ON - mkilgore/QB64pe GitHub Wiki

ON creates event procedure calls or enables event trapping.

Set the sub-procedure call for KEY(n), COM(n), PEN, PLAY, STRIG(n), TIMER, UEVENT
To turn on event trapping for ON COM (n), ON KEY (n), ON PEN, ON PLAY (n), ON STRIG (n), ON TIMER (n) and ON UEVENT.
In the case of ON ERROR the trap is also enabled until a subsequent ON ERROR statement.
ON procedures should be used only in the main program module and not inside of SUB procedures!
If you have used the $CHECKING:OFF metacommand, $CHECKING:ON will turn on c++ error checking again.

See also: