Did you know?
Over 2,000 years ago, the Roman leader Julius Caesar wrote secret messages by moving each letter three places along the alphabet. So A became D, and B became E!
Caesar's adopted son Augustus, who became a Roman emperor, is said to have used an even simpler code. He moved each letter just one place, so A became B!
SOS, the famous call for help, does not stand for any words! It was chosen because its Morse code (three short, three long, three short signals) is easy to recognise.
Try this: Crack the Code
Each letter in this secret message has moved one step forward in the alphabet (A became B, B became C, and so on). Move every letter one step back to read it: LFFQ SFBEJOH. Now write a secret reply to a friend using the same trick!
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Go further: Computers Speak in 0s and 1s
Computers use a code with only two symbols: 0 and 1. This is called binary. Think of a light switch: off is 0 and on is 1. One switch gives 2 patterns. Two switches give 4: off-off, off-on, on-off and on-on. Each extra switch doubles the patterns. Five switches give 32 patterns, which is enough to give every letter from A to Z its own code!