INT 17H 00H: Print One Character

 Expects: AH    00H
          AL    byte to print.  See ASCII and ASCII Control Codes.
          DX    port number (0=LPT1, 1=LPT2, 2=LPT3)
 Returns: AH    Bits set as in PrinterStatusRec (bit 0 set on time-out
    Info: Sends the byte in AL to the specified printer port.

          Always check the return code in AH to see if the character made
          it to the printer.

   Notes: ■ Use INT 11H to see how many printer ports are installed.

          ■ Please stop writing those applications that write ONLY to LPT1.
            That is unutterably frustrating for users.

          ■ You can write to the PRN device just by using DOS fn 40H with
            BX=0004H.  You may want to use fn 3eH now and then to flush the
            data to the printer.

See Also: INT 17H (BIOS printer support)
          ROM-BIOS Functions