A bit of history... I have 3 systems that I spend time on, a DOS 6.22 system, a Windows 95 system, and a modern Windows 7 (64-bit) system. When I upgraded to Win7-64, some of my favorite command line utilities stopped working, so I decided to re-write them myself. The only 2 compilers I have are Borland Turbo C++ 3.0 and Visual Studio 2008, and they worked fine for building 2 versions, a DOS 16-bit, and a Windows 7 32-bit (could have built 64-bit too, I guess.) The problem came with my Win95 system. The DOS version works fine there, but since I spent the time to support LFNs in the Win7 build, I wanted it with my Win95 system. So, after a lot of research, I found and purchased Visual Studio 6 (last one with Win95 support according to what I researched,) copied the code over (had to rewrite sections, of course,) and it compiled just fine, and works :)
The problem occurred the next time I had to boot my Win95 system in DOS mode. The program stopped working (of course,) because Win95 wasn't loaded. I don't really want to have 2 copies of the program installed (needing 2 different file names,) so I was hoping there was a way to link the 2 versions together into one file. If I execute it in DOS, instead of it saying it requires windows, it would just jump to the DOS section of the program. That way, it would be a single program, with LFN support if Win95 is loaded, and without if Win95 isn't loaded. Since the Win95 version also works fine in Win7-64, it would probably also produce a single version that works on all 3 systems (which would be an added bonus.)
I did some web searches, and couldn't find anything germane to what I'm looking for. So I have no idea if it is even possible. I may have to get yet another compiler, but considering how old it would have to be, I could probably afford it. My web searches did result in information that leads me to believe that it "should" be possible, though. It would just require a different exe header than the one Windows compilers put in. It may require that I re-write the DOS version for 32-bit and use a DOS extender (for protected mode, assuming I can't find a way to include it in the file itself.) That would be acceptable (though not ideal.) I would much rather have 16-bit code in the DOS section, and 32-bit code in the Windows section (for the most compatibility.)
Does anyone have any information about something like this? If you could just point me in the right direction it would be greatly appreciated.
The documentation for Visual Studio 6 describes the /STUB option here, simply point this at the DOS version of your program.
I don't have VS6 handy, so I can't be too specific, but in the project settings GUI, there should be an "additional options" setting in the linker section.