HISTORY OF C

Faizan Ali contact:- 03235356409 email:- ali.faizan0009@hotmail.com

The initial development of C occurred at AT&T Bell Labs between 1969 and 1973;^[3]according to Ritchie, the most creative period occurred in 1972. It was named "C" because its features were derived from an earlier language called "B", which according to Ken Thompson was a stripped-down version of the BCPL programming language.

The origin of C is closely tied to the development of the Unix operating system, originally implemented in assembly language on a PDP-7 by Ritchie and Thompson, incorporating several ideas from colleagues. Eventually they decided to port the operating system to aPDP-11. B's inability to take advantage of some of the PDP-11's features, notably byte addressability, led to the development of an early version of C.

K&R C

In 1978, Brian Kernighan and Dennis Ritchie published the first edition of The C Programming Language.^[1] This book, known to C programmers as "K&R", served for many years as an informal specification of the language. The version of C that it describes is commonly referred to as K&R C. The second edition of the book^[10] covers the later ANSI C standard.

K&R introduced several language features:

·         standard I/O library

·         long int data type

·         unsigned int data type

·         compound assignment operators of the form =op (such as =-) were changed to the form op= to remove the semantic ambiguity created by such constructs as i=-10, which had been interpreted as i =- 10 (decrement i by 10) instead of the possibly intended i = -10 (let i be -10)

Even after the publication of the 1989 C standard, for many years K&R C was still considered the "lowest common denominator" to which C programmers restricted themselves when maximum portability was desired, since many older compilers were still in use, and because carefully written K&R C code can be legal Standard C as well.