The Origins of DOS

Jim Isbell, W5JAI jim.isbell at
Fri Oct 27 20:57:27 CDT 2006

OK, where did TRSDOS fit in?  It was before MSDOS as far as sale to the public.

On 10/27/06, Fred Cisin <cisin at> wrote:
> Everybody who was around had hold of different pieces of that elephant.
> On Fri, 27 Oct 2006, Warren Wolfe wrote:
> >     [In the interests of avoiding problems, the following is a composite
> > of several coherent and consistent stories I got from several people who
> > were involved.  This is how I understand events to have taken place,
> > and, therefore, constitutes my singular opinion of events as they
> > occurred.  No claim of ultimate accuracy should be implied or assumed.
> > That should keep the wolves at bay...]
> >
> >     It's not at ALL surprising that MSDOS resembled CP/M.  The first
> > version of MSDOS, called simply DOS, was actually a hot copy of CP/M for
> QDOS, followed by 86-DOS and SCP-DOS
> > 8080 that had been run through a program, XLAT, (often called X-LAX by
> > those who had to clean up its output) that translated it from 8080 to
> > 8086 mnemonics.  It was produced by Seattle Computer Products (SCP) for
> > its combo 8080/8086 CPU board, from a commercial program of questionable
> > legality which "disassembled" the CP/M code running in your machine when
> > you ran it.  (I forget the name.  Anybody remember this?)  It took the
> > crappy code (in this case code generated by the PL/M compiler, and made
> > commented assembly language source.
> >     The folks at Seattle Computer Products got this disassembler, ran
> > it, took the output of that, and ran it into XLAT, and voila!  CP/M for
> > the 8086.  It was changed so that one could take the various
> > three-letter CP/M commands, and spell them out, and they would work.
> > Also, in an apparent attempt to avoid being sued by Digital Research,
> > they kept "ERASE" as an expanded command, but it only worked, in
> > abbreviated form, as "DEL".
> Tim Patterson never denied that QDOS ("Quick and Dirty OS") was based
> closely on CP/M.  Most structures were deliberately kept compatible.
> However, he liked the idea of a linked list of blocks, as used at that
> time in the Microsoft "Stand-Alone BASIC" used on some NEC machines, and
> quite similar to the OS MS wrote for the RS Coco.
> > Apparently that was sufficient, as nobody
> > got sued.  Bill Gates then bought out SCP -- I'm unclear if it was the
> > whole company or just the O/S product, and a legend was born.
> just the OS.
> and both Tim Patterson ("Falcon Tech"?) and SCP retained rights to use and
> market the OS!
> Much later (1987?) when SCP was on the rocks, a number of biggies,
> reputedly including AT&T were very interested in the asset of a royalty
> free license.  MS sued, but then they settled out of court by MS buying
> SCP.  (MUCH cheaper than the lawsuit would have been!)
> > They went
> > to work, and started cleaning up their copy, and DOS for PC was born.
> > And, if not for a significant error by Gary Kildall, creator of CP/M, it
> > might well have been Digital Research Inc, in the place of MicroSoft.
> > What a different world we would live in, eh?
> If not for the SPECIFIC incident, (Gary flying up to Oakland for the day
> when IBM was scheduled to meet), DRI (once "Intergalctic Digital
> Research"!) would still have lost it - there was an extreme level of
> culture clash.  IBM, with their dress code, etc.) was SHOCKED at what they
> saw in Pacific Grove.  And (UNCOFIRMED), when the staff at DRI first saw
> the IBM people arriving, they thought it was a drug raid.
> After his death, friends of Gary claimed that the flight to Oakland was
> essential and necessary!  (Nobody else in the company could have handled
> delivering some manuals to Godbout at the Oakland airport.)
> It would, indeed, have been a different world!
> Although the PC 5150 was released with MS-DOS (8/1981), IBM agreed to also
> sell CP/M-86, as a concession to DRI's objections to copyright violations.
> --
> Grumpy Ol' Fred                 cisin at
> XenoSoft              
> PO Box 1236                     (510) 558-9366
> Berkeley, CA 94701-1236

Jim Isbell
"If you are not living on the edge, well then,
you are just taking up too much space."

More information about the cctech mailing list