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Non to be dislocated with C++ or C#.

General-purpose programming linguistic communication

C

The C Programming Language [1] (often referred to every bit K&R), the seminal book on C
Paradigm	Multi-paradigm: imperative (procedural), structured
Designed past	Dennis Ritchie
Developer	Dennis Ritchie & Bell Labs (creators); ANSI X3J11 (ANSI C); ISO/IEC JTC1/SC22/WG14 (ISO C)
First appeared	1972; l years ago  (1972) [2]
Stable release	C17 / June 2018; 3 years ago  (2018-06)
Preview release	C2x (N2731) / October 18, 2021; 5 months ago  (2021-10-18) [3]
Typing discipline	Static, weak, manifest, nominal
OS	Cross-platform
Filename extensions	.c, .h
Website	www.iso.org/standard/74528.html world wide web.open-std.org/jtc1/sc22/wg14/
Major implementations
pcc, GCC, Clang, Intel C, C++Builder, Microsoft Visual C++, Watcom C
Dialects
Whirlwind, Unified Parallel C, Split-C, Cilk, C*
Influenced past
B (BCPL, CPL), ALGOL 68,[4] assembly, PL/I, FORTRAN
Influenced
Numerous: AMPL, AWK, csh, C++, C--, C#, Objective-C, D, Go, Java, JavaScript, JS++, Julia, Limbo, LPC, Perl, PHP, Thruway, Processing, Python, Rust, Seed7, Vala, Verilog (HDL),[5] Nim, Zig
C Programming at Wikibooks

C (, as in the letter of the alphabet c) is a general-purpose computer programming linguistic communication. Information technology was created in the 1970s and remains very widely used and influential. Past blueprint, C'southward features cleanly reflect the capabilities of the targetted CPUs. It has institute lasting use in operating systems, device drivers, protocol stacks, though decreasingly for application software, and is common in reckoner 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 Dennis Ritchie between 1972 and 1973 to construct utilities running on Unix. It was applied to re-implementing the kernel of the Unix operating arrangement.^{[half dozen]} During the 1980s, C gradually gained popularity. It has become one of the nigh widely used programming languages,^{[7] [eight]} with C compilers available for the most all modern computer architectures and operating systems. C has been standardized by ANSI since 1989 (ANSI C) and by the International Organization for Standardization (ISO).

C is an imperative procedural language supporting structured programming, lexical variable scope, and recursion, with a static type arrangement. Information technology was designed to be compiled to provide low-level access to memory and language constructs that map efficiently to car instructions, all with minimal runtime support. Despite its depression-level capabilities, the linguistic communication was designed to encourage cross-platform programming. A standards-compliant C program written with portability in mind tin can be compiled for a wide variety of computer platforms and operating systems with few changes to its source lawmaking.^[nine]

Since 2000, C has consistently ranked among the acme two languages in the TIOBE index, a measure of the popularity of programming languages.^[ten]

Overview [edit]

C is an imperative, procedural language in the ALGOL tradition. It has a static type system. In C, all executable code is contained within subroutines (also chosen "functions", though not in the sense of functional programming). Function parameters are passed past value, although arrays are passed equally pointers, i.e. the accost of the first particular in the array. Laissez passer-by-reference is simulated in C by explicitly passing pointers to the thing beingness referenced.

C program source text is free-format, using the semicolon as a statement separator and curly braces for grouping blocks of statements.

The C linguistic communication likewise exhibits the following characteristics:

• The language has a pocket-sized, fixed number of keywords, including a full set of control period primitives: if/else, for, practice/while, while, and switch. User-defined names are not distinguished from keywords by any kind of sigil.
• Information technology has a large number of arithmetics, bitwise, and logic operators: +,+=,++,&,||, etc.
• More than 1 assignment may be performed in a single statement.
• Functions:
  • Function return values tin can be ignored, when not needed.
  • Function and information pointers permit advert hoc run-time polymorphism.
  • Functions may not be defined inside the lexical scope of other functions.
  • Variables may be defined inside a role, with scope.
  • A function may call itself, so recursion is supported.
• Data typing is static, but weakly enforced; all data has a type, but implicit conversions are possible.
• User-defined (typedef) and compound types are possible.
  • Heterogeneous aggregate information types (struct) permit related data elements to be accessed and assigned equally a unit of measurement.
  • Union is a construction with overlapping members; only the last fellow member stored is valid.
  • Array indexing is a secondary notation, divers in terms of arrow arithmetics. Unlike structs, arrays are non kickoff-class objects: they cannot be assigned or compared using single built-in operators. There is no "array" keyword in utilize or definition; instead, square brackets indicate arrays syntactically, for example calendar month[11].
  • Enumerated types are possible with the enum keyword. They are freely interconvertible with integers.
  • Strings are not a distinct data type, but are conventionally implemented equally zero-terminated character arrays.
• Low-level admission to figurer memory is possible by converting machine addresses to pointers.
• Procedures (subroutines not returning values) are a special instance of function, with an untyped render type void.
• Memory can exist allocated to a program with calls to library routines.
• A preprocessor performs macro definition, source lawmaking file inclusion, and conditional compilation.
• In that location is a basic grade of modularity: files tin be compiled separately and linked together, with command over which functions and data objects are visible to other files via static and extern attributes.
• Complex functionality such every bit I/O, string manipulation, and mathematical functions are consistently delegated to library routines.
• The generated code later compilation has relatively straightforward needs on the underlying platform, which makes information technology suitable for creating operating systems and for use in embedded systems.

While C does not include certain features found in other languages (such as object orientation and garbage collection), these can be implemented or emulated, ofttimes through the use of external libraries (e.g., the GLib Object System or the Boehm garbage collector).

Relations to other languages [edit]

Many later languages have borrowed directly or indirectly from C, including C++, C#, Unix's C shell, D, Go, Java, JavaScript (including transpilers), Julia, Limbo, LPC, Objective-C, Perl, PHP, Python, Ruby, Rust, Swift, Verilog and SystemVerilog (hardware description languages).^[5] These languages have drawn many of their control structures and other basic features from C. Most of them (Python being a dramatic exception) also express highly similar syntax to C, and they tend to combine the recognizable expression and statement syntax of C with underlying type systems, data models, and semantics that can be radically different.

