text stringlengths 1 500 | source stringlengths 31 152 |
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ays accessed via keys, records in which data is mapped to names in an ordered structure, and tuples—similar to records but without names for data fields. Pointers store memory addresses, typically referencing locations on the heap where other data is stored.
The simplest user-defined type is an ordinal type, often call... | https://en.wikipedia.org/wiki/Programming_language |
lso support abstract data types, in which the representation of the data and operations are hidden from the user, who can only access an interface. The benefits of data abstraction can include increased reliability, reduced complexity, less potential for name collision, and allowing the underlying data structure to be ... | https://en.wikipedia.org/wiki/Programming_language |
their types determined before a program executes, typically at compile-time. Most widely used, statically typed programming languages require the types of variables to be specified explicitly. In some languages, types are implicit; one form of this is when the compiler can infer types based on context. The downside of... | https://en.wikipedia.org/wiki/Programming_language |
tional languages such as Haskell and ML.
With dynamic typing, the type is not attached to the variable but only the value encoded in it. A single variable can be reused for a value of a different type. Although this provides more flexibility to the programmer, it is at the cost of lower reliability and less ability fo... | https://en.wikipedia.org/wiki/Programming_language |
ssigned, in an exception to their usual static typing rules.
=== Concurrency ===
In computing, multiple instructions can be executed simultaneously. Many programming languages support instruction-level and subprogram-level concurrency. By the twenty-first century, additional processing power on computers was increas... | https://en.wikipedia.org/wiki/Programming_language |
ssors simultaneously to achieve improved performance. Interpreted languages such as Python and Ruby do not support the concurrent use of multiple processors. Other programming languages do support managing data shared between different threads by controlling the order of execution of key instructions via the use of sem... | https://en.wikipedia.org/wiki/Programming_language |
Many programming languages include exception handlers, a section of code triggered by runtime errors that can deal with them in two main ways:
Termination: shutting down and handing over control to the operating system. This option is considered the simplest.
Resumption: resuming the program near where the exception ... | https://en.wikipedia.org/wiki/Programming_language |
on from reoccurring.
Some programming languages support dedicating a block of code to run regardless of whether an exception occurs before the code is reached; this is called finalization.
There is a tradeoff between increased ability to handle exceptions and reduced performance. For example, even though array index er... | https://en.wikipedia.org/wiki/Programming_language |
s, this can clutter a program. Standard libraries in some languages, such as C, use their return values to indicate an exception. Some languages and their compilers have the option of turning on and off error handling capability, either temporarily or permanently.
== Design and implementation ==
One of the most impo... | https://en.wikipedia.org/wiki/Programming_language |
were designed to perform well on von Neumann architecture, the most common computer architecture. In von Neumann architecture, the memory stores both data and instructions, while the CPU that performs instructions on data is separate, and data must be piped back and forth to the CPU. The central elements in these lang... | https://en.wikipedia.org/wiki/Programming_language |
ages have been designed from scratch, altered to meet new needs, and combined with other languages. Many have eventually fallen into disuse. The birth of programming languages in the 1950s was stimulated by the desire to make a universal programming language suitable for all machines and uses, avoiding the need to writ... | https://en.wikipedia.org/wiki/Programming_language |
s of the variety of purposes for which code was written.
=== Tradeoffs ===
Desirable qualities of programming languages include readability, writability, and reliability. These features can reduce the cost of training programmers in a language, the amount of time needed to write and maintain programs in the language... | https://en.wikipedia.org/wiki/Programming_language |
iency over readability, the latter has grown in importance since the 1970s. Having multiple operations to achieve the same result can be detrimental to readability, as is overloading operators, so that the same operator can have multiple meanings. Another feature important to readability is orthogonality, limiting the ... | https://en.wikipedia.org/wiki/Programming_language |
iately obvious also supports readability.
Writability is the ease of use for writing code to solve the desired problem. Along with the same features essential for readability, abstraction—interfaces that enable hiding details from the client—and expressivity—enabling more concise programs—additionally help the programm... | https://en.wikipedia.org/wiki/Programming_language |
support for abstraction has increased, allowing programmers express ideas that are more remote from simple translation into underlying hardware instructions. Because programmers are less tied to the complexity of the computer, their programs can do more computing with less effort from the programmer. Most programming ... | https://en.wikipedia.org/wiki/Programming_language |
e range of circumstances. Type checking, exception handling, and restricted aliasing (multiple variable names accessing the same region of memory) all can improve a program's reliability.
