3 ms·

MS-DOS had TSRs (terminate and stay resident) programs, but those aren't exactly the same thing. I do recall some basic multitasking utilizing them in some way,

MS-DOS had TSRs (terminate and stay resident) programs, but those aren't exactly the same thing. I do recall some basic multitasking utilizing them in some way, though. My memory is too fuzzy. MS-DOS 4.0 had a multitasking release, but it was not popular and only available through retail channels. IBM didn't want it so there were OEM MS-DOS releases of 4.0 that didn't have multitasking, and that's what you got when you bought an IBM PC. This meant it didn't get a lot of support and was discontinued after MS-DOS 4.1. If it sounds like a mess, it's because this was all when IBM and Microsoft were not very happy with each other, which is kind of why everyone mostly jumped from MS-DOS 3.3 (IBM and MS mostly cooperative) to MS-DOS 5.0 (MS independent). DOSSHELL supported task switching, but only one process could execute at a time, and all tasks had to fit in memory.

EgoIncarnate 3y ago
DOSSHELL creates a swap file DOSSWAP.SWP, so all tasks don't need to fit in memory.
- da_chicken 3y ago
  I guess I could be wrong, but I thought that was only for DOSSHELL itself, not for the tasks you were launching. Perhaps it would work but only if the other tasks supported it?
  - EgoIncarnate 3y ago
    My quick test of running multiple command prompts and running free showed that each one had a full set of memory. It's not multitasking, and I believe it assumes that the tasks are well behaved (not modifying DOS internals), so tasks don't really need to do anything special if they are well behaved.
SeenNotHeard 3y ago
You're thinking of what is sometimes called "European MS-DOS 4.0" which did indeed have limited multitasking features, including shared memory and pipes: https://en.wikipedia.org/wiki/MS-DOS_4.0_(multitasking) https://en.wikipedia.org/wiki/MS-DOS_4.0_(multitasking) https://virtuallyfun.com/2013/03/17/european-ms-dos-4-00-aka-multitasking-dos/ https://virtuallyfun.com/2013/03/17/european-ms-dos-4-00-aka... It should not be confused with the mostly unrelated DOS 4.0 later released. A Microsoft executive later said the multitasking DOS should probably not have been named "4.0" because it created a lot of confusion.

EgoIncarnate 3y ago

DOSSHELL creates a swap file DOSSWAP.SWP, so all tasks don't need to fit in memory.

da_chicken 3y ago
I guess I could be wrong, but I thought that was only for DOSSHELL itself, not for the tasks you were launching. Perhaps it would work but only if the other tasks supported it?
- EgoIncarnate 3y ago
  My quick test of running multiple command prompts and running free showed that each one had a full set of memory. It's not multitasking, and I believe it assumes that the tasks are well behaved (not modifying DOS internals), so tasks don't really need to do anything special if they are well behaved.

SeenNotHeard 3y ago

You're thinking of what is sometimes called "European MS-DOS 4.0" which did indeed have limited multitasking features, including shared memory and pipes: https://en.wikipedia.org/wiki/MS-DOS_4.0_(multitasking) https://en.wikipedia.org/wiki/MS-DOS_4.0_(multitasking) https://virtuallyfun.com/2013/03/17/european-ms-dos-4-00-aka-multitasking-dos/ https://virtuallyfun.com/2013/03/17/european-ms-dos-4-00-aka... It should not be confused with the mostly unrelated DOS 4.0 later released. A Microsoft executive later said the multitasking DOS should probably not have been named "4.0" because it created a lot of confusion.