计算机专业英语Unit_9
计算机专业英语第九章部分翻译
COMMUNICATION CHANNELSCommunication channels are an essential element of every communication system. These channels actually carry the data from one computer to another. There are two categories of communication channels. One category connects sending and receiving devices by providing a physical connection such as a wire or cable. The other category is wireless.沟通渠道是一个至关重要的元素的每个通信系统。
这些渠道实际上把数据从一台计算机到另一个。
有两个类别的沟通渠道。
一个类别连接发送和接收设备通过提供一个物理连接导线或电缆等。
另一类是无线。
PHYSICAL CONNECTIONSPhysical connections use a solid medium to connect sending and receiving devices. These connections include telephone lines (twisted pair), coaxial cable,and fiber-optic cable.物理连接使用固体介质连接发送和接收设备。
这些连接包括电话线路(双绞线)、同轴电缆和光纤电缆。
Telephone lines you see strung on poles consist of twisted-pair cable,which is made up of hundreds of copper wires. A single twisted pair culminates in a wall jack into which you can plug your phone and computer. (See Figure 9-3.) Telephone lines have been the standard transmission medium for years for both voice and data. However, they are now being phased out by more technically advanced and reliable media.Coaxial cable, a high-frequency transmission cable, replaces the multiple wires of telephone lines with a single solid-copper core. (See Figure 9-4.) In terms of the number of telephone connections, a coaxial cable has over 80 times the transmission capacity of twisted pair.Coaxial cable is used to deliver television signals as well as to connect computers in a network..电话线路你看到两极串在由双绞线,是由数以百计的铜线。
计算机专业英语Unit-9
Unit 9 Computer VirusText 1 Virus IntroductionExercises1. Multiple choices.(1) A virus is a ( A ).A. programB. computerC. bad manD. beast(2) A virus is a program that reproduces its own code by ( ABC ).A. adding to the end of a fileB. inserting into the middle of a fileC. simply placing a pointerD. replacing another program(3)( AD )is a type of executable file .A. COM fileB. TXT fileC. JPG fileD. EXE file(4)Similar to viruses, you can also find malicious code in ( ABC ).A. Trojan HorsesB. wormsC. logic bombsD. Microsoft Word Documents2. Fill in the blanks.(1) A virus is a program that reproduces its own code by attaching itself to otherexecutable files in such a way that the virus code is executed when the infectedexecutable file is executed .(2)To attach might mean physically adding to the end of a file, inserting into the middle ofa file, or simply placing a pointer to a different location on the disk somewhere wherethe virus can find it.(3)Similar to viruses, you can also find malicious code in Trojan Horses, worms, andlogic bombs.3. Translate and analyze the following sentences.(1)These self-replicating codes, when caused by some event, may do a potentially harmfula ct to your computer.句子组成：when引导时间状语从句做插入语，当…的时候.翻译：当这些自复制代码被一些事件触发时，或许会做出一些对你的电脑有潜在危害的行为.(2)M ore recently, scripts written for Internet web sites and/or included in E-mail can alsob e executed and infected.句子组成：scripts written…省略的定语从句完整形式scripts which were writtened….翻译：现在，为网站编写的或者包括在E-mail中的脚本也能够被执行和感染。
计算机专业英语教程第四版习题答案
计算机专业英语（第四版）课后习题答案Unit 1[Ex 1] 1. F 2. T 3. T 4. F 5. T 6. T 7. T 8. T 9. T 10. F [Ex 2] 1. input, storage, processing, and output 2. power; speed; memory3. central processing unit4. internal; primary; memory5. keyboard; central processing unit; main memory; monitor[Ex 3] A. 1. F 2. D 3. G 4. C 5. B 6. A 7. E 8. HB. 1. user 2. monitor 3. data 4. keyboard 5. data processing6. information7. computer8. memory[Ex 4] 1. input device 2. screen, screen 3. manipulates 4. instructions 5. retrieve6. code7. hard copy8. Function[Ex. 5] 新处理器开始IT技术的新时代New Processors Open New Era of IT Technologies Last week, Intel introduced to the public in Russia and other CIS countries a family of processors Intel Xeon E5-2600. They are more powerful and reliable and, importantly, are very economical in terms of energy consumption. Their presence opens a new era in the field of IT technologies and means that the cloud technology is getting closer.These processors are primarily designed for servers, data centers (DPC) and supercomputers. The emergence of this class of devices is not accidental. According to the regional director of Intel in Russia and other CIS states Dmitri Konash who spoke at the event, the market of IT-technology is developing so rapidly that, according to forecasts, by 2015 there will be 15 billion devices connected to the Internet, and over 3 billion of active users.上周，英特尔公司向俄罗斯和其它独联体国家的公众推出了英特尔XeonE5-2600系列处理器，它们更加强大可靠，尤其是在能量消耗方面更加经济实惠。
Unit 9 Digital signals and signal processing