Programming language design often involves tradeoffs. For example, features to improve reliability typically come at the cost of per... | https://en.wikipedia.org/wiki/Programming_language |
.
Natural-language programming has been proposed as a way to eliminate the need for a specialized language for programming. However, this goal remains distant and its benefits are open to debate. Edsger W. Dijkstra took the position that the use of a formal language is essential to prevent the introduction of meaningl... | https://en.wikipedia.org/wiki/Programming_language |
guage is an artifact that the language users and the implementors can use to agree upon whether a piece of source code is a valid program in that language, and if so what its behavior shall be.
A programming language specification can take several forms, including the following:
An explicit definition of the syntax, s... | https://en.wikipedia.org/wiki/Programming_language |
nitions may be written in natural language (e.g., as in the C language), or a formal semantics (e.g., as in Standard ML and Scheme specifications).
A description of the behavior of a translator for the language (e.g., the C++ and Fortran specifications). The syntax and semantics of the language have to be inferred from... | https://en.wikipedia.org/wiki/Programming_language |
he language being specified (e.g., Prolog or ANSI REXX). The syntax and semantics of the language are explicit in the behavior of the reference implementation.
=== Implementation ===
An implementation of a programming language is the conversion of a program into machine code that can be executed by the hardware. The... | https://en.wikipedia.org/wiki/Programming_language |
e is by a compiler, which translates the source code via an intermediate-level language into machine code, known as an executable. Once the program is compiled, it will run more quickly than with other implementation methods. Some compilers are able to provide further optimization to reduce memory or computation usage ... | https://en.wikipedia.org/wiki/Programming_language |
, which translates each line of software into machine code just before it executes. Although it can make debugging easier, the downside of interpretation is that it runs 10 to 100 times slower than a compiled executable. Hybrid interpretation methods provide some of the benefits of compilation and some of the benefits ... | https://en.wikipedia.org/wiki/Programming_language |
d of time into an intermediate language, and then into machine code immediately before execution.
== Proprietary languages ==
Although most of the most commonly used programming languages have fully open specifications and implementations, many programming languages exist only as proprietary programming languages wit... | https://en.wikipedia.org/wiki/Programming_language |
roperty. Proprietary programming languages are commonly domain-specific languages or internal scripting languages for a single product; some proprietary languages are used only internally within a vendor, while others are available to external users.
Some programming languages exist on the border between proprietary an... | https://en.wikipedia.org/wiki/Programming_language |
's C# programming language, which has open implementations of most parts of the system, also has Common Language Runtime (CLR) as a closed environment.
Many proprietary languages are widely used, in spite of their proprietary nature; examples include MATLAB, VBScript, and Wolfram Language. Some languages may make the t... | https://en.wikipedia.org/wiki/Programming_language |
g languages are particularly helpful for open science applications, enhancing the capacity for replication and code sharing.
== Use ==
Thousands of different programming languages have been created, mainly in the computing field.
Individual software projects commonly use five programming languages or more.
Programmin... | https://en.wikipedia.org/wiki/Programming_language |
When using a natural language to communicate with other people, human authors and speakers can be ambiguous and make small errors, and still expect their intent to be understood. However, figuratively speaking, computers "do exactly what they are told to do", and cannot "understand" what code the programmer intended to... | https://en.wikipedia.org/wiki/Programming_language |
hat occurs when the program is executed, within the domain of control of that program. On the other hand, ideas about an algorithm can be communicated to humans without the precision required for execution by using pseudocode, which interleaves natural language with code written in a programming language.
A programming... | https://en.wikipedia.org/wiki/Programming_language |
ut automatically on that data. A programmer uses the abstractions present in the language to represent the concepts involved in a computation. These concepts are represented as a collection of the simplest elements available (called primitives). Programming is the process by which programmers combine these primitives t... | https://en.wikipedia.org/wiki/Programming_language |
a batch process without any human interaction, or a user might type commands in an interactive session of an interpreter. In this case the "commands" are simply programs, whose execution is chained together. When a language can run its commands through an interpreter (such as a Unix shell or other command-line interfa... | https://en.wikipedia.org/wiki/Programming_language |
used programming language is difficult since the definition of usage varies by context. One language may occupy the greater number of programmer hours, a different one has more lines of code, and a third may consume the most CPU time. Some languages are very popular for particular kinds of applications. For example, C... | https://en.wikipedia.org/wiki/Programming_language |
Ada in aerospace, transportation, military, real-time, and embedded applications; and C in embedded applications and operating systems. Other languages are regularly used to write many different kinds of applications.
