DOS ain't dead - DS and ES matching

DS and ES matching (Developers)

posted by kerravon , Ligao, Free World North, 19.10.2025, 10:32

> I could make ES equal to FFFF, which is an indicator that
> this is a PDOS-generic environment, so look on the stack etc.

Probably ES=1 would be better. As a segment, it would trash
the interrupt vectors. And it's not a valid selector either. So
it will hopefully be distinct from DOS 4 MT NE running in
either RM16 or PM16 - present or theoretical future.

This is all based around INT 21H calls though. I'm not really
expecting to dynamically detect that I'm in an OS/2 1.0
DLL environment and I should be calling DOSCALLS routines
instead. But I guess that would be a technical possibility.

But regardless - just like binutils has an "objcopy" utility, I'm
basically expecting to have a "execopy" facility that copies
my a.out 8086 code (plus the map file from the linker so that
I know where the individual object modules start and end),
and convert it into MSDOS MZ or MSDOS NE and in both
cases it works in both RM16 and PM16 given a suitable OS
that can load MZ into PM16 and either cope with or request
override (to int21() callback function) of INT 21H calls.

BFN. Paul.

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Complete thread:

DS and ES matching - kerravon, 18.10.2025, 11:29
- DS and ES matching - ecm, 18.10.2025, 12:48
  - DS and ES matching - kerravon, 18.10.2025, 14:43
    - DS and ES matching - PDB meaning - ecm, 18.10.2025, 18:32
      - DS and ES matching - PDB meaning - kerravon, 18.10.2025, 19:04
        DS and ES matching - PDB meaning - ecm, 18.10.2025, 19:41
        DS and ES matching - PDB meaning - kerravon, 18.10.2025, 19:59
        DS and ES matching - PDB meaning - kerravon, 18.10.2025, 20:01
- DS and ES matching - kerravon, 19.10.2025, 10:32