INT 31H 0201H: Set Real-mode Interrupt Vector

                                                    Compatibility: DPMI 0.9+ 
 Expects: AX    0201H
          BL    interrupt number
          CX:DX real-mode segment:offset to use for the vector
 Returns: CF    NC (clear) if successful; else AX = DPMI Error Code
    Info: Changes the address of a real-mode interrupt handler.

          The value return in CX must be a real-mode segment address (not a
          selector).  Thus, the real-mode interrupt handler must either
          reside in DOS memory (below 1MB) or you must allocate a real-mode
          callback address.  See INT 31H 0100H (allocate dos mem) and
          INT 31H 0303H (allocate real-mode callback address).

          When hooking hardware interrupt handlers, the memory that the
          handler uses must be locked.  See INT 31H 0600H (lock linear

See Also: DPMI API
          INT 2fH: Multiplex Interrupt
          DOS Functions