History [edit]

Early developments [edit]

Timeline of language development

Year	C Standard[9]
1972	Birth
1978	K&R C
1989/1990	ANSI C and ISO C
1999	C99
2011	C11
2017	C17
TBD	C2x

The origin of C is closely tied to the development of the Unix operating system, originally implemented in assembly language on a PDP-7 past Dennis Ritchie and Ken Thompson, incorporating several ideas from colleagues. Eventually, they decided to port the operating arrangement to a PDP-11. The original PDP-xi version of Unix was also developed in associates linguistic communication.^[6]

B [edit]

Thompson desired a programming linguistic communication to make utilities for the new platform. At first, he tried to make a Fortran compiler, but before long gave upward the thought. Instead, he created a cut-down version of the recently developed BCPL systems programming language. The official clarification of BCPL was not available at the time,^[11] and Thompson modified the syntax to be less wordy, and similar to a simplified ALGOL known as SMALGOL.^[12] The outcome was what Thompson called B.^[6] He described B as "BCPL semantics with a lot of SMALGOL syntax".^[12] Like BCPL, B had a bootstrapping compiler to facilitate porting to new machines.^[12] However, few utilities were ultimately written in B because information technology was too tiresome, and could not take advantage of PDP-xi features such equally byte addressability.

New B and outset C release [edit]

In 1971, Ritchie started to improve B, to utilise the features of the more-powerful PDP-11. A significant add-on was a grapheme type. He chosen this New B.^[12] Thompson started to employ NB to write the Unix kernel, and his requirements shaped the direction of the language development.^{[12] [xiii]} Through to 1972, richer types were added to the NB linguistic communication: NB had arrays of int and char; simply and so were added pointers, ability to generate pointers to other types, arrays of all of these, types to be returned from functions. Arrays within expressions became pointers. A new compiler was written, and the language was renamed to C. ^[six]

The C compiler and some utilities fabricated with information technology were included in Version 2 Unix.^[14]

Structures and the Unix kernel re-write [edit]

At Version 4 Unix, released in November 1973, the Unix kernel was extensively re-implemented in C.^[vi] By this time, the C linguistic communication had caused some powerful features such equally struct types.

The preprocessor was introduced around 1973 at the urging of Alan Snyder 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, generally past Mike Lesk and and then by John Reiser, to incorporate macros with arguments and conditional compilation.^[6]

Unix was one of the first operating system kernels implemented in a language other than assembly. Before instances include the Multics system (which was written in PL/I) and Master Control Programme (MCP) for the Burroughs B5000 (which was written in ALGOL) in 1961. In effectually 1977, Ritchie and Stephen C. Johnson made further changes to the language to facilitate portability of the Unix operating organization. Johnson's Portable C Compiler served every bit the basis for several implementations of C on new platforms.^[13]

K&R C [edit]

In 1978, Brian Kernighan and Dennis Ritchie published the first edition of The C Programming Language.^[i] This book, known to C programmers as K&R, served for many years as an breezy specification of the language. The version of C that it describes is ordinarily referred to equally "Thousand&R C". As this was released in 1978, it is also referred to equally C78.^[15] The second edition of the book^[16] covers the later ANSI C standard, described beneath.

Grand&R introduced several language features:

• Standard I/O library
• long int information 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 past constructs such as i=-10, which had been interpreted as i =- 10 (decrement i by ten) instead of the possibly intended i = -10 (let i be −x).

Even after the publication of the 1989 ANSI standard, for many years Thou&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 even so in use, and because advisedly written K&R C code can be legal Standard C as well.

In early versions of C, only functions that return types other than int must exist declared if used before the role definition; functions used without prior annunciation were presumed to return type int.

For instance:

                        long                                    some_function            ();                        /* int */                                    other_function            ();                        /* int */                                    calling_function            ()                        {                                                long                                    test1            ;                                                register                                    /* int */                                    test2            ;                                                test1                                    =                                    some_function            ();                                                if                                    (            test1                                    >                                    ane            )                                                test2                                    =                                    0            ;                                                else                                                test2                                    =                                    other_function            ();                                                return                                    test2            ;                        }                      

The int type specifiers which are commented out could be omitted in G&R C, merely are required in afterward standards.

Since K&R office declarations did not include any data about function arguments, function parameter type checks were not performed, although some compilers would issue a warning message if a local function was chosen with the wrong number of arguments, or if multiple calls to an external function used unlike numbers or types of arguments. Split tools such as Unix's lint utility were developed that (amongst other things) could check for consistency of part utilise across multiple source files.

In the years following the publication of K&R C, several features were added to the language, supported past compilers from AT&T (in particular PCC^[17]) and another vendors. These included:

• void functions (i.eastward., functions with no return value)
• functions returning struct or union types (rather than pointers)
• consignment for struct data types
• enumerated types

The big number of extensions and lack of agreement on a standard library, together with the language popularity and the fact that not even the Unix compilers precisely implemented the K&R specification, led to the necessity of standardization.^{[ citation needed ]}

ANSI C and ISO C [edit]

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 American National Standards Institute (ANSI) formed a committee, X3J11, to found a standard specification of C. X3J11 based the C standard on the Unix implementation; however, the non-portable portion of the Unix C library was handed off to the IEEE working grouping 1003 to go the ground 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 referred to every bit ANSI C, Standard C, or sometimes C89.

In 1990, the ANSI C standard (with formatting changes) was adopted by the International Arrangement for Standardization (ISO) equally 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, maintained by the working group ISO/IEC JTC1/SC22/WG14. National adoption of an update to the international standard typically occurs within a year of ISO publication.

1 of the aims of the C standardization procedure was to produce a superset of K&R C, incorporating many of the later introduced unofficial features. The standards committee likewise included several additional features such equally role prototypes (borrowed from C++), void pointers, support for international character sets and locales, and preprocessor enhancements. Although the syntax for parameter declarations was augmented to include the mode used in C++, the K&R interface continued to be permitted, for compatibility with existing source lawmaking.

C89 is supported past current C compilers, and almost modern C code is based on it. Any program written only in Standard C and without any hardware-dependent assumptions volition run correctly on any platform with a conforming C implementation, within its resource limits. Without such precautions, programs may compile only on a certain platform or with a detail 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 exist compilable by either standard-befitting or K&R C-based compilers, the __STDC__ macro tin can be used to split up the code into Standard and K&R sections to foreclose the utilise on a M&R C-based compiler of features available only in Standard C.

Afterward the ANSI/ISO standardization procedure, the C language specification remained relatively static for several years. In 1995, Normative Subpoena 1 to the 1990 C standard (ISO/IEC 9899/AMD1:1995, known informally as C95) was published, to correct some details and to add more extensive support for international character sets.^[18]

C99 [edit]

Main commodity: C99

The C standard was further revised in 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 3 times by Technical Corrigenda.^[19]

C99 introduced several new features, including inline functions, several new data types (including long long int and a circuitous type to stand for complex numbers), variable-length arrays and flexible array members, improved support for IEEE 754 floating point, back up for variadic macros (macros of variable arity), and back up for i-line comments starting time with //, every bit in BCPL or C++. Many of these had already been implemented equally 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 a blazon specifier no longer has int implicitly assumed. A standard macro __STDC_VERSION__ is defined with value 199901L to betoken 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.^{[20] [ needs update ]}

In addition, back up for Unicode identifiers (variable / office names) in the class of escaped characters (east.g. \U0001f431) is at present required. Support for raw Unicode names is optional.

