DOS ain't dead - ctty/dup2 in DOS4

ctty/dup2 in DOS4 (Developers)

posted by kerravon , Ligao, Free World North, 26.12.2025, 20:08

In the DOS4 source code, I can see:

cmd\command\tcmd2b.asm

ICLLOOP: ; Close basic handles MOV AH,CLOSE INT int_command INC BX LOOP ICLLOOP POP BX ; Get handle MOV AH,XDUP INT int_command ; Dup it to 0 MOV AH,XDUP INT int_command ; Dup to 1 MOV AH,XDUP INT int_command ; Dup to 2 MOV AH,CLOSE ; Close initial handle INT int_command

Now according to RBIL:

https://www.ctyme.com/intr/rb-2931.htm

BX should have the file handle. But I see 3 executions of Int int_command,
and I don't see BX changing from 0, to 1, to 2, between executions.

Any idea how this works?

Note - I'm trying to get "ctty com1:" to work on PDOS-generic, and I
don't really have the concept yet.

Thanks. Paul.

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Complete thread:

ctty/dup2 in DOS4 - kerravon, 26.12.2025, 20:08 (Developers)
- ctty/dup2 in DOS4 - ecm, 26.12.2025, 21:39