Message-ID: <004e01bff01c$1429d6a0$11fea8c0@jgsd.co.uk.invalid>
From: "Ben A L Jemmett" <ben DOT jemmett AT ukonline DOT co DOT uk>
To: <opendos AT delorie DOT com>
References: <20000717 DOT 180302 DOT -238167 DOT 0 DOT editor AT juno DOT com>
Subject: Re: Hi !
Date: Mon, 17 Jul 2000 19:23:16 +0100
Organization: Jemmett Glover Software Development
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Reply-To: opendos AT delorie DOT com

> > > Even CP/M  86, Kildall's alternative for the original IBM-PC, was
> > > released *after* M$'s PC-DOS
> > It was written at the same time,
> Yes, if you consider QDDOS and PC-DOS 1.0 to be the
> same animal.
Sort of.  However, IBM approached DRI to write CP/M-86 before they
approached MS, and MS went off and bought/modified QDOS.  So the development
work was going on concurrently, but MS had a head start with their buyin of
code.

> > but was in testing for longer ->
> > fewer bugs.
>
> No doubt about that -- it was also extremely expensive,
> assuring buggy PC-DOS's predominance in the
> marketplace.
IIRC, the three OSes available with the PC were IBM's Personal Computer DOS
(nice and cheap), CP-M/86 (extra 100 bucks or so), or the UCSD P-System
(*big* money).  It was IBM's decision to price DOS and CP/M that way, as
they were annoyed at DRI for being slow and not wanting to sign contracts
too early.

> Remember, M$ bought QDDOS from Seattle
> Microcomputer and did some adaptation to the specifics
> of the IBM-PC hardware, so PC-DOS was much less of a
> porting job than CP/M 86.
Well, yes, but QDOS was pretty much a disassembly/reassembly of CP/M-80,
wasn't it?  So the porting would be similar, although most of it was already
done I guess.

> > It was just a port of CP/M-80 though, so technically the
> > system was around for more than half a decade before MS-DOS.
>
> That's a bit of a stretch in the context of this
> thread, since CP/M wasn't designed to be portable
> between CPU architectures the porting job was
> distinctly non-trivial compared to what M$ did to
> adapt it's purchased DOS to IBM's requirements.
Yes, it's a very big stretch, but the core of CP/M - the interaction of the
BIOS, BDOS and command processor in CPM.SYS, and the BDOS calls available
etc. - were layed out in the early to mid 1970s (CP/M 1.0 was early 1974,
but was significantly different from 2.2.  CP/M-86 was based on CP/M 3, and
DOS Plus/DR DOS on CP/M 4).

Regards,
Ben A L Jemmett
(http://web.ukonline.co.uk/ben.jemmett/, http://www.deltasoft.com/)