C11 [edit]

In 2007, work began on another revision of the C standard, informally called "C1X" until its official publication on 2011-12-08. The C standards commission adopted guidelines to limit the adoption of new features that had not been tested past existing implementations.

The C11 standard adds numerous new features to C and the library, including type generic macros, anonymous structures, improved Unicode back up, diminutive operations, multi-threading, and premises-checked functions. It too makes some portions of the existing C99 library optional, and improves compatibility with C++. The standard macro __STDC_VERSION__ is defined as 201112L to betoken that C11 support is available.

C17 [edit]

Published in June 2018, C17 is the current standard for the C programming linguistic communication. It introduces no new language features, only technical corrections, and clarifications to defects in C11. The standard macro __STDC_VERSION__ is divers every bit 201710L.

C2x [edit]

Primary article: C2x

C2x is an informal proper noun for the next (subsequently C17) major C language standard revision. It is expected to be voted on in 2023 and would therefore be chosen C23.^{[21] [ better source needed ]}

Embedded C [edit]

Historically, embedded C programming requires nonstandard extensions to the C linguistic communication in order to back up exotic features such as stock-still-point arithmetic, multiple distinct memory banks, and basic I/O operations.

In 2008, the C Standards Committee published a technical report extending the C linguistic communication^[22] to address these bug by providing a common standard for all implementations to attach to. It includes a number of features not available in normal C, such as fixed-point arithmetics, named address spaces, and basic I/O hardware addressing.

Syntax [edit]

C has a formal grammar specified by the C standard.^[23] Line endings are generally not significant in C; however, line boundaries do accept significance during the preprocessing phase. Comments may announced either between the delimiters /* and */, or (since C99) following // until the stop of the line. Comments delimited past /* and */ do not nest, and these sequences of characters are not interpreted as annotate delimiters if they appear inside string or character literals.^[24]

C source files contain declarations and function definitions. Office definitions, in turn, incorporate declarations and statements. Declarations either define new types using keywords such equally struct, marriage, and enum, or assign types to and perhaps reserve storage for new variables, unremarkably by writing the blazon followed past the variable proper noun. Keywords such as char and int specify born types. Sections of lawmaking are enclosed in braces ({ and }, sometimes called "curly brackets") to limit the scope of declarations and to act as a single statement for control structures.

As an imperative linguistic communication, C uses statements to specify actions. The nigh mutual statement is an expression statement, consisting of an expression to exist evaluated, followed by a semicolon; as a side outcome of the evaluation, functions may exist chosen and variables may exist assigned new values. To modify the normal sequential execution of statements, C provides several command-catamenia statements identified past reserved keywords. Structured programming is supported by if … [else] provisional execution and by do … while, while, and for iterative execution (looping). The for argument has divide initialization, testing, and reinitialization expressions, any or all of which can be omitted. suspension and proceed tin can exist used to leave the innermost enclosing loop statement or skip to its reinitialization. In that location is besides 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.

Expressions can employ a variety of congenital-in operators and may contain function calls. The guild 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 expression argument, and the entry to and return from each function phone call. Sequence points as well occur during evaluation of expressions containing certain operators (&&, ||, ?: and the comma operator). This permits a high degree of object code optimization past the compiler, but requires C programmers to take more than care to obtain reliable results than is needed for other programming languages.

Kernighan and Ritchie say in the Introduction of The C Programming Language: "C, like any other language, has its blemishes. Some of the operators have the wrong precedence; some parts of the syntax could be better."^[25] The C standard did not attempt to right many of these blemishes, because of the impact of such changes on already existing software.

Character set [edit]

The basic C source character set includes the following characters:

• Lowercase and uppercase letters of ISO Bones Latin Alphabet: a–z A–Z
• Decimal digits: 0–9
• Graphic characters: ! " # % & ' ( ) * + , - . / : ; < = > ? [ \ ] ^ _ { | } ~
• Whitespace characters: infinite, horizontal tab, vertical tab, form feed, newline

Newline indicates the end of a text line; information technology demand not stand for to an actual single character, although for convenience C treats it as one.

Boosted multi-byte encoded characters may be used in string literals, just they are non entirely portable. The latest C standard (C11) allows multi-national Unicode characters to be embedded portably inside C source text by using \uXXXX or \UXXXXXXXX encoding (where the X denotes a hexadecimal grapheme), although this feature is not still widely implemented.

The basic C execution grapheme set contains the same characters, forth with representations for alert, backspace, and railroad vehicle return. Run-fourth dimension support for extended character sets has increased with each revision of the C standard.

Reserved words [edit]

C89 has 32 reserved words, also known every bit keywords, which are the words that cannot be used for any purposes other than those for which they are predefined:

• auto
• break
• case
• char
• const
• continue
• default
• practice
• double
• else
• enum
• extern
• float
• for
• goto
• if
• int
• long
• register
• return
• short
• signed
• sizeof
• static
• struct
• switch
• typedef
• union
• unsigned
• void
• volatile
• while

C99 reserved five more words:

• _Bool
• _Complex
• _Imaginary
• inline
• restrict

C11 reserved seven more words:^[26]

• _Alignas
• _Alignof
• _Atomic
• _Generic
• _Noreturn
• _Static_assert
• _Thread_local

Most of the recently reserved words begin with an underscore followed by a uppercase letter, considering identifiers of that form were previously reserved past the C standard for use merely by implementations. Since existing program source code should not have been using these identifiers, it would non be afflicted when C implementations started supporting these extensions to the programming language. Some standard headers practice define more user-friendly synonyms for underscored identifiers. The language previously included a reserved give-and-take called entry, merely this was seldom implemented, and has at present been removed as a reserved discussion.^[27]

Operators [edit]

C supports a rich fix of operators, which are symbols used within an expression to specify the manipulations to exist performed while evaluating that expression. C has operators for:

• arithmetic: +, -, *, /, %
• consignment: =
• augmented assignment: +=, -=, *=, /=, %=, &=, |=, ^=, <<=, >>=
• bitwise logic: ~, &, |, ^
• bitwise shifts: <<, >>
• boolean logic: !, &&, ||
• provisional evaluation: ? :
• equality testing: ==, !=
• calling functions: ( )
• increment and decrement: ++, --
• fellow member choice: ., ->
• object size: sizeof
• order relations: <, <=, >, >=
• reference and dereference: &, *, [ ]
• sequencing: ,
• subexpression grouping: ( )
• type conversion: (typename)

C uses the operator = (used in mathematics to express equality) to indicate consignment, following the precedent of Fortran and PL/I, but unlike ALGOL and its derivatives. C uses the operator == to test for equality. The similarity between these ii operators (assignment and equality) may result in the accidental use of one in identify of the other, and in many cases, the error does non produce an error message (although some compilers produce warnings). For example, the conditional expression if (a == b + 1) might mistakenly exist written as if (a = b + ane), which will be evaluated as true if a is non zippo after the assignment.^[28]

The C operator precedence is non always intuitive. For instance, the operator == binds more tightly than (is executed prior to) the operators & (bitwise AND) and | (bitwise OR) in expressions such as ten & ane == 0, which must exist written as (x & ane) == 0 if that is the coder'south intent.^[29]

"Hello, globe" instance [edit]

The "hi, world" instance, which appeared in the commencement edition of K&R, has go the model for an introductory program in well-nigh programming textbooks. The programme prints "hello, world" to the standard output, which is usually a final or screen display.

