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 fol-
       lowing list briefly describes these standards.

       V7     Version  7  (also	 known	as  Seventh Edition) UNIX, released by
	      AT&T/Bell Labs in 1979.  After this point, UNIX systems diverged
	      into two main dialects: BSD and System V.

       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 ver-
	      sion 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 consid-
	      ered the definitive System V release.

       SVID 4 System V Interface Definition version 4, issued in 1995.	Avail-
	      able online at <http://www.sco.com/developers/devspecs/>.

       C89    This was the first C language standard, ratified by ANSI (Ameri-
	      can National Standards Institute) in 1989 (X3.159-1989).	 Some-
	      times  this  is  known  as ANSI C, but since C99 is also an ANSI
	      standard, this term is ambiguous.	 This standard was also	 rati-
	      fied  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>.

       C11    This  revision of the C language standard was ratified by ISO in
	      2011 (ISO/IEC 9899:2011).

       POSIX.1-1990
	      "Portable Operating  System  Interface  for  Computing  Environ-
	      ments".	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, rati-
	      fied 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  por-
	      table  operating	systems,  ratified  by	ISO  in	 1996 (ISO/IEC
	      9945-1:1996).

       POSIX.1c
	      IEEE Std 1003.1c-1995, which describes the POSIX threads	inter-
	      faces.

       POSIX.1d
	      IEEE  Std	 1003.1c-1999,	which  describes  additional real-time
	      extensions.

       POSIX.1g
	      IEEE Std 1003.1g-2000, which describes networking APIs  (includ-
	      ing sockets).

       POSIX.1j
	      IEEE Std 1003.1j-2000, which describes advanced real-time exten-
	      sions.

       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 mul-
	      tivendor	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-systems.org/version3/>, and the interfaces that
	      it  describes are also available in the Linux manual pages pack-
	      age under sections 1p and 3p (e.g., "man 3p open").

	      The standard defines two levels of  conformance:	POSIX  confor-
	      mance,  which is a baseline set of interfaces required of a con-
	      forming 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  specifica-
	      tions.

	      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 (also known as
	      POSIX.1-2003), and TC2 in 2004 (also known as POSIX.1-2004).

       POSIX.1-2008, SUSv4
	      Work on the next revision of POSIX.1/SUS was completed and rati-
	      fied 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	 stan-
	      dard.   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	speci-
	      fication.

	      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.

	      Technical	 Corrigendum  1 (minor fixes and improvements) of this
	      standard was released in 2013 (also known as POSIX.1-2013).

	      Technical Corrigendum 2 of this standard was  released  in  2016
	      (also known as POSIX.1-2016).

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

SEE ALSO
       attributes(7), feature_test_macros(7), libc(7), posixoptions(7)

COLOPHON
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Linux				  2016-12-12			  STANDARDS(7)