On 4/17/2021 3:39 AM, TK Chia wrote:
Hello Liam, hello Tom,
And according to the mainstream account (?), CP/M-86 would not be
released until late 1981. QDOS was released earlier, in mid-1980
(https://archive.org/stream/byte-magazine-1980-08/1980_08_BYTE_05-08_The_Forth_Language#page/n173/mode/2up).
QDOS's system call interface (`call 5') was in fact based on that of the
_8O8O_ version of CP/M, while CP/M-86 decided instead to implement a
different syscall interface (`int 0xe0').
I misspoke a bit here: `call 5' was just one of QDOS's system call
interfaces (the other syscall interface supported by QDOS would be the
`int 0x21' that MS-DOS programmers are familiar with).
The "CALL 5" equivalent was never properly implemented, I guess Peterson
ran into problems with the differences of the 8080 and 8086 CPUs.
That's why the INT 21h as the actual DOS API was introduced. For which
no equivalent exists in CP/M-80. And yes, CP/M-86 didn't exist at that
time, at least not anywhere outside of Kildall's office, if at all...
And you will have a hard time to find any serious documentation on that
CALL 5 stuff for any version of DOS. And I would be surprised if there
would have been anything left after the rewrite of DOS for MS-DOS 2.0.
Ralf
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