SVID
Early UNIX operating system specification
The System V Interface Definition (SVID) is a standard that describes the AT&T UNIX System V behavior, including that of system calls, C libraries, available programs and devices. While it was not the first attempt at a standardizations document (the industry trade association /usr/group published a standard in 1984 based on System III with a few system call additions from BSD), it was an important effort in early standardization of UNIX in a period when UNIX variants were multiplying rapidly and portability was problematic at best. https://en.wikipedia.org/wiki/System_V_Interface_Definition
The System V Interface Definition (SVID) is a standard that describes the AT&T UNIX System V behavior, including that of system calls, C libraries, available programs and devices. While it was not the first attempt at a standardizations document (the industry trade association /usr/group published a standard in 1984 based on System III with a few system call additions from BSD), it was an important effort in early standardization of UNIX in a period when UNIX variants were multiplying rapidly and portability was problematic at best.
