Hello Ralf,
On a slightly related note: https://www.pcjs.org/blog/2018/05/27/ . :-)
Well, that article has a whole lot of nothing about "CALL 5".
Read on carefully. :-) There is a VM of PC-DOS 2.0 which includes a
utility that was part of Microsoft Word ... and the utility uses `call 5'.
(Apparently --- per the blog post --- the utility using `call 5'
survived the transition from the 8086 to the 80286, and it was on the
80286 that it started to cause problems (because of A20).)
(Technical Reference) manual, nor do I recall this mentioned in more
than passing in any 3rd party "DOS internal" kind of books.
The `call 5' syscall interface is quite simple:
* only syscalls 0--0x24 are allowed;
* the syscall number goes into cl, not ah;
* all other syscall parameters are as for `int 0x21'.
The interface does not really give programmers any extra power that
normal `int 0x21' calls cannot give --- which might explain why most
"DOS internal" texts do not care much about it. But it is there, and
even later versions of MS-DOS (and FreeDOS) still have it.
By and large, people just need to stop spreading the myth that "DOS is
copied/stolen from CP/M" or similar nonsense.
True that.
Thank you!
--
https://gitlab.com/tkchia :: https://github.com/tkchia
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