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.. SPDX-License-Identifier: CC-BY-SA-4.0

.. Copyright (C) 2018.
.. COMMENT: On-Line Applications Research Corporation (OAR).
 | **COPYRIGHT (c) 20188.**
.. **RTEMS Foundation, The RTEMS Documentation Project**


This chapter describes each of the standards which RTEMS tracks
API alignment with. As a general rules, these standards are related
to the POSIX or C programming language standards. Many are the result
of domain specific efforts to define subsets or profiles or the full
POSIX standard which are suitable for a specific domain. Each 
API set is considered a "profile" against which the full capability
set of RTEMS is evaluated.

The RTEMS Complete Profile is the complete set of POSIX, BSD, and
C programming language methods supported by RTEMS. This profile is
independent of any standard and represents a union of multiple
standards. For example, RTEMS supports BSD derived methods that
are not in POSIX.

The IEEE Standard 1003.1 is the POSIX standard.  Specifically, IEEE
Standard 1003.1-2008 is the 2003 edition of the POSIX standard and IEEE
Standard 1003.1-2008 is the 2008 edition.  The 2008 is is an update from
the 2003 edition. Each edition of the POSIX standard tends to add some
methods, deprecate some methods, and obsolete (e.g. remove) other methods.

PSE51 through PSE54 are Open Group defined profiles of the 2003 edition
of the POSIX standard. These profiles are:

* Profile 54 - Multipurpose

  * 1003.1-2003 Base Multi-process, Threads and File System

* Profile 53 - Dedicated

  * Multi-process, Threads and File System

* Profile 52 - Controller

  * Single Process, Threads, and File System

* Profile 51 - Minimal

  * Single Process, Threads, with No File System

The C99 Programming Language standard defines the Standard C Library. This
library is largely included by reference in the POSIX standard. 

The C11 Programming Language standard defines also defines an
updated version of the Standard C Library. It deletes a few methods
from the C99 version but adds many methods. A large portion of these
methods are optional and not commonly implemented.

The Open Group FACE Consortium (
has defined four POSIX profiles targetting the avionics application
domain. The FACE Technical Standard has been through multiple revisions
and the POSIX API profiles are identical in Editions 1.0, 2.0, 2.1,
and 2.1.1. In these editions, the profiles are as follows:

* Security - 163 APIs, single process, no FILE *

* Safety Basic - 246 APIs, single process, some FILE *

* Safety Extended - 335 APIs, multi-process, more FILE *

* General Purpose - 812 APIs, multi-process, much more

FACE Technical Standard Edition 3.0 adds the requirement for an
operating system to support ``clock_nanosleep()`` in all profiles and
defines one additional subcommand for the ``posix_devctl()`` methods.

RTEMS provides all of the methods required by the FACE Safety BASE profile
and all of the methods in the Safety Extended profile which do not require
multiple processes. Similarly, RTEMS provides most of the methods in the
General Purpose profile which do not require multiple processes.

The Software Communications Architecture (SCA) specification targets the
requirements for software-defined radios. This specification was originally
developed in support of the Joint Tactical Radio System (JTRS) program
in conjunction with the Object Management Group (OMG). This standard is
now maintained by the Wireless Innovation Forum with support from the
U.S. Navy Joint Tactical Network Center (JTNC). Some URLs of interest:

* SCA at Wireless Innovation Forum -

* JTRS -

* JTNC -

The SCA standard is hosted at the Wireless Innovation Forum with JTNC
hosting supplemental information.

RTEMS includes all methods required by the SCA POSIX profiles.