The byte at 0040:0089 in the BIOS Data Area is a set of bit flags
containing information pertaining to the status of the VGA .

VgaFlagsRec
 7 6 5 4 3 2 1 0 
 r s 0 r p m g a            0040:0089 -- VGA Miscellaneous Flags
                  bit mask
                   0: 01H  VGA is active; 0=VGA is disabled/inactive
                   1: 02H  gray-scale summing is enabled; 0=disabled
                   2: 04H  using monochrome monitor; 0=color display
                   3: 08H  default palette loading; 0=keeps same colors
                   5: 20H  DCC display switching enabled; 0=not enabled
                 7,4: 90H  text mode scan lines (bits 7 and 4 together)
bit7  bit4  masked
0    0     00H    350-line mode
0    1     10H    400-line mode
1    0     80H    200-line mode
1    1     90H    (reserved)
- -

VgaFlagsRec