### Question 11.1

What is the ``ANSI C Standard?''

In 1983, the American National Standards Institute (ANSI) commissioned a committee, X3J11, to standardize the C language. After a long, arduous process, including several widespread public reviews, the committee's work was finally ratified as ANS X3.159-1989 on December 14, 1989, and published in the spring of 1990. For the most part, ANSI C standardizes existing practice, with a few additions from C++ (most notably function prototypes) and support for multinational character sets (including the controversial trigraph sequences). The ANSI C standard also formalizes the C run-time library support routines.

More recently, the Standard has been adopted as an international standard, ISO/IEC 9899:1990, and this ISO Standard replaces the earlier X3.159 even within the United States. Its sections are numbered differently (briefly, ISO sections 5 through 7 correspond roughly to the old ANSI sections 2 through 4). As an ISO Standard, it is subject to ongoing revision through the release of Technical Corrigenda and Normative Addenda.

In 1994, Technical Corrigendum 1 amended the Standard in about 40 places, most of them minor corrections or clarifications. More recently, Normative Addendum 1 added about 50 pages of new material, mostly specifying new library functions for internationalization. The production of Technical Corrigenda is an ongoing process, and a second one is expected in late 1995. In addition, both ANSI and ISO require periodic review of their standards. This process is beginning in 1995, and will likely result in a completely revised standard (nicknamed ``C9X'' on the assumption of completion by 1999).

The original ANSI Standard included a ``Rationale,'' explaining many of its decisions, and discussing a number of subtle points, including several of those covered here. (The Rationale was ``not part of ANSI Standard X3.159-1989, but... included for information only,'' and is not included with the ISO Standard.)

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