Vinícios, essas são as funções disponíveis no conio.h
http://msdn.microsoft.com/en-us/library/7x2hy4cx(v=VS.71).aspx
Veja na documentação:
These routines read and write on your console or on the specified port. The console I/O routines are not compatible with stream I/O or low-level I/O library routines. The console or port does not have to be opened or closed before I/O is performed, so there
are no open or close routines in this category. In the Windows operating systems, the output from these functions is always directed to the console and cannot be redirected.
Ou seja, aparentemente você não pode usá-las.
Você pode usar CreateFile(..)/CloseHandle(..) para abrir uma porta paralela.
HANDLE hParallel = CreateFile("LPT1", 0, 0, NULL, OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL, NULL);
Funções de controle dessa porta depois de aberta:
http://msdn.microsoft.com/en-us/library/aa363194(v=VS.85).aspx
WriteFile/ReadFile fazem o I/O.
Abraços, cox
cox