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Secret codes(ÃÜÂë)keep messages private.Banks£¬companies£¬and government agencies use secret codes in doing business£¬especially when information is sent by computer.

People have used secret codes for thousands of years.__1__ Code breaking never lags(Âäºó)far behind code making.The science of creating and reading coded messages is called cryptography.

There are three main types of cryptography.__2__ For example£¬the first letters of ¡°My elephant eats too many eels¡± spell out the hidden message ¡°Meet me.¡±

__3__ You might represent each letter with a number£¬for example.Let's number the letters of the alphabet£¬in order£¬from 1 to 26.If we substitute a number for each

letter£¬the message ¡°Meet me¡± would read ¡°13 5 5 20 13 5.¡±

A code uses symbols to replace words£¬phrases£¬or sentences.To read the message of a real code£¬you must have a code book.__4__ For example£¬¡°bridge¡± might stand for ¡°meet¡± and ¡°out¡± might stand for ¡°me¡±£®The message ¡°Bridge out¡± would actually mean ¡°Meet me.¡± __5__ However£¬it is also hard to keep a code book secret for long.So codes must be changed frequently.

A£®It is very hard to break a code without the code book. B£®In any language£¬some letters are used more than others. C£®Only people who know the keyword can read the message. D£®As long as there have been codes£¬people have tried to break them. E£®You can hide a message by having the first letters of each word spell it out. F£®With a code book£¬you might write down words that would stand for other words.

G£®Another way to hide a message is to use symbols to stand for specific letters of the alphabet.

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1£®D ¸ù¾Ý¿Õºó¡°Code breaking never lags far behind code making.¡±¿ÉÖª£¬ÓÐÃÜÂëµÄÉèÖþÍÓÐÆÆÒëÃÜÂëµÄ´æÔÚ£¬¹ÊDÏî¡°As long as there have been codes£¬people have tried to break them.(Ö»ÒªÓÐÃÜÂë´æÔÚ£¬ÈËÃǾÍÉè·¨ÆƽâËü)¡±¿ÉÒԳнÓÉÏÏÂÎÄ¡£

2£®E ¸ù¾Ý¿ÕÇ°¡°There are three main types of cryptography.¡±¼°ºóÃæ¾ÙµÄÀý×Ó¿ÉÖª£¬±¾¿ÕÓ¦½éÉÜÉèÖÃÃÜÂëµÄµÚÒ»ÖÖ·½Ê½£ºÒªÒþ²ØÒ»ÌõÐÅÏ¢£¬¿ÉÒÔÓÃÿ¸öµ¥´ÊµÄÊ××ÖĸÀ´×é³ÉÃÜÂ룬¹ÊÑ¡EÏî¡£

3£®G ¸ù¾Ý¿Õºó¡°You might represent each letter with a number...¡±¼°ºóÃæµÄÄÚÈÝ¿ÉÒÔÅжϣ¬ÕâÊǽéÉÜÃÜÂëÉèÖõÄÁíÒ»ÖÖ·½·¨£¬¼´½«×Öĸ±íÖÐ×ÖĸÅÅÁÐ˳Ðòת»¯ÎªÊý×ÖÐÅÏ¢£¬¹ÊGÏî·ûºÏÓï¾³¡£

4£®F ¸ù¾Ý¿ÕÇ°¡°To read the message of a real code£¬you must have a code book.¡±¿ÉÖª£¬ÄãÐèÒª½èÓýâÂëÊéÀ´ÕÒ³öÃÜÂëËù¶ÔÓ¦µÄÒâ˼£¬FÏî¡°ÓÐÁ˽âÂëÊ飬Äã¾Í¿ÉÒÔдÏ´ú±í×űðµÄ´ÊÓïµÄÃÜÂ롱·ûºÏÓï¾³¡£

5£®A ¸ù¾ÝÉÏÎļ°ÏÂÒ»¾ä¡°However£¬it is also hard to keep a code book secret for long.¡±¿ÉÖª£¬ÉÏÒ»¾äÓëÏÂÒ»¾äÊÇתÕÛ¹Øϵ£¬¹ÊAÏûÓнâÂëÊéºÜÄÑÍê³É½âÃܹ¤×÷¡±·ûºÏÓï¾³¡£

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A garden that's just right for you

Have you ever visited a garden that seemed just right for you£¬where the atmosphere of the garden appeared to total more than the sum(×ܺÍ)of its parts£¿__1__£®But it doesn't happen by accident.It starts with looking inside yourself and understanding who you are with respect to the natural world and how you approach the gardening process.

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Some people may think that a garden is no more than plants£¬flowers£¬patterns and masses of color.Others are concerned about using gardening methods that require less water and fewer fertilizers(·ÊÁÏ)£®__3__£®However£¬there are a number of other reasons that might explain why you want to garden.One of them comes from our earliest years.

¡¤Recall(»ØÒä)your childhood memories

Our model of what a garden should be often goes back to childhood.Grandma's rose garden and Dad's vegetable garden might be good or bad£¬but that's not what's important.__4__¡ªhow being in those gardens made us feel.If you'd like to build a powerful bond with your garden£¬start by taking some time to recall the gardens of your youth.__5__£®Then go outside and work out a plan to translate your childhood memories into your grown-up garden.Have fun.

A£®Know why you garden

B£®Find a good place for your own garden C£®It's our experience of the garden that matters D£®It's delightful to see so many beautiful flowers

E£®Still others may simply enjoy being outdoors and close to plants F£®You can produce that kind of magical quality in your own garden£¬too

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