Various methods of measuring language popularity, each subject to a different bias over what is measur... | https://en.wikipedia.org/wiki/Programming_language |
r describe the language
estimates of the number of existing lines of code written in the language – which may underestimate languages not often found in public searches
counts of language references (i.e., to the name of the language) found using a web search engine.
Combining and averaging information from various in... | https://en.wikipedia.org/wiki/Programming_language |
C, C++, Python, C#, JavaScript, VB .NET, R, PHP, and MATLAB.
As of June 2024, the top five programming languages as measured by TIOBE index are Python, C++, C, Java and C#. TIOBE provides a list of top 100 programming languages according to popularity and update this list every month.
== Dialects, flavors and impleme... | https://en.wikipedia.org/wiki/Programming_language |
language that does not change its intrinsic nature. With languages such as Scheme and Forth, standards may be considered insufficient, inadequate, or illegitimate by implementors, so often they will deviate from the standard, making a new dialect. In other cases, a dialect is created for use in a domain-specific langua... | https://en.wikipedia.org/wiki/Programming_language |
sp dialects, although they vary wildly as do, say, Racket and Clojure. As it is common for one language to have several dialects, it can become quite difficult for an inexperienced programmer to find the right documentation. The BASIC language has many dialects.
== Classifications ==
Programming languages are often ... | https://en.wikipedia.org/wiki/Programming_language |
ent an algorithm in a specified order; they include visual programming languages such as .NET for generating graphical user interfaces. Scripting languages, which are partly or fully interpreted rather than compiled, are sometimes considered a separate category but meet the definition of imperative languages.
Functiona... | https://en.wikipedia.org/wiki/Programming_language |
for their simplicity and elegance, problems with efficiency have prevented them from being widely adopted.
Logic languages are designed so that the software, rather than the programmer, decides what order in which the instructions are executed.
Object-oriented programming—whose characteristic features are data abstract... | https://en.wikipedia.org/wiki/Programming_language |
arkup languages are not programming languages, some have extensions that support limited programming. Additionally, there are special-purpose languages that are not easily compared to other programming languages.
== See also ==
== References ==
== Further reading == | https://en.wikipedia.org/wiki/Programming_language |
C (pronounced – like the letter c) is a general-purpose programming language. It was created in the 1970s by Dennis Ritchie and remains very widely used and influential. By design, C's features cleanly reflect the capabilities of the targeted CPUs. It has found lasting use in operating systems code (especially in kern... | https://en.wikipedia.org/wiki/C_(programming_language) |
architectures that range from the largest supercomputers to the smallest microcontrollers and embedded systems.
A successor to the programming language B, C was originally developed at Bell Labs by Ritchie between 1972 and 1973 to construct utilities running on Unix. It was applied to re-implementing the kernel of the... | https://en.wikipedia.org/wiki/C_(programming_language) |
guages, with C compilers available for practically all modern computer architectures and operating systems. The book The C Programming Language, co-authored by the original language designer, served for many years as the de facto standard for the language. C has been standardized since 1989 by the American National Sta... | https://en.wikipedia.org/wiki/C_(programming_language) |
al Electrotechnical Commission (IEC).
C is an imperative procedural language, supporting structured programming, lexical variable scope, and recursion, with a static type system. It was designed to be compiled to provide low-level access to memory and language constructs that map efficiently to machine instructions, al... | https://en.wikipedia.org/wiki/C_(programming_language) |
ing. A standards-compliant C program written with portability in mind can be compiled for a wide variety of computer platforms and operating systems with few changes to its source code.
Since 2000, C has consistently ranked among the top four languages in the TIOBE index, a measure of the popularity of programming lang... | https://en.wikipedia.org/wiki/C_(programming_language) |
xecutable code is contained within subroutines (also called "functions", though not in the sense of functional programming). Function parameters are passed by value, although arrays are passed as pointers, i.e. the address of the first item in the array. Pass-by-reference is simulated in C by explicitly passing pointer... | https://en.wikipedia.org/wiki/C_(programming_language) |
used to group statements into blocks.
