INT 61 - OPTIMA 1024 VGA-Sync - CENTER ZOOM WINDOW
        AX = 0001h
        BX = X coordinate to center
        CX = Y coordinate to center
Notes:  Positions the zoom window such that the specified window-relative
          coordinates appear as close as possible to the center of the
          display.  Useful for scrolling and panning.
        INT 61h is the default interrupt; the actual interrupt number can be
          obtained by calling INT 16/AH=FFh
SeeAlso: INT 61/AX=0000h"OPTIMA",INT 61/AX=0002h"OPTIMA"