I would like to develop a little but complex “.com” program and I’m wondering which debugger to use.

I was developing in assembler some 25 years ago, and surely my then tools have been vastly improved.

This program will probably need directly access video-memory (text mode) and maybe also keyboard but more than that is the logical flow part that probably will need the most of debug.

Development environment can be Windows or Linux (or else if needed).

Suggestions?

Thank you!

You can either use emulator like bochs or qemu and deploy external debugging tool like IDA if you want to use Windows or Linux debugging tool. If you want to debug under DOS you might consider some debugger that supports 386 hardware breakpoints - it will enable you to debug memory access issues. Use either Periscope or SoftIce, Swat386 can also debug almost anything but if you are just using plain, real-mode DOS and need HW breakpoint support first two could be a better choice IMHO. Some people use Turbo Debugger - depend what are you looking for and what is your target DOS environment.

From description seems IDA is good and even if not "open" is at least free for non commercial use (v.5.0)

I'll give it a try!

Thank you!

If IDA will fit your needs consider commercial version. There used to be a plugin for DosBox debugger. Could be useful for your target. I also had a success with x86emu few times when reversing some DOS code.