C Program book in Khmer

C Program book in Khmer with Example and Practice Exercises. By Teacher:Touch Nguon Chay. Click here to download PDF File.

C Programming History

The field of computing as we know it today started in 1947 with three scientists at Bell Telephone Laboratories—William Shockley, Walter Brattain, and John Bardeen—and their groundbreaking invention: the transistor. In 1956, the first fully transistor-based computer, the TX-0, was completed at MIT. The first integrated circuit was created in 1958 by Jack Kilby at Texas Instruments, but the first high-level programming language existed even before then.

"The Fortran project" was originally developed in 1954 by IBM. A shortening of "The IBM Mathematical Formula Translating System", the project had the purpose of creating and fostering development of a procedural, imperative programming language that was especially suited to numeric computation and scientific computing. It was a breakthrough in terms of productivity and programming ease (compared to assembly language) and speed (Fortran programs ran nearly as fast as, and in some cases, just as fast as, programs written in assembly). Furthermore, Fortran was written at a high-enough level (and thus was machine independent enough) to become the first widely adopted programming language. The Algorithmic Language (Algol 58) was derived from Fortran in 1958 and evolved into Algol 60 in 1960. The Combined Programming Language (CPL) was then created out of Algol 60 in 1963. In 1967, it evolved into Basic CPL, which was itself, the base for B in 1969. Finally, B, the root of C, was created in 1971.

C was the direct successor of B, a stripped down version of BCPL, created by Ken Thompson at Bell Labs, that was also a compiled language - User's Reference to B, used in early internal versions of the UNIX operating system. As noted in Ritchie's C History : "The B compiler on the PDP-7 did not generate machine instructions, but instead 'threaded code', an interpretive scheme in which the compiler's output consists of a sequence of addresses of code fragments that perform the elementary operations. The operations typically — in particular for B — act on a simple stack machine". Thompson and Dennis Ritchie, also working at Bell Labs, improved B and called the result NB. Further extensions to NB created its logical successor, C. Most of UNIX was rewritten in NB, and then C, which resulted in a more portable operating system.

The portability of UNIX was the main reason for the initial popularity of both UNIX and C. Rather than creating a new operating system for each new machine, system programmers could simply write the few system-dependent parts required for the machine, and then write a C compiler for the new system. Since most of the system utilities were thus written in C, it simply made sense to also write new utilities in C.

The American National Standards Institute began work on standardizing the C language in 1983, and completed the standard in 1989. The standard, ANSI X3.159-1989 "Programming Language C", served as the basis for all implementations of C compilers. The standards were later updated in 1990 and 1999, allowing for features that were either in common use, or were appearing in C++.

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