Compile as DOS application?

[Hans-Bernhard Bröker]

Am 01.06.2025 um 18:47 schrieb Eric J Korpela via Cygwin:
> To be more explicit, a text mode windows program is not a DOS program.  It
> will do anything useful on a DOS system without windows.

           ^ not

> If you desire 32-bit protected mode DOS programs, DJGPP may be your best
> option.  New builds of DJGPP are available at http://www.delorie.com/djgpp/
> .  I'm not sure if the current binaries run correctly under cygwin as they
> are programs that run under a DOS extender.

They won't, and Cygwin itself has no way of changing that. 64-bit 
editions of Windows cannot run anything 16-bit (technically, the V86 
mode is gone from both the CPUs and the system).  That does mean DOS 
itself is not available, and therefore nothing expecting to run in DOS 
can run either.

What Cygwin does have is a set of cross-compilation tools to the DJGPP 
environment.  Those allow you to cross-build DJGPP executables on 
Cygwin, but they can't run  there.

It takes something like FreeDOS in a VM to get the original DJGPP 
itself, or any of the programs it builds, to run inside any remotely 
up-to-date Windows.