INT 10 - VIDEO - GET DISPLAY COMBINATION CODE (PS,VGA/MCGA)
        AX = 1A00h
Return: AL = 1Ah if function was supported
            BL = active display code (see below)
            BH = alternate display code
SeeAlso: AH=12h/BL=35h,AX=1A01h,AH=1Bh

Values for display combination code:
 00h    no display
 01h    monochrome adapter w/ monochrome display
 02h    CGA w/ color display
 03h    reserved
 04h    EGA w/ color display
 05h    EGA w/ monochrome display
 06h    PGA w/ color display
 07h    VGA w/ monochrome analog display
 08h    VGA w/ color analog display
 09h    reserved
 0Ah    MCGA w/ digital color display
 0Bh    MCGA w/ monochrome analog display
 0Ch    MCGA w/ color analog display
 FFh    unknown display type

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