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  Interrupt:   14h     Function:   01h
 
  Title:       Write Character to Communications Port
 
  See also:    Auxiliary Output
 
  Description:                                          [PC] [AT] [PS/2]
 
 
     Writes a character to the specified serial communications port,
     returning the current status of the port.
 
     Input                               Output
 
     AH = 01h                            If function successful
     AL = Character                        AH bit 7 = 0
     DX = Communications port              AH bits 0-6 = Port status
          number (0 = COM1,
          1 = COM2,...)                    Bits   Significance (if set)
 
                                           6      Transmit shift
                                                  register empty
                                           5      Transmit holding
                                                  register empty
                                           4      Break detected
                                           3      Framing error
                                                  detected
                                           2      Parity error detected
                                           1      Overrun error
                                                  detected
                                           0      Receive data ready
 
                                           AL = Character (unchanged)
 
                                         If function unsuccessful
                                         (timed-out)
                                           AH bit 7 = 1
                                           AL = Character (unchanged)
                                    -♦-