See also
- Behavioral Description Language
- Compatibility of C and C++
- C++23, C++20, C++17, C++14, C++11, C++03, C++98, versions of the C++ programming language standard
- C++ Technical Report 1
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ANSI C, ISO C, and Standard C are successive standards for the C programming language published by the American National Standards Institute (ANSI) and ISO/IEC JTC 1/SC 22/WG 14 of the International Organization for Standardization (ISO) and the International Electrotechnical Commission (IEC). Historically, the names referred specifically to the original and best-supported version of the standard (known as C89 or C90). Software developers writing in C are encouraged to conform to the standards, as doing so helps portability between compilers.
The first standard for C was published by ANSI. Although this document was subsequently adopted by ISO/IEC and subsequent revisions published by ISO/IEC have been adopted by ANSI, "ANSI C" is still used to refer to the standard. [1] While some software developers use the term ISO C, others are standards-body neutral and use Standard C.
Informal specification in 1978 (Brian Kernighan and Dennis Ritchie book The C Programming Language ).
In 1983, the American National Standards Institute formed a committee, X3J11, to establish a standard specification of C. In 1985, the first Standard Draft was released, sometimes referred to as C85. In 1986, another Draft Standard was released, sometimes referred to as C86. The prerelease Standard C was published in 1988, and sometimes referred to as C88. [2]
The ANSI standard was completed in 1989 and ratified as ANSI X3.159-1989 "Programming Language C." This version of the language is often referred to as "ANSI C". Later on sometimes the label "C89" is used to distinguish it from C90 but using the same labeling method.
The same standard as C89 was ratified by ISO/IEC as ISO/IEC 9899:1990, with only formatting changes, [3] which is sometimes referred to as C90. Therefore, the terms "C89" and "C90" refer to essentially the same language.
This standard has been withdrawn by both ANSI/INCITS [4] and ISO/IEC. [5]
In 1995, the ISO/IEC published an extension, called Amendment 1, for the ANSI-C standard. Its full name finally was ISO/IEC 9899:1990/AMD1:1995 or nicknamed C95. Aside from error correction there were further changes to the language capabilities, [6] [7] such as:
<wchar.h> and <wctype.h> as well as multi-byte I/O and for &&__STDC_VERSION__In addition to the amendment, two technical corrigenda were published by ISO for C90:
#if defined(__STDC_VERSION__) && __STDC_VERSION__ >= 199409L/* C95 compatible source code. */#elif defined(__STDC__)/* C89 compatible source code. */#endifIn March 2000, ANSI adopted the ISO/IEC 9899:1999 standard. [10] This standard is commonly referred to as C99. Some notable additions to the previous standard include:
long long, _Bool, _Complex, and _Imaginary restrict keyword stdint.h , <tgmath.h>, fenv.h, <complex.h>//, mixing declarations and code, and universal character names in identifiers intThree technical corrigenda were published by ISO for C99:
This standard has been withdrawn by both ANSI/INCITS [11] and ISO/IEC [12] in favour of C11.
C11 was officially ratified and published on December 8, 2011. Notable features include improved Unicode support, type-generic expressions using the new _Generic keyword, a cross-platform multi-threading API (threads.h), and atomic types support in both core language and the library (stdatomic.h).
One technical corrigendum has been published by ISO for C11:
As of October 2018 [update] , "C17" is the current standard for the C programming language. [14]
C17 addresses defects in C11 without introducing new language features. [15]
C23 is the informal name for the next major C language standard revision. [16]
As part of the standardization process, ISO/IEC also publishes technical reports and specifications related to the C language:
More technical specifications are in development and pending approval, including the fifth and final part of TS 18661, a software transactional memory specification, and parallel library extensions. [28]
ANSI C is now supported by almost all the widely used compilers. GCC and Clang are two major C compilers popular today, both based on the C11 with updates including changes from later specifications such as C17. [29] [30] Any source code written only in standard C and without any hardware dependent assumptions is virtually guaranteed to compile correctly on any platform with a conforming C implementation. Without such precautions, most programs may compile only 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 the reliance on compiler- or platform-specific attributes such as the exact size of certain data types and byte endianness.
To mitigate the differences between K&R C and the ANSI C standard, the __STDC__ ("standard c") macro can be used to split code into ANSI and K&R sections.
#if defined(__STDC__) && __STDC__externintgetopt(int,char*const*,constchar*);#elseexternintgetopt();#endifIn the above example, a prototype is used in a function declaration for ANSI compliant implementations, while an obsolescent non-prototype declaration is used otherwise. Those are still ANSI-compliant as of C99. Note how this code checks both definition and evaluation: this is because some implementations may set __STDC__ to zero to indicate non-ANSI compliance. [31]
List of compilers supporting ANSI C:
C is a general-purpose computer 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, device drivers, and protocol stacks, but its use in application software has been decreasing. C is commonly used on computer architectures that range from the largest supercomputers to the smallest microcontrollers and embedded systems.
C++ is a high-level, general-purpose programming language created by Danish computer scientist Bjarne Stroustrup. First released in 1985 as an extension of the C programming language, it has since expanded significantly over time; as of 1997 C++ has object-oriented, generic, and functional features, in addition to facilities for low-level memory manipulation. It is almost always implemented as a compiled language, and many vendors provide C++ compilers, including the Free Software Foundation, LLVM, Microsoft, Intel, Embarcadero, Oracle, and IBM.
