Hello Mr. Mcllroy, Well, along the lines of early UNIX preservation, I have a question. At some point SCCS began to take shape and take hold of the core of the early UNIX distributions. Google says SCCS has been around since 1972. Now, let's take my favorite UNIX releases Research 7, v7m and BSD 2.11. They are my favorite since I have access to the complete distributions and I have all working independently via simulators on dedicated hardware. Now, it's simply wonderful to view the sources. Even more wonderful, through simulation, to relink these distributions. And it's fun to read code and comments---most of it way over my head. But, is there somewhere a main distribution for Research 7, v7m 2.1, or BSD 2.11 that has all of the original SCCS deltas (leaf and non-leaf)? This would be extremely revealing. If we could view the SCCS comments (sccs prs) and the underlying code, it would be incredibly valuable. Please forgive me if this has been asked a million times. I just can't find it. Once SCCS was heavily used, was there a codebase that housed all of these distributions? I always wondered if there were some kind of SCCS or SCCS-like repository that maintained the final distribution and all of the deltas leading up to a minor or even major release. RELEASE, LEVEL, BRANCH and SEQUENCE: I do see "SCCSID" strings sprinkled throughout various distributions. So, this way the application could automatically report the RLBS to the end user. But, is there an early UNIX distribution that housed the complete SCCS repository---I want to dig deep, really deep. This way I could see the paths that were taken, the solutions that partially worked, or ended up causing other problems. Truly, Bill Corcoran