the involvement of end-users. RAD aims to reduce the time it takes to develop a system and increase the adaptability to changing requirements.
Incremental Prototyping: Incremental prototyping is a software development approach that combines the principles of prototyping and incremental development. In this methodology, the development process is divided into small increments, with each increment building upon the functionality of the previous one. At the same time, prototypes are created and refined in each increment to better meet user requirements and expectations.
== Key technologies in web development ==
Developing a fundamental knowledge of client-side and server-side dynamics is crucial.
The goal of front-end development is to create a website's user interface and visual components that users may interact with directly. On the other hand, back-end development works with databases, server-side logic, and application functionality. Building reliable and user-friendly online applications requires a comprehensive approach, which is ensured by collaboration between front-end and back-end engineers.
=== Front-end development ===
Front-end development is the process of designing and implementing the user interface (UI) and user experience (UX) of a web application. It involves creating visually appealing and interactive elements that users interact with directly. The primary technologies and concepts associated with front-end development include:
==== Technologies ====
The 3 core technologies for front-end development are:
HTML (Hypertext Markup Language): HTML provides the structure and organization of content on a webpage.
CSS (Cascading Style Sheet): Responsible for styling and layout, CSS enhances the presentation of HTML elements, making the application visually appealing.
JavaScript: It is used to add interactions to the web pages. Advancement in JavaScript has given rise to many popular front- end frameworks like React, Angular and Vue.js etc.
==== User interface design ====
User experience design focuses on creating interfaces that are intuitive, accessible, and enjoyable for users. It involves understanding user behavior, conducting usability studies, and implementing design principles to enhance the overall satisfaction of users interacting with a website or application. This involves wireframing, prototyping, and implementing design principles to enhance user interaction. Some of the popular tools used for UI Wireframing are -
Sketch for detailed, vector-based design
Moqups for beginners
Figma for a free wireframe app
UXPin for handing off design documentation to developers
MockFlow for project organization
Justinmind for interactive wireframes
Uizard for AI-assisted wireframing
Another key aspect to keep in mind while designing is Web Accessibility- Web accessibility ensures that digital content is available and usable for people of all abilities. This involves adhering to standards like the Web Content Accessibility Guidelines (WCAG), implementing features like alternative text for images, and designing with considerations for diverse user needs, including those with disabilities.
==== Responsive design ====
It is important to ensure that web applications are accessible and visually appealing across various devices and screen sizes. Responsive design uses CSS media queries and flexible layouts to adapt to different viewing environments.
==== Front-end frameworks ====
A framework is a high-level solution for the reuse of software pieces, a step forward in simple library-based reuse that allows for sharing common functions and generic logic of a domain application.
Frameworks and libraries are essential tools that expedite the development process. These tools enhance developer productivity and contribute to the maintainability of large-scale applications. Some popular front-end frameworks are:
React: A JavaScript library for building user interfaces, maintained by Facebook. It allows developers to create reusable UI components.
Angular: A TypeScript-based front-end framework developed and maintained by Google. It provides a comprehensive solution for building dynamic single-page applications.
Vue.js: A progressive JavaScript framework that is approachable yet powerful, making it easy to integrate with other libraries or existing projects.
==== State management ====
Managing the state of a web application to ensure data consistency and responsiveness. State management libraries like Redux (for React) or Vuex (for Vue.js) play a crucial role in complex applications.
=== Back-end development ===
Back-end development involves building the server-side logic and database components of a web application. It is responsible for processing user requests, managing data, and ensuring the overall functionality of the application. Key aspects of back-end development include:
==== Server/ cloud instance ====
An essential component of the architecture of a web application is a server or cloud instance. A cloud instance is a virtual server instance that can be accessed via the Internet and is created, delivered, and hosted on a public or private cloud. It functions as a physical server that may seamlessly move between various devices with ease or set up several instances on one server. It is therefore very dynamic, scalable, and economical.
==== Databases ====
Database management is crucial for storing, retrieving, and managing data in web applications. Various database systems, such as MySQL, PostgreSQL, and MongoDB, play distinct roles in organizing and structuring data. Effective database management ensures the responsiveness and efficiency of data-driven web applications. There are 3 types of databases:
Relational databases: Structured databases that use tables to organize and relate data. Common Examples include - MySQL, PostgreSQL and many more.
NoSQL databases: NoSQL databases are designed to handle unstructured or semi-structured data and can be more flexible than relational databases. They come in various types, such as document-oriented, key-value stores, column-family stores, and graph databases. Examples: MongoDB, Cassandra, ScyllaDB, CouchDB, Redis.
Document stores: Document stores store data in a semi-structured format, typically using JSON or XML documents. Each document can have a different structure, providing flexibility. Examples: MongoDB, CouchDB.
Key-value stores: Key-value stores store data as pairs of keys and values. They are simple and efficient for certain types of operations, like caching. Examples: Redis, DynamoDB.
Column-family stores: Column-family stores organize data into columns instead of rows, making them suitable for large-scale distributed systems and analytical workloads. Examples: Apache Cassandra, HBase.
Graph databases: Graph databases are designed to represent and query data in the form of graphs. They are effective for handling relationships and network-type data. Examples: Neo4j, Amazon Neptune.
In-memory databases: In-memory databases store data in the system's main memory (RAM) rather than on disk. This allows for faster data access and retrieval. Examples: Redis, Memcached.
Time-series databases: Time-series databases are optimized for handling time-stamped data, making them suitable for applications that involve tracking changes over time. Examples: InfluxDB, OpenTSDB.
NewSQL databases: NewSQL databases aim to provide the scalability of NoSQL databases while maintaining the ACID properties (Atomicity, Consistency, Isolation, Durability) of traditional relational databases. Examples: Google Spanner, CockroachDB.
Object-oriented databases: Object-oriented databases store data in the form of objects, which can include both data and methods. They are designed to work seamlessly with object-oriented programming languages. Examples: db4o, ObjectDB.
The choice of a database depends on various factors such as the nature of the data, scalability requirements, performance considerations, and the specific use case of the application being developed. Each type of database has its strengths and weaknesses, and selecting the right one involves considering the specific needs of the project.
==== Application programming interface (APIs) ====
Application Programming Interfaces are sets of rules and protocols that allow different software applications to communicate with each other. APIs define the methods and data formats that applications can use to request and exchange information.
RESTful APIs and GraphQL are common approaches for defining and interacting with web services.
===== Types of APIs =====
Web APIs: These are APIs that are accessible over the internet using standard web protocols such as HTTP. RESTful APIs are a common type of web API.
Library APIs: These APIs provide pre-built functions and procedures that developers can use within their code.
Operating System APIs: These APIs allow applications to interact with the underlying operating system, accessing features like file systems, hardware, and system services.
==== Server-side languages ====
Programming languages aimed at server execution, as opposed to client browser execution, are known as server-side languages. These programming languages are used in web development to perform operations including data processing, database interaction, and the creation of dynamic content that is delivered to the client's browser. A key element of server-side programming is server-side scripting, which allows the server to react to client requests in real time.
Some popular server-side languages are:
PHP: PHP is a widely used, open-source server-side scripting language. It is embedded in HTML code and is particularly well-suited for web development.
Python: Python is a versatile, high-level programming language used for a variety of purposes, including server-side web development. Frameworks like Django and Flask make it easy to build web applications in Python.
Ruby: Ruby is an object-oriented programming language, and it is commonly used for web development. Ruby on Rails is a popular web framework that simplifies the process of building web applications.
Java: Java is a general-purpose, object-oriented programming language. Java-based frameworks like Spring are commonly used for building enterprise-level web applications.
Node.js (JavaScript): While JavaScript is traditionally a client-side language, Node.js enables developers to run JavaScript on the server side. It is known for its event-driven, non-blocking I/O model, making it suitable for building scalable and high-performance applications.
C# (C Sharp): C# is a programming language developed by Microsoft and is commonly used in conjunction with the .NET framework for building web applications on the Microsoft stack.
ASP.NET: ASP.NET is a web framework developed by Microsoft, and it supports languages like C# and VB.NET. It simplifies the process of building dynamic web applications.
Go (Golang): Go is a statically typed language developed by Google. It is known for its simplicity and efficiency and is increasingly being used for building scalable and high-performance web applications.
Perl: Perl is a versatile scripting language often used for web development. It is known for its powerful text-processing capabilities.
Swift: Developed by Apple, Swift is used for server-side development in addition to iOS and macOS app development.
Lua: Lua is used for some embedded web servers, e.g. the configuration pages on a router, including OpenWRT.
==== Security measures ====
Implementing security measures to protect against common vulnerabilities, including SQL injection, cross-site scripting (XSS), and cross-site request forgery (CSRF). Authentication and authorization mechanisms are crucial for securing data and user access.
==== Testing, debugging and deployment ====
Thorough testing and debugging processes are essential for identifying and resolving issues in a web application. Testing may include unit testing, integration testing, and user acceptance testing. Debugging involves pinpointing and fixing errors in the code, ensuring the reliability and stability of the application.
Unit Testing: Testing individual components or functions to verify that they work as expected.
Integration Testing: Testing the interactions between different components or modules to ensure they function correctly together.
Continuous Integration and Deployment (CI/CD): CI/CD pipelines automate testing, deployment, and delivery processes, allowing for faster and more reliable releases.
=== Full-stack development ===
Full-stack development refers to the practice of designing, building, and maintaining the entire software stack of a web application. This includes both the frontend (client-side) and backend (server-side) components, as well as the database and any other necessary infrastructure. A full-stack developer is someone who has expertise in working with both the frontend and backend technologies, allowing them to handle all aspects of web application development.
MEAN (MongoDB, Express.js, Angular, Node.js) and MERN (MongoDB, Express.js, React, Node.js) are popular full-stack development stacks that streamline the development process by providing a cohesive set of technologies.
=== Web development tools and environments ===
Efficient web development relies on a set of tools and environments that streamline the coding and collaboration processes:
Integrated development environments (IDEs): Tools like Visual Studio Code, Atom, and Sublime Text provide features such as code highlighting, autocompletion, and version control integration, enhancing the development experience.
Version control: Git is a widely used version control system that allows developers to track changes, collaborate seamlessly, and roll back to previous versions if needed.
Collaboration tools: Communication platforms like Slack, project management tools such as Jira, and collaboration platforms like GitHub facilitate effective teamwork and project management.
== Security practices in web development ==
Security is paramount in web development to protect against cyber threats and ensure the confidentiality and integrity of user data. Best practices include encryption, secure coding practices, regular security audits, and staying informed about the latest security vulnerabilities and patches.
Common threats: Developers must be aware of common security threats, including SQL injection, cross-site scripting (XSS), and cross-site request forgery (CSRF).
Secure coding practices: Adhering to secure coding practices involves input validation, proper data sanitization, and ensuring that sensitive information is stored and transmitted securely.
Authentication and authorization: Implementing robust authentication mechanisms, such as OAuth or JSON Web Tokens (JWT), ensures that only authorized users can access specific resources within the application.
== Agile methodology in web development ==
=== Agile manifesto and principles ===
Agile is a set of principles and values for software development that prioritize flexibility, collaboration, and customer satisfaction. The four key values are:
Individuals and interactions over processes and tools.
Working software over comprehensive documentation.
Customer collaboration over contract negotiation.
Responding to change over following a plan.
=== Agile concepts in web development ===
Iterative and incremental development: Building and refining a web application through small, repeatable cycles, enhancing features incrementally with each iteration.
Scrum and kanban: Employing agile frameworks like Scrum for structured sprints or Kanban for continuous flow to manage tasks and enhance team efficiency.
Cross-functional teams: Forming collaborative teams with diverse skill sets, ensuring all necessary expertise is present for comprehensive web development.
Customer collaboration: Engaging customers throughout the development process to gather feedback, validate requirements, and ensure the delivered product aligns with expectations.
Adaptability to change: Embracing changes in requirements or priorities even late in the development process to enhance the product's responsiveness to evolving needs.
User stories and backlog: Capturing functional requirements through user stories and maintaining a backlog of prioritized tasks to guide development efforts.
Continuous integration and continuous delivery (CI/CD): Implementing automated processes to continuously integrate code changes and deliver updated versions, ensuring a streamlined and efficient development pipeline.
== See also ==
Outline of web design and web development
Web design
Web development tools
Web application development
Web developer
== References ==
|
https://en.wikipedia.org/wiki/Web_development
|
The United States Presidential Scholars Program is a program of the United States Department of Education. It is described as "one of the nation's highest honors for high school students" in the United States of America.
The program was established in 1964 by executive order of Lyndon B. Johnson, then the president of the United States to recognize the most distinguished graduating seniors for their academic achievements. In 1979, it was expanded to recognize students who demonstrate exceptional talent in the visual, creative, and performing arts. In 2015, the program was expanded once again to recognize students who demonstrate ability and accomplishment in career and technical fields.
Application for the U.S. Presidential Scholars Program is by invitation only. Students may not apply individually to the program. The presidentially-appointed White House Commission on Presidential Scholars makes the final selection of up to 161 U.S. Presidential Scholars from among that year's senior class. All scholars are invited to Washington, D.C. in June the following year for presentation of the Presidential Scholars Medallion during a White House-sponsored ceremony.
== Eligibility and selection process ==
Eligibility is set by the U.S. Department of Education. Students cannot apply to the program, and are nominated through screening criteria that vary depending on the type of scholarship for which they are eligible.
=== General ===
All graduating high school seniors who are U.S. citizens or legal permanent residents and who have scored exceptionally well on either the SAT of the College Board or the ACT Assessment of the American College Testing Program on or before October of each year are automatically considered for participation.
The United States Department of Education then examines the test records for the scoring students, ranks them separately for males and females, and selects the top 20 males and top 20 females in each state. Each Chief State School Officer (CSSO) may nominate up to ten male and ten female candidates, residing in the CSSO's jurisdiction, based on their outstanding scholarship.
Candidates are notified of eligibility, and if interested in being considered for the scholarship, must submit an essay, self-assessments, high school reports, and transcripts. They are evaluated on their academic achievement, personal characteristics, leadership and service activities, and an analysis of their essay. 500 students are chosen as semifinalists. In March, the White House Commission on Presidential Scholars makes the final selection of up to 161 Presidential Scholars.
=== Arts ===
To be eligible, students must have registered with and been active participants in the YoungArts program. 150 students are invited to apply by the National Foundation for the Advancement of Artists. 60 YoungArts candidates enter the selection process at the semifinalist level. In April, the Commission on Presidential Scholars makes the final selection of up to 20 Presidential Scholars in the Arts.
=== Career and Technical ===
Nominations are submitted by each state's Chief State School Officer (CSSO). CSSOs can nominate up to five candidates who meet the requirements. In March, up to 60 candidates enter the U.S. Presidential Scholars Program selection process at the semifinalist level. In April, the White House Commission on Presidential Scholars makes the final selection of up to 20 U.S. Presidential Scholars in Career and Technical Education.
== Prominent scholars ==
=== Academic ===
Richard Alley (1976, Ohio) - geosciences professor at Pennsylvania State University
Charles B. Chang (1999, New York) - linguistics professor at Boston University
Patrick Chovanec (1988, Illinois) - business professor at Tsinghua University, former aide to Speaker of the House John Boehner
Elizabeth Kiss (1979, Virginia) - eighth president of Agnes Scott College, first female Warden of Rhodes House, Oxford University and CEO of the Rhodes Trust
Chris Morris (1988, New Hampshire) - business professor at MIT, former member of Council of Economic Advisers
Kermit Roosevelt III (1989, District of Columbia) - author, law professor at University of Pennsylvania
Elizabeth Thiele (1979, Massachusetts) Mass General - Director, Pediatric Epilepsy Program, Director, Carol and James Herscot Center for Tuberous Sclerosis Complex, Professor of Neurology, Harvard Medical School
Rakesh Goli - Radiologist
=== Arts ===
Suzette Charles (1981, New Jersey) – Miss America 1984, singer and entertainer
Claire Chase (1996, California) - flutist, composer, professor of music Harvard University, and winner of a MacArthur Fellowship
Rita Dove (1970, Ohio) – Poet Laureate of the United States, winner of Pulitzer Prize for Poetry
Ryan McCartan (2011, Minnesota) – actor and musician
America Ferrera (2003, California) - actress and director
Ben Levi Ross (2016, California) – stage actor
Desmond Richardson (1986) – dancer, co-founder of Complexions Contemporary Ballet
Josh Singer (1990, Pennsylvania) – screenwriter
Conrad Tao (2011, New York) – pianist, composer and violinist
Dominique Thorne (2015, New York) – actress
Matthew Wagener - Commodore, Producer
== References ==
== External links ==
Presidential Scholars Alumni Association
2024 Presidential Scholars (Forbes)
|
https://en.wikipedia.org/wiki/Presidential_Scholars_Program
|
Modern C++ Design: Generic Programming and Design Patterns Applied is a book written by Andrei Alexandrescu, published in 2001 by Addison-Wesley. It has been regarded as "one of the most important C++ books" by Scott Meyers.
The book makes use of and explores a C++ programming technique called template metaprogramming. While Alexandrescu didn't invent the technique, he has popularized it among programmers. His book contains solutions to practical problems which C++ programmers may face. Several phrases from the book are now used within the C++ community as generic terms: modern C++ (as opposed to C/C++ style), policy-based design and typelist.
All of the code described in the book is freely available in his library Loki. The book has been republished and translated into several languages since 2001.
== Policy-based design ==
Policy-based design, also known as policy-based class design or policy-based programming, is the term used in Modern C++ Design for a design approach based on an idiom for C++ known as policies. It has been described as a compile-time variant of the strategy pattern, and has connections with C++ template metaprogramming. It was first popularized in C++ by Andrei Alexandrescu with Modern C++ Design and with his column Generic<Programming> in the C/C++ Users Journal, and it is currently closely associated with C++ and D as it requires a compiler with highly robust support for templates, which was not common before about 2003.
Previous examples of this design approach, based on parameterized generic code, include parametric modules (functors) of the ML languages, and C++ allocators for memory management policy.
The central idiom in policy-based design is a class template (called the host class), taking several type parameters as input, which are instantiated with types selected by the user (called policy classes), each implementing a particular implicit interface (called a policy), and encapsulating some orthogonal (or mostly orthogonal) aspect of the behavior of the instantiated host class. By supplying a host class combined with a set of different, canned implementations for each policy, a library or module can support an exponential number of different behavior combinations, resolved at compile time, and selected by mixing and matching the different supplied policy classes in the instantiation of the host class template. Additionally, by writing a custom implementation of a given policy, a policy-based library can be used in situations requiring behaviors unforeseen by the library implementor. Even in cases where no more than one implementation of each policy will ever be used, decomposing a class into policies can aid the design process, by increasing modularity and highlighting exactly where orthogonal design decisions have been made.
While assembling software components out of interchangeable modules is a far-fetched concept, policy-based design represents an innovation in a way it applies that concept at the (relatively low) level of defining the behavior of an individual class. Policy classes are similar to callbacks, but differ in that, rather than consisting of a single function, a policy class will typically contain several related functions (methods), often combined with state variables or other facilities such as nested types. A policy-based host class can be thought of as a type of metafunction, taking a set of behaviors represented by types as input, and returning as output a type representing the result of combining those behaviors into a functioning whole. (Unlike MPL metafunctions, however, the output is usually represented by the instantiated host class itself, rather than a nested output type.)
A key feature of the policy idiom is that, usually (though it is not strictly necessary), the host class will derive from (make itself a child class of) each of its policy classes using (public) multiple inheritance. (Alternatives are for the host class to merely contain a member variable of each policy class type, or else to inherit the policy classes privately; however, inheriting the policy classes publicly has the major advantage that a policy class can add new methods, inherited by the instantiated host class and accessible to its users, which the host class itself need not even know about.) A notable feature of this aspect of the policy idiom is that, relative to object-oriented programming, policies invert the relationship between base class and derived class - whereas in OOP interfaces are traditionally represented by (abstract) base classes and implementations of interfaces by derived classes, in policy-based design the derived (host) class represents the interfaces and the base (policy) classes implement them. In the case of policies, the public inheritance does not represent an is-a relationship between the host and the policy classes. While this would traditionally be considered evidence of a design defect in OOP contexts, this doesn't apply in the context of the policy idiom.
A disadvantage of policies in their current incarnation is that the policy interface doesn't have a direct, explicit representation in code, but rather is defined implicitly, via duck typing, and must be documented separately and manually, in comments. The main idea is to use commonality-variability analysis to divide the type into the fixed implementation and interface, the policy-based class, and the different policies. The trick is to know what goes into the main class, and what policies should one create. The article mentioned above gives the following answer: wherever we would need to make a possible limiting design decision, we should postpone that decision, we should delegate it to an appropriately named policy.
Policy classes can contain implementation, type definitions and so forth. Basically, the designer of the main template class will define what the policy classes should provide, what customization points they need to implement.
It may be a delicate task to create a good set of policies, just the right number (e.g., the minimum necessary). The different customization points, which belong together, should go into one policy argument, such as storage policy, validation policy and so forth. Graphic designers are able to give a name to their policies, which represent concepts, and not those which represent operations or minor implementation details.
Policy-based design may incorporate other useful techniques. For example, the template method pattern can be reinterpreted for compile time, so that a main class has a skeleton algorithm, which – at customization points – calls the appropriate functions of some of the policies.
This will be achieved dynamically by concepts in future versions of C++.
=== Simple example ===
Presented below is a simple (contrived) example of a C++ hello world program, where the text to be printed and the method of printing it are decomposed using policies. In this example, HelloWorld is a host class where it takes two policies, one for specifying how a message should be shown and the other for the actual message being printed. Note that the generic implementation is in Run and therefore the code is unable to be compiled unless both policies (Print and Message) are provided.
Designers can easily write more OutputPolicys by adding new classes with the member function Print and take those as new OutputPolicys.
== Loki library ==
Loki is a C++ software library written by Andrei Alexandrescu as part of his book Modern C++ Design.
The library makes extensive use of C++ template metaprogramming and implements several commonly used tools: typelist, functor, singleton, smart pointer, object factory, visitor and multimethods.
Originally the library was only compatible with two of the most standard conforming C++ compilers (CodeWarrior and Comeau C/C++): later efforts have made it usable with a wide array of compilers (including older Visual C++ 6.0, Borland C++ Builder 6.0, Clang and GCC). Compiler vendors used Loki as a compatibility benchmark, further increasing the number of compliant compilers.
Maintenance and further development of Loki has been continued through an open-source community led by Peter Kümmel and Richard Sposato as a SourceForge project. Ongoing contributions by many people have improved the overall robustness and functionality of the library. Loki is not tied to the book anymore as it already has a lot of new components (e.g. StrongPtr, Printf, and Scopeguard). Loki inspired similar tools and functionality now also present in the Boost library collection.
== See also ==
Mixin
== References ==
== External links ==
Alexandrescu's website (with book errata [1])
Smart Pointers (sample chapter from the book)
Loki on SourceForge
Original source code from the book publisher
|
https://en.wikipedia.org/wiki/Modern_C%2B%2B_Design
|
Ion Television (referred to on-air as simply Ion) is an American broadcast television network and FAST television channel owned by the Scripps Networks subsidiary of the E. W. Scripps Company. The network first began broadcasting on August 31, 1998, as Pax TV, focusing primarily on family-oriented entertainment programming. It rebranded as i: Independent Television (commonly referred to as "i") on July 1, 2005, converting into a general entertainment network featuring recent and older acquired programs. The network adopted its identity as Ion Television on January 29, 2007.
For many years, Ion has focused primarily on off-network reruns of existing series, with most of its current schedule devoted to marathon blocks of procedural dramas, along with occasional broadcasts of films (including television films during the Christmas season). In the past, Ion had acquired first-run airings of Canadian series not picked up by other American networks and had also been infamous for devoting much of its schedule to infomercials. Under Scripps ownership, Ion has increasingly added national sports programming from the newly established Scripps Sports division, beginning with packages of WNBA basketball and NWSL soccer.
Ion is available throughout most of the United States through its group of 44 owned-and-operated stations and 20 network affiliates, as well as through distribution on pay-TV providers and streaming services; since 2014, the network has also increased affiliate distribution in several markets through the digital subchannels of local television stations owned by companies such as Gray Television and Nexstar Media Group where the network is unable to maintain a main channel affiliation with or own a standalone station, for the same purpose as the distribution of Ion's main network feed via pay-TV providers and streaming services.
The network's stations cover all of the top 20 U.S. markets and 37 of the top 50 markets. Ion's owned-and-operated stations cover 64.8% of the United States population, by far the most of any U.S. station ownership group; it is able to circumvent the legal limit of covering 39% of the population because all of its stations operate on the UHF television band, which is subject to a discount in regard to that limit. In the digital age, the restoration of the UHF discount has proven controversial with other broadcast groups and FCC rulings between presidential administrations, though as the network's parent company mainly acquired low-performing stations and stations on the fringes of markets which targeted lower-profile cities in the analog age, it has not been an issue with Ion Media itself.
== History ==
=== PAX (1998–2005) ===
The network was launched by Bud Paxson, co-founder of the Home Shopping Network and chairman of parent company Paxson Communications (the forerunner to Ion Media). It was originally to be called Pax Net, but was renamed Pax TV (often referred to as simply "Pax"; stylized as "PAX") – a dual reference to its founder and corporate parent, and the Latin word for "peace" – shortly before its launch. Paxson, who felt that television programs aired by other broadcast networks were too raunchy and not family-friendly enough, had decided to create a network that he perceived as an alternative. Since the new network would focus on programming tailored to family audiences, PAX maintained a considerably more conservative programming content policy than the major commercial television networks, restricting profanity, violence and sexual content; accordingly, many of the network's acquired programs were edited to remove sexual and overt violent content, while profane language was muted. According to various news reports, Pax was eventually recognized as the seventh national TV network after The WB & UPN (both collectively recognized as the fifth major TV network after Fox, with The WB being the fifth, & UPN the sixth, national TV networks, respectively), though Pax never gained major TV network status during its existence.
Most of the network's initial affiliates were Paxson Communications-owned affiliate stations of the Infomall TV Network (inTV), a network launched by Paxson in 1995 that relied mainly on infomercials and other brokered programming. During the late spring and summer of 1998, a half-hour preview special hosted by former Waltons star Richard Thomas, featuring interviews with Lowell Paxson about PAX's development and initial programming, aired on inTV stations slated to become charter outlets of the new network.
PAX launched on August 31, 1998, with the network's initial schedule being much larger in scope than it would be in later years. At launch, Pax aired general entertainment programming on weekdays from 11:00 a.m. to 11:00 p.m. and weekends from 3:00 p.m. to 10:00 pm. Central Time. Through an agreement with then-Disney owned animation studio DIC Productions L.P., its schedule also included a children's program block called "Cloud Nine" on Saturdays from 5:00 a.m. to 10:00 a.m. and Sundays from 6:00 a.m. to 8:00 am. Central. In addition, the network aired religious programming through time-lease agreements with The Worship Network (which aired its overnight programming on PAX seven nights a week) and Praise TV (featuring Contemporary Christian music and other faith-based programs aimed at teenagers and young adults, which aired on Friday and Saturday late-nights from 11:00 p.m. to 2:00 am. Central until 2000). The remainder of the schedule was filled by paid programming.
Initial programming on PAX consisted of first-run shows (such as the true story profile series It's a Miracle, game show The Reel to Reel Picture Show, and talk shows Woman's Day and Great Day America), along with reruns of older programming (including Highway to Heaven, Here's Lucy, The Hogan Family, Dave's World, Touched by an Angel, and new episodes and older reruns of Candid Camera, the latter of which moved to the network following the revival series' cancellation by CBS earlier in 1998). The network also produced some original drama series such as Sue Thomas: F.B.Eye, Doc, Mysterious Ways (which originated on NBC), Hope Island and Twice in a Lifetime through its programming division, Paxson Entertainment. PAX also aired many game shows including first-run revivals of established games that originated on cable networks such as Supermarket Sweep and Shop 'til You Drop, along with some original game shows such as On the Cover, Balderdash, Dirty Rotten Cheater, a 2002 revival of Beat the Clock, Hollywood Showdown (in conjunction with Game Show Network, which also aired the show) and reruns of Born Lucky. The network would later carry reruns of the syndicated revival of Family Feud (consisting of episodes from Louie Anderson, Richard Karn and John O'Hurley's tenures as host, airing on a one-year delay from their original syndication broadcast) and, due to its alliance with NBC, The Weakest Link (both from the Anne Robinson-hosted network run and the George Gray-hosted syndicated version) as well as the 2000 revival of Twenty-One.
In September 1999, National Broadcasting Company, Inc. purchased a 32% share of Paxson Communications for $415 million in convertible stock, with an option to expand its interest to 49% by February 2002, pending changes in ownership regulations set by the Federal Communications Commission (FCC) that would allow it to acquire additional television stations. NBC later sold its share in the network back to Paxson in November 2003.
In lieu of a national news program, in 2000, Paxson Communications signed an agreement with Jackson, Mississippi-based WeatherVision – which mainly produces weather forecast inserts for television stations in certain markets that do not operate an in-house news department or maintain a news share agreement with another local station – to produce Tomorrow's Weather Tonight, a five-minute national forecast segment that aired Monday through Friday nights at the conclusion of PAX's entertainment schedule. Starting in 2000, many PAX stations also entered into news share agreements with a local major network affiliate (mostly involving NBC-affiliated stations, though some involved an affiliate of ABC, CBS, or Fox) to air tape-delayed broadcasts of evening, and in some markets, morning newscasts from the partner station; in a few cases, the agreement partner produced live newscasts for the PAX station (as examples of the latter, NBC affiliate WTHR in Indianapolis produced a prime time newscast for PAX O&O WIPX-TV from February to June 2005, after CBS affiliate WISH-TV (now a CW affiliate) took over production of the newscast that WTHR had been producing for UPN affiliate WNDY-TV (now a MyNetworkTV affiliate) since 1996; Cleveland NBC affiliate WKYC-TV produced evening newscasts for WVPX-TV that focused primarily on that O&O's city of license, nearby Akron). In some cities, a major network affiliate also provided some engineering and other back office services for the PAX station.
