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Comment by jmclnx | Hacker News Reader

If it was not for DRDOS 6.0, that would never have happened. DRDOS 6.0 was excellent, one thing that never got to MS-DOS was the ability to password protect files, preventing someone else to access it. Granted, that was very easy to get around, but back then the times were simple.

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DR-DOS also had some kind of limited multitasking or at least switching between tasks. I do not remember using it much or know how stable it was. I do not think MS-DOS ever copied that either?

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.

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

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?

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.

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://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.

Correct, DR-DOS had a Task Switcher, but still single processing. It was much better than the DOSSHELL Microsoft had because you could switch at the command line as opposed to having to run a bloated shell.

Incorrect. It could indeed pre-emptively multitask, on a 286 or above.

I have demo disks for download on my blog with the service configured. It's readily Googled.

Download links for boot disk images of Open DR DOS 7.01-6, 7.01-7, and the WIP 7.01-8.

https://liam-on-linux.livejournal.com/58013.html

Indeed, and I was a ViewMax fan, but eventually Microsoft managed to work around them as we all know, and like with other DOS clones compatibility never was 100% assured.

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