DW      SETCLIP         ; Define a clipping rectangle

  Input:
     AX         Upper Left X coordinate of clipping rectangle
     BX         Upper Left Y coordinate of clipping rectangle
     CX         Lower Right X coordinate of clipping rectangle
     DX         Lower Right Y coordinate of clipping rectangle

  Return:
     Nothing

The SETCLIP vector defines a rectangular clipping region on the screen. The
registers (AX,BX) - (CX,DX) define the clipping region.