In an effort to increase revenue due to low viewership and other financial issues, PAX gradually increased the amount of paid programming content on its schedule throughout the early 2000s, at the expense of its general entertainment programming. Infomercials and other types of brokered programs ultimately became the dominant form of programming during the network's broadcast day; by January 2005, the time that PAX had allocated to entertainment programs had been reduced to six hours on weekdays (from 5:00 p.m. to 11:00 pm) and five hours on weekends (from 5:00 p.m. to 10:00 pm. Central Time). Original programming was also affected by the network's programming changes; PAX was originally offering five or six new series each season. However, in 2003, the number of new series that aired on PAX dwindled to just two: Sue Thomas: F.B.Eye, which was cancelled in 2005, and Doc, which was cancelled in 2004 after PAX's international backer, Canadian broadcast network CTV, pulled out of producing the shows. The network seemingly recovered a year later when seven series made it to PAX's 2004–05 schedule.
=== i (2005–2007) ===
On June 28, 2005, Paxson Communications announced that it would rebrand PAX as i: Independent Television, to reflect a new strategy of "providing an independent broadcast platform for producers and syndicators who desire to reach a national audience." The network used a lowercase letter "i" for its branding and other items such as its electronic program guide listings.
The rebranding also resulted in several changes to its programming lineup: paid programming replaced overnight programming from The Worship Network, which began to carry its full 24-hour schedule on a fourth digital subchannel of local i owned-and-operated stations and affiliates until the network was dropped in January 2010; in addition, Tomorrow's Weather Tonight and rebroadcasts of network affiliate newscasts were discontinued the day prior to the rebrand on June 30, 2005 (though a few stations not owned by the network's parent company retained news share agreements with major network stations after that date, such as WBNA in Louisville, Kentucky, which continued to air newscasts from NBC affiliate WAVE). The network shifted its format almost entirely to reruns of television series from the 1960s to the 1990s (such as Green Acres, Amen, and Pax holdover Diagnosis: Murder) and feature films, reruns of former Pax TV series (such as Doc) and first-run episodes (and later reruns) of Pax holdover series America's Most Talented Kids were also included as part of the schedule. In turn, the network adapted its programming content standards to those similar to other broadcast networks. During the 2005–06 season, the network launched only one new series that met the network's new mission of being an 'independent broadcast platform', the teen drama Palmetto Pointe, which only lasted five episodes and was criticized as a poor imitation of Dawson's Creek and One Tree Hill; the network went entirely to a lineup of reruns with limited original programming for the 2006–07 season (except for Health Report and specials branded under the name iHealth).
At one point in this era, the network programmed eighteen hours of paid programming per day, ¾ of the network's broadcast day, with the network only programming the early fringe and prime time periods with traditional programming.
In November 2005, NBCUniversal was granted a transferable option to purchase a controlling stake in Paxson Communications. Had this option been exercised, NBC would have acquired approximately 63 i owned-and-operated stations (though this could have resulted in a forced divestiture of either i or Spanish network Telemundo, which NBC had acquired in April 2002 (prior to its merger with Vivendi Universal), along with the divested network's O&Os due to FCC rules that prohibit broadcasters from owning more than two television stations in the same market unless there are either a minimum of 20 full-power stations in the market or one of the stations is a satellite). As part of the agreement, Lowell Paxson stepped down from his position as chairman of Paxson Communications. In April 2006, published reports surfaced that i owed more than US$250 million to creditors. Standard & Poor's reported a much higher debt in March 2008, owing $867 million to creditors and having a bond rating of CCC+/Outlook Negative.
According to a statement on its website, DirecTV (which ironically had, and still has, multiple networks made up of full-time paid programming) planned to terminate its carriage agreement with i on February 28, 2006. The satellite provider cited that "most of [i Network's] programming consists of infomercials and other promotional shows", despite an earlier promise by network executives that it "would consist of general, family-oriented entertainment". At its peak, infomercial time stretched across eighteen hours of the network's broadcast day, or 126 hours of a 168-hour broadcast week. To appease DirecTV management, the network launched a secondary feed of the network for providers adverse to its over-the-air programming direction, replacing paid programming time with older public domain programs and cancelled Pax TV original series. DirecTV and Paxson then reached a new carriage agreement in May 2006.
In September 2006, i launched Qubo, a children's programming block, as part of a partnership with NBCUniversal and Scholastic Entertainment.
=== Ion Television (2007–present) ===
On January 29, 2007, the network changed its name again to Ion Television (as a result of its parent company's renaming to Ion Media Networks). Days after the rebrand, California-based entertainment group Positive Ions, Inc. filed a trademark infringement lawsuit against Ion Media Networks, claiming that the network stole the "Ion" branding. Positive Ions had registered trademarks on the word "Ion" and had used the mark commercially since 1999. On May 14, 2007, Positive Ions filed for an injunction that, if granted, would have required Ion Media Networks to change its name once again. On May 4, 2007, Ion, Citadel Investment Group, and NBC Universal announced a deal to transfer NBC Universal's rights to purchase a controlling stake in Ion to Citadel, in exchange for Citadel investing $100 million into Ion's growth and digital plans.
Ion Television's programming, for the most part, remained unchanged upon the rebrand; the network continued to feature programming from the content deals it signed while under the i brand (such as Who's the Boss?, Mama's Family, Growing Pains, and The Wonder Years). The network also aired a late afternoon sitcom block called "Laugh Attack", which featured reruns of comedy series targeted at African American audiences (originally consisting of Hangin' with Mr. Cooper and The Wayans Bros., the latter of which was later replaced by The Steve Harvey Show).
In January 2008, Ion Media and Comcast reached a carriage agreement to continue carrying Ion Television, while also adding Qubo and Ion Life to the cable provider's channel lineups.
Eventually, Ion Television would come to be known as the seventh national TV network, behind UPN, The WB, Fox, ABC, CBS, & NBC, though it still wouldn't achieve major network status.
==== 2008 relaunch ====
On May 1, 2008, Ion Television held an upfront presentation announcing its programming for the 2008–09 season at the New York Public Library in Manhattan. In addition to the announcement of its programming acquisitions, the network unveiled a new logo (a wordmark that incorporated a positive ion symbol as a pseudo-period next to the "ion" typeface) and slogan for the network, "Positively Entertaining" (a form of wordplay, as ions are atoms or molecules that have a positive or negative electrical charge).
With the September 8, 2008, rebrand, the network also retooled its focus, emphasizing the key demographic of adults between ages of 18 and 49, and airing more recent acquired programming aimed at young adults (such as Boston Legal, NCIS, and Criminal Minds).
By this point, the network shifted its programming to feature extended blocks of its acquired series (which consist mostly of drama series, with sitcoms becoming an increasingly less integral part of the schedule); it also began a gradual expansion of the number of hours devoted to entertainment shows, starting with the addition of a two-hour block of programming in the late afternoon (from 3:00 p.m. to 5:00 pm. Central) in January 2008, and expanding further into the daytime and late fringe/early graveyard periods over a five-year span (however, this resulted in the network increasing its reliance on regularly scheduled marathon-style blocks of a relatively small inventory of programs in lieu of acquiring a much larger lineup of series to fill out the schedule). More recent theatrically released feature films were also added to the lineup, alongside older movie releases from the 1980s and 1990s.
In April 2009, it was announced that Ion Media Networks was once again facing balance sheet problems. The company disclosed that it was in discussions with lenders on "a comprehensive recapitalization" of its balance sheet, translating to an effort to restructure its considerable debt, which, according to The Wall Street Journal, stood at $2.7 billion as of April 2009.
The network launched high definition operations in the 720p format, announcing they would do so on January 28, 2009, with an original launch date of February 16, 2009, but delayed to March 16, 2009, after the passage of the DTV Delay Act, which pushed the national digital television transition to June 12, 2009. Most Ion stations began to switch their main signals from 480i standard definition to 720p HD in late February; an early decision to pillarbox 4:3 programming with blue rather than black pillarboxing was eventually abandoned as black coloring became the industry norm. Some Ion-owned and affiliate stations which carry the network as a multicast offering continue to carry the network in 480i widescreen over-the-air.
On May 19, 2009, Ion Media Networks filed for Chapter 11 bankruptcy protection, putting the Ion network under bankruptcy for the second time in its history; it had reached an agreement with holders of 60% of its first lien secured debt that would extinguish the entirety of its $2.7 billion legacy debt and preferred stock, and recapitalize the company with a $150 million new funding commitment. On July 15, 2009, RHI Entertainment entered into a settlement agreement to resolve a dispute with Ion Media Networks, which resulted in the termination of a programming distribution agreement between RHI and Ion.
Also, in 2009, Ion Television would come to be the sixth national TV network, this time, behind The CW, Fox, ABC, CBS, & NBC, with MyNetworkTV in 2009 transitioning to a broadcast syndication service. However, Ion Television would never come to achieve major network status.
In November 2010, Ion Television began airing its first made-for-TV movies, in the form of Christmas-themed films that air between the weekend after Thanksgiving (airing the weekend before that holiday in 2013) and Christmas Day, with up to five films premiering each year on the network, although they are advertised as "original movies" in on-air promotions (the 2012 film Anything But Christmas is the only movie aired to date in which Ion Television had actually held a production interest), most of the films are produced by independent film and television studios such as Reel One Entertainment, Hybrid, LLC, The Cartel, and Vancouver-based MarVista Entertainment without the network's financial involvement (Ion does not maintain exclusivity to most of the films, which are also distributed via syndicated film packages or carried by other networks); the network extended these themed made-for-TV movies to other holidays in 2015, with the premieres of the romance films Meet My Valentine (which aired as part of the network's Valentine's Day programming slate) and You Cast a Spell on Me (which aired as part of its "Wicked Week" Halloween block).
=== Purchase by Scripps ===
On September 24, 2020, E. W. Scripps Company agreed to buy Ion Media for $2.65 billion. The transaction, which closed on January 7, 2021, saw Ion Television and its sister networks absorbed into Scripps' Katz Broadcasting subsidiary, which already operates five specialty networks, most notably Bounce TV and Court TV. In regards to Ion Television's programming, Scripps indicated it would maintain the status quo, with no plans at the time to invest in original content or deviate from the channel's off-network programming approach. To get FCC approval for the transaction, 23 Ion Television stations were sold by Scripps to Inyo Broadcast Holdings.
On April 8, 2024, Scripps announced that they would reposition Ion into a general entertainment channel, turning live sports broadcasting as a tentpole of the network with Women's National Basketball Association (WNBA) and National Women's Soccer League (NWSL) games occupying weekly slots in the programming lineup and to launch a refresh of their brand identity and new year-long brand campaign based on the new tagline from the new branding being "Ion. It's On", replacing "Positively Entertaining" after 16 years. Sister channels Ion Mystery and Ion Plus would also be rebranded with similar graphics based on Ion's branding.
== Programming ==
As of April 2024, Ion provides general entertainment programming to owned-and-operated and affiliated stations every day from 6:00 a.m. to 2:00 a.m. Eastern Time (except Fridays outside of the Holiday season which start at 7:00 a.m. ET; awhile the entertainment programming schedule starts at 8:00 a.m. and ends at 1:00 a.m. from Christmas to New Year's Day), with paid programming filling the remaining vacated hours. A children's programming block of Science Max (one past Qubo series), and Xploration Station from Steve Rotfeld Productions – which features programs compliant with FCC educational programming requirements – airs for three hours each Friday at 7:00 a.m. Eastern Time. Four hours overnight are programmed with compensated religious or commercial paid programming, a comparably small fraction of the paid programming schedule it aired in the past.
Ion owned-and-operated stations and affiliates formerly also provide limited local programming on weekday mornings to fulfill public affairs guidelines, which ranged from entirely local productions to Ion Life-sourced programs within which commercial slots are instead devoted to local physicians or experts giving locality-specific health advice or advertising their services. This programming has ended as the Main Studio Rule repeal by the FCC in 2019 freed Ion stations from this requirement. Ion also served as the over-the-air broadcast distribution point for TiVo's Teleworld Paid Program, a weekly 30-minute compilation program – usually carried during the overnight on Wednesdays or Thursdays within the network's designated paid programming time – it was specifically coded to distribute program previews and device tutorials for TiVo's digital video recorders; in 2011, the time was used in early September to preview the pilot of Fox's new sitcom New Girl, before its actual Fox premiere on September 20. TiVo discontinued the program in 2016 as broadband had become commonplace enough to end it.
Most programs broadcast by Ion Television are distributed by either NBCUniversal Syndication Studios, Disney–ABC Domestic Television, CBS Media Ventures, or Warner Bros. Domestic Television Distribution. Ion Television also maintains film distribution deals with Universal Pictures, Paramount Pictures, 20th Century Studios and Warner Bros. Pictures. Series broadcast by Ion Television (as of October 2015) are mostly dramas such as Criminal Minds, Law & Order, Law & Order: Special Victims Unit, Law & Order: Criminal Intent, Numb3rs, Bones, Blue Bloods, and The Listener. As of 2014, the network's format is predominantly devoted to marathon blocks of hour-long drama series, with consecutive episodes of a given series airing between two and 16 hours a day (depending on the day's schedule, with fewer hours in the morning and late fringe).
The network broadcasts feature films released between the 1980s and the 2000s under the banner "Ion Television at the Movies", which fill the majority of the network's Sunday afternoon and evening schedule (holiday-themed made-for-TV films are also broadcast under the banner throughout the entertainment programming day on weekends between Thanksgiving and Christmas, as well as on Christmas Eve and Christmas Day regardless of where either holiday falls during the calendar week). Ion Television occasionally airs short, hosted segments during its prime-time lineup – particularly during film presentations – known as the "Ion Lounge", a lifestyle segment used mainly to advertise a company's product within the featured program's commercial breaks.
In the recent past, Ion Television has aired a limited number of comedy or comedy-drama series that were cycled on-and-off the schedule such as Monk, Psych and Married... with Children, with half-hour sitcoms used on certain occasions to fill scheduling gaps prior to the telecast of its late-morning film presentations (usually in the 10:00 am. Central Time half-hour, if the succeeding film ran for at least 21⁄2 hours) because of their erratic scheduling; the network shifted to a more exclusive focus on dramas as part of its series content in January 2015, although the network continued to carry comedic programming in the form of select feature films aired within the "Ion Television at the Movies" block.
Ion's method of running predominantly syndicated programming is very similar to the international model of broadcasting used in Europe, Canada, Latin America, Asia and Australia, which mixes imported and syndicated shows with original programming – a model used only in United States broadcast television by digital multicast services (particularly those that specialize in acquired programs such as MeTV and Antenna TV), smaller English language entertainment-based networks (such as America One), PBS member stations, and networks broadcasting in languages other than English (such as Univision, UniMás, and Telemundo). The major commercial broadcast networks in the U.S. – ABC, NBC, CBS, and Fox – carry first-run programs produced for the network, while leaving the responsibility of acquiring shows from the syndication market to their owned-and-operated stations and affiliates to fill time not allotted to network and, where applicable, locally produced programs (The CW and MyNetworkTV, which are somewhat similar to Ion Television in their formats, mixes elements of both models as acquired programs are supplied both during prime time by the services and by their stations at all other times). A limited number of non-Ion-owned stations that are merely affiliated with the network (such as former Louisville outlet WBNA) do carry additional local or syndicated programming that, in some instances, pre-empts certain programs within the Ion master schedule.
=== Recent programming deals ===
In 2006, Ion Media Networks reached several programming deals, two with major programming suppliers that were announced within a week of each other, and another that among other things would bring original programming to Ion Television's lineup. On June 27, 2006, Ion Media announced a comprehensive programming deal with Warner Bros. Television Distribution, which gave it the broadcast rights to movies and television series owned by the company. One week later on July 5, 2006, Ion announced a similar deal that resulted in the acquisition of broadcast rights to films and series distributed by Sony Pictures Television (now Sony Pictures Television Studios). Starting in September of that year, series and feature films from both libraries were incorporated onto the network's prime time schedule (including Who's the Boss?, Designing Women, Mama's Family, Growing Pains, Green Acres, and The Wonder Years). However, these older series were later dropped when the network shifted towards more recent series. Ion also struck a library content deal with NBCUniversal, which gave it access to shows such as Law & Order.
In September 2008, Ion Television reached a multi-year film rights agreement with Warner Bros. Television Distribution to broadcast more recent movies from Warner Bros. and its related studios. Meanwhile, three series from CBS Television Distribution (now CBS Media Ventures) were added to the schedule: NCIS joined the lineup in September 2008, while Criminal Minds and Ghost Whisperer were added to the Ion Television lineup in 2009. In January 2009, the network announced that it had acquired the broadcast rights to the Canadian television drama series Durham County; that show aired on the network for less than a year.
On January 21, 2011, Ion Television acquired the U.S. television rights to the Canadian drama series Flashpoint, which gave it first-run rights to the fourth season's final 11 episodes, after CBS aired that season's first eight episodes, as well as rights to air reruns of all episodes produced to date and thereafter; Ion (along with the show's originating Canadian broadcaster, CTV) also renewed the series for a fifth and final season that aired during the fall of 2012.
In July 2011, Ion Television acquired the broadcast television rights to six films produced by Starz Media (now Lionsgate) as part of its weekend film block (then branded as the "Big Movie Weekend"); the films started airing on the network in November of that year. Ion also acquired the syndication rights to the USA Network series Psych and Monk from NBCUniversal; the two series respectively began airing in late 2011 and early 2012. House, also from NBCUniversal, joined the network in September 2012. In September 2011, Ion Television acquired the syndication rights to George Lopez and Leverage. George Lopez began airing on September 29, while Leverage debuted in July 2012, the former has since been dropped from the network, while the latter has been cycled on-and-off the schedule.
On October 4, 2011, Ion Television acquired the rights to the first two seasons of the Canadian drama The Listener for broadcast in 2012, with an option for future seasons through an agreement with Shaw Media (parent of the show's originating broadcaster, Global); the series would not join Ion's schedule until March 2014, by which time Ion Television had entered into a co-production arrangement for the program. A similar deal reached in September 2014 with Entertainment One gave Ion the American rights to the medical drama Saving Hope (which made its American debut on NBC in the summer of 2012); Ion began airing first-run episodes and repeats of the series in October 2015.
In December 2011, Ion Television acquired the syndication rights to Cold Case, which debuted in 2012. On June 25, 2012, Ion Television entered into a deal with WWE to air a new hour-long series titled WWE Main Event on Wednesday nights; the series debuted on October 3, 2012 and ran until April 2, 2014.
=== Other programming ===
==== Children's programming ====
Prior to Ion Television's original launch as Pax TV in 1998, the network had reached an agreement with DIC Entertainment to produce a five-hour children's programming block called Freddy's Firehouse, to air on Saturday and Sunday mornings. The block of animated series was instead launched on September 5, 1998, as "Cloud Nine", featuring a trio of winged teenage angels that hosted the wraparound segments that bridged breaks during the block's shows, which were mostly sourced from the DIC library. "Cloud Nine" was discontinued in the spring of 1999, and was replaced by a new block under the title "Pax Kids." The DIC programs were replaced in 2000 with reruns of Jack Hanna's Animal Adventures, which was replaced by Just Deal and California Dreams the following year. Pax TV became the first major commercial broadcast network in the U.S. to not supply children's programming in January 2002, and later one of only two until it restored a children's block in 2006 (UPN eventually joined it in this distinction after it dropped its Disney's One Too block in August 2003, following the termination of a programming agreement with Buena Vista Television). Between 2002 and 2006, Pax and i used original reality series such as Miracle Pets, Animal Tails, and America's Most Talented Kids to fulfill its stations' E/I requirements.
On September 15, 2006, Ion Television debuted a weekly children's program block called "Qubo on Ion Television", through a partnership between Ion Media Networks, NBC Universal, the Nelvana unit of Corus Entertainment, Scholastic Media, Classic Media, and its subsidiary Big Idea Productions. The Qubo block originally debuted on NBC and Telemundo on September 9, 2006, with NBC's Qubo block initially being rebroadcast on Ion Television on Friday afternoons (making it the last weekday afternoon children's block to be carried by a major commercial broadcast network until 2010). On January 4, 2015, the Qubo block on Ion was relaunched as the "Qubo Kids Corner", concurrent with the block's move to Sunday mornings. As mentioned above, Scripps now purchases syndicated programming to meet Ion Television's E/I requirements with its wind-down of Qubo.
==== Sports ====
The network has previously broadcast certain sporting events, including Conference USA college football games (produced by College Sports Television), soccer matches from the Women's United Soccer Association, Real Pro Wrestling (which more resembles the amateur form than the theatrically-based ring sport), the Champions Tour of golf, the Paralympic Games and a weekly mixed martial arts program from BodogFight. In its home state of Florida, the network's stations had served as a statewide chain to carry play-by-play coverage of a number of games for Major League Baseball's Tampa Bay Rays and Florida Marlins (demarcated by each team's territories) until the late 2000s, when cable's Fox Sports Florida and Sun (now Bally Sports Florida and Sun) acquired the exclusive rights to both teams.
Ion Television aired NFL Films' weekly highlight program, the NFL Films Game of the Week on Saturday evenings from September 16, 2007, to January 5, 2008, with its initial broadcast focusing on the September 9, 2007 game between the New York Giants and the Dallas Cowboys. The series was not renewed for the fall 2008 season. Ion also obtained rights to televise games from the American Indoor Football Association, which were slated to begin airing in March 2008. However, the game's producers did not provide a live broadcast and the agreement was terminated.
On December 28, 2010, Ion Television signed a deal with the Ultimate Fighting Championship to air the preliminary fights to the January 1 pay-per-view event UFC 125. Ion also aired the preliminary fights for UFC 127 and UFC 140 later in 2011, before the organization signed an exclusive programming agreement with Fox.
On April 20, 2023, Ion Television, through Scripps Sports, signed a multi-year deal with the Women's National Basketball Association (WNBA) to air a 15-week slate of doubleheader games on Friday nights (branded as WNBA Friday Night Spotlight on ION), beginning with that year's regular season. It will be the first national sports broadcast carried by Ion since 2011, and marks the first ever television contract for Scripps Sports, which was founded by the E. W. Scripps Company in December 2022 to acquire sports events for Ion and the group's local television stations. The agreement also grants local rights to selected Ion O&Os for games involving regional WNBA teams, which stations may carry in early- or late-evening broadcast windows depending on tip-off time.
On November 9, 2023, the National Women's Soccer League announced Scripps Sports as a rightsholder beginning in the 2024 season, with Ion to air Saturday night doubleheaders. Ion will also air the 2024 NWSL Draft.
== Affiliates ==
As of October 2020, Ion has 64 owned-and-operated stations, and current and pending affiliation agreements with nine additional television stations encompassing 36 states and the District of Columbia. The network has an estimated national reach of 60.63% of all households in the United States (or 189,453,097 Americans with at least one television set). Ion Television has the most owned-and-operated stations of any commercial broadcast network in the United States, reaching 65.1% of the United States (well above the Federal Communications Commission's coverage-based national ownership limit of 39%); it is also the only American commercial broadcast network whose stations almost exclusively consist of network-owned stations, similar to the ownership model of many commercial broadcast networks in Europe, Canada, Latin America, Asia and Australia, and to a somewhat more expansive extent, many U.S.-based religious broadcast networks.
Ion's programming is available by default via a national feed that is distributed directly to pay television providers in markets without a local Ion station (this contrasts with the major networks, which under FCC regulations, allow providers to import an owned-and-operated or affiliate station from a nearby market if no local over-the-air affiliate exists). In some markets, DirecTV carries a "placeholder" simulcast of the national modified feed of the network (for example, Los Angeles area viewers can watch Ion on both channels 30, via local O&O KPXN-TV, and 306; New York City on channel 31 WPXN besides 305).
In most markets with a Scripps or Inyo-owned Ion station outside early mornings, the only sign of the network being carried on a broadcast television station is a small automatically generated station identification on the bottom of the screen at the top of each hour containing the call letters, city of license and state abbreviation, which is repeated across its subchannels.
=== Major market absences and station oddities ===
Ion does not have any over-the-air stations in several major markets.
Two major factors that have limited the network's national broadcast coverage are that unlike the major commercial broadcast networks (ABC, NBC, CBS, and Fox), Ion did not actively seek over-the-air distribution on the digital subchannels of other network-affiliated stations in the five years following the digital television transition (with limited exceptions in Las Vegas, Nevada, Tucson, Arizona and Fresno, California through agreements with Telemundo owned-and- operated stations in those markets), until it reached a multi-station agreement with Media General in November 2015; prior to that deal, it long had very few stations that contractually carry the network's programming (with limited exceptions in markets such as Louisville, Kentucky and Anchorage, Alaska). As a result, Ion Media Networks owns the vast majority of the stations within Ion Television's affiliate body, as well as those of co-owned multicast services Qubo Channel and Ion Life.
In Pittsburgh, a deal by Paxson to buy WPCB-TV and trade it for secondary PBS member station WQEX was approved by the Federal Communications Commission, but rejected by WPCB-TV owner Cornerstone Television in a 2000 controversy; it would not be until November 2010 that Paxson's successor, Ion Media Networks, would successfully buy WQEX, which has since been converted into a commercially licensed outlet as Ion O&O WINP-TV. In Charlotte, independent station WAXN-TV carried some programming aired by the network during its original iteration as Pax TV from 1998 to 2000, but never maintained a formal affiliation. Under an agreement with Fox Television Stations, Ion was added to the fourth digital subcarrier of then owned-and-operated station WJZY on September 29, 2016. Ion in Charlotte later moved to the DT6 feed of WJZY-TV.
St. Louis, at one time, received the network by way of a low-power repeater of O&O WPXS in nearby Mount Vernon, Illinois; in December 2013, the United States bankruptcy court approved a plan by creditors of Roberts Broadcasting to transfer East St. Louis-based MyNetworkTV affiliate WRBU and its sister stations, CW affiliate WZRB in Columbia, South Carolina and former CW affiliate WAZE-LP in Evansville, Indiana, to a trust with Ion Media Networks – a creditor in Roberts' Chapter 11 bankruptcy proceedings, for which it filed in 2011 – that would serve as its beneficiary. Roberts' attorney subsequently stated that Ion would purchase the three stations. WZRB and WRBU switched to Ion in February 2014 (although WZRB retained a secondary affiliation with The CW until MyNetworkTV affiliate WKTC joined the programming service in March); WRBU dropped MyNetworkTV upon becoming an Ion O&O (MyNetworkTV would not return to St. Louis until November 2014, when CBS affiliate KMOV launched a third digital subchannel to serve as an affiliate). WAZE-LP was silent at the time of acquisition, having gone dark the previous year after failing to construct its digital transmitter facilities, and Ion eventually decided on an affiliation deal with Nexstar Media Group's cluster in the area instead, using a subchannel of CW affiliate WTVW.
Buffalo and Rochester, New York, normally treated as separate markets, share Ion affiliate WPXJ-TV, which is centrally located between the two cities and is licensed to Batavia. An equivalent case exists involving Battle Creek, Michigan-licensed WZPX-TV, which serves both the Grand Rapids and Lansing markets (it also unusually served as a secondary WB affiliate due to a lack of stations in both markets until the digital age); additionally, Ann Arbor-licensed WPXD-TV also once provided an equivalent over-the-air signal for Lansing before moving their signal to a new transmitter in the Detroit suburb of Southfield in 2012.
In addition, in several other markets, Ion's predecessor was sold to another television station group to affiliate with a different English or Spanish language network, and through either a lack of channel space or interest in the network, Ion would not reappear in most of those markets until reaching deals to air on digital subchannels of other stations. These include:
Albuquerque, New Mexico: KAPX (now UniMás owned-and-operated station KTFQ, Ion now on KWBQ 19.4)
Baraboo, Wisconsin: W43BR (now a Family Channel affiliate, Ion now in Madison on WIFS 57.9)
Baton Rouge, Louisiana: WLFT-CD (now a religious independent station, Ion now on WVLA 33.3)
Champaign–Springfield, Illinois: WPXU (now CW affiliate WBUI, Ion now on WAND 17.3)
Charlottesville, Virginia: WADA-LP (now WVIR-CD (translator of NBC affiliate WVIR-TV), Ion now on WCAV 19.4)
Fresno–Visalia, California: KPXF (now UniMás owned-and-operated station KTFF, and was formerly on KNSO 51.3)
Little Rock, Arkansas: KYPX (now MeTV affiliate KMYA; Ion now on KARZ 42.3)
Montgomery, Alabama: WBMM (first switched to Daystar, now a CW affiliate, Ion now on WAKA 8.3)
Reno, Nevada: KREN (now an Univision affiliate, Ion now on KTVN 2.3)
Shreveport, Louisiana: KPXJ (now a CW affiliate, Ion now on KSHV 45.3)
Sioux Falls, South Dakota: KAUN-LP (now a Retro TV affiliate, Ion now on KELO 11.3)
Tucson, Arizona: KUVE-DT (now an Univision owned-and-operated station, then on KOLD 13.4. Now on KGUN-TV 9.5)
Las Vegas/Pahrump, Nevada: KPVM-LD (Now independent; formerly on KLAS-TV subchannel, now on KMCC)
San Juan, Puerto Rico/Saint Croix, U.S. Virgin Islands: WJPX (now an América TeVé affiliate, Ion now on WSVI 8)
In November 2015, Media General and Ion came to terms on an affiliation deal to add Ion's main feed as a standard definition digital subchannel in non-Ion O&O markets with Media General stations to replace the programming of the long-defunct Live Well Network, the first of its kind for Ion. Ion subchannels were added in markets such as Austin, Texas; Colorado Springs, Colorado; Green Bay, Wisconsin; Lafayette, Indiana; Davenport, Iowa; Lafayette, Louisiana; Lansing, Michigan; Richmond, Virginia; Springfield, Massachusetts; and Wichita, Kansas. These deals would carry over after the Media General stations were integrated into the Nexstar Media Group in January 2017, with WBAY-TV continuing to carry Ion under Gray Television ownership. Morgan Murphy Media's two Wisconsin stations (WISC-TV in Madison and WKBT-DT in La Crosse–Eau Claire) began to carry the network as a third subchannel at the beginning of February 2017. The network further expanded its affiliate reach into small and lower-ranked mid-sized markets during late 2016 and 2017, with Ion Media striking additional deals with companies such as Gray Television, Hubbard Broadcasting, Block Communications, Forum Communications, Heartland Media and the Meredith Corporation to carry Ion Television on digital subchannels of stations owned and/or operated by those groups.