Unite 9 Digital signals and signal processingPart 1: Digital signal processingDigital signal processing (DSP) is the study of signals in a digital representation and the processing methods of these signals. DSP and analog signal processing are sub-fields of signal processing. DSP includes sub-fields like audio and speech signal processing, sonar and radar signal processing, sensor array processing, spectral estimation, statistical signal processing, image processing, signal processing for communications, biomedical signal processing, etc.Since the goal of DSP is usually to measure or filter continuous real-world analog signals, the first step is usually to convert the signal form an analog to a digital form, by using an analog to digital converter. Often, the required output signal is another analog output signal, which requires a digital to analog converter.The algorithms required for DSP are sometimes performed using specialized computers, which make use of specialized microprocessors called digital signal processors (also abbreviated DSP). These process signals in real time, and are generally purpose-designed application-specific integrated circuits (ASICs). When flexibility and rapid development are more important than unit costs at high volume, DSP algorithms may also be implemented using field-rogrammable gatearrays (FPGAs).DSP domainsIn DSP, engineers usually study digital signals in one of the following domains: time domain (one-dimensional signals), spatial domain (multidimensional signals), frequency domain, autocorrelation domain, and wavelet domains. They choose the domain in which to process a signal by making an informed guess (or by trying different possibilities) as to which domain best represents the essential characteristics of the signal. A sequence of samples form a measuring device produces a time or spatial domain representation, whereas a discrete Fourier transform produces the frequency domain information, that is, the frequency spectrum. Autocorrelation is defined as the cross-correlation of the signal with itself over varying intervals of time or space.Signal samplingWith the increasing use of computers the usage and need of digital signal processing has increased. In order to use an analog signal on computer it must be digitized with an analog to digital converter (ADC). Sampling is usually carried out in tow stages, discretization and quantization. In the discretization stage, the space of signals is partitioned into equivalence classes and discretization is carried out by replacing thesignal with representative signal of the corresponding equivalence class. In the quantization stage the representative signal values are approximated by values form a finite set.In order for a sampled analog signal to be exactly reconstructed, the Nyquist-Shannon sampling theorem must be satisfied. This theorem states that the sampling frequency must be greater than twice the bandwidth of the signal. In practice, the sampling frequency is often significantly more than twice the required bandwidth. The most common bandwidth scenarios are: DC~BW (“baseband”); and f BW, a frequency band centered on a carrier frequency (“direct demodulation”).Time and space domainsThe most common processing approach in the time or space domain is enhancement of the input signal through a method called filtering. Filtering generally consists of some transformation of a number of surrounding samples around the current sample of the input or output signal. There are various ways to characterize filters; for example: - A “linear” filter is a linear transformation of input samples; other filters are “non-linear.” Linear filters satisfy the superposition condition, i.e., if an input is a weighted linear combination of different signals, the output is an equally weighted linear combination of the corresponding output signals.- A “causal” filter uses only previous samples of the input or output signals; while a “non-causal” filter uses future input samples. A non-causal filter can usually be changed into a causal filter by adding a delay to it.- A “time-invariant” filter has constant properties over time; other filters such as adaptive filters change in time.- Some filters are “stable”, others are “unstable”. A stable filter produces an output that converges to a constant value with time or remains bounded within a finite interval. An unstable filter produces output which diverges.- A “finite impulse response” (FIR) filter uses only the input signal, while an “infinite impulse response” filter (IIR) uses both the input signal and previous samples of the output signal. FIR filters are always stable, while IIR filters may be unstable.Most filters can be described in Z-domain (a superset of the frequency domain) by their transfer functions. A filter may also be described as a difference equation, a collection of zeroes and poles or, if it is an FIR filter, an impulse response or step response. The output of an FIR filter to any given input may be calculated by convolving the input signal with the impulse response. Filters can also be represented by block diagrams which can then be used to derive a sample processing algorithm to implement the filter using hardware instructions.Frequency domainSignals are converted from time or space domain to the frequency domain usually through the Fourier transform. The Fourier transform converts the signal information to a magnitude and phase component of each frequency. Often the Fourier transform is converted to the power spectrum, which is the magnitude of each frequency component squared.The most common purpose for analysis