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Computer programming or coding is the composition of sequences of instructions, called programs, that computers can follow to perform tasks. It involves designing and implementing algorithms, step-by-step specifications of procedures, by writing code in one or more programming languages. Programmers typically use high-... | https://en.wikipedia.org/wiki/Computer_programming |
al processing unit. Proficient programming usually requires expertise in several different subjects, including knowledge of the application domain, details of programming languages and generic code libraries, specialized algorithms, and formal logic.
Auxiliary tasks accompanying and related to programming include analy... | https://en.wikipedia.org/wiki/Computer_programming |
ved artifacts, such as programs' machine code. While these are sometimes considered programming, often the term software development is used for this larger overall process – with the terms programming, implementation, and coding reserved for the writing and editing of code per se. Sometimes software development is kno... | https://en.wikipedia.org/wiki/Computer_programming |
rogrammable devices have existed for centuries. As early as the 9th century, a programmable music sequencer was invented by the Persian Banu Musa brothers, who described an automated mechanical flute player in the Book of Ingenious Devices. In 1206, the Arab engineer Al-Jazari invented a programmable drum machine where... | https://en.wikipedia.org/wiki/Computer_programming |
d loom could produce entirely different weaves by changing the "program" – a series of pasteboard cards with holes punched in them.
Code-breaking algorithms have also existed for centuries. In the 9th century, the Arab mathematician Al-Kindi described a cryptographic algorithm for deciphering encrypted code, in A Manus... | https://en.wikipedia.org/wiki/Computer_programming |
de-breaking algorithm.
The first computer program is generally dated to 1843 when mathematician Ada Lovelace published an algorithm to calculate a sequence of Bernoulli numbers, intended to be carried out by Charles Babbage's Analytical Engine. The algorithm, which was conveyed through notes on a translation of Luigi F... | https://en.wikipedia.org/wiki/Computer_programming |
with Babbage. However, Charles Babbage himself had written a program for the AE in 1837. Lovelace was also the first to see a broader application for the analytical engine beyond mathematical calculations.
In the 1880s, Herman Hollerith invented the concept of storing data in machine-readable form. Later a control pa... | https://en.wikipedia.org/wiki/Computer_programming |
cord equipment such as the IBM 602 and IBM 604, were programmed by control panels in a similar way, as were the first electronic computers. However, with the concept of the stored-program computer introduced in 1949, both programs and data were stored and manipulated in the same way in computer memory.
=== Machine la... | https://en.wikipedia.org/wiki/Computer_programming |
ary notation. Assembly languages were soon developed that let the programmer specify instructions in a text format (e.g., ADD X, TOTAL), with abbreviations for each operation code and meaningful names for specifying addresses. However, because an assembly language is little more than a different notation for a machine ... | https://en.wikipedia.org/wiki/Computer_programming |
-level languages made the process of developing a program simpler and more understandable, and less bound to the underlying hardware.
The first compiler related tool, the A-0 System, was developed in 1952 by Grace Hopper, who also coined the term 'compiler'. FORTRAN, the first widely used high-level language to have a... | https://en.wikipedia.org/wiki/Computer_programming |
l data processing, and Lisp for computer research.
These compiled languages allow the programmer to write programs in terms that are syntactically richer, and more capable of abstracting the code, making it easy to target varying machine instruction sets via compilation declarations and heuristics. Compilers harnessed ... | https://en.wikipedia.org/wiki/Computer_programming |
x notation.
=== Source code entry ===
Programs were mostly entered using punched cards or paper tape. By the late 1960s, data storage devices and computer terminals became inexpensive enough that programs could be created by typing directly into the computers. Text editors were also developed that allowed changes an... | https://en.wikipedia.org/wiki/Computer_programming |
ever the approach to development may be, the final program must satisfy some fundamental properties. The following properties are among the most important:
Reliability: how often the results of a program are correct. This depends on conceptual correctness of algorithms and minimization of programming mistakes, such as... | https://en.wikipedia.org/wiki/Computer_programming |
-one errors).
Robustness: how well a program anticipates problems due to errors (not bugs). This includes situations such as incorrect, inappropriate or corrupt data, unavailability of needed resources such as memory, operating system services, and network connections, user error, and unexpected power outages.
