Looking for 16-bit c compiler for x86

At a former job we had a project that was based on uc/OS running on a real-mode x86 platform. We used TopSpeed C rather than the more well-known Borland or Microsoft compilers, because TopSpeed C was the only one of the set available and viable at the time that got volatile right. Which you dearly need when building uc/OS. Both Turbo C and Microsoft C (and I think its QuickC too) miscompiled accesses to volatile variables - typically caching values in registers and similar breakage.

You'd have a hard time getting hold of TopSpeed C, though. And its assembler syntax is... unique. (I think it's based on Modula-2 or something; it ends up being very unlike MASM/TASM/nasm with which you may be 100 times more familiar.)

Check out the FreeDOS project. They have developer tools that include compilers, assemblers, and linkers. You'll probably have to modify the standard library, though, so that it uses BIOS calls rather than int 21h.

16-bit compilers? Several of them are mentioned here:

Is there a C compiler that targets the 8086?

Generally they are used for academic exercises, so if u target at educational institution you can find lots of examples too:

http://www.google.com.sg/search?q=site%3Aedu+C+compiler+8086