The original version was:^[30]

                        master            ()                        {                                                printf            (            "hello, world            \northward            "            );                        }                      

A standard-conforming "hello, earth" program is:^[a]

                        #include                                    <stdio.h>                        int                                    main            (            void            )                        {                                                printf            (            "hi, earth            \due north            "            );                        }                      

The get-go line of the plan contains a preprocessing directive, indicated past #include. This causes the compiler to replace that line with the entire text of the stdio.h standard header, which contains declarations for standard input and output functions such every bit printf and scanf. The angle brackets surrounding stdio.h indicate that stdio.h is located using a search strategy that prefers headers provided with the compiler to other headers having the same proper name, as opposed to double quotes which typically include local or project-specific header files.

The next line indicates that a function named main is beingness defined. The main function serves a special purpose in C programs; the run-time environment calls the main function to begin program execution. The blazon specifier int indicates that the value that is returned to the invoker (in this case the run-time environs) as a result of evaluating the main function, is an integer. The keyword void as a parameter list indicates that this function takes no arguments.^[b]

The opening curly brace indicates the beginning of the definition of the principal function.

The next line calls (diverts execution to) a function named printf, which in this example is supplied from a system library. In this call, the printf part is passed (provided with) a single argument, the address of the first character in the string literal "hello, globe\n". The cord literal is an unnamed assortment with elements of type char, prepare automatically by the compiler with a final 0-valued grapheme to mark the terminate of the assortment (printf needs to know this). The \northward is an escape sequence that C translates to a newline grapheme, which on output signifies the terminate of the electric current line. The return value of the printf role is of type int, but it is silently discarded since it is non used. (A more conscientious program might test the return value to determine whether or not the printf function succeeded.) The semicolon ; terminates the statement.

The endmost curly caryatid indicates the end of the lawmaking for the main function. Co-ordinate to the C99 specification and newer, the main function, unlike whatsoever other role, will implicitly return a value of 0 upon reaching the } that terminates the function. (Formerly an explicit return 0; statement was required.) This is interpreted by the run-fourth dimension system as an exit lawmaking indicating successful execution.^[31]

Data types [edit]

The type system in C is static and weakly typed, which makes it like to the type system of ALGOL descendants such as Pascal.^[32] In that location are born types for integers of diverse sizes, both signed and unsigned, floating-point numbers, and enumerated types (enum). Integer type char is often used for single-byte characters. C99 added a boolean datatype. In that location are also derived types including arrays, pointers, records (struct), and unions (spousal relationship).

C is oftentimes used in low-level systems programming where escapes from the type organization may be necessary. The compiler attempts to ensure type definiteness of most expressions, merely the programmer can override the checks in various means, either by using a blazon bandage to explicitly convert a value from one type to another, or by using pointers or unions to reinterpret the underlying $.25 of a data object in some other way.

Some find C'south announcement syntax unintuitive, particularly for function pointers. (Ritchie's thought was to declare identifiers in contexts resembling their use: "declaration reflects utilize".)^[33]

C's usual arithmetic conversions allow for efficient lawmaking to be generated, merely can sometimes produce unexpected results. For example, a comparison of signed and unsigned integers of equal width requires a conversion of the signed value to unsigned. This can generate unexpected results if the signed value is negative.

Pointers [edit]

C supports the utilise of pointers, a type of reference that records the accost or location of an object or function in retention. Pointers tin be dereferenced to admission data stored at the accost pointed to, or to invoke a pointed-to function. Pointers can be manipulated using consignment or pointer arithmetics. The run-time representation of a pointer value is typically a raw memory accost (peradventure augmented by an first-within-give-and-take field), but since a pointer'south type includes the blazon of the thing pointed to, expressions including pointers tin be blazon-checked at compile time. Pointer arithmetics is automatically scaled by the size of the pointed-to data blazon. Pointers are used for many purposes in C. Text strings are commonly manipulated using pointers into arrays of characters. Dynamic retention allotment is performed using pointers. Many information types, such every bit copse, are commonly implemented as dynamically allocated struct objects linked together using pointers. Pointers to functions are useful for passing functions every bit arguments to higher-order functions (such equally qsort or bsearch) or as callbacks to be invoked by event handlers.^[31]

A null pointer value explicitly points to no valid location. Dereferencing a null pointer value is undefined, often resulting in a segmentation fault. Null pointer values are useful for indicating special cases such as no "next" pointer in the final node of a linked list, or as an error indication from functions returning pointers. In advisable contexts in source code, such as for assigning to a pointer variable, a zilch pointer constant can be written as 0, with or without explicit casting to a pointer type, or every bit the NULL macro defined by several standard headers. In conditional contexts, null pointer values evaluate to false, while all other pointer values evaluate to truthful.

Void pointers (void *) indicate to objects of unspecified type, and tin therefore exist used as "generic" data pointers. Since the size and type of the pointed-to object is not known, void pointers cannot be dereferenced, nor is pointer arithmetic on them immune, although they can easily exist (and in many contexts implicitly are) converted to and from any other object pointer type.^[31]

Careless apply of pointers is potentially dangerous. Considering they are typically unchecked, a pointer variable can exist made to bespeak to whatever arbitrary location, which can crusade undesirable effects. Although properly used pointers point to rubber places, they tin exist made to point to unsafe places past using invalid arrow arithmetic; the objects they point to may continue to be used later deallocation (dangling pointers); they may be used without having been initialized (wild pointers); or they may be straight assigned an unsafe value using a cast, matrimony, or through another corrupt pointer. In general, C is permissive in allowing manipulation of and conversion between arrow types, although compilers typically provide options for various levels of checking. Some other programming languages address these problems past using more restrictive reference types.

Arrays [edit]

Assortment types in C are traditionally of a fixed, static size specified at compile fourth dimension. The more recent C99 standard besides allows a course of variable-length arrays. Withal, it is also possible to classify a cake of retentiveness (of arbitrary size) at run-time, using the standard library's malloc role, and treat it every bit an array.

Since arrays are always accessed (in event) via pointers, array accesses are typically not checked confronting the underlying array size, although some compilers may provide bounds checking every bit an choice.^{[34] [35]} Assortment premises violations are therefore possible and can lead to diverse repercussions, including illegal memory accesses, corruption of information, buffer overruns, and run-fourth dimension exceptions.