Usabilit... | https://en.wikipedia.org/wiki/Computer_programming |
anticipated purposes. Such issues can make or break its success even regardless of other issues. This involves a wide range of textual, graphical, and sometimes hardware elements that improve the clarity, intuitiveness, cohesiveness, and completeness of a program's user interface.
Portability: the range of computer har... | https://en.wikipedia.org/wiki/Computer_programming |
fferences in the programming facilities provided by the different platforms, including hardware and operating system resources, expected behavior of the hardware and operating system, and availability of platform-specific compilers (and sometimes libraries) for the language of the source code.
Maintainability: the ease... | https://en.wikipedia.org/wiki/Computer_programming |
and security holes, or adapt it to new environments. Good practices during initial development make the difference in this regard. This quality may not be directly apparent to the end user but it can significantly affect the fate of a program over the long term.
Efficiency/performance: Measure of system resources a pro... | https://en.wikipedia.org/wiki/Computer_programming |
n): the less, the better. This also includes careful management of resources, for example cleaning up temporary files and eliminating memory leaks. This is often discussed under the shadow of a chosen programming language. Although the language certainly affects performance, even slower languages, such as Python, can e... | https://en.wikipedia.org/wiki/Computer_programming |
eck the system, but efficient use of programmer time is also important and is related to cost: more hardware may be cheaper.
Using automated tests and fitness functions can help to maintain some of the aforementioned attributes.
=== Readability of source code ===
In computer programming, readability refers to the eas... | https://en.wikipedia.org/wiki/Computer_programming |
ity above, including portability, usability and most importantly maintainability.
Readability is important because programmers spend the majority of their time reading, trying to understand, reusing, and modifying existing source code, rather than writing new source code. Unreadable code often leads to bugs, inefficien... | https://en.wikipedia.org/wiki/Computer_programming |
he time to understand it.
Following a consistent programming style often helps readability. However, readability is more than just programming style. Many factors, having little or nothing to do with the ability of the computer to efficiently compile and execute the code, contribute to readability. Some of these factor... | https://en.wikipedia.org/wiki/Computer_programming |
, functions, procedures, etc.)
The presentation aspects of this (such as indents, line breaks, color highlighting, and so on) are often handled by the source code editor, but the content aspects reflect the programmer's talent and skills.
Various visual programming languages have also been developed with the intent to ... | https://en.wikipedia.org/wiki/Computer_programming |
ents (IDEs) aim to integrate all such help. Techniques like Code refactoring can enhance readability.
=== Algorithmic complexity ===
The academic field and the engineering practice of computer programming are concerned with discovering and implementing the most efficient algorithms for a given class of problems. For ... | https://en.wikipedia.org/wiki/Computer_programming |
emory consumption—in terms of the size of an input. Expert programmers are familiar with a variety of well-established algorithms and their respective complexities and use this knowledge to choose algorithms that are best suited to the circumstances.
=== Methodologies ===
The first step in most formal software develo... | https://en.wikipedia.org/wiki/Computer_programming |
(debugging). There exist a lot of different approaches for each of those tasks. One approach popular for requirements analysis is Use Case analysis. Many programmers use forms of Agile software development where the various stages of formal software development are more integrated together into short cycles that take ... | https://en.wikipedia.org/wiki/Computer_programming |
Object-Oriented Analysis and Design (OOAD) and Model-Driven Architecture (MDA). The Unified Modeling Language (UML) is a notation used for both the OOAD and MDA.
A similar technique used for database design is Entity-Relationship Modeling (ER Modeling).
Implementation techniques include imperative languages (object-ori... | https://en.wikipedia.org/wiki/Computer_programming |
lt to determine what are the most popular modern programming languages. Methods of measuring programming language popularity include: counting the number of job advertisements that mention the language, the number of books sold and courses teaching the language (this overestimates the importance of newer languages), an... | https://en.wikipedia.org/wiki/Computer_programming |
anguages such as COBOL).
Some languages are very popular for particular kinds of applications, while some languages are regularly used to write many different kinds of applications. For example, COBOL is still strong in corporate data centers often on large mainframe computers, Fortran in engineering applications, scri... | https://en.wikipedia.org/wiki/Computer_programming |
tion and use. New languages are generally designed around the syntax of a prior language with new functionality added, (for example C++ adds object-orientation to C, and Java adds memory management and bytecode to C++, but as a result, loses efficiency and the ability for low-level manipulation).
