计算机专业英语的第四版课后习题翻译

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1、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 many operations and controls computer. The memory

2、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 computer are connected to the buses. The part of the c

3、omputer 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 register set.Memory is also known as internal mem

4、ory 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, printer, sensor, disk, and so on. Input-output inter

5、face 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 resolve the differences that exist between the ce

6、ntral 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 computer, hard disk drives can store large amou

7、nts 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 primary CDs and DVDs are much more widely used than re

8、movable 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. Optical discs are commonly referred to as compact

9、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 speed of the baseline unit that was originally

10、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 anything else that might hinder light reflectivity on t

11、he 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 understand the difference between a class and an object

12、 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 can run on almost any operating system.(d) Acti

13、veX 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, then stored on your hard disk for later, repeat

14、ed 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 component involves at least three major aspects: c

15、ontrol 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 machines utilization. In contrast to application softwa

16、re, 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 hardware and application software are useless.

17、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 installations yet not included in the operating syste

18、m. 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 OS ensures that all actions requested by a user a

19、re 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 perform specific business tasks. Application softw

20、are 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 often classified as being either a local area ne

21、twork (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 a single building or campus of up to a few kilom

22、eters 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 are possible for LANs. The most common LAN topolo

23、gies 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 connecting a number of LANs into a large network so tha

24、t 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 the world. It provides long-distance transmission

25、 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 6Transmission media are used to transfer messages over a

26、 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 to carry messages are twisted-pair wire, coaxia

27、l 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. Wireless transmission media have become especially p

28、opular 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 computers, to connect wireless mice to a computer,

29、 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 transmission media also use radio signals to tran

30、smit 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, it is commonly called a transceiver or transmi

31、tter-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 level. (b) A database schema is specified by a

32、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 query language (SQL) is the most widely used and st

33、andard 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 bank accounts can be considered to be entities. En

34、tities 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 different operational databasesthat supports bu

35、siness 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 differs from animation in that it usually begins as a

36、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 stream of information. As you might imagine, at 3

37、0 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 exist. Some of the most common video file formats

38、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 video camera. Streaming video is frequently used

39、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 knowledge to solve problems. The most popular ty

40、pe 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, which means “to discover”. (b) The user interface

41、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 of values assigned to certain variables.(c) The k

42、nowledge 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, also called a knowledge-based system, is an artifi

43、cial 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 portion of the problem, but the manager is respo

44、nsible 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 node containing its successor. We call this the

45、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 implementation, although the constant is likely to be large

46、r 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 pessimistic, because frequently the calls to findKth are i

47、n 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 element in the original list.The insert method requi

48、res 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 A1 A2A3 A4 nullfigure 3 XUnit 11(a) A set is pur

49、e 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 grammar c

50、onsists of a finite list of rules, where each rule replaces one substring with another. The string on the left must contain at least one nonterminal. The first string produces or generates the second. Thus a rule is also called a production.(c) A finite-state machine (FSM) or finite-state automaton（

51、FA） is a mathematical abstraction sometimes used to design digital logic or computer programs. It is a behavior model composed of a finite number of states, transitions between those states, and actions, similar to a flow graph in which one can inspect the way logic runs when certain conditions are

52、met. (d) Sometimes it is inconvenient or impossible to describe a set by listing all of its elements. Another useful way to define a set is by specifying a property that the elements of the set have in common. The notation P(x) is used to denote a sentence or statement P concerning the variable obje

53、ct x. The set defined by P(x) written x | P(x), is just a collection of all the objects for which P is true.Unit 12(a) Because drawings are typically displayed in 3D, CAD is especially helpful in designing automobiles, aircraft, ships, buildings, electrical circuits (including computer chips), and e

54、ven clothing.(b) Computer-integrated manufacturing (CIM) is the manufacturing approach of using computers to control the entire production process. This integration allows individual processes to exchange information with each other and initiate actions. Through the integration of computers, manufac

55、turing can be faster and less error-prone, although the main advantage is the ability to create automated manufacturing processes.(c) In addition to supporting decision making, coordination, and control, information system may also help managers and workers analyze problems, visualize complex subjec

56、ts, and create new products.(d) Knowing the history and evolution of ERP is essential to understanding its current application and its future developments.(e) In addition to monitoring operational activities such as tracking the status of orders and inventory levels, enterprise system also improve o

57、rganization-wide reporting and decision making.Unit 13(a) There are a wide variety of educational application programs available. Educational software is designed to teach one or more skills, such as reading, math, spelling, a foreign language, world geography, or to help prepare for standardized te

58、sts.(b) Electronic business (e-business) is the use of information technology and electronic communication networks to exchange business information and conduct transactions in electronic, paperless form.(c) Word processing software allows you to use computers to create, edit, store, and print docum

59、ents. You can easily insert, delete, and move words, sentences, and paragraphswithout ever using an eraser.(d) What is a spreadsheet? Spreadsheet software takes its name from the accountants columnar worksheet, which it imitates. A spreadsheet is a worksheet consisting of a collection of cells forme

60、d by the intersection of rows and columns. Each cell can store one piece of information: a number, word or phrase, or formula.Unit 14(a) A geographic information system (GIS) is a system that captures, stores, analyzes, manages and presents data with reference to geographic location data. In the sim

61、plest terms, GIS is the merging of cartography, statistical analysis and database technology.(b) The GPS receiver uses the messages it receives to determine the transit time of each message and computes the distance to each satellite. These distances along with the satellites locations are used to c

62、ompute the position of the receiver. This position is then displayed, perhaps with a moving map display or latitude and longitude; elevation information may be included.(c) Virtual reality (VR) is a term that applies to computer-simulated environments that can simulate physical presence in the real

63、world. Most current virtual reality environments are primarily visual experiences, displayed either on a computer screen or through special stereoscopic displays, but some simulations include additional sensory information, such as sound through speakers or headphones.Unit 15(a) The software develop

64、ment process is sometimes called the software development life cycle (SDLC), because it describes the life of a software product from its conception to its implementation, delivery, use, and maintenance.(b) How can the CMM help your organization? There are three key roles the CMM plays. First, the C

65、MM helps build an understanding of software process by describing the practices that contribute to a level of process maturity. The second role of the CMM is to provide a consistent basis for conducting appraisals of software processes. The CMMs third key role is to serve as a blueprint for software process improvement.(c) The UML offers a standard way to write a systems blueprints, including conceptual things such as business processes and system functions as well as concrete things suc