INT 33h,  08h (8)        Set Minimum/Maximum Vertical Position

    Sets the minimum and maximum vertical cursor position

       On entry:      AX         08h
                      CX         Minimum Position
                      DX         Maximum Position

       Returns:       Nothing

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    Function 8 sets the minimum and maximum vertical cursor coordinates on
    the screen. Any later cursor motion is restricted to the specified area.
    The minimum and maximum values are defined by the virtual screen.

    If the cursor is outside the area when the call is made, it moves to
    just inside the area.

    If the minumum value is greater than the maximum value, the two values
    are swapped.