有用
action. In World War 2,the American “broke”, or figured out, Japan s most important navy codes
and got enough information to destroy a powerful Japanese fleet（舰队）。
Storekeepers use codes to mark their goods. The codes show how much was paid for the
goods or when they were added to the stock. Businessman use codes to hide plans from their
business enemies. Sometimes personal letters or diaries are written in code. Many people enjoy
figuring out codes and ciphers simply as a hobby.
In the 16th century, codes and ciphers were very popular among scientists. They wrote
messages to each other in code so that no one else would learn their secrets. Geronimo Gardano,
an Italian astrologer（星相家）,mathematician, and doctor, invented the trellis ciphers. He took two
sheets of paper and cut exactly the same holes in each one. Then he sent one sheet, which he
called a trellis, to a friend and kept the other for himself. Whenever he wanted to write a message,
he put his trellis, over the clean sheet of paper and wrote the secret message through the holes.
Then he removed the trellis and filed the rest of the paper with words that would make sense.
When his friends received it, He put his trellis over the writing and read the secret message.
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