I'm trying to find out why compress(1) uses .Z as filename extension.
My theory is that it was inspired by pack(1), which uses the .z extension.
However, I haven't been able to find any info on why pack(1) uses that
extension. Does anyone here know?
No idea - but yes, Zucker used a .z at Rand when he wrote.
Some searching led me to [1] which is a man page for pack from AUSAM.
It's written by Steve Zucker in 1975, so perhaps the extension is z for
Zucker?
Was Zucker's pack(1) the first, though? This message [2] talks about a
Bell version.
Zucker wrote it at Rand - early/mid 1970s. IIRC, It was later included in the original Harvard USENIX tape in the 'Rand' directory. I believe that Rand Pipes (named pipes) are in the same directory. Although some of the Rand stuff was being shared by folks on the ArpaNet before USENIX existed and I think it made it to the wild before the first USENIX tape.
It was really important back in the day. Remember RK05's are only 2.5M bytes - source archiving and packing files was pretty important given the cost / byte of disk.
I think there may have been an early version @ BTL - PWB may have distributed it also, but I'm fairly sure it was the Rand code that started it. Noel might remember more than I. I'm 90% sure we had it at CMU before we got either PWB 1.0 or UNIX/TS from Ted -- I want to say it we had it on 5th edition but maybe not.
One of the PDP-10 folks will need to chime in here. My memory is there was something like pack(1) on the CMU PDP-10s and 20s that I saw before I saw the UNIX tool [not sure why I think this, but it may have been SAIL program - I remember looking at a number of simple tools when I learn SAIL years and years ago - 74/75-ish]. IIRC they were not exactly the same format as the 10's were 36-bit words, stored 5 chars in a word, but it was the same idea.