Letter (alphabet) of sounds to make words. A letter is classed as either a consonant or a vowel, depending on how its sound is produced (vowels are "a", "e", "i", "o", "u", and sometimes "y" and "w"). The basic Roman alphabet is used by about one hundred languages, with slight variations. Some versions contain as few as twenty-one characters, some as many as thirty. Letters have specific names associated with them, which may differ with language, dialect, and history. "Z", for example, is usually called "zed" in all English-speaking countries except the US, where it is named "zee". As elements of alphabets,
Morse code 1945. Morse code was used as an international standard for maritime distress until 1999 when it was replaced by the Global Maritime Distress Safety System. When the French Navy ceased using Morse code on January 31, 1997, the final message transmitted was "Calling all. This is our last cry before our eternal silence." In the United States the final commercial Morse code transmission was on July 12, 1999, signing off with Samuel Morse's original 1844 message, "What hath God wrought", and the prosign "SK". As of 2015, the United States Air Force still trains ten people a year in Morse.