Function 25h (37)        Set Interrupt Vector

    Sets the address of an interrupt handler.

       On entry:      AH         25h
                      AL         Interrupt number
                      DS:DX      Address of interrupt handler

       Returns:       Nothing

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       Notes:         Prior to calling, you may want to get the address of
                      the current interrupt handler (via Function 35h) so
                      that your program can restore the original routine
                      when it exits. This is the preferred way to set
                      interrupt vectors.