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
error)
                                                                  
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)
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INT 17H 00H: Print One Character