qb64/internal/help/ON.md

ON creates event procedure calls or enables event trapping.

• Set the sub-procedure call for KEY(n), ON 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

• ON...GOSUB, ON...GOTO
• OFF, STOP, KEY
• $CHECKING