计算机专业英语的第四版课后习题翻译.doc

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1、如有侵权，请联系网站删除，仅供学习与交流计算机专业英语的第四版课后习题翻译【精品文档】第 9 页中译英参考答案Unit 1A computer system consists of hardware system and software system. The hardware of the computer is usually divided into three major parts or three primary subsystems: the CPU, the memory subsystem, and the I/O subsystem.The CPU performs ma

2、ny operations and controls computer. The memory subsystem is used to store program being executed by the CPU, along with the programs data. The I/O subsystem allows the CPU to interact with input and output devices such as the keyboard and monitor of a personal computer. The components of the comput

3、er are connected to the buses. The part of the computer that performs the bulk of data processing operations is called the central processing unit and is referred to as the CPU. In microcomputer, it is often called the microprocessor. The CPU is made up of three major parts: control unit, ALU, and r

4、egister set.Memory is also known as internal memory or main memory. It refers to the circuits in the computer that hold whatever programs and data are available for immediate use by the CPU.I/O subsystem includes I/O devices and interface. There are a wide variety of I/O devices, such as mouse, prin

5、ter, sensor, disk, and so on. Input-output interface provides a method for transferring information between internal storage and external I/O devices. Peripherals connected to a computer need special communication links for interfacing them with the CPU. The purpose of the communication link is to r

6、esolve the differences that exist between the central computer and each peripheral.Unit 2Storage hardware provides permanent storage of information and programs for retrieval by the computer. Hard disk drives store information in magnetic particles embedded in a disk. Usually a permanent part of the

7、 computer, hard disk drives can store large amounts of information and retrieve that information very quickly.Although fixed hard drive systems offer faster access and have a higher storage capacity than optical discs, optical disc systems use removable media a distinct benefit. Optical discs primar

8、y CDs and DVDs are much more widely used than removable hard drive systems. They are the standard today for software delivery, as well as commonly used for storing high-capacity music and video files. There are also versions of both CD and DVD drives available for home audio and home theater use. Op

9、tical discs are commonly referred to as compact discs.CD and DVD discs are read by CD and DVD drives. The speed of a CD or DVD drive is rated as 24x, 32x, 36x, and so on. These labels describe how fast the drive is compared to the first version of that drive. For example, a 36x drive is 36 times the

10、 speed of the baseline unit that was originally manufactured. Most optical discs have a title and other text printed only on one side and they are inserted into the drive with the printed side facing up. When inserting such a CD or DVD, be careful not to get dirt, fingerprints, scratches, or anythin

11、g else that might hinder light reflectivity on the discs surface.Unit 3(a) A program is a list of instructions or statements for directing the computer to perform a required data processing task. Programming is a multistep process for creating that list of instructions.(b) It is important to underst

12、and the difference between a class and an object of that class. A class is simply a specification for creating objects. Thus, a single class may create multiple objects.(c) Java is an object-oriented, network-friendly high-lever programming language that allows programmers to build applications that

13、 can run on almost any operating system.(d) ActiveX is a set of controls, or reusable components that enables programs or content of almost any type to be embedded within a Web page. Whereas a Java must be downloaded each time you visit a Web site, with ActiveX the component is downloaded only once,

14、 then stored on your hard disk for later, repeated use. (e) Programming involves a great deal of creativity. The design is guide to the function or purpose of each component, but the programmer has great flexibility in implementing the design as code. No matter what language is used, each program co

15、mponent involves at least three major aspects: control structures, algorithms, and data structures.Unit 4The software system can be divided into two broad categories: application software and system software. Application software consists of the program for performing tasks particular to the machine

16、s utilization. In contrast to application software, system software comprises a large number of programs. These programs start up the computer and function as the principle coordinator of all hardware components and application software. Without system software loaded into RAM of your computer, your

17、 hardware and application software are useless. System software can be grouped into three basic parts: operating system, utility software, and language translators. The majority of an installations utility software consists of programs for performing activities that are fundamental to computer insta

18、llations yet not included in the operating system. In a sense, utility software consists of software units that extend the capabilities of the operating system. A computers OS is the main collection of programs that manage its activities. The primary chores of an OS are management and control. The O

19、S ensures that all actions requested by a user are valid and processed in an orderly fashion. It also manages the computer systems resources to perform these operations with efficiency and consistency.Application software is the software designed to help you solve problems specific to business or pe

20、rform specific business tasks. Application software then is the layer of software closest to you. Basically, there are four categories of application software: productivity software, business and specialty software, entertainment software and education/reference software.Unit 5A computer network is

21、often classified as being either a local area network (LAN), a metropolitan area network (WAN), or a wide area network (WAN). The connection of two or more networks is called an internetwork. The worldwide Internet is a well-known example of an internetwork. LANs are privately owned networks within

22、a single building or campus of up to a few kilometers in size. They are widely used to connect personal computers and workstations in company offices and factories to share resources and exchange information. In general, a given LAN will use only one type of transmission medium. Various topologies a

23、re possible for LANs. The most common LAN topologies are bus, ring and star.A MAN is basically a bigger version of a LAN and normally uses similar technology. MAN is designed to extend over an entire city. It may be a single network such as a cable television network, or it may be a means of connect

24、ing a number of LANs into a large network so that resources may be shared LAN-to-LAN as well as device-to-device. For example, a company can use a MAN to connect the LANs in all of its offices throughout a city.A WAN spans a large geographical area that may comprise a country, a continent, or even t

25、he world. It provides long-distance transmission of data, voice, image, and video information over large geographical area.In contrast to LANs, WANs may utilize public leased, or private communication devices, usually in combinations, and can therefore span an unlimited number of miles.Unit 6Transmi