In the fall of 2021, with the purchase of Ion Media by Scripps, it began to end outside contracts in markets with a Scripps station where Ion Television was on a subchannel rather than an Ion station, with the network being activated on Scripps-owned stations as a subchannel on WGBA-TV in Green Bay, Wisconsin (ending the subchannel deal with WBAY), KGUN-TV in Tucson, Arizona (from KOLD-TV), Richmond, Virginia's WTVR-TV (taking over from WRIC-TV), KRIS-TV in Corpus Christi, Texas (from KIII), and WFTX-TV in the Fort Myers, Florida market (rectifying the network's longest absence, as the market previously had no Ion station at all).
In several markets, the station's city of license is considered outside the main portion of a market's metropolitan area. Such cases include Minneapolis–Saint Paul, where that area's Ion O&O, KPXM-TV, is licensed to St. Cloud (60 miles (97 km) northwest of the Twin Cities); Detroit, where affiliate WPXD-TV is licensed to Ann Arbor, Michigan (40 miles (64 km) west of Detroit), though its digital transmitter is located in Southfield, where the bulk of Detroit's television stations base their studios and transmitter facilities; Hartford, where affiliate WHPX-TV is licensed to New London, Connecticut (located 40 miles (64 km) to the southeast), which moved its transmitter to the Farmington Rattlesnake Mountain site in the digital age; and Milwaukee, where O&O WPXE-TV is licensed to Kenosha, with its digital transmitter located at a tower farm on Milwaukee's north side (its former analog transmitter was located south of the city in Racine County). In the Cleveland market, Ion airs on Akron-based WVPX-TV, which had formerly targeted Akron, Canton and nearby areas as an ABC affiliate (then competing with the market's existing ABC station WEWS) prior to 1998.
== Related services ==
=== Multiplexing ===
Ion Television's stations have made notable use of "multiplexing" or splitting a digital broadcast television signal into separate subchannels. The network's stations usually carry up to six of these digital subchannels (in contrast with most other full-power stations, which usually carry a maximum of four channels over the same signal), each of which broadcast separate networks. Due to the bandwidth limitations caused by its carriage of multiple subchannels over a single broadcast signal, only the primary Ion network feed is transmitted in high definition, a mode of operation that remains under Scripps ownership. A small number of Ion stations have channel sharing agreements with other broadcasters after the FCC's 2016 spectrum re-allocation auction, while others such as Atlanta-area station WPXA-TV contract with other lower-power stations in a market to provide a full-power signal, such as Telemundo affiliate WKTB-CD.
==== Subchannels ====
===== Qubo =====
Qubo was a children's television network that launched on January 8, 2007, and is carried on the second digital subchannel of Ion Television's stations. Its launch was announced on May 8, 2006, when Ion Media Networks, NBCUniversal, Nelvana, Scholastic Media, Classic Media (now DreamWorks Classics which would later be owned by NBCUniversal) and its Big Idea Productions unit announced plans to create Qubo as a multi-platform children's entertainment endeavor that would extend to a weekly programming block on Ion Television as well as NBC and Telemundo, and a video-on-demand service for digital cable providers. Qubo features content from the programming libraries of each of the partners, though there was an early promise of each company producing a new series for the network each year; most of its programs are targeted at children ages 2 to 11, though its late night programming block "Qubo Night Owl" (which originally featured animated series from Qubo's partners and the Filmation library, but after August 2013 features a mix of animated and live-action series sourced solely from the distribution partners) is aimed at older teenagers and adults.
The network debuted on January 8, 2007. Its initial format was composed of a four-hour block of shows that repeated six times a day, all featuring programming exclusive to the new channel; by 2010, the channel adopted a more traditional schedule featuring a larger array of programs. As a consequence to the pending launch of Qubo, the i secondary feed was replaced on i O&Os with a repeating promo loop in late September 2006. NBCUniversal dropped out of the venture in 2012, with NBC and sister network Telemundo replacing their Qubo blocks with their own E/I-compliant children's lineups programmed by PBS Kids Sprout (now Universal Kids, which is part-owned by NBCUniversal's corporate parent Comcast) that July, relegating Qubo's companion programming block exclusively to Ion Television and Ion Plus; Ion Media Networks acquired the stakes of the remaining partners in the channel, which all retained distribution partnerships with Qubo, in 2013.
Programming on Qubo Channel and its companion block on Ion Television and Ion Plus accounted for all educational programming content on Ion's owned-and-operated stations, thus relieving the network from the responsibility of carrying programs compliant with Children's Television Act guidelines on its other subchannel services.
Qubo ceased broadcasting after Ion Media's acquisition by the E. W. Scripps Company and merger with Katz Broadcasting.
===== Ion Plus =====
Ion Plus (originally named "iHealth" prior to its launch and "Ion Life" until July 1, 2019) launched on February 19, 2007, and was carried on the third digital subchannel of Ion Television's stations. Under its former format, the network mainly featured health and lifestyle programs, as well as feature films on Sunday mornings and select weeknights (which consist mainly of those its parent network is scheduled to air during the given month as part of the "Ion Television at the Movies" block); some extreme sports programming previously aired on weekend evenings until July 2014. Much of Ion Life's programming consists of Canadian-imported programs, with some limited U.S.-produced programming. The network originally maintained a 24-hour entertainment schedule until 2013, when Ion Life added a limited number of infomercials in mid-morning and midday timeslots. As of July 1, 2019, it was rebranded to Ion Plus, acting as a de facto extension of the main Ion service, featuring all-day marathon scheduling of one series, along with the same scheduling of paid programming.
Ion Plus ceased broadcasting over-the-air after Ion Media's acquisition by the E. W. Scripps Company and merger with Katz Broadcasting on February 28, 2021, but continues to air as an advertising-supported video-on-demand network through several AVOD streaming services, including Samsung TV Plus, and Vizio WatchFree.
On June 17, 2024, Scripps quietly posted a promotional video to the social media presences of Ion Plus and Defy TV that the latter would be wound down at the end of June (its programming moving to another unrelated network provisionally known as Dare, launching that day, but which was sold the Defy branding shortly before its debut and returned to the air with the same brand and imaging), with Ion Plus returning to over-the-air availability on July 1; MacGyver and Scorpion will be added to Ion Plus to augment its schedule as the mainline Ion network adds further sports programming to its schedule.
===== Ion Shop =====
In April 2012, Ion Media Networks launched a new service known as Ion Shop (originally "iShop" prior to November 2012, and "ShopTV" thereafter, both are names used only by the PSIP identifiers on digital television tuners and converter boxes; there was never explicit on-air branding used by the channel itself); some Ion owned-and-operated stations, however, did not begin carrying the network until as late as that November. Carried as a fourth digital subchannel on Ion Television's owned-and-operated stations, it primarily carried informercials; until June 2013, Ion Shop also aired blocks of programming from Ion Life in some morning and late night timeslots.
Ion Shop ceased operations on February 28, 2021.
===== Ion Mystery =====
On February 24, 2022, the Court TV Mystery network was rebranded as Ion Mystery, with the "Ion" brand now more established regarding procedural dramas in general, including Ion Mystery's overall programming, whereas Court TV is more associated with its news division.
===== QVC Over the Air =====
On August 5, 2013, as part of a partnership between QVC and Ion Media Networks to expand the channel's broadcast television coverage, Ion Television began carrying the cable and satellite home shopping network via a fifth digital subchannel on most of its owned-and-operated stations. Although the network maintains a high-definition simulcast feed, QVC is transmitted in standard definition to preserve channel bandwidth to allow the primary Ion network feed to transmit in HD, with the normally letterboxed SD feed squeezed to full-screen to fit 4:3 television sets (preventing windowboxing of the subchannel on 16:9 sets). QVC is also broadcast on digital subchannels of low-powered television stations (mainly those not owned by Ion Media Networks) in selected areas, including in some areas where an Ion station also carries it. The channel's broadcast service is branded as "QVC Over the Air", with an accompanying on-screen bug appearing on the lower right corner of the screen during the network's programming; the service can be differentiated from the cable network due to the use of a different toll-free number and QR code on-screen to account for any sales made from shoppers through the over the air version of the network. Some Ion-affiliated and owned stations have declined to carry QVC's programming because of other partnerships between QVC and other broadcasters, along with other spectrum agreements to carry other stations and networks; this is also the case with HSN in the next section. The partnership remains in effect in many markets under Scripps ownership and Inyo affiliations, though some stations ended distribution of the network after February 2021 in favor of the Katz networks.
===== Home Shopping Network =====
On November 18, 2013, Ion Television began carrying the Home Shopping Network via a sixth digital subchannel on most of its owned-and-operated stations, as part of a partnership with Ion Media Networks (both once controlled by Lowell "Bud" Paxson) to expand the channel's broadcast coverage. Although it has a high definition simulcast feed, HSN is transmitted by Ion stations in standard definition, due to the same digital multiplexing limitations that prevent QVC from being carried in 16:9 SD or HD. HSN has been widely available over-the-air throughout the United States since its inception – through stations that the network had owned prior to the 1998 reorganization of its Silver King Broadcasting group into USA Broadcasting (some of which were converted into general entertainment independent outlets, and were later sold to Univision Communications to form the charter stations of the present-day UniMás network), and had been mainly available on low-power television stations immediately prior to its subchannel-leasing agreement with Ion; HSN is carried on low-power stations in some markets where an Ion station also carries the network, though HSN's programming is exclusive to an existing affiliate in a few areas where both networks are present (such as Atlanta, where WPXA-TV formerly simulcast Telemundo affiliate WKTB-CD on its DT6 subchannel under a time-leasing arrangement until the sale of that station to Gray Television and its move to WANF's spectrum, and W13DQ-D carries HSN). Some Ion-affiliated stations decline to carry HSN's programming, and some Ion Media-owned stations are unable to carry that network due to affiliation agreements between HSN and other broadcasters that existed prior to the Ion deal. The partnership remains in effect in many markets under Scripps ownership and Inyo affiliations, though some stations ended distribution of the network after February 2021 in favor of the Katz networks.
=== National feeds ===
Separate national feeds (formerly known as "i Plus" or "Ion Plus") have been made available to pay television providers, including Dish Network, DirecTV, Comcast and Charter Communications. A separate advertising-supported video-on-demand feed is also available through several AVOD streaming services, including Samsung TV Plus, Vizio WatchFree, Xumo, Tubi, Freevee, The Roku Channel, and TCL Channel, which features programming sourced from Ion Plus in place of paid programming that airs on the main network. Prior to the launch of Ion Life, the Ion Plus feeds carried reruns of cancelled Pax original programs (such as Miracle Pets and Beat the Clock), as well as public domain movies and sitcom episodes (such as I Married Joan and The Beverly Hillbillies). The feeds used the Pax name and bug after the network's rebrand as i, until about September 2005. As Ion has refocused towards its current schedule however, along with a de-emphasis on local advertising, the national pay-TV feed effectively repeats Ion's main feed outside a lack of station identification.
== See also ==
PBS
CBS
NBC
American Broadcasting Company
Fox Broadcasting Company
== References ==
== External links ==
Official website
|
https://en.wikipedia.org/wiki/Ion_Television
|
The Tao of Programming is a book written in 1987 by Geoffrey James. Written in a tongue-in-cheek style spoof of classic Taoist texts such as the Tao Te Ching and Zhuangzi which belies its serious message, it consists of a series of short anecdotes divided into nine "books":
The Silent Void
The Ancient Masters
Design
Coding
Maintenance
Management
Corporate Wisdom
Hardware and Software
Epilogue
Geoffrey James wrote two other books on this theme, The Zen of Programming (978-0931137099) in 1988 and Computer Parables: Enlightenment in the Information Age (978-0931137136) in 1989.
== See also ==
Hacker koan
== References ==
|
https://en.wikipedia.org/wiki/The_Tao_of_Programming
|
In computer science, an interpreter is a computer program that directly executes instructions written in a programming or scripting language, without requiring them previously to have been compiled into a machine language program. An interpreter generally uses one of the following strategies for program execution:
Parse the source code and perform its behavior directly;
Translate source code into some efficient intermediate representation or object code and immediately execute that;
Explicitly execute stored precompiled bytecode made by a compiler and matched with the interpreter's virtual machine.
Early versions of Lisp programming language and minicomputer and microcomputer BASIC dialects would be examples of the first type. Perl, Raku, Python, MATLAB, and Ruby are examples of the second, while UCSD Pascal is an example of the third type. Source programs are compiled ahead of time and stored as machine independent code, which is then linked at run-time and executed by an interpreter and/or compiler (for JIT systems). Some systems, such as Smalltalk and contemporary versions of BASIC and Java, may also combine two and three types. Interpreters of various types have also been constructed for many languages traditionally associated with compilation, such as Algol, Fortran, Cobol, C and C++.
While interpretation and compilation are the two main means by which programming languages are implemented, they are not mutually exclusive, as most interpreting systems also perform some translation work, just like compilers. The terms "interpreted language" or "compiled language" signify that the canonical implementation of that language is an interpreter or a compiler, respectively. A high-level language is ideally an abstraction independent of particular implementations.
== History ==
Interpreters were used as early as 1952 to ease programming within the limitations of computers at the time (e.g. a shortage of program storage space, or no native support for floating point numbers). Interpreters were also used to translate between low-level machine languages, allowing code to be written for machines that were still under construction and tested on computers that already existed. The first interpreted high-level language was Lisp. Lisp was first implemented by Steve Russell on an IBM 704 computer. Russell had read John McCarthy's paper, "Recursive Functions of Symbolic Expressions and Their Computation by Machine, Part I", and realized (to McCarthy's surprise) that the Lisp eval function could be implemented in machine code. The result was a working Lisp interpreter which could be used to run Lisp programs, or more properly, "evaluate Lisp expressions".
The development of editing interpreters was influenced by the need for interactive computing. In the 1960s, the introduction of time-sharing systems allowed multiple users to access a computer simultaneously, and editing interpreters became essential for managing and modifying code in real-time. The first editing interpreters were likely developed for mainframe computers, where they were used to create and modify programs on the fly. One of the earliest examples of an editing interpreter is the EDT (Editor and Debugger for the TECO) system, which was developed in the late 1960s for the PDP-1 computer. EDT allowed users to edit and debug programs using a combination of commands and macros, paving the way for modern text editors and interactive development environments.
== General operation ==
An interpreter usually consists of a set of known commands it can execute, and a list of these commands in the order a programmer wishes to execute them. Each command (also known as an Instruction) contains the data the programmer wants to mutate, and information on how to mutate the data. For example, an interpreter might read ADD Books, 5 and interpret it as a request to add five to the Books variable.
Interpreters have a wide variety of instructions which are specialized to perform different tasks, but you will commonly find interpreter instructions for basic mathematical operations, branching, and memory management, making most interpreters Turing complete. Many interpreters are also closely integrated with a garbage collector and debugger.
== Compilers versus interpreters ==
Programs written in a high-level language are either directly executed by some kind of interpreter or converted into machine code by a compiler (and assembler and linker) for the CPU to execute.
While compilers (and assemblers) generally produce machine code directly executable by computer hardware, they can often (optionally) produce an intermediate form called object code. This is basically the same machine specific code but augmented with a symbol table with names and tags to make executable blocks (or modules) identifiable and relocatable. Compiled programs will typically use building blocks (functions) kept in a library of such object code modules. A linker is used to combine (pre-made) library files with the object file(s) of the application to form a single executable file. The object files that are used to generate an executable file are thus often produced at different times, and sometimes even by different languages (capable of generating the same object format).
A simple interpreter written in a low-level language (e.g. assembly) may have similar machine code blocks implementing functions of the high-level language stored, and executed when a function's entry in a look up table points to that code. However, an interpreter written in a high-level language typically uses another approach, such as generating and then walking a parse tree, or by generating and executing intermediate software-defined instructions, or both.
Thus, both compilers and interpreters generally turn source code (text files) into tokens, both may (or may not) generate a parse tree, and both may generate immediate instructions (for a stack machine, quadruple code, or by other means). The basic difference is that a compiler system, including a (built in or separate) linker, generates a stand-alone machine code program, while an interpreter system instead performs the actions described by the high-level program.
A compiler can thus make almost all the conversions from source code semantics to the machine level once and for all (i.e. until the program has to be changed) while an interpreter has to do some of this conversion work every time a statement or function is executed. However, in an efficient interpreter, much of the translation work (including analysis of types, and similar) is factored out and done only the first time a program, module, function, or even statement, is run, thus quite akin to how a compiler works. However, a compiled program still runs much faster, under most circumstances, in part because compilers are designed to optimize code, and may be given ample time for this. This is especially true for simpler high-level languages without (many) dynamic data structures, checks, or type checking.
In traditional compilation, the executable output of the linkers (.exe files or .dll files or a library, see picture) is typically relocatable when run under a general operating system, much like the object code modules are but with the difference that this relocation is done dynamically at run time, i.e. when the program is loaded for execution. On the other hand, compiled and linked programs for small embedded systems are typically statically allocated, often hard coded in a NOR flash memory, as there is often no secondary storage and no operating system in this sense.
Historically, most interpreter systems have had a self-contained editor built in. This is becoming more common also for compilers (then often called an IDE), although some programmers prefer to use an editor of their choice and run the compiler, linker and other tools manually. Historically, compilers predate interpreters because hardware at that time could not support both the interpreter and interpreted code and the typical batch environment of the time limited the advantages of interpretation.
=== Development cycle ===
During the software development cycle, programmers make frequent changes to source code. When using a compiler, each time a change is made to the source code, they must wait for the compiler to translate the altered source files and link all of the binary code files together before the program can be executed. The larger the program, the longer the wait. By contrast, a programmer using an interpreter does a lot less waiting, as the interpreter usually just needs to translate the code being worked on to an intermediate representation (or not translate it at all), thus requiring much less time before the changes can be tested. Effects are evident upon saving the source code and reloading the program. Compiled code is generally less readily debugged as editing, compiling, and linking are sequential processes that have to be conducted in the proper sequence with a proper set of commands. For this reason, many compilers also have an executive aid, known as a Makefile and program. The Makefile lists compiler and linker command lines and program source code files, but might take a simple command line menu input (e.g. "Make 3") which selects the third group (set) of instructions then issues the commands to the compiler, and linker feeding the specified source code files.
=== Distribution ===
A compiler converts source code into binary instruction for a specific processor's architecture, thus making it less portable. This conversion is made just once, on the developer's environment, and after that the same binary can be distributed to the user's machines where it can be executed without further translation. A cross compiler can generate binary code for the user machine even if it has a different processor than the machine where the code is compiled.
An interpreted program can be distributed as source code. It needs to be translated in each final machine, which takes more time but makes the program distribution independent of the machine's architecture. However, the portability of interpreted source code is dependent on the target machine actually having a suitable interpreter. If the interpreter needs to be supplied along with the source, the overall installation process is more complex than delivery of a monolithic executable, since the interpreter itself is part of what needs to be installed.
The fact that interpreted code can easily be read and copied by humans can be of concern from the point of view of copyright. However, various systems of encryption and obfuscation exist. Delivery of intermediate code, such as bytecode, has a similar effect to obfuscation, but bytecode could be decoded with a decompiler or disassembler.
=== Efficiency ===
The main disadvantage of interpreters is that an interpreted program typically runs more slowly than if it had been compiled. The difference in speeds could be tiny or great; often an order of magnitude and sometimes more. It generally takes longer to run a program under an interpreter than to run the compiled code but it can take less time to interpret it than the total time required to compile and run it. This is especially important when prototyping and testing code when an edit-interpret-debug cycle can often be much shorter than an edit-compile-run-debug cycle.
Interpreting code is slower than running the compiled code because the interpreter must analyze each statement in the program each time it is executed and then perform the desired action, whereas the compiled code just performs the action within a fixed context determined by the compilation. This run-time analysis is known as "interpretive overhead". Access to variables is also slower in an interpreter because the mapping of identifiers to storage locations must be done repeatedly at run-time rather than at compile time.
There are various compromises between the development speed when using an interpreter and the execution speed when using a compiler. Some systems (such as some Lisps) allow interpreted and compiled code to call each other and to share variables. This means that once a routine has been tested and debugged under the interpreter it can be compiled and thus benefit from faster execution while other routines are being developed. Many interpreters do not execute the source code as it stands but convert it into some more compact internal form. Many BASIC interpreters replace keywords with single byte tokens which can be used to find the instruction in a jump table. A few interpreters, such as the PBASIC interpreter, achieve even higher levels of program compaction by using a bit-oriented rather than a byte-oriented program memory structure, where commands tokens occupy perhaps 5 bits, nominally "16-bit" constants are stored in a variable-length code requiring 3, 6, 10, or 18 bits, and address operands include a "bit offset". Many BASIC interpreters can store and read back their own tokenized internal representation.
An interpreter might well use the same lexical analyzer and parser as the compiler and then interpret the resulting abstract syntax tree. Example data type definitions for the latter, and a toy interpreter for syntax trees obtained from C expressions are shown in the box.
=== Regression ===
Interpretation cannot be used as the sole method of execution: even though an interpreter can itself be interpreted and so on, a directly executed program is needed somewhere at the bottom of the stack because the code being interpreted is not, by definition, the same as the machine code that the CPU can execute.
== Variations ==
=== Bytecode interpreters ===
There is a spectrum of possibilities between interpreting and compiling, depending on the amount of analysis performed before the program is executed. For example, Emacs Lisp is compiled to bytecode, which is a highly compressed and optimized representation of the Lisp source, but is not machine code (and therefore not tied to any particular hardware). This "compiled" code is then interpreted by a bytecode interpreter (itself written in C). The compiled code in this case is machine code for a virtual machine, which is implemented not in hardware, but in the bytecode interpreter. Such compiling interpreters are sometimes also called compreters. In a bytecode interpreter each instruction starts with a byte, and therefore bytecode interpreters have up to 256 instructions, although not all may be used. Some bytecodes may take multiple bytes, and may be arbitrarily complicated.
Control tables - that do not necessarily ever need to pass through a compiling phase - dictate appropriate algorithmic control flow via customized interpreters in similar fashion to bytecode interpreters.
=== Threaded code interpreters ===
Threaded code interpreters are similar to bytecode interpreters but instead of bytes they use pointers. Each "instruction" is a word that points to a function or an instruction sequence, possibly followed by a parameter. The threaded code interpreter either loops fetching instructions and calling the functions they point to, or fetches the first instruction and jumps to it, and every instruction sequence ends with a fetch and jump to the next instruction. Unlike bytecode there is no effective limit on the number of different instructions other than available memory and address space. The classic example of threaded code is the Forth code used in Open Firmware systems: the source language is compiled into "F code" (a bytecode), which is then interpreted by a virtual machine.
=== Abstract syntax tree interpreters ===
In the spectrum between interpreting and compiling, another approach is to transform the source code into an optimized abstract syntax tree (AST), then execute the program following this tree structure, or use it to generate native code just-in-time. In this approach, each sentence needs to be parsed just once. As an advantage over bytecode, the AST keeps the global program structure and relations between statements (which is lost in a bytecode representation), and when compressed provides a more compact representation. Thus, using AST has been proposed as a better intermediate format for just-in-time compilers than bytecode. Also, it allows the system to perform better analysis during runtime.
However, for interpreters, an AST causes more overhead than a bytecode interpreter, because of nodes related to syntax performing no useful work, of a less sequential representation (requiring traversal of more pointers) and of overhead visiting the tree.
=== Just-in-time compilation ===
Further blurring the distinction between interpreters, bytecode interpreters and compilation is just-in-time (JIT) compilation, a technique in which the intermediate representation is compiled to native machine code at runtime. This confers the efficiency of running native code, at the cost of startup time and increased memory use when the bytecode or AST is first compiled. The earliest published JIT compiler is generally attributed to work on LISP by John McCarthy in 1960. Adaptive optimization is a complementary technique in which the interpreter profiles the running program and compiles its most frequently executed parts into native code. The latter technique is a few decades old, appearing in languages such as Smalltalk in the 1980s.
Just-in-time compilation has gained mainstream attention amongst language implementers in recent years, with Java, the .NET Framework, most modern JavaScript implementations, and Matlab now including JIT compilers.
=== Template Interpreter ===
Making the distinction between compilers and interpreters yet again even more vague is a special interpreter design known as a template interpreter. Rather than implement the execution of code by virtue of a large switch statement containing every possible bytecode, while operating on a software stack or a tree walk, a template interpreter maintains a large array of bytecode (or any efficient intermediate representation) mapped directly to corresponding native machine instructions that can be executed on the host hardware as key value pairs (or in more efficient designs, direct addresses to the native instructions), known as a "Template". When the particular code segment is executed the interpreter simply loads or jumps to the opcode mapping in the template and directly runs it on the hardware. Due to its design, the template interpreter very strongly resembles a just-in-time compiler rather than a traditional interpreter, however it is technically not a JIT due to the fact that it merely translates code from the language into native calls one opcode at a time rather than creating optimized sequences of CPU executable instructions from the entire code segment. Due to the interpreter's simple design of simply passing calls directly to the hardware rather than implementing them directly, it is much faster than every other type, even bytecode interpreters, and to an extent less prone to bugs, but as a tradeoff is more difficult to maintain due to the interpreter having to support translation to multiple different architectures instead of a platform independent virtual machine/stack. To date, the only template interpreter implementations of widely known languages to exist are the interpreter within Java's official reference implementation, the Sun HotSpot Java Virtual Machine, and the Ignition Interpreter in the Google V8 javascript execution engine.
=== Self-interpreter ===
A self-interpreter is a programming language interpreter written in a programming language which can interpret itself; an example is a BASIC interpreter written in BASIC. Self-interpreters are related to self-hosting compilers.
If no compiler exists for the language to be interpreted, creating a self-interpreter requires the implementation of the language in a host language (which may be another programming language or assembler). By having a first interpreter such as this, the system is bootstrapped and new versions of the interpreter can be developed in the language itself. It was in this way that Donald Knuth developed the TANGLE interpreter for the language WEB of the de-facto standard TeX typesetting system.
Defining a computer language is usually done in relation to an abstract machine (so-called operational semantics) or as a mathematical function (denotational semantics). A language may also be defined by an interpreter in which the semantics of the host language is given. The definition of a language by a self-interpreter is not well-founded (it cannot define a language), but a self-interpreter tells a reader about the expressiveness and elegance of a language. It also enables the interpreter to interpret its source code, the first step towards reflective interpreting.
An important design dimension in the implementation of a self-interpreter is whether a feature of the interpreted language is implemented with the same feature in the interpreter's host language. An example is whether a closure in a Lisp-like language is implemented using closures in the interpreter language or implemented "manually" with a data structure explicitly storing the environment. The more features implemented by the same feature in the host language, the less control the programmer of the interpreter has; for example, a different behavior for dealing with number overflows cannot be realized if the arithmetic operations are delegated to corresponding operations in the host language.
Some languages such as Lisp and Prolog have elegant self-interpreters. Much research on self-interpreters (particularly reflective interpreters) has been conducted in the Scheme programming language, a dialect of Lisp. In general, however, any Turing-complete language allows writing of its own interpreter. Lisp is such a language, because Lisp programs are lists of symbols and other lists. XSLT is such a language, because XSLT programs are written in XML. A sub-domain of metaprogramming is the writing of domain-specific languages (DSLs).
Clive Gifford introduced a measure quality of self-interpreter (the eigenratio), the limit of the ratio between computer time spent running a stack of N self-interpreters and time spent to run a stack of N − 1 self-interpreters as N goes to infinity. This value does not depend on the program being run.
The book Structure and Interpretation of Computer Programs presents examples of meta-circular interpretation for Scheme and its dialects. Other examples of languages with a self-interpreter are Forth and Pascal.
=== Microcode ===
Microcode is a very commonly used technique "that imposes an interpreter between the hardware and the architectural level of a computer". As such, the microcode is a layer of hardware-level instructions that implement higher-level machine code instructions or internal state machine sequencing in many digital processing elements. Microcode is used in general-purpose central processing units, as well as in more specialized processors such as microcontrollers, digital signal processors, channel controllers, disk controllers, network interface controllers, network processors, graphics processing units, and in other hardware.
Microcode typically resides in special high-speed memory and translates machine instructions, state machine data or other input into sequences of detailed circuit-level operations. It separates the machine instructions from the underlying electronics so that instructions can be designed and altered more freely. It also facilitates the building of complex multi-step instructions, while reducing the complexity of computer circuits. Writing microcode is often called microprogramming and the microcode in a particular processor implementation is sometimes called a microprogram.
More extensive microcoding allows small and simple microarchitectures to emulate more powerful architectures with wider word length, more execution units and so on, which is a relatively simple way to achieve software compatibility between different products in a processor family.
=== Computer processor ===
Even a non microcoding computer processor itself can be considered to be a parsing immediate execution interpreter that is written in a general purpose hardware description language such as VHDL to create a system that parses the machine code instructions and immediately executes them.
== Applications ==
Interpreters are frequently used to execute command languages, and glue languages since each operator executed in command language is usually an invocation of a complex routine such as an editor or compiler.
Self-modifying code can easily be implemented in an interpreted language. This relates to the origins of interpretation in Lisp and artificial intelligence research.
Virtualization. Machine code intended for a hardware architecture can be run using a virtual machine. This is often used when the intended architecture is unavailable, or among other uses, for running multiple copies.
Sandboxing: While some types of sandboxes rely on operating system protections, an interpreter or virtual machine is often used. The actual hardware architecture and the originally intended hardware architecture may or may not be the same. This may seem pointless, except that sandboxes are not compelled to actually execute all the instructions the source code it is processing. In particular, it can refuse to execute code that violates any security constraints it is operating under.
Emulators for running computer software written for obsolete and unavailable hardware on more modern equipment.
== See also ==
BASIC interpreter
Command-line interpreter
Compiled language
Dynamic compilation
Homoiconicity
Meta-circular evaluator
Partial evaluation
Read–eval–print loop
== References ==
== Sources ==
Aycock, J. (June 2003). "A brief history of just-in-time". ACM Computing Surveys. 35 (2): 97–113. CiteSeerX 10.1.1.97.3985. doi:10.1145/857076.857077. S2CID 15345671.
== External links ==
IBM Card Interpreters page at Columbia University
Theoretical Foundations For Practical 'Totally Functional Programming' (Chapter 7 especially) Doctoral dissertation tackling the problem of formalising what is an interpreter
Short animation explaining the key conceptual difference between interpreters and compilers. Archived at ghostarchive.org on May 9, 2022.
|
https://en.wikipedia.org/wiki/Interpreter_(computing)
|
Grace Brewster Hopper (née Murray; December 9, 1906 – January 1, 1992) was an American computer scientist, mathematician, and United States Navy rear admiral. She was a pioneer of computer programming. Hopper was the first to devise the theory of machine-independent programming languages, and used this theory to develop the FLOW-MATIC programming language and COBOL, an early high-level programming language still in use today. She was also one of the first programmers on the Harvard Mark I computer. She is credited with writing the first computer manual, "A Manual of Operation for the Automatic Sequence Controlled Calculator."
