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Did you know that OS/2 wasn't Microsoft's first non Unix multi-tasking operating system?

 Most people know about Microsoft’s official timeline for its operating-system like products

1. Xenix - Microsoft’s first operating system, which was a version of UNIX that we did for microprocessors. 

2. MS-DOS/PC-DOS, a 16 bit operating system for the 8086 CPU

3. Windows (not really an operating system, but it belongs in the timeline).

4. OS/2, a 16 bit operating system written in joint development with IBM.

5. Windows NT, a 32 bit operating system for the Intel i386 processor, the Mips R8800 and the DEC Alpha

But most people don’t know about Microsoft’s other multitasking operating system, MS-DOS 4.0 (not to be confused with PC-DOS 4.0)

MS-DOS 4.0 was actually a version of MS-DOS 2.0 that was written in parallel with MS-DOS 3.x (DOS 3.x shipped while DOS 4 was under development, which is why it skipped a version).

DOS 4 was a preemptive real-mode multitasking operating system for the 8086 family of processors. It had a boatload of cool features, including movable and discardable code segments, movable data segments (the Windows memory manager was a version of the DOS 4 memory manager). It had the ability to switch screens dynamically – it would capture the foreground screen contents, save it away and switch to a new window.

Bottom line: DOS 4 was an amazing product. In fact, for many years (up until Windows NT was stable), one of the DOS 4 developers continued to use DOS 4 on his desktop machine as his only operating system.

We really wanted to turn DOS 4 into a commercial version of DOS, but... Microsoft at the time was a 100% OEM shop – we didn’t sell operating systems, we sold operating systems to hardware vendors who sold operating systems with their hardware. And in general the way the market worked in 1985 was that no computer manufacturer was interested in a version of DOS if IBM wasn’t interested. And IBM wasn’t interested in DOS. They liked the idea of multitasking however, and they were very interested in working with that – in fact, one of their major new products was a product called “TopView”, which was a character mode window manager much like Windows. The wanted an operating system that had most of the capabilities of DOS 4, but that ran in protected mode on the 286 processor. So IBM and Microsoft formed the Joint Development Program that shared development resources between the two companies. And the DOS 4 team went on to be the core of Microsoft’s OS/2 team.

But what about DOS 4? It turns out that there WERE a couple of OEMs that had bought DOS 4, and Microsoft was contractually required to provide the operating system to them. So a skeleton crew was left behind to work on DOS and to finish it to the point where the existing DOS OEM’s were satisfied with it.

 

Edit: To fix the title which somehow got messed up.

Comments

  • Anonymous
    March 22, 2004
    The comment has been removed

  • Anonymous
    March 22, 2004
    Did you just make this up, or did you read something someone else had just made up?

  • Anonymous
    March 22, 2004
    see http://www.acad.humberc.on.ca/~frig8279/osessay/dos/history

    or just search google for "history of dos"

  • Anonymous
    March 22, 2004
    @pjm
    "Did you just make this up, or did you read something someone else had just made up?"

    So, you know Mr. Osterman has worked for Microsoft since the mid-80's right? And that he started there, on the DOS 4 project? You might want to check his bio.

  • Anonymous
    March 22, 2004
    Is there anywhere to get a copy of this nowadays?

  • Anonymous
    March 22, 2004
    The comment has been removed

  • Anonymous
    March 22, 2004
    The comment has been removed

  • Anonymous
    March 22, 2004
    I have Xenix.

    I also have a manual for DOS 4.0.
    When DOS 3.1 came out for the AT, I heard about the task switching stuff, ( that the DOS 5.0 shell did ), and had my friend get me a maunal from Daharan. No software, but I did get the manual. Later, DOS 5.0 had the features.

  • Anonymous
    March 22, 2004
    I have a vague memory of using this. It would have been in 1988 when I was working at STL for the summer - STL was the research part of STC (who owned ICL and was later taken over by Nortel ). Some of the ICL PCs at STL had a multitasking DOS4 on them.

  • Anonymous
    March 22, 2004
    The comment has been removed

  • Anonymous
    March 22, 2004
    if i remember correctly, Apricot also had this version of DOS as an OEM product, they were later taken over by Mitsubishi

  • Anonymous
    March 22, 2004
    The comment has been removed

  • Anonymous
    March 22, 2004
    LSN WebLog » Did you know that OS/2 wasn’t Microsoft’s first non Unix multi-tasking operating system?

