How to compile c/c++ to ms-dos .com programs?

Question

I use Code::Blocks with GNU GCC Compiler. My question is: is there any way to compile c/c++ code to ms-dos 16bit (.com) executable format?
I tried to set the build options and search the compiler parameters on the net, but i couldn't find anything.

Answer 1

You can certainly compile C and/or (an ancient dialect of) C++ to a 16-bit MS-DOS .com file. The compiler/linker you have with Code::Blocks almost certainly can't do that though.

In particular, at least to my knowledge, gcc has never even attempted to generate code for a 16-bit, segmented-memory environment. There was at least one port of gcc to a DOS extender (DJGPP, but it produces .exe files, not .com and it uses a proprietary DOS extender. This originally used an ancient version of gcc, but has since been updated to a much newer version of gcc.

If you really need to generate a .com file, there are quite a few options, but all the compilers are quite old, so especially with respect to C++ the language they accept is quite limited.

Tool chains that target(ed) MS-DOS.

_{Caveat: As already noted, all of these are very old. Generally speaking, the C they accept is reasonably conformant C89, but only for fairly small programs (both in terms of code and data size--of necessity: .com files are basically limited to a combined total of 64Kbytes of data and code). The differences between the C++ they accept and anything even sort of close to modern is much more profound (e.g., some didn't support templates at all). All mention of conformance here is relative to other compilers of the time; by modern standards, their conformance is uniformly terrible.}

1. Microsoft: Only sold C++ compilers for MS-DOS for a fairly short time--they were somewhat late into the market, and moved out of it to compilers that produced only 32-bit Windows executables fairly early. Known more for optimization than language conformance.
2. Borland: Mirror image of Microsoft. Better conformance, poorer optimization, probably the last to abandon the MS-DOS market. Their last few compilers for MS-DOS even supported C++ templates (fairly new at the time).
3. Watcom: one of the few that's still available as a free download, but without commercial support. When it was new, this was generally considered one of the best available for both conformance and optimization. It's apparently been updated (to at least some extent) relatively recently, but I haven't used a recent version so I can't really comment on those updates.
4. Metaware: Quite an expensive option at the time. I never used it, but some people I respected highly considered it the best compiler you could get. Mostly targeted embedded systems.
5. Datalight/Zortech/Symantec/Digital Mars: the other one that's still officially available. Had a small but extremely loyal following. I tried it for a while, but never found a compelling reason to prefer it over others. Digital Mars still maintains this compiler, so it's one of the few that still gets fairly regular updates.

There were quite a few more back then as well, but these probably account for well over 90% of the market at the time.

Answer 2

What you are looking for is exe2bin. This was a utility that came with DOS to convert .EXE format object code into the .COM format (code and data in one 64K segment). It came with DOS and some compiliers/assemblers.