STANDARDS(7)						     Linux Programmer's Manual						      STANDARDS(7)

NAME

       standards - C and UNIX Standards

DESCRIPTION

       The  CONFORMING	TO section that appears in many manual pages identifies various standards to which the documented interface conforms.  The
       following list briefly describes these standards.

       V7     Version 7, the ancestral UNIX from Bell Labs.

       4.2BSD This is an implementation standard defined by the 4.2 release of the Berkeley Software Distribution, released by the  University	of
	      California at Berkeley.  This was the first Berkeley release that contained a TCP/IP stack and the sockets API.  4.2BSD was released
	      in 1983.

	      Earlier major BSD releases included 3BSD (1980), 4BSD (1980), and 4.1BSD (1981).

       4.3BSD The successor to 4.2BSD, released in 1986.

       4.4BSD The successor to 4.3BSD, released in 1993.  This was the last major Berkeley release.

       System V
	      This is an implementation standard defined by AT&T's milestone 1983 release of its commercial System V (five) release.  The previous
	      major AT&T release was System III, released in 1981.

       System V release 2 (SVr2)
	      This  was  the  next System V release, made in 1985.  The SVr2 was formally described in the System V Interface Definition version 1
	      (SVID 1) published in 1985.

       System V release 3 (SVr3)
	      This was the successor to SVr2, released in 1986.  This release was formally described in the System V Interface Definition  version
	      2 (SVID 2).

       System V release 4 (SVr4)
	      This  was  the  successor  to  SVr3, released in 1989.  This version of System V is described in the "Programmer's Reference Manual:
	      Operating System API (Intel processors)" (Prentice-Hall 1992, ISBN 0-13-951294-2) This release was formally described in the  System
	      V Interface Definition version 3 (SVID 3), and is considered the definitive System V release.

       SVID 4 System V Interface Definition version 4, issued in 1995.	Available online at http://www.sco.com/developers/devspecs/ .

       C89    This  was  the first C language standard, ratified by ANSI (American National Standards Institute) in 1989 (X3.159-1989).  Sometimes
	      this is known as ANSI C, but since C99 is also an ANSI standard, this term is ambiguous.	This standard was  also  ratified  by  ISO
	      (International Standards Organization) in 1990 (ISO/IEC 9899:1990), and is thus occasionally referred to as ISO C90.

       C99    This  revision  of  the  C  language standard was ratified by ISO in 1999 (ISO/IEC 9899:1999).  Available online at http://www.open-
	      std.org/jtc1/sc22/wg14/www/standards.

       POSIX.1-1990
	      "Portable Operating System Interface for Computing Environments".  IEEE 1003.1-1990  part  1,  ratified  by  ISO	in  1990  (ISO/IEC
	      9945-1:1990).  The term "POSIX" was coined by Richard Stallman.

       POSIX.2
	      IEEE Std 1003.2-1992, describing commands and utilities, ratified by ISO in 1993 (ISO/IEC 9945-2:1993).

       POSIX.1b (formerly known as POSIX.4)
	      IEEE Std 1003.1b-1993 describing real-time facilities for portable operating systems, ratified by ISO in 1996 (ISO/IEC 9945-1:1996).

       POSIX.1c
	      IEEE Std 1003.1c-1995 describing the POSIX threads interfaces.

       POSIX.1d
	      IEEE Std 1003.1c-1999 describing additional real-time extensions.

       POSIX.1g
	      IEEE Std 1003.1g-2000 describing networking APIs (including sockets).

       POSIX.1j
	      IEEE Std 1003.1j-2000 describing advanced real-time extensions.

       POSIX.1-1996
	      A 1996 revision of POSIX.1 which incorporated POSIX.1b and POSIX.1c.

       XPG3   Released	in  1989, this was the first significant release of the X/Open Portability Guide, produced by the X/Open Company, a multi-
	      vendor consortium.  This multivolume guide was based on the POSIX standards.

       XPG4   A revision of the X/Open Portability Guide, released in 1992.

       XPG4v2 A 1994 revision of XPG4.	This is also referred to as Spec 1170, where 1170 referred to the number of  interfaces  defined  by  this
	      standard.

       SUS (SUSv1)
	      Single  UNIX  Specification.   This  was a repackaging of XPG4v2 and other X/Open standards (X/Open Curses Issue 4 version 2, X/Open
	      Networking Service (XNS) Issue 4).  Systems conforming to this standard can be branded UNIX 95.

       SUSv2  Single UNIX Specification version 2.  Sometimes also referred to as XPG5.  This standard appeared in 1997.   Systems  conforming	to
	      this standard can be branded UNIX 98.  See also http://www.UNIX-systems.org/version2/ .)

       POSIX.1-2001, SUSv3
	      This  was  a  2001 revision and consolidation of the POSIX.1, POSIX.2, and SUS standards into a single document, conducted under the
	      auspices of the Austin group  (http://www.opengroup.org/austin/  .)   The  standard  is  available  online  at  http://www.unix-sys-
	      tems.org/version3/ , and the interfaces that it describes are also available in the Linux manual pages package under sections 1p and
	      3p (e.g., "man 3p open").

	      The standard defines two levels of conformance: POSIX conformance, which is a baseline set of interfaces required  of  a	conforming
	      system; and XSI Conformance, which additionally mandates a set of interfaces (the "XSI extension") which are only optional for POSIX
	      conformance.  XSI-conformant systems can be branded UNIX 03.  (XSI conformance constitutes the Single UNIX Specification	version  3
	      (SUSv3).)

	      The POSIX.1-2001 document is broken into four parts:

	      XBD: Definitions, terms and concepts, header file specifications.

	      XSH: Specifications of functions (i.e., system calls and library functions in actual implementations).

	      XCU: Specifications of commands and utilities (i.e., the area formerly described by POSIX.2).

	      XRAT: Informative text on the other parts of the standard.

	      POSIX.1-2001 is aligned with C99, so that all of the library functions standardized in C99 are also standardized in POSIX.1-2001.

	      Two  Technical  Corrigenda  (minor  fixes and improvements) of the original 2001 standard have occurred: TC1 in 2003 (referred to as
	      POSIX.1-2003), and TC2 in 2004 (referred to as POSIX.1-2004).

       POSIX.1-2008, SUSv4
	      Work on the next revision of POSIX.1/SUS was completed and ratified in 2008.

	      The changes in this revision are not as large as those that occurred for POSIX.1-2001/SUSv3, but a  number  of  new  interfaces  are
	      added and various details of existing specifications are modified.  Many of the interfaces that were optional in POSIX.1-2001 become
	      mandatory in the 2008 revision of the standard.  A few interfaces that are  present  in  POSIX.1-2001  are  marked  as  obsolete	in
	      POSIX.1-2008, or removed from the standard altogether.

	      The revised standard is broken into the same four parts as POSIX.1-2001, and again there are two levels of conformance: the baseline
	      POSIX Conformance, and XSI Conformance, which mandates an additional set of interfaces beyond those in the base specification.

	      In general, where the CONFORMING TO section of a manual page lists POSIX.1-2001, it can be assumed that the interface also  conforms
	      to POSIX.1-2008, unless otherwise noted.

	      Further information can be found on the Austin group web site, http://www.opengroup.org/austin/ .

SEE ALSO

       feature_test_macros(7), libc(7), posixoptions(7)

COLOPHON

       This  page is part of release 3.25 of the Linux man-pages project.  A description of the project, and information about reporting bugs, can
       be found at http://www.kernel.org/doc/man-pages/.

Linux								    2009-06-01							      STANDARDS(7)