From what I remember, unistd.h contains POSIX constants and functions, so there is no equivelant for most of the functions or any of the constants in VC++. The functions that there are equivelants for are mostly prefixed with an underscore, and aren't consolidated into one specific header (but the majority of them are in io.h and stdlib.h). If you need full POSIX functionality, I recommend looking into cygwin and/or mingw.