C does non take a special provision for declaring multi-dimensional arrays, but rather relies on recursion within the type system to declare arrays of arrays, which effectively accomplishes the same matter. The index values of the resulting "multi-dimensional array" can exist idea of as increasing in row-major society. Multi-dimensional arrays are normally used in numerical algorithms (mainly from applied linear algebra) to store matrices. The structure of the C array is well suited to this particular job. Still, in early versions of C the bounds of the array must exist known fixed values or else explicitly passed to whatever subroutine that requires them, and dynamically sized arrays of arrays cannot be accessed using double indexing. (A workaround for this was to classify the array with an additional "row vector" of pointers to the columns.) C99 introduced "variable-length arrays" which address this issue.

The post-obit example using modern C (C99 or later) shows allocation of a ii-dimensional array on the heap and the utilize of multi-dimensional array indexing for accesses (which can use bounds-checking on many C compilers):

                        int                                    func            (            int                                    North            ,                                    int                                    M            )                        {                                                float                                    (            *            p            )[            N            ][            K            ]                                    =                                    malloc            (            sizeof                                    *            p            );                                                if                                    (            !            p            )                                                return                                    -1            ;                                                for                                    (            int                                    i                                    =                                    0            ;                                    i                                    <                                    Due north            ;                                    i            ++            )                                                for                                    (            int                                    j                                    =                                    0            ;                                    j                                    <                                    Grand            ;                                    j            ++            )                                                (            *            p            )[            i            ][            j            ]                                    =                                    i                                    +                                    j            ;                                                print_array            (            Due north            ,                                    M            ,                                    p            );                                                gratis            (            p            );                                                render                                    1            ;                        }                      

And hither is a like implementation using C99'southward Auto VLA characteristic:

                        int                                    func            (            int                                    North            ,                                    int                                    Grand            )                        {                                                // Caution: checks should exist made to ensure N*M*sizeof(float) does Not exceed limitations for motorcar VLAs and is within available size of stack.                                    float                                    p            [            N            ][            M            ];                                    // auto VLA is held on the stack, and sized when the office is invoked                                    for                                    (            int                                    i                                    =                                    0            ;                                    i                                    <                                    N            ;                                    i            ++            )                                                for                                    (            int                                    j                                    =                                    0            ;                                    j                                    <                                    One thousand            ;                                    j            ++            )                                                p            [            i            ][            j            ]                                    =                                    i                                    +                                    j            ;                                                // no need to gratis(p) since it volition disappear when the function exits, along with the rest of the stack frame                                    return                                    1            ;                        }                      

Array–arrow interchangeability [edit]

The subscript notation x[i] (where x designates a pointer) is syntactic sugar for *(x+i).^[36] Taking advantage of the compiler's knowledge of the arrow type, the accost that x + i points to is not the base address (pointed to by x) incremented by i bytes, but rather is defined to be the base address incremented by i multiplied by the size of an chemical element that 10 points to. Thus, x[i] designates the i+1th element of the array.

Furthermore, in well-nigh expression contexts (a notable exception is as operand of sizeof), an expression of assortment type is automatically converted to a pointer to the assortment's first chemical element. This implies that an array is never copied as a whole when named equally an argument to a office, just rather only the address of its first chemical element is passed. Therefore, although part calls in C employ pass-by-value semantics, arrays are in result passed by reference.

The total size of an array x tin be adamant by applying sizeof to an expression of array blazon. The size of an element tin can be determined by applying the operator sizeof to any dereferenced element of an array A, as in northward = sizeof A[0]. This, the number of elements in a declared array A can exist determined as sizeof A / sizeof A[0]. Note, that if only a arrow to the outset element is available as information technology is often the case in C code considering of the automatic conversion described to a higher place, the information about the full type of the array and its length are lost.

Retentiveness management [edit]

Ane of the most important functions of a programming linguistic communication is to provide facilities for managing memory and the objects that are stored in retentivity. C provides three main ways to classify retention for objects:^[31]

• Static memory allocation: space for the object is provided in the binary at compile-time; these objects have an extent (or lifetime) every bit long equally the binary which contains them is loaded into retention.
• Automatic retention allocation: temporary objects tin exist stored on the stack, and this space is automatically freed and reusable after the block in which they are declared is exited.
• Dynamic memory allocation: blocks of memory of capricious size can be requested at run-time using library functions such as malloc from a region of memory called the heap; these blocks persist until later freed for reuse by calling the library role realloc or free

These three approaches are appropriate in different situations and have various trade-offs. For case, static memory resource allotment has lilliputian allocation overhead, automatic allocation may involve slightly more overhead, and dynamic memory allocation tin can potentially have a corking deal of overhead for both allocation and deallocation. The persistent nature of static objects is useful for maintaining country information across function calls, automatic allocation is piece of cake to use but stack space is typically much more than limited and transient than either static retentiveness or heap space, and dynamic retention resource allotment allows user-friendly allocation of objects whose size is known just at run-fourth dimension. Most C programs make extensive use of all three.

Where possible, automated or static allocation is normally simplest considering the storage is managed by the compiler, freeing the programmer of the potentially error-prone task of manually allocating and releasing storage. However, many data structures can change in size at runtime, and since static allocations (and automatic allocations earlier C99) must have a stock-still size at compile-time, in that location are many situations in which dynamic allocation is necessary.^[31] Prior to the C99 standard, variable-sized arrays were a mutual example of this. (See the article on malloc for an case of dynamically allocated arrays.) Unlike automated allocation, which tin fail at run time with uncontrolled consequences, the dynamic allocation functions return an indication (in the form of a zilch pointer value) when the required storage cannot exist allocated. (Static allocation that is as well large is usually detected by the linker or loader, before the program can even brainstorm execution.)

Unless otherwise specified, static objects incorporate zero or zippo pointer values upon programme startup. Automatically and dynamically allocated objects are initialized only if an initial value is explicitly specified; otherwise they initially have indeterminate values (typically, whatever fleck blueprint happens to exist present in the storage, which might not even correspond a valid value for that type). If the program attempts to access an uninitialized value, the results are undefined. Many modern compilers attempt to detect and warn about this trouble, but both simulated positives and false negatives can occur.

Heap memory allocation has to be synchronized with its actual usage in whatever program to exist reused equally much as possible. For example, if the only pointer to a heap memory resource allotment goes out of scope or has its value overwritten earlier it is deallocated explicitly, then that retention cannot be recovered for afterwards reuse and is essentially lost to the program, a phenomenon known every bit a retentivity leak. Conversely, it is possible for memory to be freed, but is referenced subsequently, leading to unpredictable results. Typically, the failure symptoms appear in a portion of the program unrelated to the code that causes the error, making it difficult to diagnose the failure. Such bug are ameliorated in languages with automatic garbage drove.