=== Debugging ===
... | https://en.wikipedia.org/wiki/Computer_programming |
equences for its users. Some languages are more prone to some kinds of faults because their specification does not require compilers to perform as much checking as other languages. Use of a static code analysis tool can help detect some possible problems. Normally the first step in debugging is to attempt to reproduce ... | https://en.wikipedia.org/wiki/Computer_programming |
user environment and usage history can make it difficult to reproduce the problem.
After the bug is reproduced, the input of the program may need to be simplified to make it easier to debug. For example, when a bug in a compiler can make it crash when parsing some large source file, a simplification of the test case th... | https://en.wikipedia.org/wiki/Computer_programming |
nd-conquer is needed: the programmer will try to remove some parts of the original test case and check if the problem still exists. When debugging the problem in a GUI, the programmer can try to skip some user interaction from the original problem description and check if the remaining actions are sufficient for bugs t... | https://en.wikipedia.org/wiki/Computer_programming |
GDB are also used, and these often provide less of a visual environment, usually using a command line. Some text editors such as Emacs allow GDB to be invoked through them, to provide a visual environment.
== Programming languages ==
Different programming languages support different styles of programming (called pro... | https://en.wikipedia.org/wiki/Computer_programming |
vailability of third-party packages, or individual preference. Ideally, the programming language best suited for the task at hand will be selected. Trade-offs from this ideal involve finding enough programmers who know the language to build a team, the availability of compilers for that language, and the efficiency wit... | https://en.wikipedia.org/wiki/Computer_programming |
w-level" languages are typically more machine-oriented and faster to execute, whereas "high-level" languages are more abstract and easier to use but execute less quickly. It is usually easier to code in "high-level" languages than in "low-level" ones.
Programming languages are essential for software development. They a... | https://en.wikipedia.org/wiki/Computer_programming |
How To Think Like A Computer Scientist, writes:
The details look different in different languages, but a few basic instructions appear in just about every language:
Input: Gather data from the keyboard, a file, or some other device.
Output: Display data on the screen or send data to a file or other device.
Arithmetic:... | https://en.wikipedia.org/wiki/Computer_programming |
xecute the appropriate sequence of statements.
Repetition: Perform some action repeatedly, usually with some variation.
Many computer languages provide a mechanism to call functions provided by shared libraries. Provided the functions in a library follow the appropriate run-time conventions (e.g., method of passing arg... | https://en.wikipedia.org/wiki/Computer_programming |
tory related to professional standards and practices, academic initiatives and curriculum, and commercial books and materials for students, self-taught learners, hobbyists, and others who desire to create or customize software for personal use. Since the 1960s, learning to program has taken on the characteristics of a ... | https://en.wikipedia.org/wiki/Computer_programming |
movement and make institutionalize change. Through these social ideals and educational agendas, learning to code has become important not just for scientists and engineers, but for millions of citizens who have come to believe that creating software is beneficial to society and its members.
=== Context ===
In 1957, t... | https://en.wikipedia.org/wiki/Computer_programming |
elopers. In 2014, there were approximately 18.5 million professional programmers in the world, of which 11 million can be considered professional and 7.5 million student or hobbyists. Before the rise of the commercial Internet in the mid-1990s, most programmers learned about software construction through books, magazin... | https://en.wikipedia.org/wiki/Computer_programming |
fessional workers.
The first book containing specific instructions about how to program a computer may have been Maurice Wilkes, David Wheeler, and Stanley Gill's Preparation of Programs for an Electronic Digital Computer (1951). The book offered a selection of common subroutines for handling basic operations on the ED... | https://en.wikipedia.org/wiki/Computer_programming |
and materials that explained language keywords, managing program flow, working with data, and other concepts. These languages included FLOW-MATIC, COBOL, FORTRAN, ALGOL, Pascal, BASIC, and C. An example of an early programming primer from these years is Marshal H. Wrubel's A Primer of Programming for Digital Computers ... | https://en.wikipedia.org/wiki/Computer_programming |
IBM's early FORTRAN system. Daniel McCracken's A Guide to FORTRAN Programming (1961) presented FORTRAN to a larger audience, including students and office workers.
In 1961, Alan Perlis suggested that all university freshmen at Carnegie Technical Institute take a course in computer programming. His advice was published ... | https://en.wikipedia.org/wiki/Computer_programming |
rs.
