[TUHS] Why do compress(1) and pack(1) use the .Z / .z extension?

Clem Cole clemc at ccc.com
Sat Nov 28 03:16:01 AEST 2020

On Fri, Nov 27, 2020 at 8:08 AM Hans Wennborg <hans at hanshq.net> wrote:

> 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
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