DW      SAVEBITMAP      ; Write from screen memory to system memory

  Input:
     ES:BX      Points to the buffer in system memory
                to be written. ES:[BX] contains the width of the
                rectangle -1. ES:[BX+2] contains the heigth of
                the rectangle -1.

     CX         The upper left X coordinate of the rectangle.
     DX         The upper left Y coordinate of the rectangle.

  Return:
     Nothing

The SAVEBITMAP routine is a block copy routine that copies screen pixels
from a defined rectangle as specified by (SI,DI) - (CX,DX) to the system
memory.