The disC page describes a crude decompiler for DOS Turbo C 2.0 and 2.01 programs. The source is free to download. The author, Satish Kumar, also has a more general decompilation page. Satish admits that his code isn't great, and that the decompiler needs a lot of work, but it does work with small, carefully chosen programs (he has several examples of these on his page). The decompiler doesn't recognise strings, handle floating point maths, or recover types. It's basically a pattern matcher for idiomatic sequences of code that this particular compiler (which is now in the public domain, and can be downloaded from his page) produces.