Programmers soon had a range of learning texts at their disposal. Programmer's references listed keywords and functions related to a language, often in alphabetical order, as well as technical information about compilers and related systems. An early example was IBM's Programmers' Reference Manual: the FORTRAN Auto... | https://en.wikipedia.org/wiki/Computer_programming |
of a language in tutorial or step by step format. Many early primers started with a program known as “Hello, World”, which presented the shortest program a developer could create in a given system. Programmer's guides then went on to discuss core topics like declaring variables, data types, formulas, flow control, use... | https://en.wikipedia.org/wiki/Computer_programming |
omas E. Kurtz's BASIC Programming (1967), Kathleen Jensen and Niklaus Wirth's The Pascal User Manual and Report (1971), and Brian W. Kernighan and Dennis Ritchie's The C Programming Language (1978). Similar books for popular audiences (but with a much lighter tone) included Bob Albrecht's My Computer Loves Me When I Sp... | https://en.wikipedia.org/wiki/Computer_programming |
mers, there were numerous books and academic journals that introduced professional programming practices. Many were designed for university courses in computer science, software engineering, or related disciplines. Donald Knuth's The Art of Computer Programming (1968 and later), presented hundreds of computational algo... | https://en.wikipedia.org/wiki/Computer_programming |
h programming style, the idea that programs should be written not only to satisfy the compiler but human readers. Jon Bentley's Programming Pearls (1986) offered practical advice about the art and craft of programming in professional and academic contexts. Texts specifically designed for students included Doug Cooper a... | https://en.wikipedia.org/wiki/Computer_programming |
983).
=== Technical publishers ===
As personal computers became mass-market products, thousands of trade books and magazines sought to teach professional, hobbyist, and casual users to write computer programs. A sample of these learning resources includes BASIC Computer Games, Microcomputer Edition (1978), by David A... | https://en.wikipedia.org/wiki/Computer_programming |
Mitchell Waite and The Waite Group; The Peter Norton Programmer's Guide to the IBM PC (1985), by Peter Norton; Advanced MS-DOS (1986), by Ray Duncan; Learn BASIC Now (1989), by Michael Halvorson and David Rygymr; Programming Windows (1992 and later), by Charles Petzold; Code Complete: A Practical Handbook for Software... | https://en.wikipedia.org/wiki/Computer_programming |
try spurred the creation of numerous book publishers that offered programming primers and tutorials, as well as books for advanced software developers. These publishers included Addison-Wesley, IDG, Macmillan Inc., McGraw-Hill, Microsoft Press, O'Reilly Media, Prentice Hall, Sybex, Ventana Press, Waite Group Press, Wil... | https://en.wikipedia.org/wiki/Computer_programming |
ammers. A partial list of these resources includes Amiga World, Byte (magazine), Communications of the ACM, Computer (magazine), Compute!, Computer Language (magazine), Computers and Electronics, Dr. Dobb's Journal, IEEE Software, Macworld, PC Magazine, PC/Computing, and UnixWorld.
=== Digital learning / online resou... | https://en.wikipedia.org/wiki/Computer_programming |
on, as programmers moved to Internet resources to expand their access to information. This shift brought forward new digital products and mechanisms to learn programming skills. During the transition, digital books from publishers transferred information that had traditionally been delivered in print to new and expandi... | https://en.wikipedia.org/wiki/Computer_programming |
s, and custom websites focused on coding skills. New commercial resources included YouTube videos, Lynda.com tutorials (later LinkedIn Learning), Khan Academy, Codecademy, GitHub, W3Schools, and numerous coding bootcamps.
Most software development systems and game engines included rich online help resources, including ... | https://en.wikipedia.org/wiki/Computer_programming |
ment kits (SDKs) also provided a collection of software development tools and documentation in one installable package.
Commercial and non-profit organizations published learning websites for developers, created blogs, and established newsfeeds and social media resources about programming. Corporations like Apple, Micr... | https://en.wikipedia.org/wiki/Computer_programming |
ft Developer Network (MSDN). Contemporary movements like Hour of Code (Code.org) show how learning to program has become associated with digital learning strategies, education agendas, and corporate philanthropy.
== Programmers ==
Computer programmers are those who write computer software. Their jobs usually involve... | https://en.wikipedia.org/wiki/Computer_programming |
ers have strong skills in natural human languages, and that learning to code is similar to learning a foreign language.
