This Scratch program displays the semaphore flag alphabet. Semaphore is from the Greek sema, meaning sign and phero, meaning to bear or carry. These are visual telegraph (Greek: têle, "at a distance" and gráphein, "to write"). They are used to communicate over a distance without sound or electricity. Watch the letters being formed. Some, such as J, are out of their usual sequence. The first ten letters double as numbers. In the program-- Type your message to see it displayed in semaphore signal (39 characters max, no punctuation). Use the # key to signal "numbers follow." Use the @ key to signal "letters follow" after the last number is finished. Use the space bar to signal pauses in messages. Press <s> to turn the introductory text and music off. Reset using the stop sign and green flag to begin a new message.
Watercolor sketch of Navy semaphore by R. I. Dennis. Music "Clockwork TARDIS" arranged by Murray Gold, performed by BBC Orchestra Wales, from Doctor Who, 2006. The Semaphore Flag System substitutes pre-arranged flag positions for letters of the alphabet. In addition to spelling out messages, there are one- two- and three-letter series to quickly communicate with other ships. Navy and commercial ships also use pre-arranged codes signaled by combinations of flags. For further information, the Wikipedia article can get you started-- https://en.wikipedia.org/wiki/Flag_semaphore
