Compact Disks
1 If 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 reflected 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
责任编辑：sealion1986
