If you and your friends wish to share a secret, you can write it in code (编码), and no one else will be
able to read it.
Codes are one way of writing in secret. Ciphers (暗码) are another. In a code each word is written as a
secret code word or code number. In a cipher each letter is changed. Codes and ciphers have played an
important role in the history of the world. Julius Caesar, the Roman ruler who defeated almost all the countries
in Europe about 2, 000 years ago, used a cipher when he sent secret messages to his troops. During the
American Revolution, George Washington"s spies used a kind of code to send him information about the enemy
before his military (军事的) action. In World War Ⅱ, the Americans "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 (商品). Businessmen 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 cipher. 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 a clean sheet of paper and wrote the secret
message through the holes. Then he removed the trellis and filled the rest of the paper with words that would
make sense. When his friend received it, he put his trellis over the writing and read the secret message.
In the US, people prefer waiting for a table to sitting with people they don"t know. This means a hostess
may not seat a small group until a small table is available. even if a large one is. If you are sitting at a table with
people you don"t know, it is impolite to light up a cigarette without asking if it will disturb them.
At American restaurants and coffee shops you are usually served tap water (自来水) before you order.
You may find the bread and butter is free, and if you order coffee, you may get a free refill.
Most cities and towns have no rules about opening and closing time for stores or restaurants, though they
usually do make rules for bars. Especially in large cities. stores may be open 24 hours a day.
Serving in restaurants is often large. too large for many people. If you can"t finish your meal but would like
to enjoy the food later. ask your waitress or waiter for a" doggie bag". It may have a picture of a dog on it, but
everybody knows you"re taking the food for yourself.
Supper and dinner are both words for the evening meal. Some people have"Sunday dinner". This is an
especially big noon meal.
Tips are not usually added to the check. They are not included in the price of the meal, either. A tip of about 15% is expected and you should leave it On the table when you leave. In some restaurants, a check is brought
on a plate and you put your money there. Then the waiter or waitress brings you your change.
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