== See also ==
Code smell
Computer networking
Competitive programming
Programming best practices
Systems programming
== References ==
=== Sources ===
Ceruzzi, Paul E. (1998). History of Computi... | https://en.wikipedia.org/wiki/Computer_programming |
of the Women Who Made the Internet. New York: Portfolio/Penguin. ISBN 9780735211759.
Gürer, Denise (1995). "Pioneering Women in Computer Science" (PDF). Communications of the ACM. 38 (1): 45–54. doi:10.1145/204865.204875. S2CID 6626310. Archived (PDF) from the original on October 9, 2022.
Smith, Erika E. (2013). "Reco... | https://en.wikipedia.org/wiki/Computer_programming |
. doi:10.7771/1481-4374.1972.
Essinger, J., & EBSCO Publishing (Firm). (2014). Ada's algorithm: How lord byron's daughter ada lovelace launched the digital age. Melville House.
== Further reading ==
A.K. Hartmann, Practical Guide to Computer Simulations, Singapore: World Scientific (2009)
A. Hunt, D. Thomas, and W. C... | https://en.wikipedia.org/wiki/Computer_programming |
ractice of Programming, Pearson (1999)
Weinberg, Gerald M., The Psychology of Computer Programming, New York: Van Nostrand Reinhold (1971)
Edsger W. Dijkstra, A Discipline of Programming, Prentice-Hall (1976)
O.-J. Dahl, E.W.Dijkstra, C.A.R. Hoare, Structured Programming, Academic Press (1972)
David Gries, The Science ... | https://en.wikipedia.org/wiki/Computer_programming |
ions related to Programming at Wikiquote | https://en.wikipedia.org/wiki/Computer_programming |
A programming language is a system of notation for writing computer programs.
Programming languages are described in terms of their syntax (form) and semantics (meaning), usually defined by a formal language. Languages usually provide features such as a type system, variables, and mechanisms for error handling. An impl... | https://en.wikipedia.org/wiki/Programming_language |
directly executes the source code, while a compiler produces an executable program.
Computer architecture has strongly influenced the design of programming languages, with the most common type (imperative languages—which implement operations in a specified order) developed to perform well on the popular von Neumann ar... | https://en.wikipedia.org/wiki/Programming_language |
hide implementation details for greater simplicity.
Thousands of programming languages—often classified as imperative, functional, logic, or object-oriented—have been developed for a wide variety of uses. Many aspects of programming language design involve tradeoffs—for example, exception handling simplifies error han... | https://en.wikipedia.org/wiki/Programming_language |
ntation, analysis, characterization, and classification of programming languages.
== Definitions ==
Programming languages differ from natural languages in that natural languages are used for interaction between people, while programming languages are designed to allow humans to communicate instructions to machines.
T... | https://en.wikipedia.org/wiki/Programming_language |
g authors.
In one usage, programming languages are described as a subset of computer languages. Similarly, the term "computer language" may be used in contrast to the term "programming language" to describe languages used in computing but not considered programming languages. Most practical programming languages are Tu... | https://en.wikipedia.org/wiki/Programming_language |
tical constructs for programming abstract machines and computer languages as the subset thereof that runs on physical computers, which have finite hardware resources. John C. Reynolds emphasizes that formal specification languages are just as much programming languages as are the languages intended for execution. He al... | https://en.wikipedia.org/wiki/Programming_language |
the fact they are commonly not Turing-complete, and remarks that ignorance of programming language concepts is the reason for many flaws in input formats.
== History ==
=== Early developments ===
The first programmable computers were invented at the end of the 1940s, and with them, the first programming languages. ... | https://en.wikipedia.org/wiki/Programming_language |
t could be directly executed by the processor). This code was very difficult to debug and was not portable between different computer systems. In order to improve the ease of programming, assembly languages (or second-generation programming languages—2GLs) were invented, diverging from the machine language to make prog... | https://en.wikipedia.org/wiki/Programming_language |
pensive, while human resources were cheaper. Therefore, cumbersome languages that were time-consuming to use, but were closer to the hardware for higher efficiency were favored. The introduction of high-level programming languages (third-generation programming languages—3GLs)—revolutionized programming. These languages... | https://en.wikipedia.org/wiki/Programming_language |
humans. For example, arithmetic expressions could now be written in symbolic notation and later translated into machine code that the hardware could execute. In 1957, Fortran (FORmula TRANslation) was invented. Often considered the first compiled high-level programming language, Fortran has remained in use into the tw... | https://en.wikipedia.org/wiki/Programming_language |
h they could only be operated by professionals and the cost was extreme. The data and instructions were input by punch cards, meaning that no input could be added while the program was running. The languages developed at this time therefore are designed for minimal interaction. After the invention of the microprocessor... | https://en.wikipedia.org/wiki/Programming_language |
er programming languages.
