

Early Digital Research CP/M Source Code - chl
http://www.computerhistory.org/_static/atchm/early-digital-research-cpm-source-code/

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Zardoz84
And they forgot to put the posterior evolution of CP/M , with the multiuser
versions, and later in a compatible "clone of MS-DOS", called DR-DOS.

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pervycreeper
One thing I never quite understood: in a home computing context, what is the
advantage of having a system like CP/M, compared to, say, using a BASIC
interpreter which includes the same commands?

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nilsimsa
The hardware was not quite standardized at that time so CP/M had a layered
structure consisting of a BIOS, BDOS and the command line processor. The BIOS
was the hardware abstraction layer and was ported to the specific combination
of hardware. The BDOS provided the file system and the command line processor
provided a standardized interface. On top of this you would run the BASIC
interpreter as an application.

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to3m
Right, but while BASIC is running, the command line processor isn't. So if you
want to run a command... what then? Presumably the BASIC has to reimplement
it. I guess that's the point. Having this layered approach is valuable, but
having a separate command processor, perhaps less so.

(I never used CP/M but I used to have an Acorn BBC Micro and that had the
command line processing built in to the OS, in its equivalent of the BIOS, I
suppose to work around this very issue. All an application needed to do was
get a string from somewhere, then pass it to the appropriate OS routine. So
many programs ended up effectively having the standard command processor
embedded, in addition to whatever interface they might themselves support.
Though obviously the user had to be careful not to do anything silly like load
a new program that overwrote the running program or overwrote their data.
Different times.)

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toolslive
I think CP/M is where the driver letters in windows came from. Now I know who
did it.

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Moto7451
MS DOS is a clone of CP/M. Since Windows originally ran on top of DOS it
inherited the drive letter system.

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MrBuddyCasino
The sources for MS DOS 1.1 and 2.0 are available as well, if you'd like to
compare them: [http://www.computerhistory.org/atchm/microsoft-ms-dos-
early-...](http://www.computerhistory.org/atchm/microsoft-ms-dos-early-source-
code/)

