This function differs from Int 33H Function 00H in that there is no initialization of the mouse hardware.Resets the mouse driver and returns driver status. If the mouse pointer was previously visible, it is removed from the screen, and any previously installed user handlers for mouse events are disabled.
Call with:
AX = 0021H
Returns:
If mouse support is available
AX = FFFFH
BX = number of mouse buttons
If mouse support is not available
AX = 0021H
Note:
This function differs from Int 33H Function 00H in that there is no initialization of the mouse hardware.