Lisp, implemented in 1958, was the first functional programming language. Unlike Fortran, it supported recursion and conditional expressions, and it also introduced dynamic memory management on a heap and automatic garbage collection. For the next decades, Lisp dominated artificial intelligenc... | https://en.wikipedia.org/wiki/Programming_language |
ithmic Language) was released in 1958 and 1960, it became the standard in computing literature for describing algorithms. Although its commercial success was limited, most popular imperative languages—including C, Pascal, Ada, C++, Java, and C#—are directly or indirectly descended from ALGOL 60. Among its innovations a... | https://en.wikipedia.org/wiki/Programming_language |
st language to support object-oriented programming (including subtypes, dynamic dispatch, and inheritance), also descends from ALGOL and achieved commercial success. C, another ALGOL descendant, has sustained popularity into the twenty-first century. C allows access to lower-level machine operations more than other con... | https://en.wikipedia.org/wiki/Programming_language |
more difficult to write correct code.
Prolog, designed in 1972, was the first logic programming language, communicating with a computer using formal logic notation. With logic programming, the programmer specifies a desired result and allows the interpreter to decide how to achieve it.
=== 1980s to 2000s ===
During ... | https://en.wikipedia.org/wiki/Programming_language |
ntroduced in the 1980s included C++, a superset of C that can compile C programs but also supports classes and inheritance. Ada and other new languages introduced support for concurrency. The Japanese government invested heavily into the so-called fifth-generation languages that added support for concurrency to logic p... | https://en.wikipedia.org/wiki/Programming_language |
the Internet and the World Wide Web in the 1990s, new programming languages were introduced to support Web pages and networking. Java, based on C++ and designed for increased portability across systems and security, enjoyed large-scale success because these features are essential for many Internet applications. Anothe... | https://en.wikipedia.org/wiki/Programming_language |
l programs that coordinate existing applications. Due to their integration with HTML, they have also been used for building web pages hosted on servers.
=== 2000s to present ===
During the 2000s, there was a slowdown in the development of new programming languages that achieved widespread popularity. One innovation w... | https://en.wikipedia.org/wiki/Programming_language |
similar to objects in object-oriented programming, but run on a separate process. C# and F# cross-pollinated ideas between imperative and functional programming. After 2010, several new languages—Rust, Go, Swift, Zig and Carbon —competed for the performance-critical software for which C had historically been used. Mos... | https://en.wikipedia.org/wiki/Programming_language |
Some of the new programming languages are classified as visual programming languages like Scratch, LabVIEW and PWCT. Also, some of these languages mix between textual and visual programming usage like Ballerina. Also, this trend lead to developing projects that help in developing new VPLs like Blockly by Google. Many g... | https://en.wikipedia.org/wiki/Programming_language |
damental elements for describing data and the operations or transformations applied to them, such as adding two numbers or selecting an item from a collection. These elements are governed by syntactic and semantic rules that define their structure and meaning, respectively.
=== Syntax ===
A programming language's su... | https://en.wikipedia.org/wiki/Programming_language |
ers, and punctuation, much like written natural languages. On the other hand, some programming languages are graphical, using visual relationships between symbols to specify a program.
The syntax of a language describes the possible combinations of symbols that form a syntactically correct program. The meaning given to... | https://en.wikipedia.org/wiki/Programming_language |
s are textual, this article discusses textual syntax.
The programming language syntax is usually defined using a combination of regular expressions (for lexical structure) and Backus–Naur form (for grammatical structure). Below is a simple grammar, based on Lisp:
This grammar specifies the following:
an expression is... | https://en.wikipedia.org/wiki/Programming_language |
optionally preceded by a plus or minus sign;
a symbol is a letter followed by zero or more of any alphabetical characters (excluding whitespace); and
a list is a matched pair of parentheses, with zero or more expressions inside it.
