_outp, _outpw, _outpd
Outputs a byte (_outp), a word (_outpw), or a double word (_outpd) at a port.
int _outp( unsigned short port, int databyte ); unsigned short _outpw( unsigned short port, unsigned short dataword ); unsigned long _outpd( unsigned short port, unsigned long dataword );
The _outp, _outpw, and _outpd functions write a byte, a word, and a double word, respectively, to the specified output port. The port argument can be any unsigned integer in the range 0 – 65,535; databyte can be any integer in the range 0 – 255; and dataword can be any value in the range of an integer, an unsigned short integer, and an unsigned long integer, respectively.
Because these functions write directly to an I/O port, they cannot be used in user code in Windows NT, Windows 2000, Windows XP, and Windows Server 2003. For information about using I/O ports in these operating systems, search for "Serial Communications in Win32" at MSDN.