Guys, I got this message from Dennis. Warren ----- Forwarded message from Dennis Ritchie ----- Subject: Re: Trying to restore 1972 UNIX Date: Thu, 1 May 2008 00:55:35 -0400 About the assembler, I am pretty sure that it's substantially the same as that on the 5th edition tape, so it's likely that a modified version, without the syscall definitions, could be produced. I have dug up another listing of the PDP-11 assembly languge version, which seems to about contemporary with the one you have. The files mostly bear a copyright date of 1972, but like other printouts from the time, the datestamps only give month and day, not year. They are generally from May. It is post 11/45, and has segmentation and floating-point support. Incidentally, it doesn't use any of the system call names as such; 'read' is at sysread: and so on. About assembling it, I'm pretty sure we just did 'as u?.s' and the a.out was ready. This was before make, after all. Dennis ----- End forwarded message ----- I replied and asked if we could get either a scan copy of the "other listing", or if he could send a photocopy to Tim. Cheers, Warren