The C language also exhibits the following characteristics:
The language has a small, fixed number of keywords, including a full set of control flow primitives: if/else, for, do/while, while, and switch. User-defined names are not distinguished from keywords by any kind of sigil.... | https://en.wikipedia.org/wiki/C_(programming_language) |
n a single statement.
Functions:
Function return values can be ignored, when not needed.
Function and data pointers permit ad hoc run-time polymorphism.
Functions may not be defined within the lexical scope of other functions.
Variables may be defined within a function, with scope.
A function may call itself, so recurs... | https://en.wikipedia.org/wiki/C_(programming_language) |
ined (typedef) and compound types are possible.
Heterogeneous aggregate data types (struct) allow related data elements to be accessed and assigned as a unit. The contents of whole structs cannot be compared using a single built-in operator (the elements must be compared individually).
Union is a structure with overlap... | https://en.wikipedia.org/wiki/C_(programming_language) |
terms of pointer arithmetic. Whole arrays cannot be assigned or compared using a single built-in operator. There is no "array" keyword in use or definition; instead, square brackets indicate arrays syntactically, for example month[11].
Enumerated types are possible with the enum keyword. They are freely interconvertibl... | https://en.wikipedia.org/wiki/C_(programming_language) |
-level access to computer memory is possible by converting machine addresses to pointers.
Procedures (subroutines not returning values) are a special case of function, with an empty return type void.
Memory can be allocated to a program with calls to library routines.
A preprocessor performs macro definition, source co... | https://en.wikipedia.org/wiki/C_(programming_language) |
ogether, with control over which functions and data objects are visible to other files via static and extern attributes.
Complex functionality such as I/O, string manipulation, and mathematical functions are consistently delegated to library routines.
The generated code after compilation has relatively straightforward ... | https://en.wikipedia.org/wiki/C_(programming_language) |
does not include certain features found in other languages (such as object orientation and garbage collection), these can be implemented or emulated, often through the use of external libraries (e.g., the GLib Object System or the Boehm garbage collector).
=== Relations to other languages ===
Many later languages ha... | https://en.wikipedia.org/wiki/C_(programming_language) |
ia, Limbo, LPC, Objective-C, Perl, PHP, Python, Ruby, Rust, Swift, Verilog and SystemVerilog (hardware description languages). These languages have drawn many of their control structures and other basic features from C. Most of them also express highly similar syntax to C, and they tend to combine the recognizable exp... | https://en.wikipedia.org/wiki/C_(programming_language) |
istory ==
=== Early developments ===
The origin of C is closely tied to the development of the Unix operating system, originally implemented in assembly language on a PDP-7 by Dennis Ritchie and Ken Thompson, incorporating several ideas from colleagues. Eventually, they decided to port the operating system to a PDP... | https://en.wikipedia.org/wiki/C_(programming_language) |
guage for developing utilities for the new platform. He first tried writing a Fortran compiler, but he soon gave up the idea and instead created a cut-down version of the recently developed systems programming language called BCPL. The official description of BCPL was not available at the time, and Thompson modified th... | https://en.wikipedia.org/wiki/C_(programming_language) |
antics with a lot of SMALGOL syntax". Like BCPL, B had a bootstrapping compiler to facilitate porting to new machines. Ultimately, few utilities were written in B because it was too slow and could not take advantage of PDP-11 features such as byte addressability.
==== New B and first C release ====
In 1971 Ritchie s... | https://en.wikipedia.org/wiki/C_(programming_language) |
d this New B (NB). Thompson started to use NB to write the Unix kernel, and his requirements shaped the direction of the language development. Through to 1972, richer types were added to the NB language: NB had arrays of int and char. Pointers, the ability to generate pointers to other types, arrays of all types, and... | https://en.wikipedia.org/wiki/C_(programming_language) |
nd the language was renamed C.
The C compiler and some utilities made with it were included in Version 2 Unix, which is also known as Research Unix.
