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1、.2.1Opticallaserdisktechnologyeventuallymaymakemagnetic-diskandmagnetictapestorageobsolete.Withthistechnology,theread/writeheadusedinmagneticstorageisreplacedbytwolasers.Onelaserbeamwritestotherecordingsurfacebyscoringmicroscopicpitsinthedisk,andanothe
2、rlaserreadsthedatafromthelight-sensitiverecordingsurface.Alightbeamiseasilydeflectedtothedesiredplaceontheopticaldisk,soanaccessarmisnotneeded.光盘技术最终可能使磁盘和磁带存储淘汰。用这种技术，磁存储器所用的读/写头被两束激光代替。一束激光通过在光盘上刻制微小的凹点，对记录表面进行写；而另一束激光用来从光敏感的记录表面读取数据。由于光束容易被偏转到光盘上所需要
3、的位置，所以不需要存取臂。Opticallaserdisksarebecomingaveryinvitingoptionforusers.Theyarelesssensitivetoenvironmentalfluctuations,andtheyprovidemoredirect-accessstorageatacostthatismuchlesspermegabyteofstoragethanthemagnetic-diskalternative.Opticallaserdisktechnolo
4、gyisstillemergingandhasyettostabilize;however,atpresenttherearethreemaincategoriesofopticallaserdisks.TheyareCD-ROM,recordableCD-RandrewritableCD-RW,andmagneto-opticaldisk.对用户而言，光盘正成为最有吸引力的选择。它们(光盘)对环境变化不太敏感，并且它们以每兆字节比磁盘低得多的存储器价格提供更多的直接存取存储器。光盘技术仍在出现，并
5、且还需要稳定；然而，目前有三种主要类型的光盘。它们是CD-ROM、WORM盘和磁光盘。CD-ROMIntroducedin1980,theextraordinarilysuccessfulCD,orcompactdisk,isanopticallaserdiskdesignedtoenhancetherecordedreproductionofmusic.TomakeaCDrecording,theanalogsoundsofmusicaretranslatedintotheirdigitalequ
6、ivalentsandstoredona4.72-inchopticallaserdisk.Seventy-fourminutesofmusiccanberecordedoneachdiskindigitalformatby2billiondigitalbits.Withitstremendousstoragecapacity,computer-industryentrepreneursimmediatelyrecognizedthepotentialofopticallaserdisktechno
7、logy.Ineffect,anythingthatcanbedigitizedcanbestoredonopticallaserdisk:data,text,voice,stillpictures,music,graphics,andvideo.1980年引入的，非常成功的CD，或紧密盘是设计来提高音乐的录音重放质量的光盘。为了制作一张CD，把音乐的模拟声音转换成等价的数字声音，并且存储在一张4.72英寸的光盘上。在每张光盘上可以用数字格式（用20亿数字位）记录74分钟的音乐。因为它的巨大存储容量
8、，计算机工业的企业家们立刻认识到光盘技术的潜力。事实上，任何可以被数字化的东西都能存储在光盘上：数据、正文、声音、静止图象、音乐、图形和视频。CD-ROM(pronouncedcee-dee-ROM)isaspinoffofaudioCDtechnology.CD-ROMstandforcompactdisk-readonlymemory.Thenameimpliesitsapplication.CD-ROMdisks,likelong-playingrecordal
