UNIX® V7 - the mark for systems conforming to version 4 of the
Single UNIX Specification.
IEEE Std 1003.1-2017
The Austin Group
Contents Organization of the Specification
Download a pdf copy of the Base Specifications (The Open Group Members)
Download a copy of X/Open Curses Issue 7(free pdf, registration required)
How many interfaces are there?
Download the Authorized Guide to the Single UNIX Specification Version 4 (free pdf, registration required).
Extracts from the Authorized Guide:
Read the online Single UNIX specification Version 4
Certification Standard: UNIX V7:Read the Standard