==== Structures and Unix kernel re-write ====
At Version 4 Unix, released in November 1973, the Unix kernel was extensively re-implemented in C. By this time, the C lang... | https://en.wikipedia.org/wiki/C_(programming_language) |
nyder and also in recognition of the usefulness of the file-inclusion mechanisms available in BCPL and PL/I. Its original version provided only included files and simple string replacements: #include and #define of parameterless macros. Soon after that, it was extended, mostly by Mike Lesk and then by John Reiser, to i... | https://en.wikipedia.org/wiki/C_(programming_language) |
language other than assembly. Earlier instances include the Multics system (which was written in PL/I) and Master Control Program (MCP) for the Burroughs B5000 (which was written in ALGOL) in 1961. In around 1977, Ritchie and Stephen C. Johnson made further changes to the language to facilitate portability of the Unix... | https://en.wikipedia.org/wiki/C_(programming_language) |
C ===
In 1978 Brian Kernighan and Dennis Ritchie published the first edition of The C Programming Language. Known as K&R from the initials of its authors, the book served for many years as an informal specification of the language. The version of C that it describes is commonly referred to as "K&R C". As this was rel... | https://en.wikipedia.org/wiki/C_(programming_language) |
.
K&R introduced several language features:
Standard I/O library
long int data type
unsigned int data type
Compound assignment operators of the form =op (such as =-) were changed to the form op= (that is, -=) to remove the semantic ambiguity created by constructs such as i=-10, which had been interpreted as i =- 10 (d... | https://en.wikipedia.org/wiki/C_(programming_language) |
or many years K&R C was still considered the "lowest common denominator" to which C programmers restricted themselves when maximum portability was desired, since many older compilers were still in use, and because carefully written K&R C code can be legal Standard C as well.
In early versions of C, only functions that ... | https://en.wikipedia.org/wiki/C_(programming_language) |
presumed to return type int.
For example:
The int type specifiers which are commented out could be omitted in K&R C, but are required in later standards.
Since K&R function declarations did not include any information about function arguments, function parameter type checks were not performed, although some compilers... | https://en.wikipedia.org/wiki/C_(programming_language) |
rnal function used different numbers or types of arguments. Separate tools such as Unix's lint utility were developed that (among other things) could check for consistency of function use across multiple source files.
In the years following the publication of K&R C, several features were added to the language, support... | https://en.wikipedia.org/wiki/C_(programming_language) |
urn value)
functions returning struct or union types (previously only a single pointer, integer or float could be returned)
assignment for struct data types
enumerated types (previously, preprocessor definitions for integer fixed values were used, e.g. #define GREEN 3)
The large number of extensions and lack of agreeme... | https://en.wikipedia.org/wiki/C_(programming_language) |
d the K&R specification, led to the necessity of standardization.
=== ANSI C and ISO C ===
During the late 1970s and 1980s, versions of C were implemented for a wide variety of mainframe computers, minicomputers, and microcomputers, including the IBM PC, as its popularity began to increase significantly.
In 1983 the... | https://en.wikipedia.org/wiki/C_(programming_language) |
he C standard on the Unix implementation; however, the non-portable portion of the Unix C library was handed off to the IEEE working group 1003 to become the basis for the 1988 POSIX standard. In 1989, the C standard was ratified as ANSI X3.159-1989 "Programming Language C". This version of the language is often refer... | https://en.wikipedia.org/wiki/C_(programming_language) |
onal Organization for Standardization (ISO) as ISO/IEC 9899:1990, which is sometimes called C90. Therefore, the terms "C89" and "C90" refer to the same programming language.
ANSI, like other national standards bodies, no longer develops the C standard independently, but defers to the international C standard, maintaine... | https://en.wikipedia.org/wiki/C_(programming_language) |
in a year of ISO publication.
One of the aims of the C standardization process was to produce a superset of K&R C, incorporating many of the subsequently introduced unofficial features. The standards committee also included several additional features such as function prototypes (borrowed from C++), void pointers, supp... | https://en.wikipedia.org/wiki/C_(programming_language) |
s augmented to include the style used in C++, the K&R interface continued to be permitted, for compatibility with existing source code.
C89 is supported by current C compilers, and most modern C code is based on it. Any program written only in Standard C and without any hardware-dependent assumptions will run correctly... | https://en.wikipedia.org/wiki/C_(programming_language) |
nly on a certain platform or with a particular compiler, due, for example, to the use of non-standard libraries, such as GUI libraries, or to a reliance on compiler- or platform-specific attributes such as the exact size of data types and byte endianness.
In cases where code must be compilable by either standard-confor... | https://en.wikipedia.org/wiki/C_(programming_language) |
on a K&R C-based compiler of features available only in Standard C.