The C preprocessor is the macro preprocessor for several computer programming languages, such as C, Objective-C, C++, and a variety of Fortran languages. The preprocessor provides inclusion of header files, macro expansions, conditional compilation, and line control.
The C standard library or libc is the standard library for the C programming language, as specified in the ISO C standard. Starting from the original ANSI C standard, it was developed at the same time as the C library POSIX specification, which is a superset of it. Since ANSI C was adopted by the International Organization for Standardization, the C standard library is also called the ISO C library.
In the C and C++ programming languages, an inline function is one qualified with the keyword inline; this serves two purposes:
register storage class specifier, which similarly provides an optimization hint.inline is to change linkage behavior; the details of this are complicated. This is necessary due to the C/C++ separate compilation + linkage model, specifically because the definition (body) of the function must be duplicated in all translation units where it is used, to allow inlining during compiling, which, if the function has external linkage, causes a collision during linking. C and C++ resolve this in different ways.In computer programming, undefined behavior (UB) is the result of executing a program whose behavior is prescribed to be unpredictable, in the language specification to which the computer code adheres. This is different from unspecified behavior, for which the language specification does not prescribe a result, and implementation-defined behavior that defers to the documentation of another component of the platform.
C99 is an informal name for ISO/IEC 9899:1999, a past version of the C programming language standard. It extends the previous version (C90) with new features for the language and the standard library, and helps implementations make better use of available computer hardware, such as IEEE 754-1985 floating-point arithmetic, and compiler technology. The C11 version of the C programming language standard, published in 2011, updates C99.
The InterNational Committee for Information Technology Standards (INCITS),, is an ANSI-accredited standards development organization composed of Information technology developers. It was formerly known as the X3 and NCITS.
In the C programming language, data types constitute the semantics and characteristics of storage of data elements. They are expressed in the language syntax in form of declarations for memory locations or variables. Data types also determine the types of operations or methods of processing of data elements.
Watcom C/C++ is an integrated development environment (IDE) product from Watcom International Corporation for the C, C++, and Fortran programming languages. Watcom C/C++ was a commercial product until it was discontinued, then released under the Sybase Open Watcom Public License as Open Watcom C/C++. It features tools for developing and debugging code for DOS, OS/2, and Windows, Linux operating systems, which are based upon x86, IA-32, x86-64 compatible processors.
ISO/IEC 10967, Language independent arithmetic (LIA), is a series of standards on computer arithmetic. It is compatible with ISO/IEC/IEEE 60559:2011, more known as IEEE 754-2008, and much of the specifications are for IEEE 754 special values (though such values are not required by LIA itself, unless the parameter iec559 is true). It was developed by the working group ISO/IEC JTC1/SC22/WG11, which was disbanded in 2011.
In C and related programming languages, long double refers to a floating-point data type that is often more precise than double precision though the language standard only requires it to be at least as precise as double. As with C's other floating-point types, it may not necessarily map to an IEEE format.
The C and C++ programming languages are closely related but have many significant differences. C++ began as a fork of an early, pre-standardized C, and was designed to be mostly source-and-link compatible with C compilers of the time. Due to this, development tools for the two languages are often integrated into a single product, with the programmer able to specify C or C++ as their source language.
assert.h is a header file in the C standard library. It defines the C preprocessor macro assert and implements runtime assertion in C.
MISRA C is a set of software development guidelines for the C programming language developed by The MISRA Consortium. Its aims are to facilitate code safety, security, portability and reliability in the context of embedded systems, specifically those systems programmed in ISO C / C90 / C99.
IAR Systems is a Swedish computer software company that offers development tools for embedded systems. IAR Systems was founded in 1983, and is listed on Nasdaq Nordic in Stockholm. IAR is an abbreviation of Ingenjörsfirma Anders Rundgren, which means Anders Rundgren Engineering Company.
vbcc is a portable and retargetable ANSI C compiler. It supports C89 as well as parts of C99.
C11 is an informal name for ISO/IEC 9899:2011, a past standard for the C programming language. It replaced C99 and has been superseded by C17. C11 mainly standardizes features already supported by common contemporary compilers, and includes a detailed memory model to better support multiple threads of execution. Due to delayed availability of conforming C99 implementations, C11 makes certain features optional, to make it easier to comply with the core language standard.
C17 is the informal name for ISO/IEC 9899:2018, the most recent standard for the C programming language, prepared in 2017 and published in June 2018. It replaced C11, and will be superseded by C23 when it is published in 2024. Since it was under development in 2017, and officially published in 2018, C17 is sometimes referred to as C18.
C23 is the informal name for what will likely become ISO/IEC 9899:2024, the next standard for the C programming language, which will replace C17. It was started in 2016 informally as C2x, and expected to be published in 2024. The most recent publicly available working draft of C23 was released on April 1, 2023. The first WG14 meeting for the C2x draft was held in October 2019, virtual remote meetings were held in 2020 due to the COVID-19 pandemic, then various teleconference meetings continued to occur through 2023.
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