A BCheckBox object draws a labeled check box on-screen and responds to a keyboard action or a click by changing the state of the object: When the user "checks" the check box, the object displays an "x" within its border, its state is set to B_CONTROL_ON, and the invocation message is sent to the object's target. When the user "unchecks" the check box, the "x" is removed, the state is set to B_CONTROL_OFF, and the invocation message is sent.