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C Programming Language



C programming language is a structured programming language, developed by Dennis Ritchie at Bell Laboratories in 1972.
It has been written in assembly language, belonging to middle level programming language.
It’s features were derived from an earlier language called “B” (Basic Combined Programming Language – BCPL).
C language was invented for implementing UNIX operating system.
In 1978, Dennis Ritchie and Brian Kernighan published the first edition “The C Programming Language” and commonly known as K&R C.
In 1983, the American National Standards Institute (ANSI) established a committee to provide a modern, comprehensive definition of C.  The resulting definition, the ANSI standard, or “ANSI C”, was completed late 1988.
This  language is used for developing system applications that forms a major portion of operating systems such as Windows, UNIX and Linux.


Some of the features of C language :-
·         Reliability
·         Portability
·         Flexibility
·         Interactivity
·         Modularity
·         Efficiency and Effectiveness


Development of Unix System

The PDP-11 version of Unix system was written in assembly language. Assembly languages are low-level programming languages that are specific to a particular computer architecture. They are hard to write and understand.
The developers of Unix Operating system (including Dennis Ritchie and Stephen C. Johnson) decided to rewrite the system in B language. However, B couldn’t suffice some of the features of PDP-11, which led to the development of C.
In 1972, the development of C started on the PDP-11 Unix system and first appeared in Version 2 Unix. A large part of Unix was then rewritten in C  and the compiler for the Honeywell 6000 was written within the first year of C's history. By 1973, C was powerful enough to be used in Unix Kernel. Dennis Ritchie and Stephen C. Johnson made further changes to the language for several years to make it portable in Unix Operating system.
ANSI C

With the rapid growth of C language, it was necessary to be standardized. All the three standards given below are also known by the name of ANSI C  :-
C89 :-  The first standard of C was published by American National Standards Institute (ANSI) in 1989. This version is commonly popular as C89. C89 is supported by current C compilers, and most C code being written today is based on it.
C99 :-  In late 1990’s, several new features including inline functions, several new data types (including long, long int and a complex type to represent complex numbers), variable-length arrays and flexible array members, improved support for IEEE 754 floating point, support for variadic macros (macros of variable arity), and support for one-line comments beginning with //.
C11 :-  The C11 standard has new features like type generic macros, atomic operations, anonymous structures, multi-threading, and bounds-checked functions.
C18 :-  This standard is published in June 2018, C18 is the current standard for the C programming language. It introduces no new language features, only technical corrections and clarifications to defects in C11.
Applications of C language

·         Database systems
·         Graphics packages
·         Word processors
·         Spreadsheets
·         Operating system development
·         Compilers and Assemblers
·         Network drivers





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