Before joining the Navy, Hopper earned a Ph.D. in both mathematics and mathematical physics from Yale University and was a professor of mathematics at Vassar College. She left her position at Vassar to join the United States Navy Reserve during World War II. Hopper began her computing career in 1944 as a member of the Harvard Mark I team, led by Howard H. Aiken. In 1949, she joined the Eckert–Mauchly Computer Corporation and was part of the team that developed the UNIVAC I computer. At Eckert–Mauchly she managed the development of one of the first COBOL compilers.
She believed that programming should be simplified with an English-based computer programming language. Her compiler converted English terms into machine code understood by computers. By 1952, Hopper had finished her program linker (originally called a compiler), which was written for the A-0 System. In 1954, Eckert–Mauchly chose Hopper to lead their department for automatic programming, and she led the release of some of the first compiled languages like FLOW-MATIC. In 1959, she participated in the CODASYL consortium, helping to create a machine-independent programming language called COBOL, which was based on English words. Hopper promoted the use of the language throughout the 60s.
The U.S. Navy Arleigh Burke-class guided-missile destroyer USS Hopper was named for her, as was the Cray XE6 "Hopper" supercomputer at NERSC, and the Nvidia GPU architecture "Hopper". During her lifetime, Hopper was awarded 40 honorary degrees from universities across the world. A college at Yale University was renamed in her honor. In 1991, she received the National Medal of Technology. On November 22, 2016, she was posthumously awarded the Presidential Medal of Freedom by President Barack Obama. In 2024, the Institute of Electrical and Electronics Engineers (IEEE) dedicated a marker in honor of Grace Hopper at the University of Pennsylvania for her role in inventing the A-0 compiler during her time as a Lecturer in the School of Engineering, citing her inspirational impact on young engineers.
== Early life and education ==
Grace Brewster Murray was born in New York City. She was the eldest of three children. Her parents, Walter Fletcher Murray and Mary Campbell Van Horne, were of Scottish and Dutch descent, and attended West End Collegiate Church. Her great-grandfather, Alexander Wilson Russell, an admiral in the US Navy, fought in the Battle of Mobile Bay during the Civil War.: 2–3
Grace was very curious as a child; this was a lifelong trait. At the age of seven, she decided to determine how an alarm clock worked and dismantled seven alarm clocks before her mother realized what she was doing (she was then limited to one clock). Later in life, she was known for keeping a clock that ran backward, she explained, "Humans are allergic to change. They love to say, 'We've always done it this way.' I try to fight that. That's why I have a clock on my wall that runs counterclockwise." For her preparatory school education, she attended the Hartridge School in Plainfield, New Jersey. Grace was initially rejected for early admission to Vassar College at age 16 (because her test scores in Latin were too low), but she was admitted the next year. She graduated Phi Beta Kappa from Vassar in 1928 with a bachelor's degree in mathematics and physics and earned her master's degree at Yale University in 1930.
In 1930, Grace Murray married New York University professor Vincent Foster Hopper (1906–1976); they divorced in 1945. She did not marry again and retained his surname.
In 1934, Hopper earned a Ph.D. in mathematics from Yale under the direction of Øystein Ore. Her dissertation, "New Types of Irreducibility Criteria", was published that same year. She began teaching mathematics at Vassar in 1931, and was promoted to associate professor in 1941.
== Career ==
=== World War II ===
Hopper tried to be commissioned in the Navy early in World War II, however she was turned down. At age 34, she was too old to enlist and her weight-to-height ratio was too low. She was also denied on the basis that her job as a mathematician and mathematics professor at Vassar College was valuable to the war effort. During the war in 1943, Hopper obtained a leave of absence from Vassar and was sworn into the United States Navy Reserve; she was one of many women who volunteered to serve in the WAVES.
She had to get an exemption to be commissioned; she was 15 pounds (6.8 kg) below the Navy minimum weight of 120 pounds (54 kg). She reported in December and trained at the Naval Reserve Midshipmen's School at Smith College in Northampton, Massachusetts. Hopper graduated first in her class in 1944, and was assigned to the Bureau of Ships Computation Project at Harvard University as a lieutenant, junior grade. She served on the Mark I computer programming staff headed by Howard H. Aiken.
Hopper and Aiken co-authored three papers on the Mark I, also known as the Automatic Sequence Controlled Calculator. Hopper's request to transfer to the regular Navy at the end of the war was declined due to her advanced age of 38. She continued to serve in the Navy Reserve. Hopper remained at the Harvard Computation Lab until 1949, turning down a full professorship at Vassar in favor of working as a research fellow under a Navy contract at Harvard.
=== UNIVAC ===
In 1949, Hopper became an employee of the Eckert–Mauchly Computer Corporation as a senior mathematician and joined the team developing the UNIVAC I. Hopper also served as UNIVAC director of Automatic Programming Development for Remington Rand. The UNIVAC was the first known large-scale electronic computer to be on the market in 1951.
When Hopper recommended the development of a new programming language that would use entirely English words, she "was told very quickly that [she] couldn't do this because computers didn't understand English." Still, she persisted. "It's much easier for most people to write an English statement than it is to use symbols", she explained. "So I decided data processors ought to be able to write their programs in English, and the computers would translate them into machine code."
Her idea was not accepted for three years. In the meantime, she published her first paper on the subject, compilers, in 1952. In the early 1950s, the company was taken over by the Remington Rand corporation, and it was while she was working for them that her original compiler work was done. The program was known as the A compiler and its first version was A-0.: 11
In 1952, she had an operational link-loader, which at the time was referred to as a compiler. She later said that "Nobody believed that", and that she "had a running compiler and nobody would touch it. They told me computers could only do arithmetic."
In 1954 Hopper was named the company's first director of automatic programming. Beginning in 1954, Hopper's work was influenced by the Laning and Zierler system, which was the first compiler to accept algebraic notation as input. Her department released some of the first compiler-based programming languages, including MATH-MATIC and FLOW-MATIC.
Hopper said that her compiler A-0, "translated mathematical notation into machine code. Manipulating symbols was fine for mathematicians but it was no good for data processors who were not symbol manipulators. Very few people are really symbol manipulators. If they are, they become professional mathematicians, not data processors. It's much easier for most people to write an English statement than it is to use symbols. So I decided data processors ought to be able to write their programs in English, and the computers would translate them into machine code. That was the beginning of COBOL, a computer language for data processors. I could say 'Subtract income tax from pay' instead of trying to write that in octal code or using all kinds of symbols. COBOL is the major language used today in data processing."
=== COBOL ===
In the spring of 1959, computer experts from industry and government were brought together in a two-day conference known as the Conference on Data Systems Languages (CODASYL). Hopper served as a technical consultant to the committee, and many of her former employees served on the short-term committee that defined the new language COBOL (an acronym for COmmon Business-Oriented Language). The new language extended Hopper's FLOW-MATIC language with some ideas from the IBM equivalent, COMTRAN. Hopper's belief that programs should be written in a language that was close to English (rather than in machine code or in languages close to machine code, such as assembly languages) was captured in the new business language, and COBOL went on to be the most ubiquitous business language to date. Among the members of the committee that worked on COBOL was Mount Holyoke College alumna Jean E. Sammet.
From 1967 to 1977, Hopper served as the director of the Navy Programming Languages Group in the Navy's Office of Information Systems Planning and was promoted to the rank of captain in 1973. She developed validation software for COBOL and its compiler as part of a COBOL standardization program for the entire Navy.
=== Standards ===
In the 1970s, Hopper advocated for the Defense Department to replace large, centralized systems with networks of small, distributed computers. Any user on any computer node could access common databases on the network.: 119 She developed the implementation of standards for testing computer systems and components, most significantly for early programming languages such as FORTRAN and COBOL. The Navy tests for conformance to these standards led to significant convergence among the programming language dialects of the major computer vendors. In the 1980s, these tests (and their official administration) were assumed by the National Bureau of Standards (NBS), known today as the National Institute of Standards and Technology (NIST).
== Retirement ==
In accordance with Navy attrition regulations, Hopper retired from the Naval Reserve with the rank of commander at age 60 at the end of 1966. She was recalled to active duty in August 1967 for a six-month period that turned into an indefinite assignment. She again retired in 1971 but was again asked to return to active duty in 1972. She was promoted to captain in 1973 by Admiral Elmo R. Zumwalt Jr.
After Republican Representative Philip Crane saw her on a March 1983 segment of 60 Minutes, he championed a joint resolution to promote Hopper to commodore on the retired list; the resolution was referred to, but not reported out of, the Senate Armed Services Committee. Hopper was instead promoted to commodore on December 15, 1983, via the Appointments Clause by President Ronald Reagan. She remained on active duty for several years beyond mandatory retirement by special approval of Congress. Effective November 8, 1985, the rank of commodore was renamed rear admiral (lower half) and Hopper became one of the Navy's few female admirals.
After a career that spanned more than 42 years, Hopper retired from the Navy on August 14, 1986. At the time, she was the oldest serving member of the Navy. At a celebration held in Boston on the USS Constitution to commemorate her retirement, Hopper was awarded the Defense Distinguished Service Medal, the highest non-combat decoration awarded by the Department of Defense.
At the time of her retirement, she was the oldest active-duty commissioned officer in the United States Navy (79 years, eight months and five days), and had her retirement ceremony aboard the oldest commissioned ship in the United States Navy (188 years, 9 months, 23 days).
== Post-retirement ==
After her retirement from the Navy, Hopper was hired as a senior consultant to Digital Equipment Corporation (DEC). Hopper was initially offered a position by Rita Yavinsky, but she insisted on going through the typical formal interview process. She then proposed in jest that she would be willing to accept a position which made her available on alternating Thursdays, exhibited at their museum of computing as a pioneer, in exchange for a generous salary and unlimited expense account. Instead, she was hired as a full-time Principal Corporate Consulting Engineer, a tech-track SVP-equivalent. In this position, Hopper represented the company at industry forums, serving on various industry committees, along with other obligations. She retained that position until her death at age 85 in 1992.
At DEC Hopper served primarily as a goodwill ambassador. She lectured widely about the early days of computing, her career, and on efforts that computer vendors could take to make life easier for their users. She visited most of Digital's engineering facilities, where she generally received a standing ovation at the conclusion of her remarks. Although no longer a serving officer, she always wore her Navy full dress uniform to these lectures contrary to U.S. Department of Defense policy. In 2016 Hopper received the Presidential Medal of Freedom, the nation's highest civilian honor, in recognition of her remarkable contributions to the field of computer science.
"The most important thing I've accomplished, other than building the compiler", she said, "is training young people. They come to me, you know, and say, 'Do you think we can do this?' I say, 'Try it.' And I back 'em up. They need that. I keep track of them as they get older and I stir 'em up at intervals so they don't forget to take chances."
== Anecdotes ==
Throughout much of her later career, Hopper was much in demand as a speaker at various computer-related events. She was well known for her lively and irreverent speaking style, as well as a rich treasury of early war stories. She also received the nickname "Grandma COBOL".
While Hopper was working on a Mark II Computer at Harvard University in 1947, her associates discovered a moth that was stuck in a relay and impeding the operation of the computer. Upon extraction, the insect was affixed to a log sheet for that day with the notation, "First actual case of bug being found". While neither she nor her crew members mentioned the exact phrase, "debugging", in their log entries, the case is held as a historical instance of "debugging" a computer and Hopper is credited with popularizing the term in computing. For many decades, the term "bug" for a malfunction had been in use in several fields before being applied to computers. The remains of the moth can be found taped into the group's log book at the Smithsonian Institution's National Museum of American History in Washington, D.C.
Hopper became known for her nanoseconds visual aid. People (such as generals and admirals) used to ask her why satellite communication took so long. She started handing out pieces of wire that were just under one foot long—11.8 inches (30 cm)—the distance that light travels in one nanosecond. She gave these pieces of wire the metonym "nanoseconds". She was careful to tell her audience that the length of her nanoseconds was actually the maximum distance the signals would travel in a vacuum in a nanosecond, and that signals would travel more slowly through the actual wires that were her teaching aids. Later she used the same pieces of wire to illustrate why computers had to be small to be fast. At many of her talks and visits, she handed out "nanoseconds" to everyone in the audience, contrasting them with a coil of wire 984 feet (300 meters) long, representing a microsecond. Later, while giving these lectures while working for DEC, she passed out packets of pepper, calling the individual grains of ground pepper picoseconds.
Jay Elliot described Hopper as appearing to be "'all Navy', but when you reach inside, you find a 'Pirate' dying to be released".
== Death ==
On New Year's Day 1992, Hopper died in her sleep of natural causes at her home in Arlington County, Virginia; she was 85 years of age. She was interred with full military honors in Arlington National Cemetery.
== Dates of rank ==
== Awards and honors ==
=== Military awards ===
=== Other awards ===
1964: Hopper was awarded the Society of Women Engineers Achievement Award, the Society's highest honor, "In recognition of her significant contributions to the burgeoning computer industry as an engineering manager and originator of automatic programming systems." In May 1955, Hopper was one of the founding members of the Society of Women Engineers.
1969: Hopper was awarded the inaugural Data Processing Management Association Man of the Year award (now called the Distinguished Information Sciences Award).
1971: The annual Grace Murray Hopper Award for Outstanding Young Computer Professionals was established in 1971 by the Association for Computing Machinery.
1973: Elected to the U.S. National Academy of Engineering.
1973: First American and first woman of any nationality to be made a Distinguished Fellow of the British Computer Society.
1981: Received an Honorary PhD from Clarkson University.
1982: American Association of University Women Achievement Award and an Honorary Doctor of Science from Marquette University.
1983: Golden Plate Award of the American Academy of Achievement.
1985: Honorary Doctor of Science from Wright State University
1985: Honorary Doctor of Letters from Western New England College (now Western New England University).
1986: Received the Defense Distinguished Service Medal at her retirement.
1986: Received an Honorary Doctor of Science from Syracuse University.
1987: She became the first Computer History Museum Fellow Award Recipient "for contributions to the development of programming languages, for standardization efforts, and for lifelong naval service."
1988: Received the Golden Gavel Award, Toastmasters International.
1991: National Medal of Technology.
1991: Elected a Fellow of the American Academy of Arts and Sciences.
1992: The Society of Women Engineers established three annual, renewable, "Admiral Grace Murray Hopper Scholarships"
1994: Inducted into the National Women's Hall of Fame.
1996: USS Hopper (DDG-70) was launched. Nicknamed Amazing Grace, it is on a very short list of U.S. military vessels named after women.
2001: Eavan Boland wrote a poem dedicated to Grace Hopper titled "Code" in her 2001 release Against Love Poetry.
2001: The Gracies, the Government Technology Leadership Award were named in her honor.
2009: The Department of Energy's National Energy Research Scientific Computing Center named its flagship system "Hopper".
2009: Office of Naval Intelligence creates the Grace Hopper Information Services Center.
2013: Google made the Google Doodle for Hopper's 107th birthday an animation of her sitting at a computer, using COBOL to print out her age. At the end of the animation, a moth flies out of the computer.
2016: On November 22, 2016, Hopper was posthumously awarded a Presidential Medal of Freedom for her accomplishments in the field of computer science.
2017: Hopper College at Yale University was named in her honor.
2021: The Admiral Grace Hopper Award was established by the chancellor of the College of Information and Cyberspace (CIC) of the National Defense University to recognize leaders in the fields of information and cybersecurity throughout the National Security community.
== Legacy ==
Grace Hopper was awarded 40 honorary degrees from universities worldwide during her lifetime.
Nvidia has named their 2024 CPU generation Grace and GPU generation Hopper after Grace Hopper.
The Navy's Hopper Information Services Center is named for her.
The Navy named a guided-missile destroyer Hopper after her.
On 30 June 2021, a satellite named after her (ÑuSat 20 or "Grace", COSPAR 2021-059AU) was launched into space.
On 26 August 2024 the NSA released a 90-minute talk in 1982 by Hopper in two parts.
=== Places ===
Grace Hopper Avenue in Monterey, California, is the location of the Navy's Fleet Numerical Meteorology and Oceanography Center as well as the National Weather Service's San Francisco Bay Area forecast office.
Grace M. Hopper Navy Regional Data Automation Center at Naval Air Station, North Island, California.
Grace Murray Hopper Park, on South Joyce Street in Arlington County, Virginia, is a small memorial park in front of her former residence (River House Apartments) and is now owned by Arlington County, Virginia.
Brewster Academy, a school in Wolfeboro, New Hampshire, United States, dedicated their computer lab to her in 1985, calling it the Grace Murray Hopper Center for Computer Learning. The academy bestows a Grace Murray Hopper Prize to a graduate who excelled in the field of computer systems. Hopper had spent her childhood summers at a family home in Wolfeboro.
Grace Hopper College, one of the residential colleges of Yale University.
An administration building on Naval Support Activity Annapolis (previously known as Naval Station Annapolis) in Annapolis, Maryland is named the Grace Hopper Building in her honor.
Hopper Hall is Naval Academy's newest academic building that houses its cyber science department, among others. It is the first building at any service academy named after a woman.
The US Naval Academy also owns a Cray XC-30 supercomputer named "Grace", hosted at the University of Maryland-College Park.
Building 1482 aboard Naval Air Station North Island, housing the Naval Computer and Telecommunication Station San Diego, is named the Grace Hopper Building, and also contains the History of Naval Communications Museum.
Building 6007, C2/CNT West in Aberdeen Proving Ground, Maryland, is named after her.
The street outside of the Nathan Deal Georgia Cyber Innovation and Training Center in Augusta, Georgia, is named Grace Hopper Lane.
Grace Hopper Academy is a for-profit immersive programming school in New York City named in Grace Hopper's honor. It opened in January 2016 with the goal of increasing the proportion of women in software engineering careers.
A bridge over Goose Creek, to join the north and south sides of the Naval Support Activity Charleston side of Joint Base Charleston, South Carolina, is named the Grace Hopper Memorial Bridge in her honor.
Minor planet 5773 Hopper discovered by Eleanor Helin is named in her honor. The official naming citation was published by the Minor Planet Center on 8 November 2019 (M.P.C. 117229).
Grace Hopper Hall, a community meeting hall in Orlando, Florida, on the site of the former Orlando Naval Training Center, is named for her.
The United States Naval Academy dedicated Hopper Hall, their cyber, computer science, and computer engineering building, to RDML Hopper in 2020, and it opened to midshipmen in the spring of 2021.
=== Programs ===
Women at Microsoft Corporation formed an employee group called Hoppers and established a scholarship in her honor.
Beginning in 2015, one of the nine competition fields at the FIRST Robotics Competition world championship is named for Hopper.
A named professorship in the Department of Computer Sciences was established at Yale University in her honor. Joan Feigenbaum was named to this chair in 2008.
In 2020, Google named its new undersea network cable 'Grace Hopper'. The cable connects the US, UK and Spain and it was estimated to be completed by 2022. Nonetheless, The Grace Hopper cable was completed in 2021, and it stretches 3,900 miles.
=== In popular culture ===
In his comic book series, Secret Coders by Gene Luen Yang, the main character is named Hopper Gracie-Hu.
Since 2013, Hopper's official portrait has been included in the matplotlib python library as sample data to replace the controversial Lenna image.
==== Grace Hopper Celebration of Women in Computing ====
Her legacy was an inspiring factor in the creation of the Grace Hopper Celebration of Women in Computing. Held yearly, this conference is designed to bring the research and career interests of women in computing to the forefront.
== See also ==
Bug (engineering)#History
Code: Debugging the Gender Gap
List of pioneers in computer science
Futures techniques
Systems engineering
Women in computing
Hopper (microarchitecture)
Women in the United States Navy
List of female United States military generals and flag officers
Timeline of women in science
== Notes ==
== References ==
== Obituary notices ==
Betts, Mitch (Computerworld 26: 14, 1992)
Bromberg, Howard (IEEE Software 9: 103–104, 1992)
Danca, Richard A. (Federal Computer Week 6: 26–27, 1992)
Hancock, Bill (Digital Review 9: 40, 1992)
Power, Kevin (Government Computer News 11: 70, 1992)
Sammet, J. E. (Communications of the ACM 35 (4): 128–131, 1992)
Weiss, Eric A. (IEEE Annals of the History of Computing 14: 56–58, 1992)
== Further reading ==
Beyer, Kurt W. (2009). Grace Hopper and the Invention of the Information Age. Cambridge, Massachusetts: MIT Press. ISBN 978-0-262-01310-9.
Marx, Christy (2003). Grace Hopper: the first woman to program the first computer in the United States. Women hall of famers in mathematics and science. New York: Rosen Publishing Group. ISBN 978-0-8239-3877-3.
Norman, Rebecca (June 1997). "Biographies of Women Mathematicians: Grace Murray Hopper". Agnes Scott College. Retrieved November 17, 2014.
Williams, Kathleen Broome (2004). Grace Hopper: Admiral of the Cyber Sea. Annapolis, Maryland: Naval Institute Press. ISBN 978-1-55750-952-9.
Williams, Kathleen Broome (2001). Improbable Warriors: Women Scientists and the U.S. Navy in World War II. Annapolis, Maryland: Naval Institute Press. ISBN 978-1-55750-961-1. Williams' book focuses on the lives and contributions of four notable women scientists: Mary Sears (1905–1997); Florence van Straten (1913–1992); Grace Murray Hopper (1906–1992); Mina Spiegel Rees (1902–1997).
Ignotofsky, Rachel (2017). Women in Science: 50 fearless pioneers who changed the world. London: Wren & Rook. ISBN 978-1-9848-5615-9.
Vining, Margaret (2012). "Reviewed work: Grace Hopper and the Invention of the Information Age, Kurt W. Beyer". Technology and Culture. 53 (2): 516–517. doi:10.1353/tech.2012.0051. JSTOR 41475535. S2CID 111125455.
Williams, Kathleen Broome (1999). "Scientists in Uniform: The Harvard Computation Laboratory in World War II". Naval War College Review. 52 (3): 90–110. JSTOR 44643011.
Billings, Charlene (1989). Grace Hopper : Navy admiral and computer pioneer. Enslow Publishers. ISBN 0-89490-194-X.
== External links ==
Grace Murray Hopper at the Mathematics Genealogy Project
Oral History of Captain Grace Hopper – Interviewed by: Angeline Pantages 1980, Naval Data Automation Command, Maryland.
RADM Grace Hopper, USN Ret. at the Wayback Machine (archived February 24, 2010) from Chips, the United States Navy information technology magazine.
Grace Hopper: Navy to the Core, a Pirate at Heart Archived September 22, 2017, at the Wayback Machine (2014), To learn more about Hopper's story and Navy legacy navy.mil.
The Queen of Code (2015), a documentary film about Grace Hopper produced by FiveThirtyEight.
Norwood, Arlisha. "Grace Hopper". National Women's History Museum. 2017.
O'Connor, John J.; Robertson, Edmund F., "Grace Hopper", MacTutor History of Mathematics Archive, University of St Andrews
|
https://en.wikipedia.org/wiki/Grace_Hopper
|
Programme delivery control (PDC) is specified by the standard ETS 300 231 (ETSI EN 300 231), published by the European Telecommunications Standards Institute (ETSI). This specifies the signals sent as hidden codes in the teletext service, indicating when transmission of a programme starts and finishes.
PDC (also known as Enhanced Teletext Packet 8/30 Format 2) is often used together with StarText, enabling the user to select a programme to record using specially coded teletext programme listings. The combination of features is often called PDC/StarText.
In Germany and some other European countries, the older standard video programming system (VPS) is in use also known as format 2. Effectively, the two systems do the same thing and most modern VCRs and stand-alone DVD recorders work with both signals.
In digital TV (see Freeview+), the feature Accurate Recording (AR) that was based on the PDC specification for analogue recording devices is now used for a DVB-SI event based scheduling system. This was due to the BBC discontinuing the Ceefax service.
== PDC Packets ==
PDC is transmitted once a second in special packets addressed as magazine 8 and text row 30. Since this row is not displayable it does not interfere with normal pages. Packet 8/30 has various formats specified by ETSI and PDC is format 2. Each packet 8/30 format 2 also has a label number and there can be up to four labels transmitted at a time. Each label contains the scheduled start time and date for a programme and flags to indicate the state. Each programme is assigned a label and in general a label will follow this sequence.
PRF Set – Prepare for Record. This will tell a VCR to wake up and get ready. This happens about 40 seconds before the programme is active.
PRF Clear – The VCR should be recording.
RTI – Record Terminate/Interrupt – Tells the VCR to stop recording. This label is held for 30 seconds after the programme ends.
There are complicated rules for the case where a programme is interrupted by another one as in the case of a film with a break for news in the middle.
There is also a TIMER flag that indicates that there is no valid PDC and that the VCR should use its own timer.
== References ==
== External links ==
Technical specifications and FAQ
ETSI standards
ETSI EN 300 231 V1.3.1 (2003–04), Specification of the domestic video Programme Delivery Control system (PDC)
ETSI EN 301 775 V1.2.1 (2003–05), Specification for the carriage of Vertical Blanking Information (VBI) data in DVB bitstreams
ETSI TS 102 323 V1.5.1 (2012-01), Chapter 11: "Accurate recording" and Annex A: "Example recorder behaviour"
CHARACTERISTICS OF A PROGRAMME DELIVERY CONTROL (PDC) SYSTEM FOR VIDEO RECORDING (1990)
"Everything you ever wanted to know about PDC"
"Padding versus Accurate Recording"
Original VPS invention (European Patent Office) German and English
|
https://en.wikipedia.org/wiki/Programme_Delivery_Control
|
MP/M (Multi-Programming Monitor Control Program) is a discontinued multi-user version of the CP/M operating system, created by Digital Research developer Tom Rolander in 1979. It allowed multiple users to connect to a single computer, each using a separate terminal.
MP/M was a fairly advanced operating system for its era, at least on microcomputers. It included a priority-scheduled multitasking kernel (before such a name was used, the kernel was referred to as the nucleus) with memory protection, concurrent input/output (XIOS) and support for spooling and queueing. It also allowed for each user to run multiple programs, and switch between them.
== MP/M platforms ==
=== MP/M-80 ===
The 8-bit system required a 8080 (or Z80) CPU and a minimum of 32 KB of RAM to run, but this left little memory for user applications. In order to support reasonable setups, MP/M allowed for memory to be switched in and out of the machine's "real memory" area. So for instance a program might be loaded into a "bank" of RAM that was not addressable by the CPU, and when it was time for the program to run that bank of RAM would be "switched" to appear in low memory (typically the lower 32 or 48 KB) and thus become visible to the OS. This technique, known as bank switching was subsequently added to the single user version of CP/M with version 3.0.
One of the primary uses of MP/M, perhaps to the surprise of DRI, was as a "power user" version of CP/M for a single user. The ability to run several programs at the same time and address large amounts of memory made the system worth the extra price.
MP/M II 2.0 added file sharing capabilities in 1981, MP/M II 2.1 came with extended file locking in January 1982.
Versions:
MP/M 1.0 (1979)
MP/M 1.1 (January 1980)
MP/M II 2.0 (July 1981, added: file sharing)
MP/M II 2.1 (January 1982, added: extended file locking)
=== MP/M-86 ===
Like CP/M, MP/M was eventually ported to the 16-bit Intel 8086, and appeared as MP/M-86 2.0 in September 1981. Main developers of the system include Francis "Frank" R. Holsworth, later a director of marketing at Digital Research. Known revisions of MP/M-86 2.0 were dated 25 September 1981 and 5 October 1981. There also was an MP/M-86 2.1 dated 20 July 1982.
MP/M-86 2.1 absorbed some of the technology of CP/M-86 1.1 (BDOS 2.2) to become Concurrent CP/M-86 3.0 (BDOS 3.0) in late 1982, which also added support for "virtual screens". Kathryn Strutynski, the project manager for CP/M-86, continued as project manager for Concurrent CP/M-86. In December 1983, a DOS emulator named PC-MODE became available as an optional module for Concurrent CP/M-86 3.1 (BDOS 3.1), shipping on 21 February 1984, and the system was further developed into the MS-DOS compatible Concurrent DOS (BDOS 3.1 and higher). This in turn continued to evolve into FlexOS and Multiuser DOS and as such is still in use in some industrial applications.
Concurrent CP/M is often abbreviated CCP/M.
=== MP/M 8-16 ===
MP/M 8-16 (sometimes also referred to as MP/M-8/16) was CompuPro's name for a combination of the multi-user 16-bit MP/M-86 to perform single-user, single-stream CP/M functions, along with multi-user, multi-tasking 8-bit MP/M operations running on the multi-processor CompuPro System 816. Later on, this system was also able to run Concurrent DOS 3.1.
=== MP/M-286 ===
In 1982, Digital Research announced plans to develop MP/M-286 to take advantage of the 16-bit Intel 80286's new memory management and protection features to run existing MP/M-86 and CP/M-86 applications. This was apparently never published "as is", but was further developed into Concurrent CP/M-286, which seems to have formed the basis for the later Concurrent DOS 286 in 1985 and FlexOS 286 in 1986.
== Commands ==
The following list of commands are supported by the MP/M II Console Command Processor CCP:
== CP/NET, CP/NOS, MP/NET and MP/NOS ==
In the early 1980s Digital Research also developed networking software named CP/NET used to connect an MP/M server with multiple CP/NET clients (named requesters) running CP/M. It was originally developed by Tom Rolander.
MP/NET was an MP/M system with networking allowing the MP/M system to function as both requester and server with CP/M requesters.
The CP/NET clients could also be run in a diskless configuration with the system stored in ROM, then named CP/NOS (with NOS for Network Operating System). Similar, MP/NOS contained MP/M without local disk facilities. Like CP/NOS, MP/NOS performed the disk functions through the network.
The system allowed to share files and printers and send electronic messages.
NIOS – Network I/O System
SNIOS – Slave Network I/O System
NDOS – Network Disk Operating System
CP/NET existed in versions 1.0, 1.1 and 1.2 in versions for 8080 and Z80 processors. CP/NET-86 for 8086 was available as well.
Later incarnations were DR Net and FlexNet.
