Int 10h, 1Bh            Return Functionality Information            MCGA, VGA

    This service returns information about the video equipment and
    state.

        Entry   AH    = 1Bh
                BX    = 0
                ES:DI = Address of 64-byte buffer

        Return  AL = 1Bh   If function supported
                Buffer filled


    Format of receive buffer:

        Offset     Description
        0          Offset of functionality information
        2          Segment of functionality information
        4          Video mode
        5          Columns on screen
        7          Length of regenerator buffer in bytes
        9          Starting address of regenerator buffer
        0Bh        Cursor position for eight display pages
        1Bh        Cursor type setting
        1Dh        Active display page
        1Eh        CRT controller address
        20h        Current setting of 03x8h register
        21h        Current setting of 03x9h register
        22h        Rows on screen
        23h        Character height in scan lines
        25h        Display Code
        26h        Display Code (alternate)
        27h        Colors supported in current mode
        29h        Display pages supported
        2Ah        Scan lines in current mode
                           0 : 200 scan lines
                           1 : 350 scan lines
                           2 : 400 scan lines
                           3 : 480 scan lines
                           (4 - 255 reserved)
        2Bh        Primary character block
                           0 → block 0
                           1 → block 1
                                :
                           255 → block 255
        2Ch        Secondary character block
                           0 → block 0
                           1 → block 1
                                :
                           255 → block 255
        2Dh        State information
                           Bits 7, 6 reserved
                           Bit  5 = 0 → background intensity
                                    1 → blinking
                           Bit  4 = 1 → cursor emulation active
                           Bit  3 = 1 → default palette loading diabled
                           Bit  2 = 1 → monochrome display attached
                           Bit  1 = 1 → summing active
                           Bit  0 = 1 → all modes on all displays active
        2Eh        Reserved
        31h        Video memory available
                           0 → 64K
                           1 → 128K
                           2 → 192K
                           3 → 256K
        32h        Save pointer state information
                           Bits 7, 6 reserved
                           Bit  5 = 1 → DCC extension active
                           Bit  4 = 1 → palette override active
                           Bit  3 = 1 → graphics font override active
                           Bit  2 = 1 → alpha font override active
                           Bit  1 = 1 → dynamic save area active
                           Bit  0 = 1 → 512 character set active
        33h        Reserved
        3Fh        End

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    This Service returns information about the current video state,
    including most of the settings now active. The information
    returned by this service is lengthy.

    Service 1Bh is normally used by operating system software.