On 7 Dec 2024, at 13:34, Henry Bent
<henry.r.bent(a)gmail.com> wrote:
Also interesting; I wonder if the "capability to run multiple MS-DOS applications
under Unix" was shipped in a functional form, and what relation it might or might not
have had to what was running on the AT&T hardware.
I used to run an 80286 “Taiwan clone” (as we called them in Italy) with Xenix 286 and,
later, its 386 version which was SCO by then (memory a bit fuzzy on when Xenix became SCO
Xenix and the Unix) and I definitely could run MS-DOS programs on the 386 - you would use
the dos command which mapped drives either to physical drives (i.e. A: was the floppy) or
directories within the filesystem.
It was often used for businesses which had their inventory on MS-DOS bespoke software but
wanted to “multitask” so we had some very dirty code which would run the DOS program on
the serial terminals writing to a “network” drive which was actually a directory in the
Unix filesystem.
In the meantime I was busy writing a migration layer which would allow us to compile the
MS-DOS C code on Unix natively replacing, for example, code writing the pretty box
characters on MS-DOS with curses equivalents. Fortunately the DB stuff was all
C-ISAM for which a portable library existed.
All of this was strictly with licenses found off the back of a truck, of course. Licensing
bypass in Italy was a national sport.
(this was all done using the VM86 extension which, incidentally, still exists in Intel
chips… this opens a whole other story about forgotten Intel extensions lingering in 2024
cores which can be used nefariously).
Arrigo