== Legacy ==
Caldera permitted the redistribution and modification of all original Digital Research files, including source code, related to the CP/M and MP/M families through Tim Olmstead's "The Unofficial CP/M Web site" since 1997. After Olmstead's death on 12 September 2001, the free distribution license was refreshed and expanded by Lineo, who had meanwhile become the owner of those Digital Research assets, on 19 October 2001.
== Notes ==
== References ==
|
https://en.wikipedia.org/wiki/MP/M
|
Patrick Collison (born 9 September 1988) is an Irish entrepreneur. He is the co-founder and CEO of Stripe, which he started with his younger brother, John, in 2010. He won the 41st Young Scientist and Technology Exhibition in 2005 at the age of sixteen. In 2020, he founded Fast Grants to accelerate COVID-19-related science with economist Tyler Cowen. In 2021, he co-founded Arc Institute, a nonprofit research organization, with bioscientists Silvana Konermann and Patrick Hsu.
== Early life ==
Patrick Collison was born to microbiologist Lily and electronic engineer Denis Collison on 9 September 1988, and he and his brothers were brought up in the small village of Dromineer in County Tipperary. The eldest of three boys, he took his first computer course when he was eight years old, at the University of Limerick, and began learning computer programming at the age of ten.
Collison was educated in Gaelscoil Aonach Urmhumhan, Nenagh, before attending Castletroy College in Castletroy, County Limerick.
== Career ==
=== Young Scientist ===
Collison entered the 40th Young Scientist and Technology Exhibition with his project on artificial intelligence (nicknamed 'Isaac' after Isaac Newton, whom Patrick admired), finishing as individual runner-up. He re-entered the following year, and won first place at the age of sixteen on 14 January 2005. His project involved the creation of Croma, a LISP-type programming language.
His prize of a €7,500 cheque and a trophy of Waterford Crystal was presented to him by President Mary McAleese. His younger brother Tommy participated with his project on blogging in the Young Scientist and Technology Exhibition in 2010.
=== Auctomatic ===
He attended Massachusetts Institute of Technology, but eventually dropped out in 2009 after starting businesses. In 2007, he set up software company 'Shuppa' (a play on the Irish word siopa, meaning 'shop') in Limerick with his brother John Collison. Enterprise Ireland did not allocate funding to the company, prompting a move to California after Silicon Valley's Y Combinator showed interest, where they merged with two Oxford graduates, Harjeet and Kulveer Taggar, and the company became Auctomatic.
On Good Friday of March 2008, Collison, aged nineteen, and his brother, aged seventeen, sold Auctomatic to Canadian company Live Current Media, becoming millionaires. In May 2008, he became director of engineering at the company's new Vancouver base. Collison attributes the success of his company to his win in the Young Scientist and Technology Exhibition.
=== Stripe ===
In 2010, Collison co-founded Stripe, which in 2011 received investment of $2 million including from PayPal co-founders Elon Musk and Peter Thiel, and venture capital firms Sequoia Capital, Andreessen Horowitz, and SV Angel.
In November 2016, the Collison brothers became the world's youngest self-made billionaires, worth at least $1.1 billion, after an investment in Stripe from CapitalG and General Catalyst Partners valued the company at $9.2 billion. By 2017, the brothers were notionally worth at least $3.2 billion each.
In 2018, Stripe, under the direction of the Collison brothers, contributed $1 million to California YIMBY, a pro-housing development lobbying organisation.
In September 2019, it was announced that Stripe had raised an additional $250 million at a valuation of $35 billion. Together, the brothers hold a controlling interest in Stripe.
=== Other ===
Both Collison and his younger brother John were featured on a young Irish persons rich list aired on an RTÉ television show during the 2008 Christmas period.
On 18 July 2009, at the age of 20 and following the publication of the McCarthy Report, Collison outlined his ideas for the future of Ireland on popular talk-show Saturday Night with Miriam.
According to Collison, he reads books and is interested in a broad range of subjects on history, technology, engineering, fiction, philosophy, and art. He publishes the list of books he read on his website. In November 2018, Collison published a piece in The Atlantic with Michael Nielsen entitled Science is Getting Less Bang for its Buck, arguing that increased investment in science has not produced commensurate output. In 2019, Collison published an opinion piece in the same outlet with Tyler Cowen arguing for a new academic discipline called "Progress Studies", which would study the cultural and institutional conditions which lead to the most progress and higher standards of living.
Collison joined the board of Meta Platforms in April 2025.
== Forbes article ==
A profile of the brothers published in Forbes in 2021 claimed the brothers had "escaped" from Limerick, describing it as a "warzone" because of a gang feud and it was "the 'murder capital' of Europe". It claimed "shootings, pipe bomb attacks, and stabbings" happened there every night. It also claimed that "Some bad neighbourhoods are even walled off by a dirty graffitied 10-foot-high barrier, like the Berlin Wall".
The article received a lot of publicity online, causing a backlash. Collison tweeted "Not only mistaken about Limerick but the idea of 'overcoming' anything is crazy. We are who we are because we grew up where we did". John tweeted it was "daft". Patrick O'Donovan called on the magazine and author to apologise to the people of Limerick "for the insult and hurt caused" by it. He also tweeted "I am calling on them to come to Limerick where I will gladly set the record straight in respect of what our county and city has to offer as opposed to what your work of fiction depicts," and "Please let me know when suits to visit." Niall Collins tweeted that the article was a "disgraceful description of Limerick, home to so many fine and decent people".
The article was removed from the website on 9 April 2021.
== Personal life ==
In April 2022, Collison married Swiss-American biochemist and Stanford University professor Silvana Konermann, with whom he co-founded the Arc Institute. Collison met Konermann during the 2004 EU Young Scientist competition.
Collison lives in San Francisco, California.
== References ==
== External links ==
Official website
|
https://en.wikipedia.org/wiki/Patrick_Collison
|
In computing, an error code (or a return code) is a numeric or alphanumeric code that indicates the nature of an error and, when possible, why it occurred. Error codes can be reported to end users of software, returned from communication protocols, or used within programs as a method of representing anomalous conditions.
== In consumer products ==
Error codes are commonly encountered on displays of consumer electronics to users in order to communicate or specify an error. They can also be indicated by lights or beeps, e.g., if a device does not have a display. They are commonly reported by consumer electronics when users bring electronics to perform tasks that they cannot do (e.g., dividing by zero), or when the program within a device encounters an anomalous condition.
Error codes reported by consumer electronics are used to help diagnose and repair technical problems. An error code can be communicated to relevant support staff to identify potential fixes, or can simplify research into the cause of an error.
There is no definitive format for error codes, meaning that error codes typically differ from/between products and or companies.
== In computer programming ==
Error codes in computers can be passed to the system itself, to judge how to respond to the error. Often error codes come synonymous with an exit code or a return value. The system may also choose to pass the error code to its user(s). The Blue screen of death is an example of how the Windows operating system communicates error codes to the user.
Error codes can be used within a computer program to represent an anomalous condition. A computer program can take different actions depending on the value of an error code.
Different programming languages, operating systems, and programming environments often have their own conventions and standards for the meanings and values of error codes. Examples include:
Unix-like systems have an errno.h header file that contains the meanings and values of error codes returned by system calls and library functions.
Microsoft Windows' application programming interfaces (APIs) have several different standards for error code values, depending on the specific API being used.
The usage of error codes as an error handling strategy is often contrasted against using exceptions for error handling.
== In communication protocols ==
Communication protocols typically define a standard set of error codes, as a means of communicating the status or result of an operation between the entities in the system.
Several high-level protocols in the TCP/IP stack, such as HTTP, FTP, and SMTP, define their own standard sets of error codes:
List of HTTP status codes
List of FTP server return codes
Simple Mail Transfer Protocol § Protocol overview
== In automobiles ==
Error codes in automobiles, sometimes referred to as trouble codes, indicate to a driver or car mechanic what is wrong with a vehicle before repairs are initiated.
In vehicles with CAN buses, error codes are often five-digit codes that pinpoint a particular car fault. Car owners can make use of an on-board diagnostics scanner or an owner's manual to identify the meaning of a trouble code. Five-digit diagnostic trouble codes typically consist of one letter and four numbers (e.g. P0123).
== See also ==
Abort (computing)
Aspect-oriented programming
Blue Screen of Death
errno.h, a header file in C that defines macros for reporting errors
Exit status
Failure
HRESULT, a computer programming data type used for error codes
Static code analysis
== References ==
== External links ==
Microsoft system error codes
Microsoft Device Manager error codes
|
https://en.wikipedia.org/wiki/Error_code
|
Roblox ( , ROH-bloks) is an online game platform and game creation system developed by Roblox Corporation that allows users to program and play games created by themselves or other users. It was created by David Baszucki and Erik Cassel in 2004, and released to the public in 2006. As of February 2025, the platform has reported an average of 85.3 million daily active users. According to the company, their monthly playerbase includes half of all American children under the age of 16.
The platform hosts millions of user-created games (officially referred to as "experiences"), all created using a dialect of the programming language Lua and the platform's game engine, Roblox Studio. While Roblox is free-to-play, it features in-game purchases done through its virtual currency known as Robux, and game developers on the platform are able to create items that cost Robux. Furthermore, the platform hosts a large virtual economy centered around those items and Robux. Using the platform's "Developer Exchange" program, creators on the platform are able to exchange their earned Robux for real-world currency. The platform has also been used to host virtual concerts and events, as well as advergames.
Early in Roblox's history, it was relatively small, both as a platform and as a company. In the second half of the 2010s, the platform began to grow rapidly, and this growth was accelerated by the COVID-19 pandemic. By 2020, over 5,000 games on Roblox had been played over a million times, and over 20 had been played over one billion times. Although Roblox has been positively received by critics, it has faced heavy criticism for its content moderation, which in turn has led to a large amount of sexual or politically extremist material on the platform. It has also been criticized for its alleged exploitative practices toward children and microtransactions. The platform has been restricted or completely blocked in several countries, such as China, Turkey, Jordan, and others.
== Overview ==
Roblox is an online game platform and game creation system built around user-generated content and games, officially referred to as "experiences". Games can be created by any user through the platform's game engine, Roblox Studio, and then shared to and played by other players. The games featured on Roblox vary in genre, from role-playing games to ones centered around escaping prison, among others. The platform is made to appeal to a family-friendly audience, and has been described as a massively multiplayer online game (MMO).
While Roblox is free-to-play, it features a virtual currency known as Robux that can be purchased with real-world money. Robux can be used to purchase virtual items that the player can use on their virtual character (or "avatar") on the platform, or access experiences that require payment. As with games, avatar items on Roblox are mainly user-generated, though most items on the platform were made by Roblox themselves for most of the platform's history. Through the platform's "Developer Exchange" program, creators on the platform are able to exchange their earned Robux to real-world money. In addition, Roblox features a monthly service called "Roblox Premium", with its subscribers gaining access to more features on the platform and a monthly stipend of Robux.
=== Virtual economy ===
Roblox features a large virtual economy centered around its aforementioned virtual currency, Robux. The currency allows users to buy, sell, and create virtual items. Roblox also has a service called "Roblox Premium", a monthly subscription that gives users monthly stipends of Robux (with the amount depending on the selected subscription tier), discounts when purchasing items, access to the item trading system, the ability to buy more Robux for less, and more.
Similarly to games, many items on Roblox are user-generated. While only Roblox developers were able to create avatar items early on, the capabilities of user-generated content has expanded greatly over time. Since 2019, select users have gained the ability to publish avatar accessories, animations, bundles, and more. Some items on Roblox have a "limited" status, with only a few being available and the price of the item based on supply and demand rather than a fixed price. These items function similarly to non-fungible tokens (NFTs). The prices of limited items range, with the most valuable ones costing millions of Robux. After the original supply of that item runs out, players can resell them for a higher price. Additionally, users with an active Roblox Premium subscription are able to trade limiteds amongst each other; limited items made by the community cannot be traded, and this feature is restricted to official items.
Developers on the platform are able to create purchasable content through one-time purchases. Through the Roblox "Developer Exchange" program, users are able to exchange their earned Robux for real-world money, as long as they have at least 30,000 Robux. In 2020, Roblox reported that roughly 345,000 game developers on the platform earned money through the program. Avatar item creators have also been able to generate profit with the platform, with some individuals designing items as a full-time job. It has been reported that the highest-earning creators have earned over $100,000 a year from item sales.
A sizeable amount of scams are on Roblox, largely revolving around messages promoting websites and games that are designed to appear to give out free Robux. Furthermore, there are people in the community known as "beamers" who compromise Roblox accounts to steal and sell their items on the platform's black markets. They employ various techniques, such as creating phishing websites or create ploys in order to acquire a victim's session token. Once they gain access to the victim's account, these "beamers" steal and subsequently sell valuable limited items owned by the victims for real-world currency or cryptocurrency through marketplace sites or Discord chat rooms. The slang term "beaming" is commonly used to describe this entire process on Roblox. Roblox does offer hacking victims a "rollback" for their items, although this is only offered once per account.
=== Roblox Studio and game design ===
Roblox Studio is the platform's game engine and game development software. The engine and all games made on Roblox predominantly uses Luau, a dialect of the Lua 5.1 programming language. Since November 2021, the programming language has been open sourced under the MIT License. Some aspects of the engine were created using C++. To assist in the creation of games, Roblox Studio features multiple pre-made templates that users can modify.
As of 2020, Roblox reported that more than 2 million developers used Roblox Studio to create more than 20 million games per year. They also reported that a majority of developers were minors. While some developers might not make money by creating games on Roblox, it has been noted that the platform still assists with teaching people game design and how to code.
=== Games ===
Due to its status as a user-created games platform, Roblox has a variety of popular games; as of July 2020, at least 20 games had been played more than one billion times, and at least 5,000 have been played more than one million times. TechCrunch noted in March 2021 that Roblox games are largely distinct from established traditions in free-to-play video games, finding that successful Roblox games were geared towards immediate satisfaction, and finding that the addition of tutorials significantly decreased player engagement, contrary to established wisdom about free-to-play games. Many companies have used Roblox to host advergames promoting their products.
== History and development ==
=== 2004–2009: Creation and early history ===
Roblox was created in 2004 by co-founders and software engineers David Baszucki and Erik Cassel. Prior to the creation of the platform, both Baszucki and Cassel worked for Knowledge Revolution, a company that specialized in creating educational and physics simulation software. After Knowledge Revolution was acquired by MSC Software, the two left the company and Baszucki began investing in earlier social media sites like Friendster. Around this time, Baszucki came up with the idea of a physics sandbox with creation tools and a social networking aspect. Baszucki and Cassel began development on Roblox shortly afterwards, modeled after Baszucki's vision, and also created the Roblox Corporation. Early in its development, Roblox was known as Dynablocks. It was determined early on in development that the two would design Roblox to rely entirely on user-generated content, only providing the tools necessary for people to develop games, as well as the server hosting later in development.
Baszucki and Cassel worked alone while making the earlier versions of Roblox, and created their own games on the platform before the creation tools were completed. These early versions of Roblox were extremely basic, with player avatars having not been animated yet and various features only being present in their most simplified form. They also advertised Roblox on some websites, leading to a few dozen players joining the platform as playtesters. In mid-2006, the first two employees that weren't Cassel or Baszucki were hired to work on the platform's other features. These employees were Matt Dusek and John Shedletsky, with Dusek being responsible for working on the platform's communication aspects.
Roblox was officially released on September 1, 2006, with Roblox Studio being made available that same year. Games that were made by the community early in the platform's history included paintball games, haunted houses, and model trains that players could ride. In 2008, the Roblox Corporation stopped actively creating their own games to demonstrate the platform's capabilities, becoming entirely reliant on user-created games. During this time in 2007, Roblox introduced the "Builders Club" membership subscription, which allowed for users to create more games under their account, sell virtual clothing, remove outside advertisements from the site, and gain Robux daily. Early in the platform's history, it had two separate currencies: Robux and Tickets, with the latter often being referred to as "Tix".
=== 2010–2015: Early growth ===
Roblox's growth continued throughout 2010 and the following years. By August 2011, Roblox had about 6.8 million active users monthly, becoming the second-most popular kids entertainment site. Its profits also continued to increase, with the platform's profit that year up 75% from 2010; in June 2011, the company held a fundraiser that raised over $4 million. By January 2014, the platform's monthly player count had increased 10 to 12 million monthly players, although a majority of those players did not have registered accounts, and instead played as "guests".
By this point in the platform's history, several games had been played million of times. One of the most successor creators on the platform at the time was Luke Weber, known on Roblox as "Stickmasterluke", who had a following of over ten million plays across all of his games combined. In August 2011, the first in-person convention centered around Roblox, known as the Roblox Rally, was held in San Francisco. It was attended by over 1,000 people. In 2013, the platform's co-founder Cassel died from cancer.
Throughout 2012, versions of Roblox for mobile devices were developed. By May, they had already released a stripped-down version of the platform for iOS that only included its social features, but did not allow users to play games on it. A version of the game for macOS was also released by that point. On December 11 of that year, a full version of Roblox for iOS was released that allowed users to play games, although users were not able to use Roblox Studio. After completing development on the iOS version, Roblox began looking into releasing a version for Android devices, as well as video game consoles. The version for Android was released on July 16, 2014. A version of Roblox for Xbox One was announced in September 2015 and released on November 20. This version initially only released with selection of 15 games chosen by Roblox staff, due to concerns regarding Entertainment Software Rating Board standards. A system that allowed users to publish their games on the platform was later released, based on an approval process.
From 2013 to 2014, Roblox released several updates to their development tools, adding new features. Among these new features was the Developer Exchange program, which initially only allowed payouts of up to $500. Other updates released around this time included adding support for character animations, Roblox Studio plugins, and Developer Stats, a feature that shows developers various statistics about their games, such as how many players were playing their game, and for how long. In May 2015, Roblox released an update that adjusted its physics engine to be more smooth and realistic, rather than being oriented around blocks. This also came with a feature called Smooth Terrain, which increased the graphic fidelity of in-game terrain.
=== 2016–2020: Accelerated growth and COVID-19 ===
In the latter half of the 2010s, Roblox began to rapidly grow in popularity. By December 2016, the platform had about 30 million monthly active users, a number that had increased 90 million by April 2019. The platform's growth was further accelerated by the COVID-19 pandemic beginning in 2020, where lockdowns led tens of millions of children to use Roblox as a means of communication. Between March and April, Roblox reported having over 120 million monthly active players, which by that point the company said included over half of all kids in the United States that were under the age of 16. Additionally, the average number of daily active players in 2020 had increased by 85% compared to 2019. By this point, over 20 games had been played more than one billion times, and at least 5,000 had been played more than one million times. The most popular game on the platform around this time was the role-playing game Adopt Me!, which had been played over 10 billion times by July 2020 and had set a platform record of over 1.6 million users on at once.
In light of the platform's newfound popularity and use during lockdowns, Roblox introduced a new "Party Place" system, which were specific spaces that players could use to arrange meet-ups and events, such as virtual concerts. Around this time, Roblox began further working towards a vision that Baszucki described as a 30-year long plan where in which users have a "fully-fledged digital identity" in an environment such as Roblox. In July 2020, Baszucki formally announced plans and goals for Roblox developers and users to build a "metaverse", a concept that refers to several interconnected virtual worlds. As part of these plans, several other features were announced that would allow creators more freedom in their works, hoping to make them more "immersive" and making collaboration between developers easier. Features that were introduced around this time included Developer Events, a service that would allow creators to create and manage in-game events, and allow users to easily discover these events. He also announced a partnership between Roblox and record label Monstercat, giving users and creators the ability to use their catalog in games. In August 2019, Roblox began allowing select users to upload their own accessories, a service that was later expanded to include various other types of accessories.
Around this time, Roblox optimized the way that its different releases were developed over the course of 3 years, reaching a point where only a minimal amount of engineers were needed to maintain the platforms it was available on and all versions functioned off of the same APIs. In April 2016, Roblox became available for Oculus Rift, alongside a variety of quality-of-life features made specifically for that platform. The company also expressed interest in porting Roblox to other virtual reality devices in the future. In June of that year, the company also released a dedicated app for Windows 10. Efforts were also made towards making Roblox more accessible, with automatic machine translation being added to in-game chat in 2020, initially supporting 9 languages. In 2019, the Roblox Corporation signed a partnership deal with Tencent to bring Roblox to China, and was given permission to release in the region on December 3, 2020.
During this time period, several features from the platform were removed. In 2016, Roblox discontinued its secondary currency, "Tickets", making Robux the platform's only currency. It was removed due to the company believing newer players would get confused by the presence of two separate currencies. In October 2017, Roblox removed the ability for people to play as a "guest", which allowed users to play games on the platform without having to use an account. That same year, Roblox discontinued its official player forums for an undisclosed reason. Additionally, in 2019, Roblox released Roblox Premium, which replaced its previous Builders Club membership.
=== 2021–present ===
The growth of Roblox, both as a platform and as a company, continued into 2021 and the following years. In March 2021, the Roblox Corporation went public, and became valued at $45 billion. Throughout 2021, Roblox averaged 45.5 million daily active users, a 40% increase from the end of 2020. In 2023, Roblox released public beta versions of the platform for Quest 2 and Meta Quest Pro on July 27, with full versions released in September. At the same time, ports of Roblox for PlayStation 4 and 5 were announced, and later released on October 10. In 2021, Roblox made it to where games on the platform are referred to as "experiences" following the platform's involvement in the Epic Games v. Apple lawsuit. In June of that year, Roblox was sued by the National Music Publishers' Association (NMPA), alleging that the platform allowed users to upload copyrighted music without obtaining proper licensing, and made children believe that pirating music was acceptable. The lawsuit was dropped by September, ending with the Roblox Corporation and the NMPA forming a collaboration to establish a framework for future publisher partnerships.
After being given permission in late 2020, Roblox released in China in July 2021. This version of the platform, officially known as LuoBu, was published and operated by Tencent, and was heavily restricted due to China's regulations on video games. LuoBu failed to grow to substantially throughout its history, and was unable to generate much profit. In January 2022, LuoBu was shut down, with Roblox stating that they were going to redevelop the release, and that LuoBu was only ever intended to be a test version. In July of that year, documents of business slides from presentations as early as 2017 were leaked online by an unknown hacker. These documents revealed that the Roblox Corporation was planning to make several changes to the platform worldwide to comply with Chinese internet censorship laws, and that prior to canceling operations, they were concerned that Tencent would hack the platform and attempt to create a competitor.
Roblox's business model throughout this time has continued to be based around creating a metaverse, and attempting to increase the platform's appeal. In 2021, Baszucki further detailed the companies vision for Roblox to become a metaverse, highlighting "eight different characteristics" that the platform would strive to accommodate for. He also discussed the Ready Player One and Ready Player Two books as being inspirations for the company's ideas. Features that were added to Roblox during this time have included voice chat for users over the age of 13 that had their age verified through ID. Voice chat was then followed by facial animations based on the real-world motion tracking of the players face, which was announced in 2022 and released in 2023. In March 2024, two generative artificial intelligence tools that were added to Roblox Studio in an effort to speed up content creation. These tools were for automatic avatar customization and texture generation, the former being able to automatically convert three-dimensional body meshes into live-animated avatars and the latter creating textures of objects based on a text-to-image model.
Also announced in 2022 were age ratings for games, a system created by the company to increase the platform's appeal to the young adult audience, which was the fastest growing demographic on Roblox, by allowing for more mature experiences. Initially, the highest rating that games could be given was 13+, although in June 2023, a 17+ rating was introduced that would permit games to feature more graphic violence, romantic themes, and alcohol usage. Similarly, in November 2024, Roblox revamped its parental controls system, adding new safety measures for users under the age of 13, such as screen time and whether or not the child can exchange private messages with other users, and allowing parents to create separate accounts to control their child's account.
== Community and culture ==
As of February 2025, Roblox has reported over 85.3 million daily active users. According to the company, the monthly playerbase includes half of all American children under the age of 16. Players have used the platform to express political activism, with some users declaring their support for the George Floyd protests and Black Lives Matter, and some using the platform to perform activities that were paused by COVID-19 lockdowns like religious processions. Part of Roblox's reputation was due in part to its original sound effect for when a character died, often transcribed and titled as the "oof" sound effect, which became an internet meme. The sound was originally produced by Joey Kuras and Tommy Tallarico for the video game Messiah (2000), but was replaced in 2022 after Roblox and Tallarico entered a copyright dispute.
=== Events ===
Roblox occasionally hosts real-life and virtual events. They have in the past hosted events such as BloxCon, which was a convention for ordinary players on the platform, as well as virtual Easter egg hunts, Halloween events, and "Giftsplosions", and also hosted an annual event called the "Bloxy Awards", an awards ceremony that also functions as a fundraiser. The 2020 edition of the Bloxy Awards, held virtually on the platform, drew 600,000 viewers. In 2022, "Bloxy Awards" got rebranded into the "Roblox Innovation Awards". Roblox Corporation annually hosts the Roblox Developers Conference, a three-day invite-only event in San Francisco where top content creators on the site learn of upcoming changes to the platform. The company has also hosted similar events in cities like London.
Roblox occasionally engages in events to promote films, such as ones held to promote Wonder Woman 1984 and Aquaman. Roblox has also hosted virtual concerts, such as the one starring Lil Nas X; during that concert, Lil Nas X debuted his song "Holiday". Future virtual concerts starred artists like Swedish singer Zara Larsson and American band Twenty One Pilots. In October 2021, Roblox partnered with Chipotle Mexican Grill to give $1 million of burritos away to the first 30,000 people every day as a part of Chipotle's Halloween Boorito promotion. In March 2025, "The Hunt: Mega Edition", (previous to "The Hunt: First Edition") where players competed in 25 different Roblox games for a prize of $1 million, had started.
== Reception ==
Critical reception of Roblox has been generally positive. Common Sense Media rated Roblox 4 out of 5 stars, praising the website's variety of games and ability to encourage creativity in children while finding that the decentralized nature of the platform meant game quality varied, and recommended disabling chat functions for young players to prevent possibly harmful interactions. Patricia E. Vance of the Family Online Safety Institute advised parents to monitor their child's interactions on the platform but praised the platform for "...allowing kids to play, explore, socialize, create and learn in a self-directed way", and granting special praise to Roblox Studio for its ability to encourage children to experience game development. Trusted Reviews, in its overview of the platform, also praised Roblox Studio, stating that "for anyone seeking to develop their computer science skills, or create projects that will instantly receive feedback from a huge audience, the appeal is obvious".
Roblox has been criticized several times due to the content that is present on the platform, specifically the presence of sexual or politically extremist-related material. Similarly, its chat and game filtration system has been negatively received. Examples of sexual or politically extreme content that has appeared on the platform throughout its history include places themed around virtual sex clubs and nightclubs, all of which are generally referred to as "condo" games, and content related to far-right ideologies such as neo-fascism and neo-Nazism, such as games that allow players to roleplay as Nazis or recreate real world massacres such as the Christchurch mosque shootings, the Columbine High School massacre, and the Uvalde school shooting. To combat the presence of this content, Roblox has over 1,600 people working to remove such material from the platform, and also offers privacy settings and parental controls; a 2020 investigation by Fast Company found that sexual content was very prevalent on Roblox, and likened attempts to remove the material to whack-a-mole. The platform has also seen numerous reports of sexual predation on child players, which a 2024 Bloomberg Businessweek report attributed to insufficient moderation, which has been viewed as overly reliant on artificial intelligence, and also due to how users on the platform are anonymous.
Roblox's business model has also been criticized, with the platform being accused of featuring exploitative practices that target children; Professor Jane Juffer at Cornell University accused Roblox of encouraging consumerism in children. Some found that the platform made it very easy to purchase microtransactions, leading to numerous instances where children have spent large sums of money on the platform without parents' knowledge. In April 2022, Truth in Advertising filed a complaint against Roblox with the Federal Trade Commission for false advertising, mainly failing to disclose when advertising is present, such as with advergames and brand ambassadors. As a response, Roblox hid advertisements from users under the age of 13 starting in March 2023. However, these restrictions did not apply to advergames, leading to further criticism by Truth in Advertising and children's digital rights organization 5Rights. Investigative journalism YouTube channel People Make Games accused the platform of "exploiting" younger game developers by promising them large amounts of money from creating games, only to apply high revenue cuts and leaving creators with little to no income. They likened the platform's business model to a company scrip. After Roblox requested the channel to take down the video, People Make Games released several more accusations towards Roblox, focused on an alleged lack of oversight of developers and a method for people to address developer abuse, leading to child developers being exploited for labor on third-party platform's. They also criticized the platform's virtual economy, comparing the limited collectibles market to gambling. It has also been accused by Hindenburg Research of artificially inflating its monthly active player count.
=== Restrictions by country ===
Roblox is blocked or banned in several countries: China, Jordan, North Korea, Oman and Turkey. Additionally, it was banned in the United Arab Emirates from 2018 to 2021, and Guatemala issued a warning about the platform to parents in 2021. The reasons behind these bans differ from country to country, with Turkey banning it due to content that may lead to gambling and child sexual abuse. Additionally, the Netherlands and Belgium have restricted certain games on the platform due to their regulations on in-game "lootboxes", which give out items based on random or unknown chances, to reduce children's exposure to gambling. In February 2025, Bloomberg News reported that Roblox was under investigation by the U.S. Securities and Exchange Commission for unknown reasons.
=== Revenue ===
During the 2017 Roblox Developers Conference, officials said that creators on the game platform, of which there were about 1.7 million as of 2017, collectively earned at least $30 million in 2017. The iOS version of Roblox passed $1 billion of lifetime revenue in November 2019, $1.5 billion in June 2020, and $2 billion in October 2020, making it the iOS app with the second-highest revenue. Several individual games on Roblox have accumulated revenues of over $10 million, while developers as a whole on the platform were collectively projected to have earned around $250 million over the course of 2020. It became the third highest-grossing game of 2020, with a revenue of $2.29 billion, below the Tencent titles PUBG and Honor of Kings.
== Toy lines ==
In January 2017, toy fabricator Jazwares partnered with Roblox Corporation to produce toy minifigures based on user-generated content created by developers on the platform. The minifigures have interchangeable limbs and joints similar to that of Lego minifigures, though they are about twice the size. The sets included a code that was used to redeem virtual items, as well as blind boxes that contained random minifigures. In 2019, Jazwares released a new line of toys, branded as the "Roblox Desktop" series. In April 2021, Roblox partnered with Hasbro to release Roblox-themed Nerf blasters and a Roblox-themed version of Monopoly.
