This is a pretty ill-judged claim, IMO - but not for any particulars about the Organick book, etc. The problem is more global. When was UNIX 'complete' - when the first people were able to do real work on the PDP-7? When non-programmer clerks from the patent group were able to use the assembler UNIX on the PDP-11 to format parent documents? When it was re-written in C for the 4th Edition (since the _portability_ of UNIX was IMO perhaps the greatest factor in its eventual domination)? Etc, etc, etc. The exact same problem applies to the question of 'when was Multics 'complete''. The third printing _is_ the first edition. Anyway, it doesn't matter - see above. And of course even if the book _wriring_ was finished at time T, it wouldn't have been printed until some unknown time later. So that's really pretty useless as a temporal marker; we have much better ones availablw. My 3rd printing says 3rd was 1980, 2nd in 1976, and copyright 1972. Yes; I'm not sure if the version described in it was ever available for general usege (which could be my definition of 'complete') - or even usage my Multics system programmers. I don't remember all the details of the differences (it's been way too long since I read it, and I don't know the details of the 'first operational' Multics well enough), but for instance: ISTR that it describes a version which had a linkage segment (holding intermediate locations in outbound links - since segment >a>b>c might well have different segment numbers assigned to it in the address spaces of processes X and Y, so one copy of >a>b>c, shared between X and Y, couldn't contain direct outbound links) _per segment_ (data or code) - but operational Multics (I don't know if this is from 'first available to users', or 'first available to Multics system programmers', or what) collapsed all the linkage info into a 'combined linkage segment', in which the linkage info from all the segments in a process' address space were combined (by copying) into a single linkage segment. Etc, etc, etc. I'm not sure that the 6180 made that big a difference to the environment the average use saw. My understanding (not having been there) was that the big _architectural_ difference was that cross-ring inter-segment references were done and monitored in hardware, so a host of security holes caused by insufficient checking of cross-ring inter-segment pointers were caught automatically. (The 6180 was also built out of SSI chips, unlike the 645 which was individual transistors, like a KA10.) Noel