INT 17 - PRINTER - WRITE CHARACTER
        AH = 00h
        AL = character to write
        DX = printer number (00h-02h)
Return: AH = printer status
            bit 7: not busy
                6: acknowledge
                5: out of paper
                4: selected
                3: I/O error
                2: unused
                1: unused
                0: timeout
SeeAlso: AH=F1h,INT 16/AX=FFE3h,INT 1A/AH=11h"NEC"