Studing subject. A lot of nuances. It is good that today they guessed to use one flag for one character, but 200 years ago there were only 10 types of flags and you have had to use them in combination by 3 flags to encode whole word or even clause. Number of such clauses was (as it easy to calculate) 3000, and all of them were combined in a huge handbook. Somebody had to have good memory after all, lol.
It is funny but in famous Nelson's signal, he sent before The Battle of Trafalgar, "England expects that every man will do his duty", every word was encoded except duty. I think that every Englishman proud of this signal and hide inside his soul stinging awkwardness at the same time. Well, this word was signaled character by character, each character was encoded by 2 flags to point index of the character in the alphabet. This resulted that each letter was imprinted into mind like a hammer blow, and gave truly English pathos to the whole phrase.
And here is my signal (actually my nickname) encoded in modern International Maritime signal flags rules. Not such glorious as Nelson's one however, lol.