Very cool ? thanks for the snippet, Paul! I?ve seen mention in various RT-11 manuals that the sources were made available by DEC at the time (perhaps only on fiche?) I would love to read through the V4.00 sources, if anybody knows where I could track them down? cheers, ?FritzM.

Yes, RT11 (when it introduced Sysgen, which was later than V2) did so by supplying sources that had been stripped of their comments. So they were useful for sysgen but not (easily) useable for custom OS changes. DEC did offer source licenses for many of its operating systems, at extremely high prices. They also offered listings, typically on microfiche, still substantially more expensive than the binary licenses but not nearly as crazy as source. And sometimes you could get source or listings as a special deal. In college we started out with RSTS-11 V4, which had a major reliability problem (as in: roughly daily crash). As part of trying to keep the customer placated, DEC supplied full OS sources, 5 dectapes. We printed them (on our 30 cps Silent 733 terminals). I used them to learn about RSTS as a student, which got me hired by the computer center. ("I make it my habit to hire students before they become dangerous" -- Michael A. Hall, director of computer services.) I still have copies of those files. paul