Code Flag "Answer"
 
At the dip (about half-way up the halyard): Ready to receive message
 
Close up: Message has been received and understood (the flag is then hauled back at the dip to receive the next hoist
 
Hauled down: Signals end of message.
 
With numerals: Decimal point
 
By a warship: When flown over a hoist, indicates the message is to be read according to the ICS.