After the ANSI/ISO standardization process, the C language specification remained relatively static for several years. In 1995, Normative Amendment 1 to the 1990 C standard (ISO/IEC 9899/AMD1:1995, known informally as C95) was published, to correct som... | https://en.wikipedia.org/wiki/C_(programming_language) |
the late 1990s, leading to the publication of ISO/IEC 9899:1999 in 1999, which is commonly referred to as "C99". It has since been amended three times by Technical Corrigenda.
C99 introduced several new features, including inline functions, several new data types (including long long int and a complex type to represen... | https://en.wikipedia.org/wiki/C_(programming_language) |
ariadic macros (macros of variable arity), and support for one-line comments beginning with //, as in BCPL or C++. Many of these had already been implemented as extensions in several C compilers.
C99 is for the most part backward compatible with C90, but is stricter in some ways; in particular, a declaration that lacks... | https://en.wikipedia.org/wiki/C_(programming_language) |
e that C99 support is available. GCC, Solaris Studio, and other C compilers now support many or all of the new features of C99. The C compiler in Microsoft Visual C++, however, implements the C89 standard and those parts of C99 that are required for compatibility with C++11.
In addition, the C99 standard requires suppo... | https://en.wikipedia.org/wiki/C_(programming_language) |
e names.
=== C11 ===
Work began in 2007 on another revision of the C standard, informally called "C1X" until its official publication of ISO/IEC 9899:2011 on December 8, 2011. The C standards committee adopted guidelines to limit the adoption of new features that had not been tested by existing implementations.
The ... | https://en.wikipedia.org/wiki/C_(programming_language) |
e support, atomic operations, multi-threading, and bounds-checked functions. It also makes some portions of the existing C99 library optional, and improves compatibility with C++. The standard macro __STDC_VERSION__ is defined as 201112L to indicate that C11 support is available.
=== C17 ===
C17 is an informal name... | https://en.wikipedia.org/wiki/C_(programming_language) |
only technical corrections, and clarifications to defects in C11. The standard macro __STDC_VERSION__ is defined as 201710L to indicate that C17 support is available.
=== C23 ===
C23 is an informal name for the current major C language standard revision. It was informally known as "C2X" through most of its developme... | https://en.wikipedia.org/wiki/C_(programming_language) |
that C23 support is available.
=== C2Y ===
C2Y is an informal name for the next major C language standard revision, after C23 (C2X), that is hoped to be released later in the 2020s, hence the '2' in "C2Y". An early working draft of C2Y was released in February 2024 as N3220 by the working group ISO/IEC JTC1/SC22/WG1... | https://en.wikipedia.org/wiki/C_(programming_language) |
features such as fixed-point arithmetic, multiple distinct memory banks, and basic I/O operations.
In 2008, the C Standards Committee published a technical report extending the C language to address these issues by providing a common standard for all implementations to adhere to. It includes a number of features not a... | https://en.wikipedia.org/wiki/C_(programming_language) |
as a formal grammar specified by the C standard. Line endings are generally not significant in C; however, line boundaries do have significance during the preprocessing phase. Comments may appear either between the delimiters /* and */, or (since C99) following // until the end of the line. Comments delimited by /* and... | https://en.wikipedia.org/wiki/C_(programming_language) |
cter literals.
C source files contain declarations and function definitions. Function definitions, in turn, contain declarations and statements. Declarations either define new types using keywords such as struct, union, and enum, or assign types to and perhaps reserve storage for new variables, usually by writing the t... | https://en.wikipedia.org/wiki/C_(programming_language) |
{ and }, sometimes called "curly brackets") to limit the scope of declarations and to act as a single statement for control structures.
As an imperative language, C uses statements to specify actions. The most common statement is an expression statement, consisting of an expression to be evaluated, followed by a semico... | https://en.wikipedia.org/wiki/C_(programming_language) |
l execution of statements, C provides several control-flow statements identified by reserved keywords. Structured programming is supported by if ... [else] conditional execution and by do ... while, while, and for iterative execution (looping). The for statement has separate initialization, testing, and reinitializatio... | https://en.wikipedia.org/wiki/C_(programming_language) |
rmost enclosing loop statement and continue is used to skip to its reinitialisation. There is also a non-structured goto statement which branches directly to the designated label within the function. switch selects a case to be executed based on the value of an integer expression. Different from many other languages, c... | https://en.wikipedia.org/wiki/C_(programming_language) |
nd may contain function calls. The order in which arguments to functions and operands to most operators are evaluated is unspecified. The evaluations may even be interleaved. However, all side effects (including storage to variables) will occur before the next "sequence point"; sequence points include the end of each e... | https://en.wikipedia.org/wiki/C_(programming_language) |
ions containing certain operators (&&, ||, ?: and the comma operator). This permits a high degree of object code optimization by the compiler, but requires C programmers to take more care to obtain reliable results than is needed for other programming languages.
