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Comment by ZenoArrow | Hacker News Reader

>"multiple independent vendors"

Unless I'm missing something, there weren't multiple vendors for MS-DOS pre-Windows.

There was MS-DOS, and also Digital Research, later Novell, then Caldera, etc DOS which tended to have features that wouldn't be around until a version or two of MS DOS later. There were also nasty power plays involving the two -- early betas of Windows 3.1 would refuse to run on DR-DOS.

There was also IBM PC DOS, which was essentially a rebranded MS-DOS but later diverged into its own thing, with support for REXX scripting, etc.

Don't forget 4DOS. I loved that OS:

https://en.m.wikipedia.org/wiki/4DOS

Actually, I looked that up because that's what I remembered using as a "DOS alternative". Seems like it was actually just a shell replacement, leaving the actual OS stuff (such as handling INT 21h requests) to the underlaying OS, whether DOS, Windows or OS/2.

I guess wee me back in the day didn't know the difference :)

Well son of a gun. I assumed it was a full DOS implementation but you're right. Well TIL... 20 years later...

And PTS-DOS

IBM PCs came with PC DOS which you could also buy separately, which was an (essentially identical) licensed version of MS DOS. It was vendor independent, though.

IBM PCs had BASIC built into the ROM (licensed from Microsoft). BASIC.COM and BASICA.COM (advanced BASIC) which came with PC-DOS would call subroutines in the ROM (except for ones that had errata), so you needed a real IBM PC to run it. Clones didn't have BASIC in ROM, so MS-DOS came with GWBASIC.COM which included all the subroutines. Turns out GWBASIC runs faster than BASICA because the RAM had faster access than ROM.

More details at: https://en.wikipedia.org/wiki/IBM_BASIC

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