Libraries [edit]

The C programming linguistic communication uses libraries equally its chief method of extension. In C, a library is a prepare of functions independent within a single "annal" file. Each library typically has a header file, which contains the prototypes of the functions contained inside the library that may exist used by a program, and declarations of special data types and macro symbols used with these functions. In order for a plan to use a library, information technology must include the library'southward header file, and the library must be linked with the program, which in many cases requires compiler flags (e.g., -lm, autograph for "link the math library").^[31]

The most common C library is the C standard library, which is specified past the ISO and ANSI C standards and comes with every C implementation (implementations which target express environments such as embedded systems may provide only a subset of the standard library). This library supports stream input and output, memory allocation, mathematics, character strings, and time values. Several separate standard headers (for example, stdio.h) specify the interfaces for these and other standard library facilities.

Some other mutual set of C library functions are those used past applications specifically targeted for Unix and Unix-like systems, especially functions which provide an interface to the kernel. These functions are detailed in diverse standards such as POSIX and the Single UNIX Specification.

Since many programs have been written in C, in that location are a wide multifariousness of other libraries available. Libraries are often written in C because C compilers generate efficient object code; programmers and then create interfaces to the library then that the routines tin be used from college-level languages like Coffee, Perl, and Python.^[31]

File handling and streams [edit]

File input and output (I/O) is non part of the C language itself but instead is handled by libraries (such as the C standard library) and their associated header files (e.g. stdio.h). File handling is more often than not implemented through high-level I/O which works through streams. A stream is from this perspective a data period that is independent of devices, while a file is a concrete device. The high-level I/O is done through the clan of a stream to a file. In the C standard library, a buffer (a memory area or queue) is temporarily used to store information before it'southward sent to the final destination. This reduces the time spent waiting for slower devices, for example a hard drive or solid state drive. Low-level I/O functions are not part of the standard C library^{[ description needed ]} only are by and large role of "bare metal" programming (programming that'due south independent of any operating system such every bit virtually embedded programming). With few exceptions, implementations include low-level I/O.

Language tools [edit]

A number of tools accept been developed to assist C programmers observe and prepare statements with undefined behavior or possibly erroneous expressions, with greater rigor than that provided by the compiler. The tool lint was the first such, leading to many others.

Automated source code checking and auditing are beneficial in any language, and for C many such tools exist, such as Lint. A common practice is to utilise Lint to find questionable code when a program is first written. Once a program passes Lint, it is then compiled using the C compiler. Also, many compilers can optionally warn almost syntactically valid constructs that are likely to actually be errors. MISRA C is a proprietary set of guidelines to avoid such questionable code, developed for embedded systems.^[37]

There are as well compilers, libraries, and operating system level mechanisms for performing actions that are not a standard function of C, such every bit bounds checking for arrays, detection of buffer overflow, serialization, dynamic memory tracking, and automatic garbage collection.

Tools such as Purify or Valgrind and linking with libraries containing special versions of the retentivity allocation functions can assist uncover runtime errors in retentivity usage.

Uses [edit]

The C Programming Language

C is widely used for systems programming in implementing operating systems and embedded system applications.^[38] This is for several reasons:

• The code generated subsequently compilation doesn't demand many system features, and tin can be invoked from some boot code in a straightforward manner - information technology's simple to execute.
• The C language statements and expressions typically map well on to sequences of instructions for the target processor, and consequently in that location is a low run-time demand on system resource - it'due south fast to execute.
• The linguistic communication makes it easy to overlay structures onto blocks of binary information, assuasive the information to exist comprehended, navigated and modified - it can write data structures, even file systems.
• The language supports a rich set of operators, including chip manipulation, for integer arithmetic and logic, and perhaps dissimilar sizes of floating point numbers - it can process appropriately-structured data finer.
• Platform hardware tin can be accessed with pointers and type punning, so system-specific features (e.g. Control/Status Registers, I/O registers) tin be configured and used with code written in C - it interacts well with the platform information technology's running on.
• Depending on the linker and surroundings, C code can also phone call libraries written in assembly linguistic communication, and may be called from assembly language - it interoperates well with other code.
• C has a very mature and broad ecosystem, including open source compilers, debuggers and utilities, and is the de-facto standard. It'southward probable the drivers already exist in C, or that there is a similar CPU architecture as a back-end of a C compiler, so at that place is reduced incentive to choose another linguistic communication.

Historically, C was sometimes used for web development using the Common Gateway Interface (CGI) as a "gateway" for information between the web application, the server, and the browser.^[39] C may have been called over interpreted languages because of its speed, stability, and near-universal availability.^[forty] It is no longer common practice for spider web development to be done in C,^[41] and many other web development tools exist.

A consequence of C'southward wide availability and efficiency is that compilers, libraries and interpreters of other programming languages are often implemented in C. For example, the reference implementations of Python, Perl, Ruby, and PHP are written in C.

C enables programmers to create efficient implementations of algorithms and data structures, considering the layer of abstraction from hardware is thin, and its overhead is low, an important criterion for computationally intensive programs. For example, the GNU Multiple Precision Arithmetic Library, the GNU Scientific Library, Mathematica, and MATLAB are completely or partially written in C. Many languages support calling library functions in C, for example, the Python-based framework NumPy uses C for the loftier-performance and hardware-interacting aspects.

C is sometimes used as an intermediate language by implementations of other languages. This approach may exist used for portability or convenience; by using C as an intermediate language, additional machine-specific code generators are non necessary. C has some features, such as line-number preprocessor directives and optional superfluous commas at the end of initializer lists, that back up compilation of generated code. However, some of C's shortcomings have prompted the evolution of other C-based languages specifically designed for employ as intermediate languages, such as C--.

C has also been widely used to implement end-user applications.^{[ citation needed ]} Even so, such applications tin likewise be written in newer, higher-level languages.

Limitations [edit]

While C has been pop, influential and hugely successful, it has drawbacks, including:

• The standard dynamic memory treatment with malloc and gratis is error prone. Bugs include: Retention leaks when retentivity is allocated but not freed; and admission to previously-freed memory.
• The use of pointers and the direct manipulation of memory means corruption of memory is possible, perhaps due to programmer error, or insufficient checking of bad data.
• Since the code generated by the compiler contains few checks itself, there is a burden on the developer to consider all possible outcomes, and protect against buffer overruns, array premises checking, stack overflows, memory exhaustion, race conditions, thread isolation, etc.
• The utilise of pointers and the run-fourth dimension manipulation of these means there may be 2 ways to access the same data (aliasing), which is not determinable at compile fourth dimension. This means that some optimisations that may be available to other languages are non possible in C. FORTRAN is considered faster.
• Some of the standard library functions, e.g. scanf, can lead to buffer overruns.
• There is limited standardisation in back up for low-level variants in generated code, for case: unlike function calling conventions; dissimilar construction packing conventions; different byte ordering within larger integers (including endianness). In many language implementations, some of these options may exist handled with the preprocessor directive #pragma,^[42] and some with additional keywords e.yard. use __cdecl calling convention. But the directive and options are not consistently supported.^[43]
• The linguistic communication does not directly support object orientation, introspection, run-time expression evaluation, generics, exceptions.
• At that place are few guards against inappropriate apply of language features, which may lead to unmaintainable code.

