INT 17 - PRINTER - WRITE CHARACTER
        AH = 00h
        AL = character to write
        DX = printer number (00h-02h)
Return: AH = printer status (see below)
SeeAlso: AH=02h,AH=84h"AX",AH=F1h,INT 16/AX=FFE3h,INT 1A/AH=11h"NEC"

Bitfields for printer status:
 bit 7  not busy
 bit 6  acknowledge
 bit 5  out of paper
 bit 4  selected
 bit 3  I/O error
 bits 2,1 unused
 bit 0  timeout

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