Subj : Re: BBSing on CP/M
To   : Fratm
From : Dr. What
Date : Sat Sep 18 2021 20:15:00

-=> Fratm wrote to Dr. What <=-

 DW> That's just MS-DOS 1.0.  8)

 Fr> But didn't CP/M support multiuser, kind of like UNIX did?  It's been
 Fr> about 30 years since I touched a CP/M machine, so I might be confused
 Fr> lol

Sort of.  Not multi-user like Linux (where multiple people can use the same box
at the same time), but it had a "user" attribute that you could put on files as
a way to group them or hide them.

CP/M didn't support subdirectories.  Which wasn't a surprise in a day when the
only storage media you had was single or double sided 5.25" floppies.  So we
are talking 180K or 360K.  You basically had a floppy with the software you
wanted to run in the A: drive, then your data disk in the B: drive.

I need to research the reason that the "user" attribute was created in the
first place.  I don't know off hand.  But when hard drives started coming down
in price, not supporting subdirectories was a big problem.  Imaging doing a
"dir" command and having to scroll through 100+ files - most unrelated to what
you were doing.

So CP/M used the "user" attribute as sort of a way to handle subdirectories.

user 0 would be all the system utils, for example, and seen by all.  Then you
switched to user 1 when you wanted to program.  Maybe switched to user 2 for
writing that research paper.  Switching to a different user would hide the
files for the other users.  Now your "dir" command only showed the files
related to the user you had set.

Right now, my CP/M machines are Kaypros and my RC2014s - all running CP/M 2.2
on a Z80.  So they may have addressed this in newer versions of CP/M.  I have
it on my list to play with CP/M-86 to see what that does.  I think I can run
that one my MS-DOS machines.


.... Women who seek to be equal to men lack ambition.
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