Compact Disks
1If someone says to you your music CDs don’t really hold any music on them，and they only have numbers recorded on them，you may not believe it．In fact，he is right in that sound is actually recorded onto the CDs as special numbers—a digital codel．The code is pressed onto the CD as bumps on a long spiral track almost five kilometers long． These bumps are an average of 0．5 microns wide
2 A small laser bearn shines onto the bumDs as the CD turns．The light is reflected back to a receiver that records how the laser light bounces back．This lets the CD player2 turn the eflected light back into the original code．This means you can hear the original code as music．
3 Digital codes are used with many technologies．E—mail needs these kinds of code numbers．Space probes cornmunicate with their ground station on earth using digital codes．Bar codes are read as digital codes in computer systerns．Digital communications with cell phones need digital codes．Weather radios also tune in to specific signals using these codes．
4 There are many types of compact disks．One format is called CD—RWs．They can be recorded on and re—recorded on(rewritten on)as you would do with a floppy disk3．Another format is the CD—ROM．The technology for recording on these disks is different from other CDs．These CDs have a dye layer that the CD writer can darken or leave clear．The clear and dark spots are the digital code．CD—ROM stands for Compact Disc—Read Only Memory4．This disk is like a“super”floppy disk that can hold lots of information．One CD—ROM can hold the same amount of data as 500 floppy disks．Information is permanently recorded onto it．Computer games and other programs are considered to be CD—ROMs．
5 CDs were first sold to the public in l982．These CDs still play well and sonnd fine．Current CDs are expected to last between 70 to 200 years．Of course，you can make sure your CDs last a long time by taking care of them．
6 Science keeps on developing．It may not be many more years before a completely new technology is invented5 and introduced to the public for music recording．In the meantime，there is no doubt you will continue to enjoy listening to your favorite music on CDs6 and playing your favorite computer games on CD—ROMs．
词汇：
bump n．隆块，隆起floppy disk软(磁)盘
spiral adj．螺旋形的format n．格式
probe n．探测器dye n．染色
floppy adj．松软的Permanently adv．永久地
注释：
1．he is right in that sound is actually rdcorded onto the CDs as special numbers—a digital code：他说的对，因为实际上声音以特殊的数字的形式，即数码，刻录在CD碟片上．in that是“因为”，如：Water is essential in that without it all living things would die．(水是基本要素，因为没有水，所有生物都要死亡．)
2．CD player：CD播放机
3．as you would do with a floppy disk：就象你使用软磁盘一样
4．CD—ROM stands for Compact Disc—Read Only Memory"：CD—ROM是Compact Disc—Read Only Memory这五个词首字母的组成的缩写词．
5．It may not be many more years before a completely new technology is invented：过不了几年，说不定又会发明一种全新的技术…．many more years是“再过许多年”．
6．“there is no doubt you will continue to enjoy listening to your favorite music on CDs”语法上可以理解为“there is no doubt(about the fact that)you will continue to enjoy listening to your favorite music on CDs”．
练习：
1．Paragraphs 1&2____
2．Paragraph 3____
3．Paragraph 4____
4．Paragraph 5____
A．Digital code has wide applications．
B．Floppy disks are outdated．
C．CDs are durable．D．CDs working principle is explained．
E．CD-RWs play better than CD—ROMs．
F．CDs are of many formats．
5．One advantage of CD—RWs is that they ean____like floppy disks．
6．The author predicts it will not____before a new technology is invented for music recording．
7．The laser beam—emitting device and the receiver are considered to____of a CD player．
8．Space probes could not____without using digital codes．
A．shine on bumps
B．take many more years
C．be the key parts
D．restore the original code
E．be written on and rewritten on
F．keep contact with their ground station efficiently
1．D．第一、二段介绍了CD的工作原理．声音以数码的形式刻录到CD碟片上．要回听声音，就得用CD放音机，CD机用激光照射cD，接收器收和分析从CD反射回来的激光波，还原为原来的数码，再转换为原来的声音．所以，D是答案．
2．A．第三段第一句(“Digital codes are used with many technologies．”)是主题句．本段其它句子提供例证，即应用领域．作者例举了5个领域：电邮、航天通讯、条码、手机和天气预报．选项A的“Digital code has wide applications”与主题句的意思完全吻合，所以是答案．
3．F．第四段第一句(“There are many types of compact disks”)是主题句．本段其它句子列举了两种常用的CD格式(format)，一种是CD—RW，另一种是CD—ROM．选项F的“CDs are of many formats”概括了本段的大意，是答案．
4．C．第五段说的是CD碟片经久耐用，1982年上市的cD碟片至今还能使用，其音质依旧．现在上市的CD，更加耐用，如果使用得当，其寿命可达70—200年．选项C用了durable予以概括是很恰当的，所以，C是答案．
5．E．第四段中出现CD—RW这个词，介绍了They can be recorded Oil and re—recorded on(rewritten on)．这就是选E的依据．
6．B．第六段能找到与答案有关的句子，即It may not be many more years before a completely new technology is invented and introduced to the public for music recordin9．
7．C．第二段说到在CD机上还原数码时依靠的是激光发射装置和接收器．由此我们可以推论出激光发射器和接收器是CD机的主要部件．所以C是答案．
8．F．第三段第三句(“Space probes communicate with their ground station on earth using digital codes”)是选F的依据．