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Authored by: Wol on Monday, April 15 2013 @ 06:38 PM EDT |
I'm not sure how far it was IBM's design, and how much it was DOS casting that
fact into stone.
I think the original PC was limited to 1Mb of address space, and DOS was written
to assume all that "interesting" stuff lay between 640K and 1M. So
when PCs with a bigger address space came along, they couldn't move it without
breaking DOS.
Oops.
Because CP/M did everything via the low-memory jump table, using a tactic like
that would have made it easy to move those buffers etc out of the way.
Cheers,
Wol[ Reply to This | Parent | # ]
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Authored by: Anonymous on Monday, April 15 2013 @ 06:39 PM EDT |
CP/M was written for 8-bits microcomputers ( i.e. for Intel 8008, 8080 ) all of
which started at address 0000H after reset. Intel 8086 and 8088 didn't exist at
that time.
The structure of CP/M ( command syntax and memory layout ) is fairly close to
what was current in the mini computer world at that time ( say operating system
for DEC PDP-8 and PDP-11 among others ). So who copied whom?
A program like PIP existed with exactly the same syntax and behavior in CP/M as
in OS/8 ( PDP-8 ) and RT11 and RSX for PDP-11 )
Most programming is not invention, it is following the custom so not to confuse
the users.
[ Reply to This | Parent | # ]
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