The Original MS-DOS 4.0

From: Hans Franke <>
Date: Fri Jun 30 13:14:45 2000

> This might be a topic better posted in the alt.folklore.computers
> USENET group, but let me try here first. This is from memory, and
> it's not as reliable as I'd like it to be.

> IIRC, OS/2 was not Microsoft's first attempt to create a
> multitasking operating system. They were working on, and
> I believe mostly finished, a DOS 4.0 that was multitasking.
> This was not the PC-DOS 4.0 for IBM, nor was it the MS-DOS
> 4.0 that we finally saw here in the states.

> This multitasking DOS 4.0 (from Microsoft, not a third party)
> was supplied with a computer that was old only in either the
> UK or more widely in Europe. It seems that the first letter
> of the computer manufacturer was an 'A', so the machine could
> have been an Apricot, an Amstrad, an Acorn, or lord knows.

> I read about this machine either in Byte during the late 80s
> or in a BIX conference (I MISS BIX!). I've searched the web
> for references to this multitasking MS-DOS 4, and have found
> nothing.

> Does anyone else remember this? Was the Byte article reviewing
> a sample of a product that never shipped? Did anyone get their
> hands on one? Does anyone have it?

Well, I never heared about the version you are refering to, but
DOS was basicly starting from 2.0 able to do task switching.
All Informations necersary where contained within a series of
structures with a single root. The only missing thing was a
table of task pointers to switch between - and a service to
store and restore the screen content. There have been several
products offering this service. And with DOS 4 MS supplied the
infamous shell, capable of doing this. You could load several
applications and switch via a hot key combination. Windows is
still today (at least Win9x) based on this very same mechanism
for context switching. Also the functions for 'background'
applications/drivers where designed to support application
switching. The famous TSR mechanism was not only ment to steal
some memory for crude interrupt handlers, but also for true
serviceprovider tasks within the OS ... well, I guess most
programmers never realized the potential offered and kept
limited to a simple one programm state of mind.

All this was already available starting with DOS 2.x, just
it has never been 'official' until DOS 4.x


VCF Europa 2.0 am 28./29. April 2001 in Muenchen
Received on Fri Jun 30 2000 - 13:14:45 BST

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