  • Anonymous
    March 22, 2004
    I have MS-DOS 4.01, but for sure is the one that in reality is 9.x right?

  • Anonymous
    March 22, 2004
    3.x excuse me :)

  • Anonymous
    March 22, 2004
    The comment has been removed

  • Anonymous
    March 22, 2004
    The comment has been removed

  • Anonymous
    March 23, 2004
    Steve,
    My guess is that you used the Microsoft version of PC-DOS 4.0 instead of multitasking MS-DOS 4.0 - Multitasking DOS 4.0 was only delivered to Goupil in France to my knowledge, It'd surprise me immensely if it made it outside there.

  • Anonymous
    March 23, 2004
    You mention that NT ran on the MIPS R8800 which never existed, the NT kernel was developed on R3000 and R4000 before being ported to other architectures.

  • Anonymous
    March 23, 2004
    You're right j, I got the numbers wrong :(.

  • Anonymous
    March 23, 2004
    Wasn't there a version of NT for PowerPC as well? I thought it ran on the RS/6000 43p?

  • Anonymous
    March 23, 2004
    Sure, that was NT 3.51. But my listing above was in operating system families, not the specific versions of the various operating systems - I'd almost certainly get it wrong so...

  • Anonymous
    March 23, 2004
    In case you don't know, osnews.com links your weblog to their main page.

    http://www.osnews.com/story.php?news_id=6452

  • Anonymous
    March 23, 2004
    The comment has been removed

  • Anonymous
    March 23, 2004
    Nope, there was parallel development.

    The product known as multi-tasking MS-DOS 4.0 lived on as OS/2, while the product known as MS-DOS 3.1 continued on in parallel through DOS 3.2, DOS 3.3, DOS 4.0, DOS 5.0 and DOS 6.0.

  • Anonymous
    March 23, 2004
    So there are two different products called DOS 4? One regular version and one "amazing" version? Clear as mud.

  • Anonymous
    March 23, 2004
    Is Dos 4.0 and 4.1 freewhare now, if so, whare can i download it? Also, is Xenix still sold?

  • Anonymous
    March 23, 2004
    The comment has been removed

  • Anonymous
    March 23, 2004
    Sorry for the ugly link. I though you were supporting tags.

  • Anonymous
    March 24, 2004
    The comment has been removed

  • Anonymous
    March 24, 2004
    Sorry, I also have SCO's version of Xenix with MS Word for Xenix.

    MMMM. Imaging Windows like Mac OS X, Win on Unix. That would be great.

  • Anonymous
    April 19, 2004
    Why use an acient architecture? I'd prefer BeOS approach of a complete rewrite.

  • Anonymous
    April 20, 2004
    An ancient architecture?

    Um. We're talking about 1984 here. It wasn't ancient back then.

    BeOS is a much more recent vintage OS and it had the advantage of a processor that had virtual memory protection.

    NT WAS a complete rewrite with a modern architecture.

  • Anonymous
    May 14, 2004
    The comment has been removed

  • Anonymous
    May 14, 2004
    You're 99.9% accurate Peter, I'm impressed that anyone remembered :)

    The version of DOS that ICL used didn't have screen swapping - that functionality was there but not exposed on the ICL machines because they didn't require it. When the DOS 4 project was modified for the remaining customers, we removed a bunch of stuff that they weren't interested in, including the screen swapping stuff.

  • Anonymous
    May 24, 2004
    Can we download MS-Dos now ?

  • Anonymous
    May 25, 2004
    Not to my knowledge.

    Just because a product has reached it's End-of-life for support doesn't mean that Microsoft's going to make it available all of a sudden for free.

    And it would be an absolute support nightmare to have an MS-DOS download - DOS requires machines have floppy disks, but many computers (including the one I'm writing on right now) don't have them.

  • Anonymous
    June 17, 2004
    where can i download OS/2. is there aby freeware or shareware available

  • Anonymous
    June 17, 2004
    if there is, can share it to me at miranda_abonzo@yaho.com my email

    thank you very much


    nonoy
    miranda_abonzo@yaho.com

  • Anonymous
    June 18, 2004
    If you want OS/2, download eComStaion on ur fav p2p.

    os/2 warp 4 is a little harder to find (all the version floating around are german or dutch) but it can be found, and so can advanced server.

    Workers of the world unite!

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