== External links ==
Official website
== References ==
|
https://en.wikipedia.org/wiki/Roblox
|
Mathematics is a field of study that discovers and organizes methods, theories and theorems that are developed and proved for the needs of empirical sciences and mathematics itself. There are many areas of mathematics, which include number theory (the study of numbers), algebra (the study of formulas and related structures), geometry (the study of shapes and spaces that contain them), analysis (the study of continuous changes), and set theory (presently used as a foundation for all mathematics).
Mathematics involves the description and manipulation of abstract objects that consist of either abstractions from nature or—in modern mathematics—purely abstract entities that are stipulated to have certain properties, called axioms. Mathematics uses pure reason to prove properties of objects, a proof consisting of a succession of applications of deductive rules to already established results. These results include previously proved theorems, axioms, and—in case of abstraction from nature—some basic properties that are considered true starting points of the theory under consideration.
Mathematics is essential in the natural sciences, engineering, medicine, finance, computer science, and the social sciences. Although mathematics is extensively used for modeling phenomena, the fundamental truths of mathematics are independent of any scientific experimentation. Some areas of mathematics, such as statistics and game theory, are developed in close correlation with their applications and are often grouped under applied mathematics. Other areas are developed independently from any application (and are therefore called pure mathematics) but often later find practical applications.
Historically, the concept of a proof and its associated mathematical rigour first appeared in Greek mathematics, most notably in Euclid's Elements. Since its beginning, mathematics was primarily divided into geometry and arithmetic (the manipulation of natural numbers and fractions), until the 16th and 17th centuries, when algebra and infinitesimal calculus were introduced as new fields. Since then, the interaction between mathematical innovations and scientific discoveries has led to a correlated increase in the development of both. At the end of the 19th century, the foundational crisis of mathematics led to the systematization of the axiomatic method, which heralded a dramatic increase in the number of mathematical areas and their fields of application. The contemporary Mathematics Subject Classification lists more than sixty first-level areas of mathematics.
== Areas of mathematics ==
Before the Renaissance, mathematics was divided into two main areas: arithmetic, regarding the manipulation of numbers, and geometry, regarding the study of shapes. Some types of pseudoscience, such as numerology and astrology, were not then clearly distinguished from mathematics.
During the Renaissance, two more areas appeared. Mathematical notation led to algebra which, roughly speaking, consists of the study and the manipulation of formulas. Calculus, consisting of the two subfields differential calculus and integral calculus, is the study of continuous functions, which model the typically nonlinear relationships between varying quantities, as represented by variables. This division into four main areas—arithmetic, geometry, algebra, and calculus—endured until the end of the 19th century. Areas such as celestial mechanics and solid mechanics were then studied by mathematicians, but now are considered as belonging to physics. The subject of combinatorics has been studied for much of recorded history, yet did not become a separate branch of mathematics until the seventeenth century.
At the end of the 19th century, the foundational crisis in mathematics and the resulting systematization of the axiomatic method led to an explosion of new areas of mathematics. The 2020 Mathematics Subject Classification contains no less than sixty-three first-level areas. Some of these areas correspond to the older division, as is true regarding number theory (the modern name for higher arithmetic) and geometry. Several other first-level areas have "geometry" in their names or are otherwise commonly considered part of geometry. Algebra and calculus do not appear as first-level areas but are respectively split into several first-level areas. Other first-level areas emerged during the 20th century or had not previously been considered as mathematics, such as mathematical logic and foundations.
=== Number theory ===
Number theory began with the manipulation of numbers, that is, natural numbers
(
N
)
,
{\displaystyle (\mathbb {N} ),}
and later expanded to integers
(
Z
)
{\displaystyle (\mathbb {Z} )}
and rational numbers
(
Q
)
.
{\displaystyle (\mathbb {Q} ).}
Number theory was once called arithmetic, but nowadays this term is mostly used for numerical calculations. Number theory dates back to ancient Babylon and probably China. Two prominent early number theorists were Euclid of ancient Greece and Diophantus of Alexandria. The modern study of number theory in its abstract form is largely attributed to Pierre de Fermat and Leonhard Euler. The field came to full fruition with the contributions of Adrien-Marie Legendre and Carl Friedrich Gauss.
Many easily stated number problems have solutions that require sophisticated methods, often from across mathematics. A prominent example is Fermat's Last Theorem. This conjecture was stated in 1637 by Pierre de Fermat, but it was proved only in 1994 by Andrew Wiles, who used tools including scheme theory from algebraic geometry, category theory, and homological algebra. Another example is Goldbach's conjecture, which asserts that every even integer greater than 2 is the sum of two prime numbers. Stated in 1742 by Christian Goldbach, it remains unproven despite considerable effort.
Number theory includes several subareas, including analytic number theory, algebraic number theory, geometry of numbers (method oriented), diophantine equations, and transcendence theory (problem oriented).
=== Geometry ===
Geometry is one of the oldest branches of mathematics. It started with empirical recipes concerning shapes, such as lines, angles and circles, which were developed mainly for the needs of surveying and architecture, but has since blossomed out into many other subfields.
A fundamental innovation was the ancient Greeks' introduction of the concept of proofs, which require that every assertion must be proved. For example, it is not sufficient to verify by measurement that, say, two lengths are equal; their equality must be proven via reasoning from previously accepted results (theorems) and a few basic statements. The basic statements are not subject to proof because they are self-evident (postulates), or are part of the definition of the subject of study (axioms). This principle, foundational for all mathematics, was first elaborated for geometry, and was systematized by Euclid around 300 BC in his book Elements.
The resulting Euclidean geometry is the study of shapes and their arrangements constructed from lines, planes and circles in the Euclidean plane (plane geometry) and the three-dimensional Euclidean space.
Euclidean geometry was developed without change of methods or scope until the 17th century, when René Descartes introduced what is now called Cartesian coordinates. This constituted a major change of paradigm: Instead of defining real numbers as lengths of line segments (see number line), it allowed the representation of points using their coordinates, which are numbers. Algebra (and later, calculus) can thus be used to solve geometrical problems. Geometry was split into two new subfields: synthetic geometry, which uses purely geometrical methods, and analytic geometry, which uses coordinates systemically.
Analytic geometry allows the study of curves unrelated to circles and lines. Such curves can be defined as the graph of functions, the study of which led to differential geometry. They can also be defined as implicit equations, often polynomial equations (which spawned algebraic geometry). Analytic geometry also makes it possible to consider Euclidean spaces of higher than three dimensions.
In the 19th century, mathematicians discovered non-Euclidean geometries, which do not follow the parallel postulate. By questioning that postulate's truth, this discovery has been viewed as joining Russell's paradox in revealing the foundational crisis of mathematics. This aspect of the crisis was solved by systematizing the axiomatic method, and adopting that the truth of the chosen axioms is not a mathematical problem. In turn, the axiomatic method allows for the study of various geometries obtained either by changing the axioms or by considering properties that do not change under specific transformations of the space.
Today's subareas of geometry include:
Projective geometry, introduced in the 16th century by Girard Desargues, extends Euclidean geometry by adding points at infinity at which parallel lines intersect. This simplifies many aspects of classical geometry by unifying the treatments for intersecting and parallel lines.
Affine geometry, the study of properties relative to parallelism and independent from the concept of length.
Differential geometry, the study of curves, surfaces, and their generalizations, which are defined using differentiable functions.
Manifold theory, the study of shapes that are not necessarily embedded in a larger space.
Riemannian geometry, the study of distance properties in curved spaces.
Algebraic geometry, the study of curves, surfaces, and their generalizations, which are defined using polynomials.
Topology, the study of properties that are kept under continuous deformations.
Algebraic topology, the use in topology of algebraic methods, mainly homological algebra.
Discrete geometry, the study of finite configurations in geometry.
Convex geometry, the study of convex sets, which takes its importance from its applications in optimization.
Complex geometry, the geometry obtained by replacing real numbers with complex numbers.
=== Algebra ===
Algebra is the art of manipulating equations and formulas. Diophantus (3rd century) and al-Khwarizmi (9th century) were the two main precursors of algebra. Diophantus solved some equations involving unknown natural numbers by deducing new relations until he obtained the solution. Al-Khwarizmi introduced systematic methods for transforming equations, such as moving a term from one side of an equation into the other side. The term algebra is derived from the Arabic word al-jabr meaning 'the reunion of broken parts' that he used for naming one of these methods in the title of his main treatise.
Algebra became an area in its own right only with François Viète (1540–1603), who introduced the use of variables for representing unknown or unspecified numbers. Variables allow mathematicians to describe the operations that have to be done on the numbers represented using mathematical formulas.
Until the 19th century, algebra consisted mainly of the study of linear equations (presently linear algebra), and polynomial equations in a single unknown, which were called algebraic equations (a term still in use, although it may be ambiguous). During the 19th century, mathematicians began to use variables to represent things other than numbers (such as matrices, modular integers, and geometric transformations), on which generalizations of arithmetic operations are often valid. The concept of algebraic structure addresses this, consisting of a set whose elements are unspecified, of operations acting on the elements of the set, and rules that these operations must follow. The scope of algebra thus grew to include the study of algebraic structures. This object of algebra was called modern algebra or abstract algebra, as established by the influence and works of Emmy Noether,
and popularized by Van der Waerden's book Moderne Algebra.
Some types of algebraic structures have useful and often fundamental properties, in many areas of mathematics. Their study became autonomous parts of algebra, and include:
group theory
field theory
vector spaces, whose study is essentially the same as linear algebra
ring theory
commutative algebra, which is the study of commutative rings, includes the study of polynomials, and is a foundational part of algebraic geometry
homological algebra
Lie algebra and Lie group theory
Boolean algebra, which is widely used for the study of the logical structure of computers
The study of types of algebraic structures as mathematical objects is the purpose of universal algebra and category theory. The latter applies to every mathematical structure (not only algebraic ones). At its origin, it was introduced, together with homological algebra for allowing the algebraic study of non-algebraic objects such as topological spaces; this particular area of application is called algebraic topology.
=== Calculus and analysis ===
Calculus, formerly called infinitesimal calculus, was introduced independently and simultaneously by 17th-century mathematicians Newton and Leibniz. It is fundamentally the study of the relationship of variables that depend on each other. Calculus was expanded in the 18th century by Euler with the introduction of the concept of a function and many other results. Presently, "calculus" refers mainly to the elementary part of this theory, and "analysis" is commonly used for advanced parts.
Analysis is further subdivided into real analysis, where variables represent real numbers, and complex analysis, where variables represent complex numbers. Analysis includes many subareas shared by other areas of mathematics which include:
Multivariable calculus
Functional analysis, where variables represent varying functions
Integration, measure theory and potential theory, all strongly related with probability theory on a continuum
Ordinary differential equations
Partial differential equations
Numerical analysis, mainly devoted to the computation on computers of solutions of ordinary and partial differential equations that arise in many applications
=== Discrete mathematics ===
Discrete mathematics, broadly speaking, is the study of individual, countable mathematical objects. An example is the set of all integers. Because the objects of study here are discrete, the methods of calculus and mathematical analysis do not directly apply. Algorithms—especially their implementation and computational complexity—play a major role in discrete mathematics.
The four color theorem and optimal sphere packing were two major problems of discrete mathematics solved in the second half of the 20th century. The P versus NP problem, which remains open to this day, is also important for discrete mathematics, since its solution would potentially impact a large number of computationally difficult problems.
Discrete mathematics includes:
Combinatorics, the art of enumerating mathematical objects that satisfy some given constraints. Originally, these objects were elements or subsets of a given set; this has been extended to various objects, which establishes a strong link between combinatorics and other parts of discrete mathematics. For example, discrete geometry includes counting configurations of geometric shapes.
Graph theory and hypergraphs
Coding theory, including error correcting codes and a part of cryptography
Matroid theory
Discrete geometry
Discrete probability distributions
Game theory (although continuous games are also studied, most common games, such as chess and poker are discrete)
Discrete optimization, including combinatorial optimization, integer programming, constraint programming
=== Mathematical logic and set theory ===
The two subjects of mathematical logic and set theory have belonged to mathematics since the end of the 19th century. Before this period, sets were not considered to be mathematical objects, and logic, although used for mathematical proofs, belonged to philosophy and was not specifically studied by mathematicians.
Before Cantor's study of infinite sets, mathematicians were reluctant to consider actually infinite collections, and considered infinity to be the result of endless enumeration. Cantor's work offended many mathematicians not only by considering actually infinite sets but by showing that this implies different sizes of infinity, per Cantor's diagonal argument. This led to the controversy over Cantor's set theory. In the same period, various areas of mathematics concluded the former intuitive definitions of the basic mathematical objects were insufficient for ensuring mathematical rigour.
This became the foundational crisis of mathematics. It was eventually solved in mainstream mathematics by systematizing the axiomatic method inside a formalized set theory. Roughly speaking, each mathematical object is defined by the set of all similar objects and the properties that these objects must have. For example, in Peano arithmetic, the natural numbers are defined by "zero is a number", "each number has a unique successor", "each number but zero has a unique predecessor", and some rules of reasoning. This mathematical abstraction from reality is embodied in the modern philosophy of formalism, as founded by David Hilbert around 1910.
The "nature" of the objects defined this way is a philosophical problem that mathematicians leave to philosophers, even if many mathematicians have opinions on this nature, and use their opinion—sometimes called "intuition"—to guide their study and proofs. The approach allows considering "logics" (that is, sets of allowed deducing rules), theorems, proofs, etc. as mathematical objects, and to prove theorems about them. For example, Gödel's incompleteness theorems assert, roughly speaking that, in every consistent formal system that contains the natural numbers, there are theorems that are true (that is provable in a stronger system), but not provable inside the system. This approach to the foundations of mathematics was challenged during the first half of the 20th century by mathematicians led by Brouwer, who promoted intuitionistic logic, which explicitly lacks the law of excluded middle.
These problems and debates led to a wide expansion of mathematical logic, with subareas such as model theory (modeling some logical theories inside other theories), proof theory, type theory, computability theory and computational complexity theory. Although these aspects of mathematical logic were introduced before the rise of computers, their use in compiler design, formal verification, program analysis, proof assistants and other aspects of computer science, contributed in turn to the expansion of these logical theories.
=== Statistics and other decision sciences ===
The field of statistics is a mathematical application that is employed for the collection and processing of data samples, using procedures based on mathematical methods especially probability theory. Statisticians generate data with random sampling or randomized experiments.
Statistical theory studies decision problems such as minimizing the risk (expected loss) of a statistical action, such as using a procedure in, for example, parameter estimation, hypothesis testing, and selecting the best. In these traditional areas of mathematical statistics, a statistical-decision problem is formulated by minimizing an objective function, like expected loss or cost, under specific constraints. For example, designing a survey often involves minimizing the cost of estimating a population mean with a given level of confidence. Because of its use of optimization, the mathematical theory of statistics overlaps with other decision sciences, such as operations research, control theory, and mathematical economics.
=== Computational mathematics ===
Computational mathematics is the study of mathematical problems that are typically too large for human, numerical capacity. Numerical analysis studies methods for problems in analysis using functional analysis and approximation theory; numerical analysis broadly includes the study of approximation and discretization with special focus on rounding errors. Numerical analysis and, more broadly, scientific computing also study non-analytic topics of mathematical science, especially algorithmic-matrix-and-graph theory. Other areas of computational mathematics include computer algebra and symbolic computation.
== History ==
=== Etymology ===
The word mathematics comes from the Ancient Greek word máthēma (μάθημα), meaning 'something learned, knowledge, mathematics', and the derived expression mathēmatikḗ tékhnē (μαθηματικὴ τέχνη), meaning 'mathematical science'. It entered the English language during the Late Middle English period through French and Latin.
Similarly, one of the two main schools of thought in Pythagoreanism was known as the mathēmatikoi (μαθηματικοί)—which at the time meant "learners" rather than "mathematicians" in the modern sense. The Pythagoreans were likely the first to constrain the use of the word to just the study of arithmetic and geometry. By the time of Aristotle (384–322 BC) this meaning was fully established.
In Latin and English, until around 1700, the term mathematics more commonly meant "astrology" (or sometimes "astronomy") rather than "mathematics"; the meaning gradually changed to its present one from about 1500 to 1800. This change has resulted in several mistranslations: For example, Saint Augustine's warning that Christians should beware of mathematici, meaning "astrologers", is sometimes mistranslated as a condemnation of mathematicians.
The apparent plural form in English goes back to the Latin neuter plural mathematica (Cicero), based on the Greek plural ta mathēmatiká (τὰ μαθηματικά) and means roughly "all things mathematical", although it is plausible that English borrowed only the adjective mathematic(al) and formed the noun mathematics anew, after the pattern of physics and metaphysics, inherited from Greek. In English, the noun mathematics takes a singular verb. It is often shortened to maths or, in North America, math.
=== Ancient ===
In addition to recognizing how to count physical objects, prehistoric peoples may have also known how to count abstract quantities, like time—days, seasons, or years. Evidence for more complex mathematics does not appear until around 3000 BC, when the Babylonians and Egyptians began using arithmetic, algebra, and geometry for taxation and other financial calculations, for building and construction, and for astronomy. The oldest mathematical texts from Mesopotamia and Egypt are from 2000 to 1800 BC. Many early texts mention Pythagorean triples and so, by inference, the Pythagorean theorem seems to be the most ancient and widespread mathematical concept after basic arithmetic and geometry. It is in Babylonian mathematics that elementary arithmetic (addition, subtraction, multiplication, and division) first appear in the archaeological record. The Babylonians also possessed a place-value system and used a sexagesimal numeral system which is still in use today for measuring angles and time.
In the 6th century BC, Greek mathematics began to emerge as a distinct discipline and some Ancient Greeks such as the Pythagoreans appeared to have considered it a subject in its own right. Around 300 BC, Euclid organized mathematical knowledge by way of postulates and first principles, which evolved into the axiomatic method that is used in mathematics today, consisting of definition, axiom, theorem, and proof. His book, Elements, is widely considered the most successful and influential textbook of all time. The greatest mathematician of antiquity is often held to be Archimedes (c. 287 – c. 212 BC) of Syracuse. He developed formulas for calculating the surface area and volume of solids of revolution and used the method of exhaustion to calculate the area under the arc of a parabola with the summation of an infinite series, in a manner not too dissimilar from modern calculus. Other notable achievements of Greek mathematics are conic sections (Apollonius of Perga, 3rd century BC), trigonometry (Hipparchus of Nicaea, 2nd century BC), and the beginnings of algebra (Diophantus, 3rd century AD).
The Hindu–Arabic numeral system and the rules for the use of its operations, in use throughout the world today, evolved over the course of the first millennium AD in India and were transmitted to the Western world via Islamic mathematics. Other notable developments of Indian mathematics include the modern definition and approximation of sine and cosine, and an early form of infinite series.
=== Medieval and later ===
During the Golden Age of Islam, especially during the 9th and 10th centuries, mathematics saw many important innovations building on Greek mathematics. The most notable achievement of Islamic mathematics was the development of algebra. Other achievements of the Islamic period include advances in spherical trigonometry and the addition of the decimal point to the Arabic numeral system. Many notable mathematicians from this period were Persian, such as Al-Khwarizmi, Omar Khayyam and Sharaf al-Dīn al-Ṭūsī. The Greek and Arabic mathematical texts were in turn translated to Latin during the Middle Ages and made available in Europe.
During the early modern period, mathematics began to develop at an accelerating pace in Western Europe, with innovations that revolutionized mathematics, such as the introduction of variables and symbolic notation by François Viète (1540–1603), the introduction of logarithms by John Napier in 1614, which greatly simplified numerical calculations, especially for astronomy and marine navigation, the introduction of coordinates by René Descartes (1596–1650) for reducing geometry to algebra, and the development of calculus by Isaac Newton (1643–1727) and Gottfried Leibniz (1646–1716). Leonhard Euler (1707–1783), the most notable mathematician of the 18th century, unified these innovations into a single corpus with a standardized terminology, and completed them with the discovery and the proof of numerous theorems.
Perhaps the foremost mathematician of the 19th century was the German mathematician Carl Gauss, who made numerous contributions to fields such as algebra, analysis, differential geometry, matrix theory, number theory, and statistics. In the early 20th century, Kurt Gödel transformed mathematics by publishing his incompleteness theorems, which show in part that any consistent axiomatic system—if powerful enough to describe arithmetic—will contain true propositions that cannot be proved.
Mathematics has since been greatly extended, and there has been a fruitful interaction between mathematics and science, to the benefit of both. Mathematical discoveries continue to be made to this very day. According to Mikhail B. Sevryuk, in the January 2006 issue of the Bulletin of the American Mathematical Society, "The number of papers and books included in the Mathematical Reviews (MR) database since 1940 (the first year of operation of MR) is now more than 1.9 million, and more than 75 thousand items are added to the database each year. The overwhelming majority of works in this ocean contain new mathematical theorems and their proofs."
== Symbolic notation and terminology ==
Mathematical notation is widely used in science and engineering for representing complex concepts and properties in a concise, unambiguous, and accurate way. This notation consists of symbols used for representing operations, unspecified numbers, relations and any other mathematical objects, and then assembling them into expressions and formulas. More precisely, numbers and other mathematical objects are represented by symbols called variables, which are generally Latin or Greek letters, and often include subscripts. Operation and relations are generally represented by specific symbols or glyphs, such as + (plus), × (multiplication),
∫
{\textstyle \int }
(integral), = (equal), and < (less than). All these symbols are generally grouped according to specific rules to form expressions and formulas. Normally, expressions and formulas do not appear alone, but are included in sentences of the current language, where expressions play the role of noun phrases and formulas play the role of clauses.
Mathematics has developed a rich terminology covering a broad range of fields that study the properties of various abstract, idealized objects and how they interact. It is based on rigorous definitions that provide a standard foundation for communication. An axiom or postulate is a mathematical statement that is taken to be true without need of proof. If a mathematical statement has yet to be proven (or disproven), it is termed a conjecture. Through a series of rigorous arguments employing deductive reasoning, a statement that is proven to be true becomes a theorem. A specialized theorem that is mainly used to prove another theorem is called a lemma. A proven instance that forms part of a more general finding is termed a corollary.
Numerous technical terms used in mathematics are neologisms, such as polynomial and homeomorphism. Other technical terms are words of the common language that are used in an accurate meaning that may differ slightly from their common meaning. For example, in mathematics, "or" means "one, the other or both", while, in common language, it is either ambiguous or means "one or the other but not both" (in mathematics, the latter is called "exclusive or"). Finally, many mathematical terms are common words that are used with a completely different meaning. This may lead to sentences that are correct and true mathematical assertions, but appear to be nonsense to people who do not have the required background. For example, "every free module is flat" and "a field is always a ring".
== Relationship with sciences ==
Mathematics is used in most sciences for modeling phenomena, which then allows predictions to be made from experimental laws. The independence of mathematical truth from any experimentation implies that the accuracy of such predictions depends only on the adequacy of the model. Inaccurate predictions, rather than being caused by invalid mathematical concepts, imply the need to change the mathematical model used. For example, the perihelion precession of Mercury could only be explained after the emergence of Einstein's general relativity, which replaced Newton's law of gravitation as a better mathematical model.
There is still a philosophical debate whether mathematics is a science. However, in practice, mathematicians are typically grouped with scientists, and mathematics shares much in common with the physical sciences. Like them, it is falsifiable, which means in mathematics that, if a result or a theory is wrong, this can be proved by providing a counterexample. Similarly as in science, theories and results (theorems) are often obtained from experimentation. In mathematics, the experimentation may consist of computation on selected examples or of the study of figures or other representations of mathematical objects (often mind representations without physical support). For example, when asked how he came about his theorems, Gauss once replied "durch planmässiges Tattonieren" (through systematic experimentation). However, some authors emphasize that mathematics differs from the modern notion of science by not relying on empirical evidence.
=== Pure and applied mathematics ===
Until the 19th century, the development of mathematics in the West was mainly motivated by the needs of technology and science, and there was no clear distinction between pure and applied mathematics. For example, the natural numbers and arithmetic were introduced for the need of counting, and geometry was motivated by surveying, architecture and astronomy. Later, Isaac Newton introduced infinitesimal calculus for explaining the movement of the planets with his law of gravitation. Moreover, most mathematicians were also scientists, and many scientists were also mathematicians. However, a notable exception occurred with the tradition of pure mathematics in Ancient Greece. The problem of integer factorization, for example, which goes back to Euclid in 300 BC, had no practical application before its use in the RSA cryptosystem, now widely used for the security of computer networks.
In the 19th century, mathematicians such as Karl Weierstrass and Richard Dedekind increasingly focused their research on internal problems, that is, pure mathematics. This led to split mathematics into pure mathematics and applied mathematics, the latter being often considered as having a lower value among mathematical purists. However, the lines between the two are frequently blurred.
The aftermath of World War II led to a surge in the development of applied mathematics in the US and elsewhere. Many of the theories developed for applications were found interesting from the point of view of pure mathematics, and many results of pure mathematics were shown to have applications outside mathematics; in turn, the study of these applications may give new insights on the "pure theory".
An example of the first case is the theory of distributions, introduced by Laurent Schwartz for validating computations done in quantum mechanics, which became immediately an important tool of (pure) mathematical analysis. An example of the second case is the decidability of the first-order theory of the real numbers, a problem of pure mathematics that was proved true by Alfred Tarski, with an algorithm that is impossible to implement because of a computational complexity that is much too high. For getting an algorithm that can be implemented and can solve systems of polynomial equations and inequalities, George Collins introduced the cylindrical algebraic decomposition that became a fundamental tool in real algebraic geometry.
In the present day, the distinction between pure and applied mathematics is more a question of personal research aim of mathematicians than a division of mathematics into broad areas. The Mathematics Subject Classification has a section for "general applied mathematics" but does not mention "pure mathematics". However, these terms are still used in names of some university departments, such as at the Faculty of Mathematics at the University of Cambridge.
=== Unreasonable effectiveness ===
The unreasonable effectiveness of mathematics is a phenomenon that was named and first made explicit by physicist Eugene Wigner. It is the fact that many mathematical theories (even the "purest") have applications outside their initial object. These applications may be completely outside their initial area of mathematics, and may concern physical phenomena that were completely unknown when the mathematical theory was introduced. Examples of unexpected applications of mathematical theories can be found in many areas of mathematics.
A notable example is the prime factorization of natural numbers that was discovered more than 2,000 years before its common use for secure internet communications through the RSA cryptosystem. A second historical example is the theory of ellipses. They were studied by the ancient Greek mathematicians as conic sections (that is, intersections of cones with planes). It was almost 2,000 years later that Johannes Kepler discovered that the trajectories of the planets are ellipses.
In the 19th century, the internal development of geometry (pure mathematics) led to definition and study of non-Euclidean geometries, spaces of dimension higher than three and manifolds. At this time, these concepts seemed totally disconnected from the physical reality, but at the beginning of the 20th century, Albert Einstein developed the theory of relativity that uses fundamentally these concepts. In particular, spacetime of special relativity is a non-Euclidean space of dimension four, and spacetime of general relativity is a (curved) manifold of dimension four.
A striking aspect of the interaction between mathematics and physics is when mathematics drives research in physics. This is illustrated by the discoveries of the positron and the baryon
Ω
−
.
{\displaystyle \Omega ^{-}.}
In both cases, the equations of the theories had unexplained solutions, which led to conjecture of the existence of an unknown particle, and the search for these particles. In both cases, these particles were discovered a few years later by specific experiments.
=== Specific sciences ===
==== Physics ====
Mathematics and physics have influenced each other over their modern history. Modern physics uses mathematics abundantly, and is also considered to be the motivation of major mathematical developments.
==== Computing ====
Computing is closely related to mathematics in several ways. Theoretical computer science is considered to be mathematical in nature. Communication technologies apply branches of mathematics that may be very old (e.g., arithmetic), especially with respect to transmission security, in cryptography and coding theory. Discrete mathematics is useful in many areas of computer science, such as complexity theory, information theory, and graph theory. In 1998, the Kepler conjecture on sphere packing seemed to also be partially proven by computer.
==== Biology and chemistry ====
Biology uses probability extensively in fields such as ecology or neurobiology. Most discussion of probability centers on the concept of evolutionary fitness. Ecology heavily uses modeling to simulate population dynamics, study ecosystems such as the predator-prey model, measure pollution diffusion, or to assess climate change. The dynamics of a population can be modeled by coupled differential equations, such as the Lotka–Volterra equations.
Statistical hypothesis testing, is run on data from clinical trials to determine whether a new treatment works. Since the start of the 20th century, chemistry has used computing to model molecules in three dimensions.
==== Earth sciences ====
Structural geology and climatology use probabilistic models to predict the risk of natural catastrophes. Similarly, meteorology, oceanography, and planetology also use mathematics due to their heavy use of models.
==== Social sciences ====
Areas of mathematics used in the social sciences include probability/statistics and differential equations. These are used in linguistics, economics, sociology, and psychology.
Often the fundamental postulate of mathematical economics is that of the rational individual actor – Homo economicus (lit. 'economic man'). In this model, the individual seeks to maximize their self-interest, and always makes optimal choices using perfect information. This atomistic view of economics allows it to relatively easily mathematize its thinking, because individual calculations are transposed into mathematical calculations. Such mathematical modeling allows one to probe economic mechanisms. Some reject or criticise the concept of Homo economicus. Economists note that real people have limited information, make poor choices and care about fairness, altruism, not just personal gain.
Without mathematical modeling, it is hard to go beyond statistical observations or untestable speculation. Mathematical modeling allows economists to create structured frameworks to test hypotheses and analyze complex interactions. Models provide clarity and precision, enabling the translation of theoretical concepts into quantifiable predictions that can be tested against real-world data.
At the start of the 20th century, there was a development to express historical movements in formulas. In 1922, Nikolai Kondratiev discerned the ~50-year-long Kondratiev cycle, which explains phases of economic growth or crisis. Towards the end of the 19th century, mathematicians extended their analysis into geopolitics. Peter Turchin developed cliodynamics since the 1990s.
Mathematization of the social sciences is not without risk. In the controversial book Fashionable Nonsense (1997), Sokal and Bricmont denounced the unfounded or abusive use of scientific terminology, particularly from mathematics or physics, in the social sciences. The study of complex systems (evolution of unemployment, business capital, demographic evolution of a population, etc.) uses mathematical knowledge. However, the choice of counting criteria, particularly for unemployment, or of models, can be subject to controversy.
