There's a rather more sophisticated DOS SDK available: doslib from the guy who maintains dosbox-x.

https://github.com/joncampbell123/doslib

Most of the stuff that's emulated in DosBox-X has a corresponding SDK in doslib. It's a treasure-trove of information

You can get a free C and C++ compiler for DOS at:

https://www.digitalmars.com/download/freecompiler.html

320x240 mode was the coolest thing back in the days - https://github.com/Scalibq/DOS_SDK/blob/main/C/VGA.c#L38

Unchained modes FTW!

https://en.wikipedia.org/wiki/Mode_X

not really sure what this is about - i was programming in assembler and c on ibm xt and at in the early to mid 1980s, with no problems.

> An equivalent for the IBM PC platform, or PC DOS/MS-DOS/compatible environments has never been available

As usual - you will never know the difference until you try.

well, as i said, i did program for those environments - don't feel much urge to re-start now

Not sure why you think we care.