INT 14H 01H: Send a Character

 Expects: AH    01H
          AL    byte to send
          DX    COMM port number (0 to 3)
 Returns: AH    bit 7=0 if no error;
                else, bits 0-6 have Line Status see BIOS COM status codes
    Info: Transmits the character in AL over the specified COM line.

   Notes: The return status code cannot indicate a time out error, since
          bit 7 is used to flag any error.  Thus, after any error, you
          should use INT 14H 03H to get the full story on what went wrong.

See Also: INT 14H: Serial Port I/O
          Asynchronous Adapter Ports
          BIOS Data Area
          ROM-BIOS Functions