🚀 go-pugleaf

Mircrosoft MS-DOS (formerly Seattle Ssytems QDOS) bears more than a
passing similarity to Digital Research CP/M-86 (Control Program for
Microprocessors).  The -86 version of CP/M was designed for the
Intel 80x86 series of CPUs.

The FCB (File Control Block) methodology of accessing files in
MS-DOS was pretty much wholesale lifted from CP/M at the code interface
level.  Basically you load a register with the function code, then
do a long jump to the DOS handler.  This worked in both CP/M and
DOS at least up through DOS version 2.11.  I don't know the level
of similarity of code internal to early DOS and CP/M-86.

I recall that to get CP/M-86 Wordstar 2.5 to run in MS-DOS, one
only had to patch one byte in the executable.

The other area of amusement is that the TOS+GEM interface on the
Atari ST computers is more than slightly reminiscent of MS-DOS
interrupt functions..

For Microsoft and Digital Research to be competitors, there seems
to be a surprising level of cross-fertilization in their products.

Bill

-- 
Bill Mayhew      NEOUCOM Computer Services Department
Rootstown, OH  44272-9995  USA    phone: 216-325-2511
wtm@uhura.neoucom.edu   ....!uunet!aablue!neoucom!wtm
via internet: (140.220.001.001)