[geeks] Oldest OS Still Developed

[Mike Meredith]

On Wed, 18 Oct 2006 23:46:43 +0200, Geoffrey S. Mendelson wrote:
> IBM had two main timesharing operating systems at the time. One was
> TSO a part of MVS and the other was VM. VM was the more popular (BTW,
> it was distributed in source code). TSO was used by systems
> programmers.

Depends which systems programmers you mean :) From the earliest days of
MVS, it was running under VM because in part of the lack of prototype
370s for them to use. This at a time when IBM were 'hoping' that S/370
customers wouldn't need virtual machines.

My father (who I think always worked on the MVS side of things ... well
after MVS was born at least) almost certainly encountered VM at Yorktown
Heights between 1974-1976 if not earlier, and quickly grew addicted to
having his 'own' S/370.

Melinda Varian has a fascinating paper on the history of VM on her page
at :-

http://www.princeton.edu/~melinda/

> When IBM dropped VM, they found that their VM customers were not
> migrating to TSO, they were looking at DEC's offerings. So IBM
> reversed their decision and kept VM. They also took a bunch of public

Hit 'em over the head hard enough with a brick and even the dumbest
corporate type will see the light ... with the exception of DEC ones :)

> The same thing happened to DEC years later. When they decided to drop
> UNIX  to force their users into runing VMS, customers started making
> plans to drop DEC entirely and convert their VMS useage to UNIX.

I was under the impression that it was DEC dropping the 36-bit line that
caused their customers to revolt, and look into alternatives. Pre-VMS I
don't think DEC had a UNIX product, even if some of their customers were
running it. I think it was only later that DEC went with the flow, and
launched Ultrix for the VAX ... well after BSD was running on the VAX.

-- 
Mike Meredith (http://zonky.org/)
  Some people, when confronted with a problem, think ``I know, I'll use
  regular expressions.'' Now they have two problems.  -- Jamie Zawinski