You may very well be right about this; I would like to understand it
better.

I agree with your comment about the vdm.  But what limitation
in dos/windows would prevent multiple vdm's from running?
nt has permitted multiple vdm's since its early versions.
(I consider nt 3.50 to be early.)  This facility in nt has many
times let me run 'rogue' 16-bit apps without messing up
other stuff I was running.

Also, I remember that when w95 came out, and microsoft
(under the influence of some of their marketing-puffery
types) denied that it had *any* dos in it, that independent
observers made two points.  One, that it still contained
a lot of legacy 16-bit dos and (old) windows code, and
two, that the claims of 'apps can't crash one another'
wasn't completely true, although there were *some*
substantive improvements.

I've never understood the complete story.  But if dos/windows
has complete pre-emptive multitasking, how can a single rogue
app consistently hang the whole os?  (In nt, this *rarely* happens
to me --- I can almost *always* kill off the rogue app with the
task manager, and the os and the rest of the apps are fine.)

Whether it's cooperative multitasking, or something else,
the isolation between apps (i.e., processes) in dos/windows
is much less than in nt (and I'm speaking about modern, 32-bit
apps, not just legacy 16-bit dos apps.)

Like I said, I would love to understand this better.  I would
like to square the behavior I see on the surface with an
accurate understanding of what is going on under the hood.

Thanks for any color on this.


Earl Truss <[log in to unmask]> wrote:

> Windows has not used co-operative multi-tasking since Windows 3.1.
> Preemptive multi-tasking was introduced in Windows 95.  Perhaps what you
> are thinking of is that all 16-bit programs run in one virtual machine.

     Frank R.Brown
     Frank.R.Brown@MailAndNews

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