Revision as of 22:45, 29 November 2013

C is a general-purpose, procedural, imperative, high-level programming language developed by Dennis Ritchie at AT&T Bell Labs between 1969 and 1973.

History

The C programming language was developed at AT&T Bell Labs between 1969 and 1973 by Dennis Ritchie. It was named "C" due to it's influence from the "B" programming language, another language developed at Bell Labs by Ken Thompson and Dennis Ritchie, as well as the BCPL programming language.

C is actually a by-product of an operating system called UNIX which was developed at AT&T Bell Labs at that time as well. The operating system ran on a DEC PDP-7 machine. UNIX was originally written in assembly language like most programs of the time. Debugging was difficult and slow. Ken Thompson, the author of UNIX, decided a high-level was more appropriate.

A small language by the name of B was designed. B was heavily influenced by another system programming language called BCPL which was developed in the mid 60s. In the early 70s, a DEC PDP-11 machine was acquired for the UNIX project. Large protions of UNIX were ported to B with the help of Ritchie. By 71 it became clear that B did not serve well for the PDP-11 as it did for the PDP-7. Constant modification of the B language, lead to a development of a new language that eventually became to be known as C. By 1973 C was complete enough that UNIX could be entirely written in C. By writing UNIX in C, all they had to do is have a compiler for a specific machine and be able to run UNIX on it.

Standards

For many years, the only authoritative reference on C was the first edition of The C Programming Language. In 1983, the American National Standards Institute (ANSI) established a committee to formally describe the C language. In 1989, the C standard was ratified as ANSI X3.159-1989. That version is largely referred to as ANSI C or C89. In 1990, the ANSI C standard was adopted by the International Organization for Standardization (ISO) as ISO/IEC 9899:1990. That version is called C90. Both C89 and C90 refer to the same exact language.

In 1995 Normative Addendum 1 was published to support international character sets. The term C94 or C95 are used to refer to the C89 plus Amendment 1.

In 1999 A new standard was published known as ISO/IEC 9899:1999. This standard is often referred to as C99.

In 2011 ISO published a new standard known as ISO/IEC 9899:2011. This standard is the current standard of the C language and is referred to as C11.

Standard library

Main article: C standard library

The C language provides a set of functions for performing common tasks such as string handling, threading managements, memory management, and I/O processing called the C standard library. The library is broken down into 29 headers, 3 of which are optional.