Release Date: March, 1977
Released By: UNIX Support Group
Source Code: None Available
Documentation: MERT_Release_0's UNIX portion is based on the Issue 3 manual, and the introduction can be consulted as to which pages have been replaced as part of MERT Release 0

UNIX Program Generic Issue 3, otherwise known as PG-1C300, is a version of the UNIX operating system issued by the UNIX Support Group in March of 1977. The Program Generic line was used as a standard, supported UNIX base on which to base other projects and supply a computing environment to a larger group of users than the Research group could support.

PG 3 would go on to serve as the base of the real-time MERT Release 0 system. The majority of the pages in the above manual descend from the Issue 3 manual.

One curious matter is the exclusion of a page called “lines” in section V (File Formats). In the available CB-UNIX manual, there is a partially included lines(5) page that bears striking similarity to the nearby inittab(5) page, which of course would go on to be the inittab introduced commercially with System V. This page which has been omitted from MERT Release 0 may very well represent an appearance of a CB-UNIX-like init environment in Issue 3 in 1977. An owner of an Issue 2 manual (in an email that will be linked when found) confirmed that Issue 2's init system was more in line with that of Research UNIX, making this lines-based init an Issue 3 feature.