The following are examples of well-formed token sequences in this grammar: 12345, () an... | https://en.wikipedia.org/wiki/Programming_language |
less ill-formed, per the language's rules; and may (depending on the language specification and the soundness of the implementation) result in an error on translation or execution. In some cases, such programs may exhibit undefined behavior. Even when a program is well-defined within a language, it may still have a mea... | https://en.wikipedia.org/wiki/Programming_language |
ning to a grammatically correct sentence or the sentence may be false:
"Colorless green ideas sleep furiously." is grammatically well-formed but has no generally accepted meaning.
"John is a married bachelor." is grammatically well-formed but expresses a meaning that cannot be true.
The following C language fragment i... | https://en.wikipedia.org/wiki/Programming_language |
ue having a complex type and p->im is not defined because the value of p is the null pointer):
If the type declaration on the first line were omitted, the program would trigger an error on the undefined variable p during compilation. However, the program would still be syntactically correct since type declarations pro... | https://en.wikipedia.org/wiki/Programming_language |
sky hierarchy. The syntax of most programming languages can be specified using a Type-2 grammar, i.e., they are context-free grammars. Some languages, including Perl and Lisp, contain constructs that allow execution during the parsing phase. Languages that have constructs that allow the programmer to alter the behavior... | https://en.wikipedia.org/wiki/Programming_language |
ontrast to Lisp's macro system and Perl's BEGIN blocks, which may contain general computations, C macros are merely string replacements and do not require code execution.
=== Semantics ===
The term semantics refers to the meaning of languages, as opposed to their form (syntax).
==== Static semantics ====
Static se... | https://en.wikipedia.org/wiki/Programming_language |
ms. For compiled languages, static semantics essentially include those semantic rules that can be checked at compile time. Examples include checking that every identifier is declared before it is used (in languages that require such declarations) or that the labels on the arms of a case statement are distinct. Many imp... | https://en.wikipedia.org/wiki/Programming_language |
o a function name), or that subroutine calls have the appropriate number and type of arguments, can be enforced by defining them as rules in a logic called a type system. Other forms of static analyses like data flow analysis may also be part of static semantics. Programming languages such as Java and C# have definite ... | https://en.wikipedia.org/wiki/Programming_language |
ce data has been specified, the machine must be instructed to perform operations on the data. For example, the semantics may define the strategy by which expressions are evaluated to values, or the manner in which control structures conditionally execute statements. The dynamic semantics (also known as execution semant... | https://en.wikipedia.org/wiki/Programming_language |
s of defining execution semantics. Natural language is often used to specify the execution semantics of languages commonly used in practice. A significant amount of academic research goes into formal semantics of programming languages, which allows execution semantics to be specified in a formal manner. Results from th... | https://en.wikipedia.org/wiki/Programming_language |
system ===
A data type is a set of allowable values and operations that can be performed on these values. Each programming language's type system defines which data types exist, the type of an expression, and how type equivalence and type compatibility function in the language.
According to type theory, a language is ... | https://en.wikipedia.org/wiki/Programming_language |
typed language, such as most assembly languages, allows any operation to be performed on any data, generally sequences of bits of various lengths. In practice, while few languages are fully typed, most offer a degree of typing.
Because different types (such as integers and floats) represent values differently, unexpec... | https://en.wikipedia.org/wiki/Programming_language |
runtime type checking is more costly). With strong typing, type errors can always be detected unless variables are explicitly cast to a different type. Weak typing occurs when languages allow implicit casting—for example, to enable operations between variables of different types without the programmer making an explici... | https://en.wikipedia.org/wiki/Programming_language |
supported types ====
Early programming languages often supported only built-in, numeric types such as the integer (signed and unsigned) and floating point (to support operations on real numbers that are not integers). Most programming languages support multiple sizes of floats (often called float and double) and inte... | https://en.wikipedia.org/wiki/Programming_language |
t leads to integer overflow. The most common way of representing negative numbers with signed types is twos complement, although ones complement is also used. Other common types include Boolean—which is either true or false—and character—traditionally one byte, sufficient to represent all ASCII characters.
Arrays are ... | https://en.wikipedia.org/wiki/Programming_language |
erences to data stored elsewhere and support elements of varying types. Depending on the programming language, sequences of multiple characters, called strings, may be supported as arrays of characters or their own primitive type. Strings may be of fixed or variable length, which enables greater flexibility at the cost... | https://en.wikipedia.org/wiki/Programming_language |
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