The original Appendix is only 40 pages, while this section of the standard is twice as long.
Section 7: The C runtime library (81 pages). This is a list of the library calls that a conforming
implementation must provide—the standard services and routines to carry out essential or helpful
functions. The ANSI C standard's section 7 on the C runtime library is based on the /usr/group 1984
standard, with the UNIX-specific parts removed. "/usr/group" started life as an international user
group for UNIX. In 1989 it was renamed "UniForum", and is now a nonprofit trade association
dedicated to the promotion of the UNIX operating system.
UniForum's success in defining UNIX from a behavioral perspective encouraged many related
initiatives, including the X/Open portability guides (version 4, XPG/4 came out in October 1992),
IEEE POSIX 1003, the System V Interface Definition, and the ANSI C libraries. Everyone
coordinated with the ANSI C working group to ensure that all their draft standards were mutually
consistent. Thank heaven.
The ANSI C standard also features some useful appendices:
Appendix F: Common warning messages. Some popular situations for which diagnostic messages
are not required, but when it is usually helpful to generate them nonetheless.
Appendix G: Portability issues. Some general advice on portability, collected into one place from
throughout the standard. It includes information on behavior that is unspecified, undefined, and
implementation-defined.