电子信息类专业英语（第二版）李白萍主编第五单元译文第五单元A compact disc (CD) is a laser-read (also termed “optically read”) data storage device on which audio, video, or textual material can be stored. Although it has been used primarily to record stereophonic sound and has supplanted the long-playing PHONOGRAPH record as the principal medium for music storage, it offers a huge potential as the medium for the storage of massive amounts of many types of information.[1]一个光盘（CD）是在其上的音频，视频或文本材料可被存储在激光读取（也称为“光学读取”）数据存储设备。
虽然它被主要用来记录立体声声音，并已经取代了留声机成为了主要的音乐存储媒体，但它作为能存储大量多种信息的媒体仍具有巨大的潜力。
Unlike the conventional phonograph record, the CD stores information in digital form. Stereophonic (two-channel) sound signals are digitally sampled at a rate of 44,100 times per second per channel. Each sample is expressed as a binary number value consisting of 16 binary digits, or bits. The sampled digital values, along with error correction data, tracking codes, and cueing data, are recorded on a digital tape, which is used to make compression-molded plastic discs 12 cm (4.72in) in diameter, each covered by a thin, reflective metallic layer and protected by a clear plastic coating.[2] During playback, a low-powered laser beam reads the digital data through the reflective rear surface of the disk.[1]与传统的照片记录不同，光盘以数字形式存储的信息。
立体声（双声道）声音信号以每秒44,100次每信道的速率进行数字采样。
每个样本被表示为二进制数的值由16个二进制数位，或比特组成。
样本数值，以及误差校正数据，跟踪代码和暗示的数据，记录在数字磁带上，它是用来制成直径为12厘米（4.72英寸）的压缩成形的塑料盘，各由一个薄的、反射性的金属层和一个透明的塑料涂层保护。
在播放过程中，低功率激光束通过光盘表面的反射后读取数据。
The CD improves over conventional records and tape recordings with its more uniform and accurate frequency response, a complete absence of background noise, a wider dynamic range (the difference between the softest and loudest recordable musical sounds), and longer wear—since nothing mechanical touches the surface of the disc when it is played.光盘改善了传统的记录和录音------更均匀、精确的频率响应，完全没有背景噪音，更宽的动态范围（不同于最柔软的和最大可录制音乐地声音），而且更耐用。
因为当它被播放时没有机械接触光盘的表面。
Introduced in 1992, the Sony MiniDisc measures only 6.35cm(2.5in) in diameter, but it can be used to record as well as play up to 74 minutes of music. Its small size ismade possible by a system of data reduction that uses psycho-acoustic principles to eliminate data that is not normally heard by the listener-thereby reducing the data density to one-fifth that required for conventional CDs. Mini-Discs can be used only with their own recorder-player.引进于1992年的索尼迷你光碟直径仅6.35厘米（2.5英寸）长，但它可以被用来记录以及播放长达74分钟的音乐。
数据压缩系统使光盘的小尺寸成为可能，该系统利用心理声学原理来消除数据，被听众聆听是不正常的。
因而通过降低数据密度的五分之一，需要对传统的CDs提出要求.迷你光盘只能在特定的录放机中使用。
A second important application of CD technology is the CD-ROM (Compact Disc Read Only Memory), a text/graphics/sound storage medium that is accessed through the CD-ROM drive in a computer. A CD-ROM can store in excess of 500 megabytes (millions of bytes)of data—as compared with a computer’s hard disk, whose maximum storage capacity is about 200 megabytes. (The Academic American Encyclopedia was the first encyclopedia to be made available as a CD-ROM, in 1986). New data compression techniques, which can filter out massive quantities of unneeded data, have expanded CD-ROM capacities to include sound and image as well as text storage: in 1993 the first movie (A Hard Day’s Night) was recorded on a CD-ROM .CD技术的第二个重要的应用是CD-ROM（光盘只读存储器），一种通过在一台电脑的CD-ROM驱动器访问的文本/图形/声音存储媒体。
与一个电脑的硬盘最大存储容量大约为200兆字节进行比较，一个只读存储器能存储超过500兆字节的数据（百万字节）。
（美国百科全书是在1986年第一个被制成CD-ROM的百科全书）。
新的数据压缩技术，可以过滤掉大量不需要的数据，这扩大了CD-ROM 的容量包括声音和图像以及文本存储；在1993年的第一部电影“艰难的一天一夜”被记录的CD-ROM上。
The Interactive Compact Disc, or CD-I, is essentially a CD-ROM that can be accessed via a CD-I player attached to a television set. With an on-screen cursor and a handheld control pad the user can choose his or her own path through a game, an art history tour, or a “How To”tutorial that includes CD-quality sound and thousands of full-color images as well as text. Among the variation of the CD-I is the Photo CD, which records still photos digitally, for display on a TV screen. Improveddata compression techniques for video will eventually allow movie storage on CD-Is, with a quality comparable to boy’s laser-recorded videodiscs.交互式光盘或CD-1，基本上是一个CD-ROM，它可以通过CD-1播放机连接到电视机。
利用屏幕上的光标移动和手持式控制面板，用户可以选择他或她自己的方式访问光盘，通过游戏，艺术历史之旅，或“如何做”的教程，教程包括CD质量的声音和数以千计的全彩色图像和文本。
其中CD-1的变化就是照片的CD，它记录静态照片的数字，以显示在电视屏幕上。
改进的视频数据压缩技术最终将允许电影存储在CD-Is上，那是可以和当今的激光记录视盘媲美。
Passage B Hard Disks and Optical Disks 硬盘和光盘The hard disk drive provides increased storage capabilities and faster access. Hard disks were developed by IBM in 1973. The early ones were extremely expensive; however, with mass production of the personal computer, a hard disk drive is now available for as little as $200, and it is incorporated into the computer system. A fixed, hard disk usually has one or more disk platters coated with a metal oxide substance that allows information to be magnetically stored on it. This storage system includes the disk, a read/write head assembly, and the connections between the drive and the computer.硬盘驱动器提供了增加的存储能力和更快的访问。