### A.5 I/O code sample

    #include "w89k.h"

    /*
     * outbyte -- shove a byte out the serial port. We wait till the byte
     */
    int
    outbyte(byte)
         unsigned char byte;
    {
      while ((inp(RS232REG) & TRANSMIT) == 0x0) {  } ;
      return (outp(RS232PORT, byte));
    }

    /*
     * inbyte -- get a byte from the serial port
     */
    unsigned char
    inbyte()
    {
      while ((inp(RS232REG) & RECEIVE) == 0x0) { };
      return (inp(RS232PORT));
    }