of signals in the frequency domain is analysis of signal properties. The engineer can study the spectrum to get information of which frequencies are present in the input signal and which are missing.There are some commonly used frequency domain transformations. For example, the cepstrum converts a signal to the frequency domain through Fourier transform, takes the logarithm, and then applies another Fourier transform. This emphasizes the frequency components with smaller magnitude while retaining the order of magnitudes of frequency components.ApplicationsThe main applications of DSP are audio signal processing, audio compression, digital image processing, video compression, speech processing, speech recognition, digital communications, radar, sonar,seismology, and biomedicine. Specific examples are speech compression and transmission in digital mobile phones, room matching equalization of sound in HiFi and sound reinforcement applications, weather forecasting, economic forecasting, seismic data processing, analysis and control of industrial processes, computer-generated animations in movies, medical imaging such as CAT scans and MRI, image manipulation, high fidelity loudspeaker crossovers and equalization, and audio effects for use with electric guitar amplifiers.ImplementationDigital signal processing is often implemented using specialized microprocessors such as the MC560000 and the TMS320. These often process data using fixed-point arithmetic, although some versions are available which use floating point arithmetic and are more powerful. For faster applications FPGAs might be used. Beginning in 2007, multicore implementations of DSPs have started to emerge. For faster applications with vast usage, ASICs might be designed specifically. For slow applications, a traditional slower processor such as microcontroller can cope.Part 2: General concepts of digital signal processingThere have been tremendous demands in the use of digital computersand special-purpose digital circuitry for performing varied signal processing functions that were originally achieved with analog equipment. The continued evolution of inexpensive integrated circuits has led to a variety of microcomputers and minicomputers that can be used for various signal processing functions. It is now possible to build special-purpose digital processors within much smaller size and lower cost constraints of systems previously all analog in nature.We will provide a general discussion of the basic concepts associated with digital signal processing. To do so, it is appropriate to discuss some common terms and assumptions. Wherever possible the definitions and terminology will be established in accordance with the recommendations of the IEEEE Group on Audio and Electroacoustics.An analog signal is a function that is defined over a continuous range of time and in which the amplitude may assume a continuous range of values. Common examples are the sinusoidal function, the step function, the output of a microphone, etc. the term analog apparently originated from the field of analog computation, in which voltages and currents are used to represent physical variables, but it has been extended in usage.Continuous-time signal is a function that is defined over a continuous range of time, but in which the amplitude may either have a continuous ranger of values or a finite number of possible values. In this context, an analog signal could be considered as a special case of continuous-timesignal. In practice, however, the terms analog and continuous-time are interchanged casually in usage and are often used to mean the same thing. Because of the association of the term analog with physical analogies, preference has been established for the term continuous-time. Nevertheless, there will be cases in which the term analog will be used for clarity, particularly where it relates to the term digital.The term quantization describes the process of representing a variable by a set of distinct values. A quantized variable is one that may assume only distinct values.A discrete-time signal is a function that is defined only at a particular set of values of time. This means that the independent variable, time, is quantized. If the amplitude of a discrete-time signal is permitted to assume a continuous range of values, the function is said to be a sampled-data signal. A sampled-data signal could arise from sampling an analog signal at discrete values of time.A digital signal is a function in which both time and amplitude are quantized. A digital signal may always be represented by a sequence of numbers in which each number has a finite number of digits.The terms discrete-time and digital are often interchanged in practice and are often used to mean the same thing. A great deal of the theory underlying discreet-time signals is applicable to purely digital signals, so it is not always necessary to make rigid distinctions. The term。
Unit 09计算机英语
expensive item such as a sofa before they purchase it.
Electronic commerce
Disadvantages
Many people also consider shopping a social experience.