For some purposes, restricted styles of C have been adopted, due east.g. MISRA C, in an endeavor to reduce the opportunity for bugs. There are tools that can mitigate against some of these drawbacks. Some of these drawbacks accept prompted the construction of other languages.

[edit]

The TIOBE alphabetize graph, showing a comparing of the popularity of various programming languages^[44]

C has both directly and indirectly influenced many later languages such equally C#, D, Go, Java, JavaScript, Limbo, LPC, Perl, PHP, Python, and Unix'south C trounce.^[45] The well-nigh pervasive influence has been syntactical; all of the languages mentioned combine the argument and (more or less recognizably) expression syntax of C with type systems, data models, and/or large-scale plan structures that differ from those of C, sometimes radically.

Several C or near-C interpreters be, including Ch and CINT, which can also exist used for scripting.

When object-oriented programming languages became popular, C++ and Objective-C were two different extensions of C that provided object-oriented capabilities. Both languages were originally implemented equally source-to-source compilers; source code was translated into C, and so compiled with a C compiler.^[46]

The C++ programming language (originally named "C with Classes") was devised past Bjarne Stroustrup as an approach to providing object-oriented functionality with a C-like syntax.^[47] C++ adds greater typing strength, scoping, and other tools useful in object-oriented programming, and permits generic programming via templates. Nearly a superset of C, C++ now supports most of C, with a few exceptions.

Objective-C was originally a very "thin" layer on acme of C, and remains a strict superset of C that permits object-oriented programming using a hybrid dynamic/static typing prototype. Objective-C derives its syntax from both C and Smalltalk: syntax that involves preprocessing, expressions, function declarations, and function calls is inherited from C, while the syntax for object-oriented features was originally taken from Smalltalk.

In improver to C++ and Objective-C, Ch, Cilk, and Unified Parallel C are nearly supersets of C.

Run across also [edit]

• Compatibility of C and C++
• Comparing of Pascal and C
• Comparing of programming languages
• International Obfuscated C Code Competition
• List of C-based programming languages
• List of C compilers

Notes [edit]

1. ^ The original example lawmaking will compile on about modernistic compilers that are not in strict standard compliance style, but it does not fully arrange to the requirements of either C89 or C99. In fact, C99 requires that a diagnostic message be produced.
2. ^ The principal role really has two arguments, int argc and char *argv[], respectively, which can be used to handle command line arguments. The ISO C standard (department v.one.ii.ii.1) requires both forms of main to be supported, which is special treatment non afforded to any other function.

References [edit]

