The System V Interface Definition (or SVID) is a standard that describes the AT&T

AT&T

AT&T Inc. is an American multinational telecommunications corporation headquartered in Whitacre Tower, Dallas, Texas, United States. It is the largest provider of mobile telephony and fixed telephony in the United States, and is also a provider of broadband and subscription television services...

 UNIX System V

UNIX System V

Unix System V, commonly abbreviated SysV , is one of the first commercial versions of the Unix operating system. It was originally developed by American Telephone & Telegraph and first released in 1983. Four major versions of System V were released, termed Releases 1, 2, 3 and 4...

 behavior, including that of system call

System call

In computing, a system call is how a program requests a service from an operating system's kernel. This may include hardware related services , creating and executing new processes, and communicating with integral kernel services...

s, C libraries, available programs and devices. While it was not the first attempt at a standardizations document (the industry trade association /usr/group published a standard in 1984 based on System III with a few system call additions from BSD), it was an important effort of early standardization of UNIX in a period when UNIX variants were multiplying rapidly and portability was problematic at best. By 1986, AT&T required conformance with SVID issue 2 if vendors were to actually brand their products "System V R3". By the 1990s, however, its importance was largely eclipsed by POSIX

POSIX

POSIX , an acronym for "Portable Operating System Interface", is a family of standards specified by the IEEE for maintaining compatibility between operating systems...

 and the Single UNIX Specification

Single UNIX Specification

The Single UNIX Specification is the collective name of a family of standards for computer operating systems to qualify for the name "Unix"...

, which were based in part upon the SVID. Part of the reason for this was undoubtedly their vendor-independent approach (see Unix wars

Unix wars

The Unix wars were the struggles between vendors of the Unix computer operating system in the late 1980s and early 1990s to set the standard for Unix thenceforth.- Origins :...

).

Versions of SVID

• Version 1, based on System V Release 2, published Spring, 1985
• Version 2, based on System V Release 3, published 1986 (3 volumes)
• Version 3, based on System V Release 4, published 1989
• Version 4, updated for compliance with XPG4 and POSIX
  POSIX
  POSIX , an acronym for "Portable Operating System Interface", is a family of standards specified by the IEEE for maintaining compatibility between operating systems...
  
   1003.1-1990, published 1995

External links

• SVID Fourth Edition in PDF
  Portable Document Format
  Portable Document Format is an open standard for document exchange. This file format, created by Adobe Systems in 1993, is used for representing documents in a manner independent of application software, hardware, and operating systems....
  
  form.

Volume 1a

Volume 1b

Base System

Kernel Extension

Multithreading Extension

Volume 2

Basic Utilities Extension

Advanced Utilities Extension

Administered Systems Extension

Volume 3

Programming Language Specification

Software Development Extension

Terminal Interface Extension

Real Time and Memory Management Extension

Remote Services Extension

Window System Extension

Enhanced Security Extension

Auditing Extension

Remote Administration Extension