INT 33,18 - Set alternate subroutine call mask and address

AX = 18h

DX = offset to function

CX = user interrupt mask:

�F-8�7�6�5�4�3�2�1�0� user interrupt mask in CX

� � � � � � � � +--- alt key pressed during event

� � � � � � � +---- ctrl key pressed during event

� � � � � � +----- shift key pressed during event

� � � � � +------ right button up event

� � � � +------- right button down event

� � � +-------- left button up event

� � +--------- left button down event

� +---------- cursor moved

+------------ unused

- entire mask is set to zero when ~INT 33,0~ is called

- up to three handlers may be defined with this call

- mask should be cleared before program exit

- when handler is called it receives parameters in the following

registers:

AX = condition mask causing call

CX = horizontal cursor position

DX = vertical cursor position

DI = horizontal counts

SI = vertical counts

DS = mouse driver data segment

BX = button state:

�F-2�1�0�

� � +--- left button (1 = pressed)

� +---- right button (1 = pressed)

+------ unused