This topic is still primarily UNIX but is getting near the edge of COFF, so I'll CC there if people want to follow up. As I mentioned to Will, during the time Research was doing the work/put out their 'editions', the 'releases' were a bit more ephemeral - really a set of bits (binary and hopefully matching source, but maybe not always) that become a point in time. With 4th (and I think 5th) Editions it was a state of disk pack when the bits were copies, but by 6th edition, as Noel points out, there was a 'master tape' that the first site at an institution received upon executing of a signed license, so the people at each institution (MIT, Purdue, CMU, Harvard) passed those bits around inside. But what is more, is what Noel pointed out, we all passed source code and binaries between each other, so DNA was fairly mixed up [sorry Larry - it really was 'Open Source' between the licensees]. Sadly, it means some things that actually were sourced at one location and one system, is credited sometimes credited from some other place the >>wide<< release was in USG or BSD [think Jim Kulp's Job control, which ended up in the kernel and csh(1) as part in 4BSD, our recent discussions on the list about more/pg/less, the different networking changes from all of MIT/UofI/Rand, Goble's FS fixes to make the thing more crash resilient, the early Harvard ar changes - *a.k.a.* newar(1) which became ar(1), CMU fsck, e*tc*.]. Eventually, the AT&T Unix Support Group (USG) was stood up in Summit, as I understand it, originally for the Operating Companies as they wanted to use UNIX (but not for the licenses, originally). Steve Johnson moved from Research over there and can tell you many more of the specifics. Eventually (*i.e.* post-Judge Green), distribution to the world moved from MH's Research and the Patent Licensing teams to USG and AT&T North Carolina business folks. That said, when the distribution of UNIX moved to USG in Summit, things started to a bit more formal. But there were still differences inside, as we have tried to unravel. PWB/TS and eventually System x. FWIW, BSD went through the same thing. The first BSD's are really the binary state of the world on the Cory 11/70, later 'Ernie.' By the time CSRG gets stood up because their official job (like USG) is to support Unix for DARPA, Sam and company are acting a bit more like traditional SW firms with alpha/beta releases and a more formal build process. Note that 2.X never really went through that, so we are all witnessing the wonderful efforts to try to rebuild early 2.X BSD, and see that the ephemeral nature of the bits has become more obvious. As a side story ... the fact is that even for professional SW houses, it was not as pure as it should be. To be honest, knowing the players and processes involved, I highly doubt DEC could rebuild early editions of VMS, particularly since the 'source control' system was a physical flag in Cutler's office. The fact is that the problem of which bits were used to make what other bits was widespread enough throughout the industry that in the mid-late 80s when Masscomp won the bid to build the system that Nasa used to control the space shuttle post-Challenger, a clause of the contract was that we have put an archive of the bits running on the build machine ('Yeti'), a copy of the prints and even microcode/PAL versions so that Ford Aerospace (the prime contractor) could rebuild the exact system we used to build the binaries for them if we went bankrupt. I actually, had a duplicate of that Yeti as my home system ('Xorn') in my basement when I made some money for a couple of years as a contract/on-call person for them every time the shuttle flew. Anyway - the point is that documentation and actual bits being 100% in sync is nothing new. Companies work hard to try to keep it together, but different projects work at different speeds. In fact, the 'train release' model is what is usually what people fall into. You schedule a release of some piece of SW and anything that goes with it, has to be on the train or it must wait for the next one. So developers and marketing people in firms argue what gets to be the 'engine' [hint often its HW releases which are a terrible idea, but that's a topic for COFF].