Unification Attempts...

Several efforts were made in order to unify the fragmented Unix market, and specify a standard set of utilities and APIs.

ANSI C (1989) - defining a standard for the C programming language.

X/Open XPG3 (1989) - X/Open Portability Guide.

IEEE POSIX (1988) - Portable Operating System Interface.

Unix 95/ Unix 98 - the latest attempts to defragment the market.

AT&T SVID (1989) - Requirements for a SysVR4-compliant system.