Click above to get retro games delivered to your door ever month!

        Return user alternate interrupt vector

        Entry:
          AX = 0019h
          CX = call mask

        Return:
          BX:DX = user interrupt vector
          CX = call mask (0 if not found)

        Note:   Attempts to find a user event handler, (defined by function
                18h), whose call mask matches CX