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 (4.72 in) 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 6.35 cm (2.5 in) in diameter,
but it can be used to record as well as play up to 74 minutes of music. Its small size is
made 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. Improved
data 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。硬盘是由美国国际商用机器公司在1973年生产的。早期的硬盘极其昂贵;然而,大规模生产的个人电脑,硬盘驱动器现在仅售价为200美元,而且它纳入计算机系统。固态硬盘通常有一个或多个涂有一层金属氧化物磁性物质的磁盘,使信息在它上面存储。这个存储系统包括磁盘、读/写磁头组件,驱动和计算机之间的连接。
At first, these disk drives used 14 inch disks, but now they use 5 1/4 inch, 3 1/2 inch,2 1/2 inch, and 1 4/5 inch diameters. In contrast to the floppy disk drive, hard disk drives hold from 80 megabytes to gigabytes and terabytes of information. When purchasing a hard disk, consider storage capacity and seek time, a measure of a hard disk’s access speed. The smaller the numbers, the faster the disk. In the past, 65 milliseconds was the standard access time, but today the standard is less than 7 milliseconds.
起初,这些磁盘驱动器使用14英寸的磁盘,但现在他们使用5 1/4英寸,3 1/2英寸,2 1/2英寸,14/5英寸直径的磁盘。与软盘驱动器相反，硬盘驱动器拥有从80字节到千兆字节和兆兆字节的信息。购买硬盘时,考虑存储容量和寻道时间用来衡量硬盘的访问速度。数字越小,硬盘访问速度越快。在过去,65毫秒是标准的访问时间,但是今天这个标准小于7毫秒。
How Is Data Stored on a Hard Disk?
数据如何在硬盘上存储呢？
Storing data on hard disks is similar to storing data on diskettes. In order to read or write data on the surface of the spinning disk platter, the disk drives are designed with access arms, or actuators. The access arms, or actuators, contain one or more read/write heads per disk surface. As the disk rotates at a high rate of speed, usually 3,600 revolution per minute, the read/write heads move across its surface. These read/write heads float on a cushion of air and do not actually touch the surface of the disk. The distance between the head and the surface varies from approximately ten to twenty millionths of an inch. If some form of contamination is introduced or if the alignment of the read/write heads is altered by something accidentally jarring the computer, the disk head can collide and damage the disk surface, causing a loss of data. This event is known as a head crash. Because of the time needed to repair the disk and to reconstruct the data that was lost, head crashes can be extremely costly to users in terms of both time and money.
将数据存储在硬盘上类似于在磁盘上存储数据。为了在旋转的磁盘表面读或写数据,磁盘驱动器的设计提供设备或制动器。存储设备或制动器,每一个磁盘表面包含一个或多个读/写磁头。当磁盘以高速旋转,通常每分钟3600转,读/写头在其表面移动。这些读/写头漂浮在空气垫上,不是真正地接触到磁盘的表面。头和表面之间的距离从大约十到20/20百万英寸不等。如果一些污染的形式被侵入或读/写磁头的排列是被电脑的意外震动所改变，磁盘头可以碰撞和损坏磁盘表面,造成数据丢失。这个事件被称为磁头冲撞。因为修复磁盘所需的时间和重建丢失的数据,磁头碰撞对于用户来说在时间和金钱上都是昂贵的。
How Is Data Physical Organized on a Hard Disk?
在硬盘上数据如何物理地组织在一起？
Depending on the type of disk drive, data is physically organized in one of two ways. One way is the sector method and the other is the cylinder method.
取决于磁盘驱动的种类，数据通过一种或两种方式被物理地组织起来。一种办法是扇区法另一种方法是柱面法。
The sector method for physically organizing data on disks divides each track on the disk surface into individual storage areas called sectors. Each sectors can contain a specified number of bytes. Data is referenced by indicating the surface, track, and sector where the data is stored.
在磁盘上物理组织数据的扇区法，将磁盘表面的每一个磁道划分成为单个的存储区域，称之为扇区。每一个扇区可以包含规定数目的比特数。数据表明表面、跟踪和行业数据存储的地方。数据通过数据存储的表面、磁道、扇区指示被引用。
With the cylinder method, all tracks of the same number on each recording surface are considered part of the same cylinder. For example, the fifth track on all surfaces would be considered part of cylinder five. All twentieth tracks would be part of cylinder twenty and so on. When the computer requests data from a disk using the cylinder method, it must specify the cylinder, recording surface, and record number. Because the access arms containing the read/write heads all move together, they are always over the same track on all surfaces. Thus, using the cylinder method to record data down the disk surfaces reduces the movement of the read/write head during both reading and writing of data.
使用柱面法,相同数量的所有磁道在每个记录表面上被认为是同一柱面的一部分。例如,所有表面的第五磁道将被视为柱面5的一部分。所有第20磁道将会成为二十柱面的一部分等等。当计算机使用柱面法请求数据,它必须指定柱面,记录表面,并记录数量。因为包含读/写磁头的访问设备一起移动,它们总是在所有表面的同一轨道。因此,在读写数据时，使用柱面的方法在磁盘表面记录数据减少读/写磁头的运动。
Advantage of Using a Hard Disk on a Personal Computer
使用个人电脑硬盘的优势
A hard drive on a personal computer provides many advantages for users. Because of its large storage capacity, a hard disk can store many software application programs and data files. When a user wants to run a particular application or access a particular data file on a hard disk, it is always available. The user does not have to find the appropriate diskette and insert it into the drive. In addition, the faster access time of a hard disk reduces the time needed to load programs and access data.
个人电脑上的硬盘驱动为用户提供了许多优势。因为它的存储容量大,硬盘可以存储很多软件应用程序和数据文件。当用户想要运行一个特定的应用程序或访问一个特定的硬盘上的数据文件,它总是可用的。用户的确不必再找到合适的磁盘,并将其插入到驱动器。此外,硬盘的更快的访问时间减少加载程序和访问数据所需的时间。
Enormous quantities of information are stored on optical disks by using a laser to burn microscopic holes on the surface of a hard plastic disk.
通过使用激光烧录硬塑料磁盘表面上的微孔巨大数量的信息存储在光盘上。
A lower power laser reads the disk by reflecting light off the disk surface. The reflected light is converted into a series of bits that the computer can process.
电子信息类专业英语第五单元译文 李白萍主编