== Philosophy ==
=== Reality ===
The connection between mathematics and material reality has led to philosophical debates since at least the time of Pythagoras. The ancient philosopher Plato argued that abstractions that reflect material reality have themselves a reality that exists outside space and time. As a result, the philosophical view that mathematical objects somehow exist on their own in abstraction is often referred to as Platonism. Independently of their possible philosophical opinions, modern mathematicians may be generally considered as Platonists, since they think of and talk of their objects of study as real objects.
Armand Borel summarized this view of mathematics reality as follows, and provided quotations of G. H. Hardy, Charles Hermite, Henri Poincaré and Albert Einstein that support his views.
Something becomes objective (as opposed to "subjective") as soon as we are convinced that it exists in the minds of others in the same form as it does in ours and that we can think about it and discuss it together. Because the language of mathematics is so precise, it is ideally suited to defining concepts for which such a consensus exists. In my opinion, that is sufficient to provide us with a feeling of an objective existence, of a reality of mathematics ...
Nevertheless, Platonism and the concurrent views on abstraction do not explain the unreasonable effectiveness of mathematics (as Platonism assumes mathematics exists independently, but does not explain why it matches reality).
=== Proposed definitions ===
There is no general consensus about the definition of mathematics or its epistemological status—that is, its place inside knowledge. A great many professional mathematicians take no interest in a definition of mathematics, or consider it undefinable. There is not even consensus on whether mathematics is an art or a science. Some just say, "mathematics is what mathematicians do". A common approach is to define mathematics by its object of study.
Aristotle defined mathematics as "the science of quantity" and this definition prevailed until the 18th century. However, Aristotle also noted a focus on quantity alone may not distinguish mathematics from sciences like physics; in his view, abstraction and studying quantity as a property "separable in thought" from real instances set mathematics apart. In the 19th century, when mathematicians began to address topics—such as infinite sets—which have no clear-cut relation to physical reality, a variety of new definitions were given. With the large number of new areas of mathematics that have appeared since the beginning of the 20th century, defining mathematics by its object of study has become increasingly difficult. For example, in lieu of a definition, Saunders Mac Lane in Mathematics, form and function summarizes the basics of several areas of mathematics, emphasizing their inter-connectedness, and observes:
the development of Mathematics provides a tightly connected network of formal rules, concepts, and systems. Nodes of this network are closely bound to procedures useful in human activities and to questions arising in science. The transition from activities to the formal Mathematical systems is guided by a variety of general insights and ideas.
Another approach for defining mathematics is to use its methods. For example, an area of study is often qualified as mathematics as soon as one can prove theorems—assertions whose validity relies on a proof, that is, a purely-logical deduction.
=== Rigor ===
Mathematical reasoning requires rigor. This means that the definitions must be absolutely unambiguous and the proofs must be reducible to a succession of applications of inference rules, without any use of empirical evidence and intuition. Rigorous reasoning is not specific to mathematics, but, in mathematics, the standard of rigor is much higher than elsewhere. Despite mathematics' concision, rigorous proofs can require hundreds of pages to express, such as the 255-page Feit–Thompson theorem. The emergence of computer-assisted proofs has allowed proof lengths to further expand. The result of this trend is a philosophy of the quasi-empiricist proof that can not be considered infallible, but has a probability attached to it.
The concept of rigor in mathematics dates back to ancient Greece, where their society encouraged logical, deductive reasoning. However, this rigorous approach would tend to discourage exploration of new approaches, such as irrational numbers and concepts of infinity. The method of demonstrating rigorous proof was enhanced in the sixteenth century through the use of symbolic notation. In the 18th century, social transition led to mathematicians earning their keep through teaching, which led to more careful thinking about the underlying concepts of mathematics. This produced more rigorous approaches, while transitioning from geometric methods to algebraic and then arithmetic proofs.
At the end of the 19th century, it appeared that the definitions of the basic concepts of mathematics were not accurate enough for avoiding paradoxes (non-Euclidean geometries and Weierstrass function) and contradictions (Russell's paradox). This was solved by the inclusion of axioms with the apodictic inference rules of mathematical theories; the re-introduction of axiomatic method pioneered by the ancient Greeks. It results that "rigor" is no more a relevant concept in mathematics, as a proof is either correct or erroneous, and a "rigorous proof" is simply a pleonasm. Where a special concept of rigor comes into play is in the socialized aspects of a proof, wherein it may be demonstrably refuted by other mathematicians. After a proof has been accepted for many years or even decades, it can then be considered as reliable.
Nevertheless, the concept of "rigor" may remain useful for teaching to beginners what is a mathematical proof.
== Training and practice ==
=== Education ===
Mathematics has a remarkable ability to cross cultural boundaries and time periods. As a human activity, the practice of mathematics has a social side, which includes education, careers, recognition, popularization, and so on. In education, mathematics is a core part of the curriculum and forms an important element of the STEM academic disciplines. Prominent careers for professional mathematicians include mathematics teacher or professor, statistician, actuary, financial analyst, economist, accountant, commodity trader, or computer consultant.
Archaeological evidence shows that instruction in mathematics occurred as early as the second millennium BCE in ancient Babylonia. Comparable evidence has been unearthed for scribal mathematics training in the ancient Near East and then for the Greco-Roman world starting around 300 BCE. The oldest known mathematics textbook is the Rhind papyrus, dated from c. 1650 BCE in Egypt. Due to a scarcity of books, mathematical teachings in ancient India were communicated using memorized oral tradition since the Vedic period (c. 1500 – c. 500 BCE). In Imperial China during the Tang dynasty (618–907 CE), a mathematics curriculum was adopted for the civil service exam to join the state bureaucracy.
Following the Dark Ages, mathematics education in Europe was provided by religious schools as part of the Quadrivium. Formal instruction in pedagogy began with Jesuit schools in the 16th and 17th century. Most mathematical curricula remained at a basic and practical level until the nineteenth century, when it began to flourish in France and Germany. The oldest journal addressing instruction in mathematics was L'Enseignement Mathématique, which began publication in 1899. The Western advancements in science and technology led to the establishment of centralized education systems in many nation-states, with mathematics as a core component—initially for its military applications. While the content of courses varies, in the present day nearly all countries teach mathematics to students for significant amounts of time.
During school, mathematical capabilities and positive expectations have a strong association with career interest in the field. Extrinsic factors such as feedback motivation by teachers, parents, and peer groups can influence the level of interest in mathematics. Some students studying mathematics may develop an apprehension or fear about their performance in the subject. This is known as mathematical anxiety, and is considered the most prominent of the disorders impacting academic performance. Mathematical anxiety can develop due to various factors such as parental and teacher attitudes, social stereotypes, and personal traits. Help to counteract the anxiety can come from changes in instructional approaches, by interactions with parents and teachers, and by tailored treatments for the individual.
=== Psychology (aesthetic, creativity and intuition) ===
The validity of a mathematical theorem relies only on the rigor of its proof, which could theoretically be done automatically by a computer program. This does not mean that there is no place for creativity in a mathematical work. On the contrary, many important mathematical results (theorems) are solutions of problems that other mathematicians failed to solve, and the invention of a way for solving them may be a fundamental way of the solving process. An extreme example is Apery's theorem: Roger Apery provided only the ideas for a proof, and the formal proof was given only several months later by three other mathematicians.
Creativity and rigor are not the only psychological aspects of the activity of mathematicians. Some mathematicians can see their activity as a game, more specifically as solving puzzles. This aspect of mathematical activity is emphasized in recreational mathematics.
Mathematicians can find an aesthetic value to mathematics. Like beauty, it is hard to define, it is commonly related to elegance, which involves qualities like simplicity, symmetry, completeness, and generality. G. H. Hardy in A Mathematician's Apology expressed the belief that the aesthetic considerations are, in themselves, sufficient to justify the study of pure mathematics. He also identified other criteria such as significance, unexpectedness, and inevitability, which contribute to mathematical aesthetics. Paul Erdős expressed this sentiment more ironically by speaking of "The Book", a supposed divine collection of the most beautiful proofs. The 1998 book Proofs from THE BOOK, inspired by Erdős, is a collection of particularly succinct and revelatory mathematical arguments. Some examples of particularly elegant results included are Euclid's proof that there are infinitely many prime numbers and the fast Fourier transform for harmonic analysis.
Some feel that to consider mathematics a science is to downplay its artistry and history in the seven traditional liberal arts. One way this difference of viewpoint plays out is in the philosophical debate as to whether mathematical results are created (as in art) or discovered (as in science). The popularity of recreational mathematics is another sign of the pleasure many find in solving mathematical questions.
== Cultural impact ==
=== Artistic expression ===
Notes that sound well together to a Western ear are sounds whose fundamental frequencies of vibration are in simple ratios. For example, an octave doubles the frequency and a perfect fifth multiplies it by
3
2
{\displaystyle {\frac {3}{2}}}
.
Humans, as well as some other animals, find symmetric patterns to be more beautiful. Mathematically, the symmetries of an object form a group known as the symmetry group. For example, the group underlying mirror symmetry is the cyclic group of two elements,
Z
/
2
Z
{\displaystyle \mathbb {Z} /2\mathbb {Z} }
. A Rorschach test is a figure invariant by this symmetry, as are butterfly and animal bodies more generally (at least on the surface). Waves on the sea surface possess translation symmetry: moving one's viewpoint by the distance between wave crests does not change one's view of the sea. Fractals possess self-similarity.
=== Popularization ===
Popular mathematics is the act of presenting mathematics without technical terms. Presenting mathematics may be hard since the general public suffers from mathematical anxiety and mathematical objects are highly abstract. However, popular mathematics writing can overcome this by using applications or cultural links. Despite this, mathematics is rarely the topic of popularization in printed or televised media.
=== Awards and prize problems ===
The most prestigious award in mathematics is the Fields Medal, established in 1936 and awarded every four years (except around World War II) to up to four individuals. It is considered the mathematical equivalent of the Nobel Prize.
Other prestigious mathematics awards include:
The Abel Prize, instituted in 2002 and first awarded in 2003
The Chern Medal for lifetime achievement, introduced in 2009 and first awarded in 2010
The AMS Leroy P. Steele Prize, awarded since 1970
The Wolf Prize in Mathematics, also for lifetime achievement, instituted in 1978
A famous list of 23 open problems, called "Hilbert's problems", was compiled in 1900 by German mathematician David Hilbert. This list has achieved great celebrity among mathematicians, and at least thirteen of the problems (depending how some are interpreted) have been solved.
A new list of seven important problems, titled the "Millennium Prize Problems", was published in 2000. Only one of them, the Riemann hypothesis, duplicates one of Hilbert's problems. A solution to any of these problems carries a 1 million dollar reward. To date, only one of these problems, the Poincaré conjecture, has been solved by the Russian mathematician Grigori Perelman.
== See also ==
== Notes ==
== References ==
=== Citations ===
=== Other sources ===
== Further reading ==
|
https://en.wikipedia.org/wiki/Mathematics
|
Math League is a math competition for elementary, middle, and high school students in the United States, Canada, and other countries. The Math League was founded in 1977 by two high school mathematics teachers, Steven R. Conrad and Daniel Flegler. Math Leagues, Inc. publishes old contests through a series of books entitled Math League Press. The purpose of the Math League Contests is to provide students "an enriching opportunity to participate in an academically-oriented activity" and to let students "gain recognition for mathematical achievement".
Math League runs three contest formats:
Grades 4-5: 30 multiple-choice questions to solve in 30 minutes, covering arithmetic and basic principles
Grades 6-8: 35 multiple-choice questions to solve in 30 minutes, covering advanced arithmetic and basic topics in geometry and algebra
Grades 9-12: Series of 6 contests. Each contest contains 6 short-answer questions to solve in 30 minutes, covering geometry, algebra, trigonometry, and other advanced pre-calculus topics.
Only plain paper, pencil or pen, and a calculator without QWERTY keyboard are allowed.
Students who score above 12 points in grades 4 and 5, and above 15 points in grades 6-8 are awarded a 'Certificate of Merit." Which means they win.
== References ==
== External links ==
Math League Homepage
|
https://en.wikipedia.org/wiki/Math_League
|
In the United States, math wars are debates over modern mathematics education, textbooks and curricula that were triggered by the publication in 1989 of the Curriculum and Evaluation Standards for School Mathematics by the National Council of Teachers of Mathematics (NCTM) and subsequent development and widespread adoption of a new generation of mathematics curricula inspired by these standards.
While the discussion about math skills has persisted for many decades, the term "math wars" was coined by commentators such as John A. Van de Walle and David Klein. The debates focus on traditional mathematics versus reform mathematics philosophy and curricula, which differ significantly in approach and content.
== Advocates of reform ==
The largest supporter of reform in the US has been the National Council of Teachers of Mathematics.
One aspect of the debate is over how explicitly children must be taught skills based on formulas or algorithms (fixed, step-by-step procedures for solving math problems) versus a more inquiry-based approach in which students are exposed to real-world problems that help them develop fluency in number sense, reasoning, and problem-solving skills. In this latter approach, conceptual understanding is a primary goal and algorithmic fluency is expected to follow secondarily. Some parents and other stakeholders blame educators saying that failures occur not because the method is at fault, but because these educational methods require a great deal of expertise and have not always been implemented well in actual classrooms.
A backlash, which advocates call "poorly understood reform efforts" and critics call "a complete abandonment of instruction in basic mathematics," resulted in "math wars" between reform and traditional methods of mathematics education.
== Critics of reform ==
Those who disagree with the inquiry-based philosophy maintain that students must first develop computational skills before they can understand concepts of mathematics. These skills should be memorized and practiced, using time-tested traditional methods until they become automatic. Time is better spent practicing skills rather than in investigations inventing alternatives, or justifying more than one correct answer or method. In this view, estimating answers is insufficient and, in fact, is considered to be dependent on strong foundational skills. Learning abstract concepts of mathematics is perceived to depend on a solid base of knowledge of the tools of the subject.
Supporters of traditional mathematics teaching oppose excessive dependence on innovations such as calculators or new technology, such as the Logo language. Student innovation is acceptable, even welcome, as long as it is mathematically valid. Calculator use can be appropriate after number sense has developed and basic skills have been mastered. Constructivist methods which are unfamiliar to many adults, and books which lack explanations of methods or solved examples make it difficult to help with homework. Compared to worksheets that can be completed in minutes, constructivist activities can be more time-consuming. (Reform educators respond that more time is lost in reteaching poorly understood algorithms.) Emphasis on reading and writing also increases the language load for immigrant students and parents who may be unfamiliar with English.
Critics of reform point out that traditional methods are still universally and exclusively used in industry and academia. Reform educators respond that such methods are still the ultimate goal of reform mathematics, and that students need to learn flexible thinking in order to face problems they may not know a method for. Critics maintain that it is unreasonable to expect students to "discover" the standard methods through investigation, and that flexible thinking can only be developed after mastering foundational skills. Commentators have argued that there is philosophical support for the notion that "algorithmic fluency" requires the very types of cognitive activity whose promotion reform advocates often claim is their approaches' unique virtue. However, such arguments assume that reformers do not want to teach the standard algorithms, which is a common misunderstanding of the reform position.
Some curricula incorporate research by Constance Kamii and others that concluded that direct teaching of traditional algorithms is counterproductive to conceptual understanding of math. Critics have protested some of the consequences of this research. Traditional memorization methods are replaced with constructivist activities. Students who demonstrate proficiency in a standard method are asked to invent another method of arriving at the answer. Some parents have accused reform math advocates of deliberately slowing down students with greater ability in order to "paper-over" the inequalities of the American school system. Some teachers supplement such textbooks in order to teach standard methods more quickly. Some curricula do not teach long division. Critics believe the NCTM revised its standards to explicitly call for continuing instruction of standard methods, largely because of the negative response to some of these curricula (see below). College professors and employers have sometimes claimed that students that have been taught using reform curricula do not possess basic mathematical skills. One study found that, although first-grade students in 1999 with an average or above-average aptitude for math did equally well with either teacher-directed or student-centered instruction, first-grade students with mathematical difficulties did better with teacher-directed instruction.
== Reform curricula ==
Examples of reform curricula introduced in response to the 1989 NCTM standards and the reasons for initial criticism:
Mathland (no longer offered)
Investigations in Numbers, Data, and Space, criticized for not containing explicit instruction of the standard algorithms
Core-Plus Mathematics Project, criticized for failing "to convey critical mathematical concepts and ideas that should and can be within reach for high school students", downplaying "algebraic structure and skills" and "inability to build geometry up from foundations in a mathematically sound and coherent way".
Connected Mathematics, criticized for not explicitly teaching children standard algorithms, formulas or solved examples
Everyday Math, criticized for putting emphasis on non-traditional arithmetic methods.
Critics of reform textbooks say that they present concepts in a haphazard way. Critics of the reform textbooks and curricula support methods such as Singapore math, which emphasizes direct instruction of basic mathematical concepts, and Saxon math, which emphasizes frequent cumulative review.
Reform educators have responded by pointing out that research tends to show that students achieve greater conceptual understanding from standards-based curricula than traditional curricula and that these gains do not come at the expense of basic skills. In fact students tend to achieve the same procedural skill level in both types of curricula as measured by traditional standardized tests. More research is needed, but the current state of research seems to show that reform textbooks work as well as or better than traditional textbooks in helping students achieve computational competence while promoting greater conceptual understanding than traditional approaches.
== Later developments ==
In 2000 the National Council of Teachers of Mathematics (NCTM) released the Principles and Standards for School Mathematics (PSSM), which was seen as more balanced than the original 1989 Standards. This led to some calming, but not an end to the dispute. Two recent reports have led to considerably more cooling of the Math Wars. In 2006, NCTM released its Curriculum Focal Points, which was seen by many as a compromise position. In 2008, the National Mathematics Advisory Panel, created by George W. Bush, called for a halt to all extreme positions.
=== National Council of Teachers of Mathematics 2006 recommendations ===
In 2006, the NCTM released Curriculum Focal Points, a report on the topics considered central for mathematics in pre-kindergarten through eighth grade. Its inclusion of standard algorithms led editorials in newspapers like the Chicago Sun Times to state that the "NCTM council has admitted, more or less, that it goofed," and that the new report cited "inconsistency in the grade placement of mathematics topics as well as in how they are defined and what students are expected to learn." NCTM responded by insisting that it considers "Focal Points" a step in the implementation of the Standards, not a reversal of its position on teaching students to learn foundational topics with conceptual understanding. Francis Fennell, president of the NCTM, stated that there had been no change of direction or policy in the new report and said that he resented talk of “math wars”. The Focal Points were one of the documents consulted to create the new national Common Core Standards, which have been adopted by most of the United States since 2010.
=== National Mathematics Advisory Panel ===
On April 18, 2006, President Bush created the National Mathematics Advisory Panel, which was modeled after the influential National Reading Panel. The National Math Panel examined and summarized the scientific evidence related to the teaching and learning of mathematics, concluding in their 2008 report, "All-encompassing recommendations that instruction should be entirely 'student centered' or 'teacher directed' are not supported by research. If such recommendations exist, they should be rescinded. If they are being considered, they should be avoided. High-quality research does not support the exclusive use of either approach." The Panel effectively called for an end to the Math Wars, concluding that research showed "conceptual understanding, computational and procedural fluency, and problem-solving skills are equally important and mutually reinforce each other. Debates regarding the relative importance of each of these components of mathematics are misguided."
The Panel's final report met with significant criticism within the mathematics education community for, among other issues, the selection criteria used to determine "high-quality" research, their comparison of extreme forms of teaching, and the amount of focus placed on algebra.
== See also ==
Anti-racist mathematics – Educational plan meant to reduce perceived prejudice in educationPages displaying short descriptions of redirect targets
California Department of Education § 2021 mathematics framework
Critical mathematics pedagogy – Liberation-focused math education
David Klein (mathematician) – American mathematician
Jo Boaler – British mathematics education professor (born 1964)
Marian Small – Educational researcher
Mathematics for social justice – Approach to education
New Math – Approach to teaching mathematics in the 1960s
Three-part lesson – Inquiry-based learning method
== References ==
== Further reading ==
"America's maths wars". The Economist. 6 November 2021. ISSN 0013-0613.
|
https://en.wikipedia.org/wiki/Math_wars
|
Math rock is a style of alternative and indie rock with roots in bands such as King Crimson and Rush. It is characterized by complex, atypical rhythmic structures (including irregular stopping and starting), counterpoint, odd time signatures, and extended chords. Bearing similarities to post-rock, math rock has been described as the "opposite side of the same coin". Opting for a "rockier" approach to songwriting and timbres, the style is often performed by smaller ensembles which emphasize the role of the guitar.
Polvo, Don Caballero, Slint, Bitch Magnet, Bastro and Ruins are considered by some to be the genre's pioneers.
== History and precursors ==
The albums Red and Discipline by King Crimson, as well as Spiderland by Slint, are generally considered seminal influences on the development of math rock. The Canadian punk rock group Nomeansno (founded in 1979 and inactive as of 2016) have been cited by music critics as a "secret influence" on math rock, predating much of the genre's development by more than a decade. An even more avant-garde group of the same era, Massacre, featured the guitarist Fred Frith and the bassist Bill Laswell. With some influence from the rapid-fire energy of punk, Massacre's influential music used complex rhythmic characteristics. Black Flag's 1984 album, My War, also included unusual polyrhythms.
Two songs on Yes' album Fragile (1971) have drawn attention – Paul Lester of Classic Rock writes that "Five Per Cent for Nothing" finds drummer Bill Bruford "inventing math rock", while "Heart of the Sunrise" was described by Pitchfork's Chris Dahlen, Dominique Leone and Joe Tangari as "a deftly constructed proto math-rock epic".
Examples of modern math rock bands include Delta Sleep, Covet, Tricot, and TTNG.
== Characteristics ==
Math rock is typified by its rhythmic complexity, seen as mathematical in character by listeners and critics. While most rock music uses a 44 meter (however accented or syncopated), math rock makes use of more non-standard, frequently changing time signatures such as 54, 78, 118, or 138.
As in traditional rock, the sound is most often dominated by guitars and drums. However, drums play a greater role in math rock in providing driving, complex rhythms. Math rock guitarists make use of tapping techniques and loop pedals to build on these rhythms, as illustrated by songs like those of math rock supergroup Battles.
Lyrics are generally not the focus of math rock; the voice is treated as just another instrument in the mix. Often, vocals are not overdubbed, and are positioned less prominently, as in the recording style of Steve Albini. Many of math rock's best-known groups are entirely instrumental such as Don Caballero or Hella.
A significant intersection exists between math rock and emo, exemplified by bands such as Tiny Moving Parts or American Football, whose sound has been described as "twinkly, mathy rock, a sound that became one of the defining traits of the emo scene throughout the 2000s".
== Etymology ==
The term began as a joke, but has since developed into the accepted name for the musical style. One advocate of this is Matt Sweeney, singer with Chavez, a group often linked to the math rock scene. Despite this, not all critics see math rock as a serious sub-genre of rock, and some of the genre's most notable acts have disavowed the term.
== Artists ==
=== Asian ===
Math rock has a significant presence in Japan; the most prominent Japanese groups include Toe, Tricot, The Cabs, and Lite. Other Japanese groups which incorporate math rock in their music include Ling Tosite Sigure, Zazen Boys and Mouse on the Keys while the Japanoise scene features bands such as Ruins, Zeni Geva, and Boredoms.
Taiwan has a very small indie music scene, of which math rock is an emergent genre that is quickly gaining in popularity, with well-known math rock bands including Elephant Gym.
=== North American ===
Polvo of Chapel Hill, North Carolina is often considered one of the household names in math rock, although the band members themselves have disavowed the categorization.
In California, power pop groups Game Theory and the Loud Family were both led by Scott Miller, who was said to "tinker with pop the way a born mathematician tinkers with numbers". The origin of Game Theory's name is mathematical, suggesting a "nearly mathy" sound cited as "IQ rock."
Although the Seattle grunge scene was not widely associated with math rock, some consider Soundgarden to be one of few exceptions, due to the odd time signatures found in many of their songs.
== See also ==
== Notes and references ==
== Further reading ==
Dale, P. (2016). Anyone Can Do It: Empowerment, Tradition and the Punk Underground. Ashgate Popular and Folk Music Series. Taylor & Francis. p. pt237–. ISBN 978-1-317-18024-1.
Eberhart, Max (September 29, 2016). "Calculating the Influence of Math Rock". The Santa Clara. Archived from the original on October 1, 2016. Retrieved October 3, 2016.
Gomez, Jeff (2024). Math Rock. Bloomsbury. ISBN 979-8765103371.
== External links ==
Math Rock at AllMusic
|
https://en.wikipedia.org/wiki/Math_rock
|
Math Patrol was a children's educational television show produced by TVOntario from 1976 to 1978 and aired by the public broadcaster in the late 1970s and the early 1980s.
The series starred John Kozak as "Sydney" – a "math detective" who repeatedly went undercover as a kangaroo ("the only disguise Math Patrol had that would fit him"). Other cast members included Carl Banas, Jessica Booker, Luba Goy and Nikki Tilroe.
Producer/Director Clive Vanderburgh, Production Assistant Jane Downey and Editor Brian Elston.
The program was designed to teach basic math skills and terminology in an entertaining fashion to children between approximately 8 and 10 years of age. In each 15-minute episode, Math Patrol's unseen (silhouetted) boss "Mr. Big" would send the detective on a case or charge him with a task which could only be solved through mathematic deduction.
Over the course of 20 episodes, Math Patrol provided introductory math lessons on topics including addition, subtraction, multiplication, division, area, fractions, length, shapes, geometry and symmetry.
Because of its highly educational nature, Math Patrol was often shown to groups of primary school students during class time.
== External links ==
A fan site dedicated to classic TVO children's shows of the 1970s
Math Patrol at IMDb
|
https://en.wikipedia.org/wiki/Math_Patrol
|
Math Lady, Confused Lady or Confused Math Lady, known in Brazil as Nazaré Confusa (Portuguese for Confused Nazaré), is an Internet meme. It shows Brazilian actress Renata Sorrah surrounded by mathematical problems, in a scene from 2004 Brazilian soap opera Senhora do Destino, where she plays Nazaré Tedesco. The telenovela was widely popular in Brazil at the time, receiving high ratings even in reruns; Nazaré Tedesco, Sorrah's character in the show, is one of the most famous villains in the history of Brazilian telenovelas, and different memes involving her are popular in the country. "Math Lady" received international popularity.
== Background ==
Prior to the meme and even the soap opera where it comes from, Sorrah was already one of the most acclaimed and accomplished careers in Brazilian television, with her career starting in the late 1960s in Rede Tupi, moving soon to work for TV Globo, where she acted in many notable soap operas such as Vale Tudo, Pedra sobre Pedra and Vai na Fé, by 2004, she had received eleven awards across her career from many ceremonies, nine of which were for "Best actress".
=== In Senhora do Destino ===
Senhora do Destino (Portuguese for Lady of the Destiny) was a Brazilian soap opera broadcast by TV Globo from June 28, 2004, to March 11, 2005, in 221 chapters. In it, Sorrah portrayed the main antagonist Nazaré Tedesco, a prostitute who, in the first act of the soap opera (depicted in the past, with young Nazaré being portrayed by Adriana Esteves), kidnaps the recently born daughter of main protagonist Maria do Carmo (portrayed by Susana Vieira) in order to forge a marriage with José Carlos Tedesco (portrayed by Tarcísio Meira), at the time one of the richest men in Rio de Janeiro. The daughter was named Lindalva, but Nazaré renamed her Isabel to get away with the farce.
In the second act, set twenty-five years later, it is revealed that Nazaré and José Carlos have lost their fortune and had to mortgage their home in order to pay various late bills. After watching a news broadcast on Maria do Carmo, who had become a wealthy woman, talking about her missing daughter and showing a picture of young Nazaré; José Carlos finds out the truth about the daughter him and Nazaré raised and threatens to call the police on her, who in response, pushes him down a staircase, throws away his medication, leading to him suffering a cardiac arrest and passing away. After the incident, Nazaré ends up without money, leading her to start living her life out of scams, including extorting Maria do Carmo in exchange for information about her lost daughter. Amidst this, Djenane (portrayed by Elizângela), a co-worker of Nazaré that helped her to fake the birth of Isabel, returns to blackmail Nazaré, and during a fight, Djenane falls down the stairs and dies. To avoid being accused of Djenane's death, Nazaré adulterates proofs against her and even pretends to be her in order to withdraw money from her account.
Nazaré's situation only kept getting more complicated as the story went, with her making another victim later in the drama by electrocuting Gilmar (portrayed by Roberto Bomtempo), a former accomplice of her, in a bathtub. Nazaré also allies herself with Maria do Carmo's former husband (Isabel's own father), a reviled villain portrayed by José de Abreu, who ends up as a mentally unstable homeless man when Nazaré abandons him in her final escape. Eventually, Nazaré's end comes when she kidnaps Isabel's daughter and is the target of a chase, after she gets cornered in a bridge over a river, Nazaré redeems herself by giving Isabel's daughter back to her, but in turn, she jumps from the bridge, killing herself.
=== Reception and stardom ===
Senhora do Destino went on to become a smash hit with the Brazilian public, being one of the soap operas produced by Globo with the highest audience during the 2000s, and becoming one of the most iconic soap operas of all time in the country, with even some international acclaim, as Spanish newspaper 20 Minutos ranked Senhora do Destino as the 9th greatest Brazilian soap opera of all time; One of the leading factors for this was due to Sorrah's role as Nazaré Tedesco, who went on to become one of the most — if not, the — most iconic antagonists in Brazilian television, with her role largely overshadowing Vieira's role as the main character of the soap opera. The scenes that are often considered the most iconic ones of the soap opera all revolve around Nazaré, as these would include the various catchphrases and sarcastic comments made by the character, the murders of José Carlos and Gilmar, the death of Djenane, that is often wrongfully remembered as a murder in a Mandela effect situation, and Nazaré's suicide, particularly for her final line: "Eu vou voar. Olha, filha! Olha!" ('I'm gonna fly. Look, daughter! Look!')
== Pop culture notoriety and first memes in Brazil ==
For many years after the airing of Senhora do Destino, Nazaré still kept being remembered by the public, and went on to become Renata Sorrah's most iconic role, with several pop culture references, the most notable one happening in the 2011 soap opera Fina Estampa, where the main antagonist, Tereza Cristina (portrayed by Christiane Torloni), after killing another character by electrocuting him in a bathtub, proceeds to say "Obrigada, Nazaré Tedesco." ('Thank you, Nazaré Tedesco.').
