STANDARDS(7)               Linux Programmer's Manual              STANDARDS(7)
       Standards - C and UNIX Standards

       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, 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 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 .

       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

       C99    This  revision of the C language standard was ratified by ISO in
              1999 (ISO/IEC 9899:1999).

              "Portable Operating  System  Interface  for  Computing  Environ-
              ments".   IEEE  1003.1-1990  part  1,  ratified  by  ISO in 1990
              (ISO/IEC 9945-1:1990).  Further information can be found in Don-
              ald  Lewine's "POSIX Programmer's Guide" (O'Reilly & Associates,
              Inc., 1991, ISBN 0-937175-73-0).  The term "POSIX" was coined by
              Richard Stallman.

              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
              portable  operating  systems,  ratified  by ISO in 1996 (ISO/IEC
              9945-1:1996).  For further information, see  "POSIX.4:  Program-
              ming  for the real world" by Bill O. Gallmeister (O'Reilly & As-
              sociates, Inc. ISBN 1-56592-074-0).

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

              IEEE Std 1003.1c-1999  describing  additional  real-time  exten-

              IEEE  Std  1003.1g-2000  describing  networking  APIs (including

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

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

       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 multi-volume 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

       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-

       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  (
      .)   The  standard  is  available  online  at
      , 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-

              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   standardised   in   C99  are  also  standardised  in

              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).


Linux                             2006-08-03                      STANDARDS(7)