On the subject of tac (concatenate and print files in reverse), I can report that the tool was written by my late friend Jay Lepreau in the Department of Computer Science (now, School of Computing) at the University of Utah. The GNU coreutils distribution for src/tac.c contains a copyright for 1988-2020. I searched my TOPS-20 PDP-10 archives, and found no source code for tac, but I did find an older TOPS-20 executable in Jay's personal directory with a file date of 17-Mar-1987. There isn't much else in that directory, so I suspect that he just copied over a needed tool from his Department of Computer Science TOPS-20 system to ours in the College of Science. ---------------------------------------- P.S. Jay was the first to get Steve Johnson's Portable C Compiler, pcc, to run on the 36-bit PDP-10, and once we had pcc, we began the move from writing utilities in Pascal and PDP-10 assembly language to doing them in C. The oldest C file for pcc in our PDP-10 archives is dated 17-Mar-1981, with other pcc files dated to mid-1983, and final compiler executables dated 12-May-1986. Four system header files are dated as late as 4-Oct-1986, presumably patched after the compiler was built. Later, Kok Chen and Ken Harrenstien's kcc provided another C compiler that added support for byte datatypes, where a byte could be anything from 1 to 36 bits. The oldest distribution of kcc in our archives is labeled "Fifth formal distribution snapshot" and dated 20-Apr-1988. My info-kcc mailing list archives date from the list beginning, with an initial post from Ken dated 27-Jul-1986 announcing the availability of kcc at sri-nic.arpa. By mid-1987, we had a dozen Sun workstations and NFS fileserver; they marked the beginning of our move to a Unix workstation environment, away from large, expensive, and electricity-gulping PDP-10 and VAX mainframes. By the summer of 1991, those mainframes were retired. I recall speaking to a used-equipment vendor about our VAX 8600, which cost about US$450K (discounted academic pricing) in 1986, and was told that its value was depreciating about 20% per month. Although many of us missed TOPS-20 features, I don't think anyone was sad to say goodbye to VMS. We always felt that the VMS developers worked in isolation from the PDP-10 folks, and thus learned nothing from them. ------------------------------------------------------------------------------- - Nelson H. F. Beebe Tel: +1 801 581 5254 - - University of Utah FAX: +1 801 581 4148 - - Department of Mathematics, 110 LCB Internet e-mail: beebe(a)math.utah.edu - - 155 S 1400 E RM 233 beebe(a)acm.org beebe(a)computer.org - - Salt Lake City, UT 84112-0090, USA URL: http://www.math.utah.edu/~beebe/ - -------------------------------------------------------------------------------