I'm not quite certain what you're looking for - are you looking for help on writing serial I/O programs on Windows, or UNIX?
I recently wrote a decent, very simple serial API wrapper that compiles and runs on both. The code should be simple enough to read (it is extremely similar to the POSIX read/write functions) that you can learn the TTY API for both OSes quickly and modify it to suit your needs.
Attached are the files, it should compile just fine with default options to MSVC or gcc. If that wasn't what you need or if you have any questions, feel free to PM me