26、ssion media are used to transfer messages over a network. For instance, the transmission media used in a network may be a privately owned set of cables, the public phone lines, or a satellite system. Transmission media can either be wired or wireless.The three types of wired media most commonly used

27、 to carry messages are twisted-pair wire, coaxial cable, and fiber-optic cable. One of the most successful developments in transmission media in recent years has been fiber optics. Fiber-optic cable is commonly used for the high-speed backbone lines of a network, or for Internet infrastructure. Wire

28、less transmission media have become especially popular in recent years. They support communications in situations in which physical wiring is impractical or inconvenient, as well as facilitate mobility. Wireless media are commonly used to connect devices to a network, to share information between co

29、mputers, to connect wireless mice to a computer, and for handheld PCs, wireless phones, and other mobile devices. Radio signals transferred through the air are the heart of most types of wireless media. In addition to conventional broadcast radio application, the microwave, cellular, and satellite t

30、ransmission media also use radio signals to transmit data.Radio transmissions require the use of a transmitter to send the radio signals through the air. A receiver (usually containing some type of antenna) accepts the date at the other end. When a device functions as both a receiver and transmitter

31、, it is commonly called a transceiver or transmitter-receiver.Unit 7(a) Since many database systems users are not computer trained, developers hide the complexity from users through several levels of abstraction, to simplify users interactions with the system: physical level, logical level, and view

32、 level. (b) A database schema is specified by a set of definitions expressed by a special language called a data-definition language (DDL). The result of compilation of DDL statements is a set of tables that is stored in a special file called data dictionary, or data directory.(c) The structured que

33、ry language (SQL) is the most widely used and standard query language for relational database management systems. It is a kind of non-procedural language.(d) An entity is a “thing” or “object” in the real world that is distinguishable from other objects. For example, each person is an entity, and ba

34、nk accounts can be considered to be entities. Entities are described in a database by a set of attributes.(e) Data warehouse is one of the newest and hottest buzzwords and concepts in the IT field and the business environment. A data warehouse is a logical collection of informationgathered from many

35、 different operational databasesthat supports business analysis activities and decision-making tasks.Unit 8Animation is the term used to describe a series of graphical images that are displayed one after the other to simulate movement. Cartoons on television are one example of animation.Video differ

36、s from animation in that it usually begins as a continuous stream of visual information that is broken into separate images or frames when the video is recorded. When the frames are projectedtypically at a rate of 30 frames per secondthe effect is a smooth reconstruction of the original continuous s

37、tream of information. As you might imagine, at 30 frames per second, the amount of data involved in displaying a video during a multimedia presentation can require a substantial amount of storage space. Consequently, video datalike audio datais often compressed. A variety of compression standards ex

38、ist. Some of the most common video file formats are .avi, .mpeg, .mov, .rm.For multimedia presentation, video may be recorded using a standard (analog) video camera and then converted to digital form as it is input into a computer. Alternatively, the film can be recording digitally using a digital v

39、ideo camera. Streaming video is frequently used on Web pages to reduce file size. Similar to streaming audio, Streaming video files can begin playing once a portion of the video has been downloaded.Unit 9(a) AI is currently being applied in business in the form of knowledge systems, which use human

40、knowledge to solve problems. The most popular type of knowledge-based system is the expert system. An expert system is a computer program that attempts to represent the knowledge of human experts in the form of heuristics. The term heuristic is derived from the same Greek root as the word eureka, wh

41、ich means “to discover”. (b) The user interface enables the manager to enter instructions and information into the expert system and to receive information from it. The instructions specify the parameters that guide the expert system through its reasoning processing. The information is in the form o

42、f values assigned to certain variables.(c) The knowledge base contains both facts that describe the problem area and knowledge representation techniques that describe how the facts fit together in a logical manner. The term problem domain is used to describe the problem area.(d) An expert system, al

43、so called a knowledge-based system, is an artificial intelligence system that applies reasoning capabilities to reach a conclusion. Expert systems are excellent for diagnostic and prescriptive problems.(e) The DSS is not intended to replace the manager. The computer can be applied to the structured

44、portion of the problem, but the manager is responsible for the unstructured portionapplying judgment or intuition and conducting analyses.Unit 10The linked list (see figure 1) consists of a series of nodes, which are not necessarily adjacent in memory. Each node contains the element and a link to a

45、node containing its successor. We call this the next link. The last cells next link references null.To execute printList or find(x) we merely start at the first node in the list and then traverse the list by following the next links. This operation is clearly linear-time, as in the array implementat

46、ion, although the constant is likely to be larger than if an array implementation were used. The findKth operation is no longer quite as efficient as an array implementation; findKth(i) takes O(i) time and works by traversing down the list in the obvious manner. In practice, this bound is pessimisti

47、c, because frequently the calls to findKth are in sorted order (by i). As an example, findKth(2), findKth(3), findKth(4), and findKth(6) can all be executed in one scan down the list.The remove method can be executed in one next reference change. Figure 2 shows the result of deleting the second elem

48、ent in the original list.The insert method requires obtaining a new node from the system by using a new call and then executing two reference maneuvers. The general idea is shown in figure 3. The dashed line represents the old next reference. A0 A1 A2A3 A4 nullfigure 1 A0 A1 A2A3 A4 nullfigure 2 A0

49、A1 A2A3 A4 nullfigure 3 XUnit 11(a) A set is pure if all of its members are sets, all members of its members are sets, and so on. For example, the set containing only the empty set is a nonempty pure set.(b) A language is a describable set of finite strings, drawn from a fixed alphabet. A grammar is one way to describe the language. The gramma