I/O Port Access in Watcom C

Watcom C provides access to the I/O ports on the 80x86 CPU via the predefined functions inp / inpw and outp / outpw. 

  unsigned int inp(int portid);   /* returns a byte read from the I/O port portid */

 unsigned int inpw(int portid);   /* returns a word read from the I/O port portid */

 unsigned int outp(int portid,    /* writes the byte value to the I/O port portid */
                  int value);     /* returns the data actually written            */

unsigned int outpw(int portid,    /* writes the word value to the I/O port portid */
             unsigned int value); /* returns the data actually written            */
portid can be any unsigned integer in the range 0-65535 

#include <conio.h>

#define Data    0x378
#define Status  0x379
#define Control 0x37a

int Bits,     /* 0 <= bits <=255 */ dummy; dummy=outp(Data,Bits); /* output webstripperattrwas webstripperlinkwas=http://www.doc.ic.ac.uk/~ih/doc/par/doc/data/outp(Data,Bits); */ bits=inp(Status); /* input webstripperattrwas webstripperlinkwas=http://www.doc.ic.ac.uk/~ih/doc/par/doc/data/inp(Status); */

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last updated: 13-Mar-97 Ian Harries <ih@doc.ic.ac.uk>