不等长编码的优越性总体上减少码字的长度 不等长编码的特殊问题 ①唯一可译性,或者叫做可识别性。对于一个码,如果 存在一种译码方法,使任意若干个码字所组成的字母串 只能唯一地被翻译成这几个码字所对应的事件序列。这 个码就被称为是唯一可译的 解决方案:适当地编码,使得每个码字都具有识别标记。 (注解:一个唯一可译的、码字长度不超过N的D元码,其 码字个数小于D(D~-1)(D-1)个。这是因为两个码字c)和 c(2)连接成的字母串cc(2)不能是码字)

目录 译者序 编者序 1.因特网与生物学家 1.1因特网基础 1.2与因特网连接 1.3电子邮件 1.4文件传输协议 1. 5 GOPHER

Questions on the text Did people have to attend on machines hundreds of years ago? What happened to industry about a hundred years ago? What is the operation of automatic machines based on?

1. In what physical condition is the writer's grandmother? with her? 3. Is she happy Why or why not? 4 Are retirement homes all bad? 5. What did the writer's mother decide to do when Grandma could not live on her own? 6. How are elderly people treated in many cultures? 7. Why are old people unhappy in a nursing home? 8. What is the writer's opinion concerning the treatment of aging people? 9. What is your own opinion concerning the old people n general?

Teaching Outline Background information Pre-reading questions Passage analysis Style and structure Spellings Word derivations Language points Useful expressions Weekly quiz

Pre-reading Questions 1. Why were the girls warned that they should not regard school as \Brighton beach\ and what was implied in the warning? 2.What is the purpose of education according to the author?

Alexander graham bell an inspired black-haired scotsman of twenty eight, on the eve of marriage, vibrant and alive to new ideas Alexander Graham bell. The Man who invented the Telephone A| xander graham be‖l 1847to1922

Teaching Outline Pre -reading- Questions Famous Quotations of Study Passage Analysis A spelling word derivation language points useful expression

Teaching outline Duty report dictation Practice of the key sentence patterns Retell dialogue工 Role-play: Traffic problems in a big city Background information about language famil Questions for group discussion Passage analysis Weekly quiz

Questions on the text 1. Define daydreaming 2. What sort of people show particular interest indaydream research? 3. When and where is one most likely to daydream? 4. In what way does daydreaming differ fromfantasy?