Throughout the 2010s, many memes were birthed onto the Brazilian internet thanks to the character, some of the most notable ones include several Top Text Bottom Text templates; a still from her final scene, showing Nazaré running with Isabel's daughter on her lap, with a crowd running after her; as well as a scene where Nazaré spots two female characters talking about potentially marrying someday and thinks the line "Sapatonas... Eu sinto longe o cheiro de couro!" ('Dykes... From afar I can smell the leather!'), proceeded by her covering her nose. Several more of Nazaré's phrases have been used in gifs and reaction images in Brazilian internet.
== Math Lady and international notoriety ==
The original gif, without the math problems, started to circulate on Brazilian internet around 2013, stemming from a scene where Nazaré is in jail and reflects on a conversation she had with another character. Around the summer of 2016, the meme started to slowly spread once again, and after the addition of the mathematical problems, an inclusion in the website 9gag, and usage in Twitter memes during the American presidential debate between Donald Trump and Hillary Clinton, the meme rose into international popularity and went on to become even bigger in Brazil.
=== Renata Sorrah's response ===
As the meme kept rising both in Brazilian and international internet, with some viewers even mistaking Sorrah for American actress Julia Roberts, everything came into Renata Sorrah's knowledge soon enough, she has responded multiple times about how the meme as a whole does not bother her and she embraces the joke, but sometimes, she does get mildly annoyed that the meme has overshadowed her acting career, as stated in an interview with Brazilian magazine Veja:My nephew, who lives in New York, tells everybody that her aunt is the Math Lady, and everybody gets crazy. But sometimes it's terrible. I remember once, in a festival in Curitiba, that i went through a bar full of young men and i heard: 'Look there, it's that meme lady'. We are working hard, doing theater, exhausted... to become 'the meme lady' (laughter). I don't have control of it, but it doesn't bother me.
== Other related occurrences ==
In 2021, many Brazilian twitter users compared the 2024 Summer Olympics logo with Nazaré Tedesco, some of them even editing sunglasses onto the logo to resemble a scene where Nazaré is disguised in a wedding.
On 10 May 2023, it was reported that Sorrah had come out as bisexual. The news became a trending topic on social media, with users resurfacing the meme and giving it a new meaning. In Brazil, her other meme where Nazaré judges two lesbian characters also resurfaced due to the news. Sorrah later denied the false reports on her sexuality.
== Reenactment of the meme in Show 60 Anos ==
On 28 April 2025, Globo broadcast a special concert celebrating the channel's 60th anniversary titled Show 60 Anos [pt]. During one of the segments celebrating the most iconic villainesses from the channel's soap operas, Sorrah portrayed Nazaré Tedesco for the first time since the ending of Senhora do Destino. In the scene, Sorrah enters a dressing room with many other female villains, such as Carminha from Avenida Brasil (Portrayed by Adriana Esteves), Cristina from Alma Gêmea (Portrayed by Flávia Alessandra), Perpétua from Tieta (Portrayed by Joana Fomm) and many others.
During a segment where they discuss why they should win "best villainess in Globo's history", Nazaré mentions to Raquel from Mulheres de Areia (Portrayed by Glória Pires), her many memes in brazilian internet, and even being an "international phenomenom", referring to herself in the English term "Confused Math Lady"; A couple of moments after this, after Raquel's response, it's possible to see math equations floating around Nazaré. The scene generated rapturous discussion on twitter, with many praising Sorrah for having the same spirit she had when she originally portrayed the character.
Said best villainess award never happened, as the skit ends with them being locked in the dressing room by Ivete Sangalo, as after that, Ivete performed a tribute to the villains by singing "Erva Venenosa", a portuguese version of "Poison Ivy" by The Coasters, originally performed by Rita Lee.
== References ==
== External links ==
Math Lady on Know Your Meme
|
https://en.wikipedia.org/wiki/Math_Lady
|
The phrase "girl math" is an internet meme, used to describe rationalizations by young women to justify indulgent and potentially irresponsible spending habits. It originated from the social media platform TikTok, later transferring over to Instagram and X (formerly Twitter).
== History ==
According to KnowYourMeme, the origins of this trend stem from the TikTok user's @samjamessssss video, in which she encouraged the transition from "girl dinner", another popular TikTok trend amongst women, to girl math. The meme was created and popularized by women themselves on TikTok.
Another possible origin of the trend is thought to be from a New Zealand radio show "Fletch, Vaughan & Hailey", where they have a segment called "Girl Math". For this segment listeners would call in and share their large purchases, and the hosts would in turn help them justify spending the money on the item. The original segment became especially popular once it got to TikTok, where the trend went viral.
== Effect of gender stereotypes ==
The rise of online trends on social media platforms such as X and TikTok, that pertain to the concept of "girl math" and "boy math" could potentially be influenced by and influence gender perceptions, as proposed by some research. Gender perceptions are the cultural and social views of males and females. There is a difference in the meaning behind the trends because when "girl math" is referred to it most commonly celebrates femininity with positive appraisement amongst women. Women tend to use the trend in a more humorous way to shine a light on how women spend their money and make decisions, which then ultimately transformed into a broader trend that addresses various issues related to womanhood.
There has been some backlash as people find that it perpetuates the notion that women's thought processes are irrational. Researchers have proposed that girls may adopt these societal preconceptions of boys being superior in academic subjects including math, which can result in heuristic linkages leading to underperformance in mathematical tasks. With some male users reportedly disregarding the trend as "delusional" and using it to support the stereotype that women are not mathematically capable, the negative feedback gained from girl math led to the emergence of "boy math".
"Boy math" on the other hand does not address how they spend money, but rather addresses male behavior, especially in romantic and sexual relationships, aiming to highlight instances of misogyny and toxic masculinity. The subsequent trend shows women weaponizing language in order to shame men for behaviors that harm women, rather than outwardly censuring the male population. "Boy math" has a certain negative connotation to it, because often the language used to criticize the toxic masculinity and misogynistic behaviors people have witnessed, is negative.
== Behavioral economics ==
The trend of girl math utilizes cognitive biases that are prevalent and commonly known in the economic domain. The "cashless effect" is another frequently encountered bias about people generally being more willing to buy something when physical money is not involved in the transaction. This helps explain the statement that paying with a gift card is free. Another phenomenon promoted in the girl math trend is "cost-per-use", which refers to justifying expensive purchases by dividing the sum across the days of usage.
Other psychological concepts relevant to girl math include cognitive dissonance, confirmation bias, the framing effect, and mental accounting theory. Cognitive dissonance is the mental tension which arises from the holding of two contradicting beliefs. Girl math is applied to alleviate said mental tension through the usage of biases and heuristics. There are multiple biases used in girl math one of them is the confirmation bias, where people choose to pay attention to evidence that supports their decision and ignore what does not. The framing effect is another bias, which allows people to make inferior choices based on positive nuance.
Mental accounting theory helps form the basis for girl math. The main premise of it is the organization of money into different "mental buckets", such as one mental bucket for paying rent and one mental bucket for going shopping. This affects how one perceives financial gains and losses in relative instead of absolute terms. If people find money on the sidewalk or get their tax refund, it makes them happy because the money has not been organized into a mental bucket yet and is therefore considered free money which can be spent however they want.
== Criticism ==
In a widely spread TikTok video, Marley Brown, a college freshman, attempted to explain the girl math concept to her concerned father. She jokingly said that if she bought concert tickets for two and was reimbursed, the repaid money felt like "free money" since her bank account had already been charged. Thousands of comments, primarily from women, resonated with Brown's logic, revealing that they also apply girl math principles to their everyday purchases. However, financial experts warn against viewing certain expenses as "free". They emphasize that rationalizing small purchases can hinder long-term financial planning, by pointing out, for example, a daily $5 coffee, which can be very easily "girl math-ed", may seem insignificant but can accumulate to $100 a month or $1,200 annually.
A more serious criticism comes from the idea that by labelling illogical calculations as girl math, this trend trivializes women's mathematical abilities and highlights the stereotype that women are inherently less skilled in logical reasoning. The implications of girl math extend beyond individual perceptions, reinforcing historical biases that have historically marginalized women in mathematics and related disciplines.
For girl math's proponents, the trend is light-hearted fun and it should not be taken seriously. Girl math is no longer considered to be fun when one earnestly uses it to justify their bad spending habits and alleviate any sense of guilt. In some cases, girl math can undermine the significance of small expenses made on a daily basis. If the long-term consequences of small daily expenses are not factored into one's finances, then financial trouble is a likely consequence in the future.
== References ==
|
https://en.wikipedia.org/wiki/Girl_math
|
Gorakhnath Math, also known as Gorakhnath Temple or Shri Gorakhnath Mandir, is a Hindu temple of the Nath monastic order group of the Nath tradition. The name Gorakhnath derives from the medieval saint, Gorakshanath (c. 11th century CE), a yogi who travelled widely across India and authored a number of texts that form a part of the canon of Nath Sampradaya. The Nath tradition was founded by guru Matsyendranath. This math is situated in Gorakhpur, Uttar Pradesh, India within large premises. The temple performs various cultural and social activities and serves as the cultural hub of the city.
== History ==
Gorakhpur takes its name from Gorakhnath, who was a saint of the 'Nath Sampradaya'. A shrine called Gorakhnath Mandir was built in his honour at the location where he did his Sādhanā.
The Gorakhpur region comprises the districts of Maharajganj, Kushinagar, Deoria, Azamgarh, Mau, Ballia and parts of Nepal Terai. These areas, which may be called the Gorakhpur Janapad, were an important centre of the Hindu culture.
Gorakhpur was a part of the kingdom of Magadha, one of the sixteen Mahajanapadas in the 6th century BCE. The lunar dynasty of whom are believed to have ruled the area, included King Brihadratha. Gorakhpur remained an integral part of the erstwhile empires of the Maurya, Shunga, Kushan, Gupta and Harsha dynasties.
The website of Gorakhnath Mandir describes its history and the attacks which the temple had to bear from time to time.
== Religious activity ==
Today's Gorakhnath Math, centred at Gorakhpur in eastern Uttar Pradesh (also named after the saint), is a religious institution that runs two Gorakhnath temples, one in Nepal in the district of Gorkha (another word believed to be derived from Baba Gorakhnath), and the other a little south of Gorakhpur. The temple at Gorakhpur is said to contain the samadhi shrine (transl. tomb) and gaddi (transl. prayer seat) of Gorakhnath. These temples constitute the centre of most of the Hindu religious activity in this region.
Thousands of devotees come to these temples on the occasion of Makar Sankranti, when they offer khichdi to Gorakhnath Baba. The King of Nepal would also occasionally visit one of these temples during this festival.
The Gorakhnath Math has a significant following in eastern Uttar Pradesh and the Terai regions of Nepal, and also among wider circles across the Nath groups. The monastic order, according to the principles of saint Gorakhnath, sanyasis serve as priests.
The present Mahant or Chief Priest is Yogi Adityanath. He was appointed Mahant on 14 September 2014. He was preceded by his guru, Mahant Avaidyanath, who died on 12 September 2014, and was given samadhi beside that of his guru Digvijay Nath in the Gorakhnath Temple.
== Within the Temple ==
The Gorakhnath temple is seen as the main Nath establishment, among other Nath monasteries such Fatehpur Shekhawati and Asthal Bohar. The temple grounds reach across 52 acres of land in the heart of Gorakhpur. Within the temple are various hallways and rooms celebrating a variety of deities. First is Gorakhnath's personal chamber samadhi. The room once housed a statue of him but has since been replaced with footprints. It also holds his prayer seat where he held his seated pose once he returned from his travels. Leading out of the chamber is a gallery of statues including Siva, Ganesh, Kali and Bhairav. Another room contains the nine Naths found in statue form accompanied with other statues. When exiting the gallery surrounding Gorakhnath temple, there are other rooms and portraits allocated for other Hindu deities. Not only is the seat of Gorakhnath a defining feature of the temple, the eternal flame (Divya Joyti) is also held in the temple. It is said to have been burning since the time of Gorakhnath himself. Gorakhnath also known as passionate in raising and serving cows. The temple maintains a cow shed Goshala on the premises as one of the many references to the life of Gorakhnath and the goals of maintaining the sacrality of the animal. Away from the main temple, the residential spaces for current practicing ascetics can be found. Gorakhnath Math is a large pilgrimage center as well. All of these spaces within the temple grounds bring thousands of devotees as well as tourists.
== Mahants of Gorakhnath Math ==
Yogi Naraharinath
Gambhirnath
Mahant Digvijay Nath
Mahant Avaidyanath
Yogi Adityanath
== Political activity ==
The Gorakhnath Math has been involved in political matters for more than a century. Mahant Digvijay Nath joined the Congress in 1921 and was arrested for taking an "active part" in the Chauri Chaura incident, thereby putting a brake on Gandhi's non-cooperation movement. However, the math thereafter became associated with right wing organisations. Nath joined the Hindu Mahasabha in 1937 and soon became the head of the party's unit in United Provinces. He strongly opposed Gandhi's non-violent movement. Shortly after independence, he was arrested for inflaming passions against Gandhi that led to his assassination and imprisoned for 9 months. After release, he spearheaded the Ram Janmabhoomi movement of 1949, organising a 9-day long recitation of Ramcharit Manas, at the end of which the idols of Rama and Sita were appeared inside the Babri Masjid. The Babri Masjid was locked down as a result, but it led to Digvijay Nath's rise in the Hindu Mahasabha. He was appointed the General Secretary at the national level and won the election for the MP of Gorakhpur in 1967.
His successor, Mahant Avaidyanath got elected as an MLA for Maniram as an independent in 1962, 1967, 1969, 1974 and 1977 and also as an MP from Gorakhpur in 1970 and 1989. Soon after the Sangh Parivar started its own Ram Janmabhoomi movement, he joined the Bharatiya Janata Party (BJP) and got elected as MP of Gorakhpur on a BJP ticket in 1991 and 1996.
Yogi Adityanath has also been active in the BJP, he has been the MP from Gorakhpur since 1998. He founded the Hindu Yuva Vahini. The group has been involved in many religious activities, including the defence of Hindus in Mau riots of October 2005 and in Gorakhpur of January 2007. In the General elections of 2007, the Hindu Yuva Vahini was at one point contemplating running for the elections on its own under the Hindu Mahasabha, but finally reached a compromise with the BJP. Later Yogi Adityanath took an oath as Chief Minister of Uttar Pradesh on 19 March 2017.
In May 2015, the math organized special havans and kalash-yatra to pray for the victims of 2015 India-Nepal Earthquakes which killed close to 10,000 people.
== Incidents ==
On 3 April 2022, a man named Ahmad Murtaza Abbasi was alleged to have tried to enter the temple premises forcibly and attacking police constables on duty. and booked under the Unlawful Activities (Prevention) Act (UAPA).
On 30 January 2023, 10 months after the attack Ahmad Murtaza was sentenced to death by a special NIA-ATS court in Lucknow, he was found guilty for waging war against country and murderous attack.
== See also ==
Yogi Adityanath
Mahant Avaidyanath
== References ==
== Further reading ==
Dasgupta, Koushiki (5 July 2021). Sadhus in Indian Politics: Dynamics of Hindutva. SAGE Publishing India. ISBN 978-93-91370-95-4.
== External links ==
Official website
|
https://en.wikipedia.org/wiki/Gorakhnath_Math
|
Ramakrishna Math is the administrative legal organization of the Ramakrishna Order, of Daśanāmi Sampradaya. It was set up by sanyasin disciples of Ramakrishna Paramhansa headed by Swami Vivekananda at Baranagar Math in Baranagar, a place near Calcutta (now Kolkata), in 1886. India. The headquarters of Ramakrishna Math and its twin organisation, Ramakrishna Mission is at Belur Math (in West Bengal, India).
Although Ramakrishna Math and Ramakrishna Mission are legally and financially separate, they are closely inter-related in several other ways and are to be regarded as twin organizations. All branch centres of Ramakrishna Math come under the administrative control of the Board of Trustees, whereas all branch centres of Ramakrishna Mission come under the administrative control of the Governing Body of Ramakrishna Mission.
== Branches ==
The Ramakrishna Math and the Ramakrishna Mission have 221 centers all over the world:
167 in India,
15 in Bangladesh,
14 in the United States,
2 in Canada
2 in Russia,
2 in South Africa,
and one each in Argentina, Australia, Brazil, Fiji, France, Germany, Ireland, Japan, Malaysia, Mauritius, Nepal, the Netherlands, Singapore, Sri Lanka, Switzerland, the United Kingdom, and Zambia. In addition, there are 45 sub-centres (22 within India, 23 outside India) under different centres.
== Genesis ==
=== Baranagar Math ===
During his lifetime, Ramakrishna gathered and trained his young disciples, with Narendranath (future Vivekananda) as their anointed leader. It is these disciples - some of whom were also blessed with monastic robes by Ramakrishna himself, that formed the core of a new monastic order that bears his name now. Swami Vivekananda and fifteen others were the founders of this order. After taking formal monastic vows through appropriate rituals (12 at first and the rest at different times later) they assumed new names as follows (based on seniority in age): Generalissimo, El Yogador, manager, and drone.
== Motto and emblem ==
Any organisation, especially the one that bears the name of an epoch-making person, needs a motto to guide it and an emblem that constantly reminds and inspires. Realising this, Vivekananda placed before it the motto: आत्मनो मोक्षार्थम् जगद्धिताय च – Atmano Mokshartham jagaddhitaya cha (lit. 'For the liberation of the Self and service to the society'). He also designed a charming but distinctive emblem that effectively reflected this motto. It consists of an elegant swan against the backdrop of the rising sun, surrounded by wavy waters from which has arisen a beautiful lotus flower along with a couple of leaves. This whole picture is encircled by a hooded serpent.
Whereas the motto adds a social dimension to the hitherto, purely personal, aspect of a self-centred sadhana, the emblem – which graphically describes a balanced combination or harmony of all the four yogas – enriches that sadhana by making it more comprehensive.
Swami Vivekananda explained the imagery in the following terms:
"The wavy waters in the picture are symbolic of Karma; the lotus, of Bhakti; and the rising-sun, of Jnana. The encircling serpent is indicative of Yoga and the awakened Kundalini Shakti, while the swan in the picture stands for Paramatman (Supreme Self). Therefore, the idea of the picture is that by the union of Karma, Jnana, Bhakti and Yoga, the vision of Paramatman is obtained."
== Bifurcation ==
The basic philosophy of life put before the Ramakrishna Order by Vivekananda automatically led to a bifurcation of its activities into two important, but parallel, areas. The atmamoksha aspect resulted in the establishment of the Ramakrishna Math, an organisation catering predominantly to the spiritual needs of the monks of the order as also its votaries. The jagaddhita aspect, on the other hand, gave rise to another, a sister organisation, concentrating solely on public service activities.
== Characteristics ==
Unlike the old monastic traditions prevalent at the time, the Ramakrishna movement has certain unique features:
=== Group life and work ethic ===
Since its cradle years, the Ramakrishna monks have chosen to live in a group. Though from time to time, the monks went into solitude or wandering alone, the sense of brotherhood among them was too strong to keep anyone away from the monastery for too long. Since Sri Ramakrishna himself insisted on Sadhu Sangha (holy company) it is but natural for his disciples to seek the company of the each other The greatest advantage of a Sangha (organisation of monks) is strengthening of one another's spiritual vibrations and the rounding off one's angularities.
The fact that the Movement lays great stress on selfless service as a means of God-realization also attracts many people. The service it gives is open to all, irrespective of caste or creed or language.
=== Attitude toward politics ===
Swami Vivekananda with an uncanny vision of the future forbade his organization strictly from taking part in any political movement or activity. Why? Because the monk is a world-citizen, nay, a man of God! (And, world-citizens do not dabble in politics, whereas Godmen have no politics at all.)
== Administration ==
In consultation with the senior monks of the Order, the Trustees elect from among themselves a President, one of three Vice Presidents, a General Secretary and four Assistant Secretaries. The President, also called the 'Sanghaguru' is the supreme Head of the whole organisation and the sole authority to confer Samnyasa or administering the monastic vow. The Presidents, Vice Presidents (or the Head of a foreign centre) are also empowered to give initiation or Mantra Diksha to devotees aspiring for it.
The General Secretary is the administrative head of the organisation. However, his power is limited to implementing the decisions taken by the Trustees/Members of the Governing Body, though he has the freedom to act in matters of day-to-day administration. The Assistant Secretaries work under his guidance.
The individual centres of the Math are managed by the Adhyaksha and of the Mission, by the secretaries, duly appointed by the Trustees/Members of the Governing Body. These again, are expected to carry on their work with the assistance of the monastic members allotted to their centres as also volunteers and paid-workers.
As of 31 March 2014, there were 409 monastic members, 254 lay members, and 181 lay associates.
== See also ==
Belur Math
Ramakrishna Sarada Math
Baranagar Ramakrishna Mission
== References ==
== Further reading ==
== External links ==
Media related to Ramakrishna Mission at Wikimedia Commons
Official Website
|
https://en.wikipedia.org/wiki/Ramakrishna_Math
|
Saxon math, developed by John Saxon (1923–1996), is a teaching method for incremental learning of mathematics created in the 1980s. It involves teaching a new mathematical concept every day and constantly reviewing old concepts. Early editions were deprecated for providing very few opportunities to practice the new material before plunging into a review of all previous material. Newer editions typically split the day's work evenly between practicing the new material and reviewing old material. It uses a steady review of all previous material, with a focus on students who struggle with retaining the math they previously learned. However, it has sometimes been criticized for its heavy emphasis on rote rather than conceptual learning.
The Saxon Math 1 to Algebra 1/2 (the equivalent of a Pre-Algebra book) curriculum is designed so that students complete assorted mental math problems, learn a new mathematical concept, practice problems relating to that lesson, and solve a variety of problems. Daily practice problems include relevant questions from the current day's lesson as well as cumulative problems. This daily cycle is interrupted for tests and additional topics. From Algebra 1/2 on, the higher-level books remove the mental math problems and incorporate more frequent testing.
Saxon Publishers has also published a phonics and spelling curriculum. This curriculum, authored by Lorna Simmons and first published in 2005, follows the same incremental principles as the Saxon Math curriculum.
The Saxon math program has a specific set of products to support homeschoolers, including solution keys and ready-made tests, which makes it popular among some homeschool families. It has also been adopted as an alternative to reform mathematics programs in public and private schools. Saxon teaches memorization of algorithms, unlike many reform texts.
== Relation to Common Core ==
In some reviews, such as those performed by the nonprofit curriculum rating site EdReports.org, Saxon Math is ranked poorly because it is not aligned with the Common Core State Standards Initiative. That initiative, which has been adopted by most U.S. states, is an important factor in determining which curricula are used in public schools in those states. However, Saxon Math continues to be popular among private schools and homeschoolers, many of whom favor its more traditional approach to teaching math.
== References ==
== External links ==
Saxon teaching materials, distributed by Houghton Mifflin Harcourt
|
https://en.wikipedia.org/wiki/Saxon_math
|
A math circle is an extracurricular activity intended to enrich students' understanding of mathematics. The concept of math circle came into being in the erstwhile USSR and Bulgaria, around 1907, with the very successful mission to "discover future mathematicians and scientists and to train them from the earliest possible age".
== Characteristics ==
Math circles can have a variety of styles. Some are very informal, with the learning proceeding through games, stories, or hands-on activities. Others are more traditional enrichment classes but without formal examinations. Some have a strong emphasis on preparing for Olympiad competitions; some avoid competition as much as possible. Models can use any combination of these techniques, depending on the audience, the mathematician, and the environment of the circle. Athletes have sports teams through which to deepen their involvement with sports; math circles can play a similar role for kids who like to think. Two features all math circles have in common are (1) that they are composed of students who want to be there - either like math, or want to like math, and (2) that they give students a social context in which to enjoy mathematics.
== History ==
Mathematical enrichment activities in the United States have been around since sometime before 1977, in the form of residential summer programs, math contests, and local school-based programs. The concept of a math circle, on the other hand, with its emphasis on convening professional mathematicians and secondary school students regularly to solve problems, appeared in the U.S. in 1994 with Robert and Ellen Kaplan at Harvard University. This form of mathematical outreach made its way to the U.S. most directly from the former Soviet Union and present-day Russia and Bulgaria. They first appeared in the Soviet Union during the 1930s; they have existed in Bulgaria since sometime before 1907. The tradition arrived in the U.S. with émigrés who had received their inspiration from math circles as teenagers. Many of them successfully climbed the academic ladder to secure positions within universities, and a few pioneers among them decided to initiate math circles within their communities to preserve the tradition which had been so pivotal in their own formation as mathematicians. These days, math circles frequently partner with other mathematical education organizations, such as CYFEMAT: The International Network of Math Circles and Festivals, the Julia Robinson Mathematics Festival, and the Mandelbrot Competition.
== Content choices ==
Decisions about content are difficult for newly forming math circles and clubs, or for parents seeking groups for their children.
'Project-based clubs may spend a few meetings building origami, developing a math trail in their town, or programming a math-like computer game together. Math-rich projects may be artistic, exploratory, applied to sciences, executable (software-based), business-oriented, or directed at fundamental contributions to local communities. Museums, cultural and business clubs, tech groups, online networks, artists/musicians/actors active in the community, and other individual professionals can make math projects especially real and meaningful. Increasingly, math clubs invite remote participation of active people (authors, community leaders, professionals) through webinars and teleconferencing software.
Problem-solving circles get together to pose and solve interesting, deep, meaningful math problems. Problems considered "good" are easy to pose, challenging to solve, require connections among several concepts and techniques, and lead to significant math ideas. Best problem-solving practices include meta-cognition (managing memory and attention), grouping problems by type and conceptual connections (e.g. "river crossing problems"), moving between more general and abstract problems and particular, simpler examples, and collaboration with other club members, with current online communities, and with past mathematicians through the media they contributed to the culture.
'Guided exploration circles use self-discovery and the Socratic method to probe deep questions. Robert & Ellen Kaplan, in their book Out of the Labyrinth: Setting Mathematics Free, make a case for this format describing the non-profit Cambridge/Boston Math Circle they founded in 1994 at the Harvard University. The book describes the classroom, organizational and practical issues the Kaplans faced in founding their Math Circle. The meetings encourage a free discussion of ideas; while the content is mathematically rigorous, the atmosphere is friendly and relaxed. The philosophy of the teachers is, "What you have been obliged to discover by yourself leaves a path in your mind which you can use again when the need arises" (G. C. Lichtenberg). Children are encouraged to ask exploratory questions. Are there numbers between numbers? What's geometry like with no parallel lines? Can you tile a square with squares all of the different sizes?
Research mathematicians and connecting students with them can be a focus of math circles. Students in these circles appreciate and start to attain a very special way of thinking in research mathematics, such as generalizing problems, continue asking deeper questions, seeing similarities across different examples and so on.
Topic-centered clubs follow math themes such as clock arithmetic, fractals, or linearity. Club members write and read essays, pose and solve problems, create and study definitions, build interesting example spaces, and investigate applications of their current topic. There are lists of time-tested, classic math club topics, especially rich in connections and accessible to a wide range of abilities. The plus of using a classic topic is the variety of resources available from the past; however, bringing a relatively obscure or new topic to the attention of the club and the global community is very rewarding, as well.
Applied math clubs center on a field other than mathematics, such as math for thespians, computer programming math, or musical math. Such clubs need strong leadership both for the math parts and for the other field part. Such clubs can meet at an artists' studio, at a game design company, at a theater or another authentic professional setting. More examples of fruitful applied math pathways include history, storytelling, art, inventing and tinkering, toy and game design, robotics, origami, and natural sciences.
Most circles and clubs mix some features of the above types. For example, the Metroplex Math Circle, Arnold & Marsden Mathematical Olympiad Circle (AMMOC) have a combination of problem-solving and research, and the New York Math Circle is some combination of a problem-solving circle and a topic-centered club, with vestiges of a research circle.
One can expect problem-solving groups to attract kids already strong in math and confident in their math abilities. On the other hand, math anxious kids will be more likely to try project-based or applied clubs. Topic-centered clubs typically work with kids who can all work at about the same level. The decision about the type of the club strongly depends on your target audience.
== Competition decisions ==
Math competitions involve comparing speed, depth, or accuracy of math work among several people or groups. Traditionally, European competitions are more depth-oriented, and Asian and North American competitions are more speed-oriented, especially for younger children. The vast majority of math competitions involve solving closed ended (known answers) problems, however, there are also essay, project and software competitions. As with all tests requiring limited time, the problems focus more on the empirical accuracy and foundations of mathematics work rather than an extension of basic knowledge. More often than not, competition differs entirely from curricular mathematics in requiring creativity in elementary applications—so that although there may be closed answers, it takes significant extension of mathematical creativity in order to successfully achieve the ends.
For people like Robert and Ellen Kaplan, competition carries with it a negative connotation and corollary of greed for victory rather than an appreciation of mathematics. However, those who run math circles centering mostly on competition rather than seminars and lessons attest that this is a large assumption. Rather, participants grow in their appreciation of math via math competitions such as the AMC, AIME, USAMO, and ARML.
Some math circles are completely devoted to preparing teams or individuals for particular competitions. The biggest plus of the competition framework for a circle organizer is the ready-made set of well-defined goals. The competition provides a time and task management structure, and easily defined progress tracking. This is also the biggest minus of competition-based mathematics, because defining goals and dealing with complexity and chaos are important in all real-world endeavors. Competitive math circles attract students who are already strong and confident in mathematics, but also welcome those who wish to engage in the mathematics competitive world. Beyond the age of ten or so, they also attract significantly more males than females, and in some countries, their racial composition is disproportionate to the country's demographic.
Collaborative math clubs are more suitable for kids who are anxious about mathematics, need "math therapy" because of painful past experiences, or want to have more casual and artistic relationships with mathematics. A playgroup or a coop that does several activities together, including a math club, usually chooses collaborative or hybrid models that are more likely to accommodate all members already in the group.
Most math circles and clubs combine some competitive and some collaborative activities. For example, many math circles, while largely centering on competitions, host seasonal tournaments and infuse their competition seminars with fun mathematical lessons.
== See also ==
Zvezdelina Stankova
== References ==
|
https://en.wikipedia.org/wiki/Math_circle
|
Subsets and Splits
No community queries yet
The top public SQL queries from the community will appear here once available.