Editing C (programming language) (section)

=== ANSI C and ISO C ===
{{Main|ANSI C}}

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During the late 1970s and 1980s, versions of C were implemented for a wide variety of [[mainframe computer]]s, [[minicomputer]]s, and [[microcomputer]]s, including the [[IBM PC]], as its popularity began to increase significantly.

In 1983 the [[American National Standards Institute]] (ANSI) formed a committee, X3J11, to establish 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 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 referred to as [[ANSI C]], Standard C, or sometimes '''C89'''.

In 1990 the ANSI C standard (with formatting changes) was adopted by the [[International 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, 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.

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 prototype]]s (borrowed from C++), <code>void</code> pointers, support for international [[character sets]] and [[Locale (computer software)|locales]], and preprocessor enhancements. Although the [[C syntax|syntax]] for parameter declarations was 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 on any [[Computing platform|platform]] with a conforming C implementation, within its resource limits.  Without such precautions, 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 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-conforming or K&R C-based compilers, the <code>__STDC__</code> macro can be used to split the code into Standard and K&R sections to prevent the use 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 some details and to add more extensive support for international character sets.<ref name="NWUon">{{cite book |author=<!--Staff writer(s); no by-line.--> |title=C Integrity |url=https://www.iso.org/standard/23909.html |publisher=International Organization for Standardization |date=March 30, 1995 |access-date=July 24, 2018 |archive-date=July 25, 2018 |archive-url=https://web.archive.org/web/20180725033429/https://www.iso.org/standard/23909.html |url-status=live }}</ref>