International Code of Signals
GeneralThe International Code of Signals is a system for communication, by use of radiotelegraphy or lights by use of the morse code or by use of flag.
FlagsThe International Code of Signals consists of a set of forty flags. The twenty-six letters of the Latin alphabet, the ten digits for the numbers, three substitute flags and the answering pennant.
UseThe signal flags are not used to spell out whole sentences, but they are used to form codes. These codes can be found in a book that is supposed to be onboard every vessel.
The single letter meanings are to be learned by head to be a qualified navigator. For example the signal flag Alfa has the single letter meaning of "I have a diver below, keep clear and pass with slow speed." But the combination Alha with a number is a direction.
All the signal flags stringed together in random order and run from bow over the top of the masts to the stern is a way to decorate a vessel during festivities.