INT 10h, 1Ah (26)      Read/Write Display Type                   PS/2, VGA

     Lets you read or set the type of display connected to the computer.

        On entry:     AL          0 . Return Display Code in BX (see below)
                                  1 . Install new Display Code from BX

                Display Code    Means
                ------------    -----
                00h             No display
                01h             MDA
                02h             CGA
                03h             Reserved
                04h             EGA color
                05h             EGA monochrome
                06h             Professional Graphics Display
                07h             VGA monochrome
                08h             VGA color
                09h             Reserved
                0Ah             Reserved
                0Bh             MCGA monochrome
                0Ch             MCGA color
                FFH             Unknown

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     You can get or set the display type connected to the computer with this
     Service. If you want to get the display type, put 0 in AL and call it;
     the display code (see above) is returned in BX. If you want to set the
     display type, put 1 in AL and the display code in BX.

     This Service sets BIOS' only indication of the type of display in use,
     so you should not use it lightly.