1. ^ ^{a b} Kernighan, Brian W.; Ritchie, Dennis M. (Feb 1978). The C Programming Language (1st ed.). Englewood Cliffs, NJ: Prentice Hall. ISBN978-0-xiii-110163-0.
2. ^ Ritchie (1993): "Thompson had fabricated a brief attempt to produce a organisation coded in an early on version of C—before structures—in 1972, simply gave up the effort."
3. ^ Fruderica (December 13, 2020). "History of C". The cppreference.com. Archived from the original on October 24, 2020. Retrieved October 24, 2020.
4. ^ Ritchie (1993): "The scheme of blazon limerick adopted by C owes considerable debt to Algol 68, although information technology did not, possibly, sally in a form that Algol'due south adherents would approve of."
5. ^ ^{a b} "Verilog HDL (and C)" (PDF). The Inquiry School of Calculator Science at the Australian National Academy. June 3, 2010. Archived from the original (PDF) on November 6, 2013. Retrieved August 19, 2013. 1980s: ; Verilog starting time introduced ; Verilog inspired past the C programming language
6. ^ ^{a b c d east f} Ritchie (1993)
7. ^ "Programming Linguistic communication Popularity". 2009. Archived from the original on January 16, 2009. Retrieved January 16, 2009.
8. ^ "TIOBE Programming Community Alphabetize". 2009. Archived from the original on May 4, 2009. Retrieved May half-dozen, 2009.
9. ^ ^{a b} "History of C". en.cppreference.com. Archived from the original on May 29, 2018. Retrieved May 28, 2018.
10. ^ "TIOBE Index for October 2021". Retrieved October seven, 2021.
11. ^ Ritchie, Dennis. "BCPL to B to C". Archived from the original on December 12, 2019. Retrieved September 10, 2019.
12. ^ ^{a b c d e} Jensen, Richard (December 9, 2020). ""A damn stupid thing to practise"—the origins of C". Ars Technica . Retrieved March 28, 2022.
13. ^ ^{a b} Johnson, South. C.; Ritchie, D. M. (1978). "Portability of C Programs and the UNIX Organization". Bong System Tech. J. 57 (6): 2021–2048. CiteSeerXx.1.1.138.35. doi:10.1002/j.1538-7305.1978.tb02141.x. S2CID 17510065. (Annotation: The PDF is an OCR scan of the original, and contains a rendering of "IBM 370" as "IBM 310".)
14. ^ McIlroy, 1000. D. (1987). A Research Unix reader: annotated excerpts from the Programmer'southward Manual, 1971–1986 (PDF) (Technical report). CSTR. Bong Labs. p. 10. 139. Archived (PDF) from the original on Nov 11, 2017. Retrieved Feb 1, 2015.
15. ^ "C transmission pages". FreeBSD Miscellaneous Data Manual (FreeBSD thirteen.0 ed.). May 30, 2011. Archived from the original on Jan 21, 2021. Retrieved January xv, 2021. [1] Archived January 21, 2021, at the Wayback Car
16. ^ Kernighan, Brian Westward.; Ritchie, Dennis K. (March 1988). The C Programming Language (2nd ed.). Englewood Cliffs, NJ: Prentice Hall. ISBN978-0-thirteen-110362-seven.
17. ^ Stroustrup, Bjarne (2002). Sibling rivalry: C and C++ (PDF) (Report). AT&T Labs. Archived (PDF) from the original on August 24, 2014. Retrieved April fourteen, 2014.
18. ^ C Integrity. International Organisation for Standardization. March 30, 1995. Archived from the original on July 25, 2018. Retrieved July 24, 2018.
19. ^ "JTC1/SC22/WG14 – C". Domicile page. ISO/IEC. Archived from the original on February 12, 2018. Retrieved June ii, 2011.
20. ^ Andrew Binstock (October 12, 2011). "Interview with Herb Sutter". Dr. Dobbs. Archived from the original on August two, 2013. Retrieved September 7, 2013.
21. ^ "Revised C23 Schedule WG 14 N 2759" (PDF). www.open-std.org. Archived (PDF) from the original on June 24, 2021. Retrieved October x, 2021.
22. ^ "TR 18037: Embedded C" (PDF). ISO / IEC. Archived (PDF) from the original on February 25, 2021. Retrieved July 26, 2011.
23. ^ Harbison, Samuel P.; Steele, Guy L. (2002). C: A Reference Manual (5th ed.). Englewood Cliffs, NJ: Prentice Hall. ISBN978-0-13-089592-9. Contains a BNF grammar for C.
24. ^ Kernighan & Ritchie (1996), p. 192.
25. ^ Kernighan & Ritchie (1978), p. 3.
26. ^ "ISO/IEC 9899:201x (ISO C11) Commission Draft" (PDF). Archived (PDF) from the original on December 22, 2017. Retrieved September 16, 2011.
27. ^ Kernighan & Ritchie (1996), pp. 192, 259.
28. ^ "10 Mutual Programming Mistakes in C++". Cs.ucr.edu. Archived from the original on October 21, 2008. Retrieved June 26, 2009.
29. ^ Schultz, Thomas (2004). C and the 8051 (3rd ed.). Otsego, MI: PageFree Publishing Inc. p. 20. ISBN978-i-58961-237-two. Archived from the original on July 29, 2020. Retrieved February ten, 2012.
30. ^ Kernighan & Ritchie (1978), p. 6.
31. ^ ^{a b c d e f g} Klemens, Ben (2013). 21st Century C. O'Reilly Media. ISBN978-ane-4493-2714-9.
32. ^ Feuer, Alan R.; Gehani, Narain H. (March 1982). "Comparing of the Programming Languages C and Pascal". ACM Computing Surveys. 14 (one): 73–92. doi:10.1145/356869.356872. S2CID 3136859.
33. ^ Kernighan & Ritchie (1996), p. 122.
34. ^ For example, gcc provides _FORTIFY_SOURCE. "Security Features: Compile Fourth dimension Buffer Checks (FORTIFY_SOURCE)". fedoraproject.org. Archived from the original on Jan 7, 2007. Retrieved Baronial 5, 2012.
35. ^ เอี่ยมสิริวงศ์, โอภาศ (2016). Programming with C. Bangkok, Thailand: SE-EDUCATION PUBLIC COMPANY LIMITED. pp. 225–230. ISBN978-616-08-2740-4.
36. ^ Raymond, Eric S. (October 11, 1996). The New Hacker's Dictionary (3rd ed.). MIT Press. p. 432. ISBN978-0-262-68092-9. Archived from the original on November 12, 2012. Retrieved August 5, 2012.
37. ^ "Human Folio for lint (freebsd Section ane)". unix.com. May 24, 2001. Retrieved July fifteen, 2014.
38. ^ Dale, Nell B.; Weems, Chip (2014). Programming and problem solving with C++ (6th ed.). Burlington, MA: Jones & Bartlett Learning. ISBN978-1449694289. OCLC 894992484.
39. ^ Dr. Dobb's Sourcebook. UsA.: Miller Freeman, Inc. November–December 1995.
40. ^ "Using C for CGI Programming". linuxjournal.com. March ane, 2005. Archived from the original on February 13, 2010. Retrieved January 4, 2010.
41. ^ Perkins, Luc (September 17, 2013). "Web development in C: crazy? Or crazy like a play a joke on?". Medium.
42. ^ "#pragma Directive in C/C++". GeeksforGeeks. September 11, 2018. Retrieved Apr 10, 2022.
43. ^ "Pragmas". Intel . Retrieved April ten, 2022.
44. ^ McMillan, Robert (August 1, 2013). "Is Java Losing Its Mojo?". Wired. Archived from the original on February 15, 2017. Retrieved March v, 2017.
45. ^ O'Regan, Gerard (September 24, 2015). Pillars of computing : a compendium of select, pivotal technology firms. ISBN978-3319214641. OCLC 922324121.
46. ^ Rauchwerger, Lawrence (2004). Languages and compilers for parallel computing : 16th international workshop, LCPC 2003, College Station, TX, USA, October ii-iv, 2003 : revised papers. Springer. ISBN978-3540246442. OCLC 57965544.
47. ^ Stroustrup, Bjarne (1993). "A History of C++: 1979−1991" (PDF). Archived (PDF) from the original on February 2, 2019. Retrieved June 9, 2011.

Sources [edit]

• Ritchie, Dennis M. (March 1993). "The Development of the C Linguistic communication". ACM SIGPLAN Notices. ACM. 28 (three): 201–208. doi:x.1145/155360.155580.
  • By courtesy of the author, also at Ritchie, Dennis M. "Chistory". world wide web.bell-labs.com . Retrieved March 29, 2022.
• Ritchie, Dennis 1000. (1993). "The Evolution of the C Language". The 2nd ACM SIGPLAN Conference on History of Programming Languages (HOPL-2). ACM. pp. 201–208. doi:x.1145/154766.155580. ISBN0-89791-570-4 . Retrieved November 4, 2014.
• Kernighan, Brian W.; Ritchie, Dennis M. (1996). The C Programming Language (2nd ed.). Prentice Hall. ISBN7-302-02412-X.

Farther reading [edit]

• Kernighan, Brian; Ritchie, Dennis (1988). The C Programming Language (2 ed.). Prentice Hall. ISBN978-0131103627. (archive)
• Plauger, P.J. (1992). The Standard C Library (1 ed.). Prentice Hall. ISBN978-0131315099. (source)
• Banahan, M.; Brady, D.; Doran, 1000. (1991). The C Book: Featuring the ANSI C Standard (2 ed.). Addison-Wesley. ISBN978-0201544336. (complimentary)
• Harbison, Samuel; Steele Jr, Guy (2002). C: A Reference Manual (5 ed.). Pearson. ISBN978-0130895929. (archive)
• King, K.North. (2008). C Programming: A Modern Approach (2 ed.). W. W. Norton. ISBN978-0393979503. (annal)
• Griffiths, David; Griffiths, Dawn (2012). Caput Kickoff C (one ed.). O'Reilly. ISBN978-1449399917.
• Perry, Greg; Miller, Dean (2013). C Programming: Accented Beginner's Guide (3 ed.). Que. ISBN978-0789751980.
• Deitel, Paul; Deitel, Harvey (2015). C: How to Programme (8 ed.). Pearson. ISBN978-0133976892.
• Gustedt, Jens (2019). Modernistic C (2 ed.). Manning. ISBN978-1617295812. (free)

External links [edit]

• ISO C Working Grouping official website
  • ISO/IEC 9899, publicly available official C documents, including the C99 Rationale
  • "C99 with Technical corrigenda TC1, TC2, and TC3 included" (PDF). (iii.61 MB)
• comp.lang.c Frequently Asked Questions
• A History of C, by Dennis Ritchie

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Source: https://en.wikipedia.org/wiki/C_%28programming_language%29

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