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INT 10h,  12h (18)       Alternate Select                                 EGA

    Returns information on the Enhanced Display Adapter (EGA) and allows
    the selection of an alternative EGA Print Screen routine.

       On entry:      AH         12h
                      BL         Subservice
                                 10h - Return EGA information
                                 20h - Select alternative EGA Print Screen
                                 routine

       Returns:       (for Subservice 10h only):
                      BH         Display mode in effect
                                 00h    Color mode (3Dxh address range)
                                 01h    Monochrome mode (3Bxh address range)
                      BL         EGA memory
                                 00h    64K
                                 01h    128K
                                 02h    192K
                                 03h    256K
                      CH         Adapter bits
                      CL         Switch setting

  --------------------------------------------------------------------------

       Notes:         The value returned in CL (Switch setting) represents
                      the DIP switch settings on the EGA. The Adapter bits
                      (CH) is defined as follows:

                              Adapter bits (CH)

                          7 6 5 4 3 2 1 0
                          x x x x . . . .       Unused
                          . . . . x x . .       Reserved
                          . . , . . . x .       FEAT1 (pin 17)
                          . . . . . . . x       FEAT0 (pin 19)

                      To print the screen contents when the number of rows
                      changes, use Subservice 20h (Set Alternative Print
                      Screen) to install a Print Screen routine that will
                      work correctly with the row change.