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MS-DOS a.k.a. PC-DOS nee QDOS, was commonly just referred to as DOS. But 'disk operating system' is a very obvious acronym; there must have been previous operating systems so called.

What was the first operating system called DOS?

hippietrail
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rwallace
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    Lol I always thought DOS meant "dirty operating system" – Thomas Cook Nov 26 '19 at 16:51
  • I always thought D(isk) was a strange way to start the acronym. I mean, the OS is operating so much more than the disk. "Disk operating system" sounds more like disk controller firmware than an actual operating system. – dwizum Nov 26 '19 at 19:20
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    @ThomasCook, given that MS-DOS/PC-DOS was based on QDOS, which was "Quick and Dirty OS", you were right. – Ray Butterworth Nov 26 '19 at 19:53
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    Display On Screen – Aequitas Nov 27 '19 at 00:23
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    @dwizum - it's not that the System is Operating the Disk, it is that the Operating System is Disk-based, in contrast to the many predecessors which were not disk-based (and probably ran on computers which had no disks - because disks were expensive luxuries). – dave Dec 02 '19 at 23:26
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    @RayButterworth - well, that's another question (maybe you should post it?). Who came up with the name "PC-DOS" - IBM or Microsoft? If IBM, I think it most likely that the men in suits named PC-DOS in the same way that they had named DOS/360,, DOS/VS, DOS/VSE -- in which case it's D for Disk. – dave Dec 02 '19 at 23:30
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    @another-dave IBM came up with the name PC DOS. – JeremyP Jun 13 '22 at 12:24

1 Answers1

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DOS/360

(As distinct from TOS/360, the tape OS)

Announced at the end of 1964 per Wikipedia.

dave
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