A somewhat less common, but still very useful form for a single argument function, is an event. In this form there is an input argument but no output argument. The overall program is meant to interpret the function call as an event and use the argument to alter the state of the system, for example, void passwordAttemptFailedNtimes(int attempts). Use this form with care. It should be very clear to the reader that this is an event. Choose names and contexts carefully.
