INT 10 - VIDEO - DISPLAY COMBINATION (PS,VGA/MCGA)
        AH = 1Ah
        AL = 00h read display combination code
                Return: BL = active display code (see below)
                        BH = alternate display code
             01h set display combination code
                BL = active display code (see below)
                BH = alternate display code
Return: AL = 1Ah if function was supported

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