Kernighan and Ritchie say in the Introduction of The C Pr... | https://en.wikipedia.org/wiki/C_(programming_language) |
the syntax could be better." The C standard did not attempt to correct many of these blemishes, because of the impact of such changes on already existing software.
=== Character set ===
The basic C source character set includes the following characters:
Lowercase and uppercase letters of the ISO basic Latin alphabe... | https://en.wikipedia.org/wiki/C_(programming_language) |
s: space, horizontal tab, vertical tab, form feed, newline
The newline character indicates the end of a text line; it need not correspond to an actual single character, although for convenience C treats it as such.
Additional multi-byte encoded characters may be used in string literals, but they are not entirely portab... | https://en.wikipedia.org/wiki/C_(programming_language) |
ng (where X denotes a hexadecimal character).
The basic C execution character set contains the same characters, along with representations for alert, backspace, and carriage return. Run-time support for extended character sets has increased with each revision of the C standard.
=== Reserved words ===
The following re... | https://en.wikipedia.org/wiki/C_(programming_language) |
than those for which they are predefined:
C99 added five more reserved words: (‡ indicates an alternative spelling alias for a C23 keyword)
C11 added seven more reserved words: (‡ indicates an alternative spelling alias for a C23 keyword)
C23 reserved fifteen more words:
Most of the recently reserved words begin wi... | https://en.wikipedia.org/wiki/C_(programming_language) |
only by implementations. Since existing program source code should not have been using these identifiers, it would not be affected when C implementations started supporting these extensions to the programming language. Some standard headers do define more convenient synonyms for underscored identifiers. Some of those... | https://en.wikipedia.org/wiki/C_(programming_language) |
ry was reserved as a keyword. In the second edition of their book The C Programming Language, which describes what became known as C89, Kernighan and Ritchie wrote, "The ... [keyword] entry, formerly reserved but never used, is no longer reserved." and "The stillborn entry keyword is withdrawn."
=== Operators ===
C ... | https://en.wikipedia.org/wiki/C_(programming_language) |
valuating that expression. C has operators for:
arithmetic: +, -, *, /, %
assignment: =
augmented assignment: +=, -=, *=, /=, %=, &=, |=, ^=, <<=, >>=
bitwise logic: ~, &, |, ^
bitwise shifts: <<, >>
Boolean logic: !, &&, ||
conditional evaluation: ? :
equality testing: ==, !=
calling functions: ( )
increment and decr... | https://en.wikipedia.org/wiki/C_(programming_language) |
rence and dereference: &, *, [ ]
sequencing: ,
subexpression grouping: ( )
type conversion: (typename)
C uses the operator = (used in mathematics to express equality) to indicate assignment, following the precedent of Fortran and PL/I, but unlike ALGOL and its derivatives. C uses the operator == to test for equality. T... | https://en.wikipedia.org/wiki/C_(programming_language) |
in many cases the mistake does not produce an error message (although some compilers produce warnings). For example, the conditional expression if (a == b + 1) might mistakenly be written as if (a = b + 1), which will be evaluated as true unless the value of a is 0 after the assignment.
The C operator precedence is no... | https://en.wikipedia.org/wiki/C_(programming_language) |
| (bitwise OR) in expressions such as x & 1 == 0, which must be written as (x & 1) == 0 if that is the coder's intent.
== "Hello, world" example ==
The "hello, world" example that appeared in the first edition of K&R has become the model for an introductory program in most programming textbooks. The program prints "... | https://en.wikipedia.org/wiki/C_(programming_language) |
ing "hello, world" program is:
The first line of the program contains a preprocessing directive, indicated by #include. This causes the compiler to replace that line of code with the entire text of the stdio.h header file, which contains declarations for standard input and output functions such as printf and scanf. Th... | https://en.wikipedia.org/wiki/C_(programming_language) |
vided with the compiler to other headers having the same name (as opposed to double quotes which typically include local or project-specific header files).
The second line indicates that a function named main is being defined. The main function serves a special purpose in C programs; the run-time environment calls the ... | https://en.wikipedia.org/wiki/C_(programming_language) |
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