社交体验
For instance, they may enjoy going to a shopping mall
Electronic commerce is a system [ that includes 电子商务 not only transactions that center on buying and selling 交易
goods and services to directly generate revenue,
virus
名词 n. [C] 1. 病毒;滤过性病毒 2. 病毒感染 We should be watchful of computer viruses. 警惕 antivirus n. 杀毒软件
spy
名词 n. 1. 间谍;密探[C] She liked the adventures of a spy. 不及物动词 vi. 1. 当间谍;暗中监视;刺探[(+on/upon/into)] We spied on the man. 及物动词 vt. 1. 暗中监视;侦察出 He sent out a party to spy the enemy. 小分队
《计算机英语》
Unit 9 Electronic commerce 电子商务
encrypt [en‘kript] v.加密 encryption n. 【电脑】加密 encryption software
电子信息类专业英语Unit 9 Digital Signal Processing
Unit 9 Digital Signal Processing
Figure 9.1 Analog-to-Digital Conversions
Unit 9 Digital Signal Processing
After a brief acquisition time, during which a sample is acquired, the sample and hold circuit holds the sample steady for the remainder of the sampling interval. This hold time is needed to allow time for an A/D converter to generate a digital code that best corresponds to the analog sample.
Unit 9 Digital Signal Processing
A digital signal is represented by a set of vertical lines with circles at the top to mark the quantization levels selected for each sample. The bit rate for an A/D converter is the Nfs, where fs is the sampling rate.
计算机专业英语Unit09
computing
ESSENTIALS
Security Measures
Protecting information, hardware, software Principle methods Encrypting messages Pretty Good Privacy Restricting access Passwords, firewalls Anticipating disasters Disaster recovery plan Backing up data In case other measures fail
Dept.Of Computer Science,XYNC 4
computing
ESSENTIALS
Large Databases
Information on citizens and consumers compiled daily Banks, utilities, grocery stores Hospitals, doctor’s offices Government Social Security Number Used for ID number on forms Information resellers Contact data is valuable
computing
ESSENTIALS
9
1
Privacy and Security
Dept.Of Computer Science,XYNC.
computing
ESSENTIALS
《计算机英语》课件Chapter 9 Computer Network
Chapter 9 Computer Network
Objective After reading this chapter, you should be able to: Know OSI reference model. Know TCP/IP reference model. Explain network architecture. Describe local area, metropolitan area, and wide area networks.
9.1 Computer Network
A computer network is a group of interconnected computers.
The network ws computers to communicate with each other and share resources and information.
✓ Local Area Network (LAN). A computer network covering a small physical area.
✓ Metropolitan Area Network (MAN). A network that connects two or more local area networks or campus area networks together but does not extend beyond the boundaries of the immediate town/city.
9.3 Network Topology
Figure 9-3 Network topologies
计算机 专业 英语 教案
.教案首页（第11次课，2学时）授课题目Unit 9 Data Transimission Media教学目的通过讲授，使学生了解各种传输媒介的英文描述与要求教学重点传输媒介的专业术语教学难点课文的理解、翻译教学内容：单词、课文教学过程教学方法：讲授法课后作业P128-133，1-5教学后记Unit 9 Data Transimission Media一、传输媒介支持数据传输的传输媒介有：电话线、同轴电缆、微波信号、卫星系统和光纤。
电话线即为双绞线，它由四对线组成，其中每对由两条带绝缘层的导线以螺旋形式绞合在一起。
传输距离小，抗干扰能力弱、但价格便宜。
同轴电缆：由内外两个导体构成，内导体是一根铜质导线，外导体是铜箔构成，起屏蔽干扰作用。
传输距离适中、抗干扰能力强。
光纤：光缆纤缆作为信号传输介质，把电信号转换成光信号，进行传输。
传输距离远、抗干扰能力强、传输信号量大且信号不失真，但价格贵。
二、New Words1．amplifier n.放大器，扩音机2. antenna n.触角，触须；天线3. boost vt.提高；推动；宣扬n.增涨；推动，激励Boost an electric current增强电流Give sb’s confidence a boost增强某人的信心4. channel n.频道；信道；沟渠；海峡，航道Your favourite channel你最喜欢的频道5. circuit n.电路，线路；环行，环行道The circuit of the city is three miles.环城线路有三英里。
6. coaxial同轴的; 共轴; 共轴的7. compensate v.补偿，弥补，抵消She was compensated by the insurance company for her injuries.她受伤后获得保险公司的赔偿。
8. curvature弧度，曲率，弯曲The curvature of the earth ‘s surface.地球表面的曲度。
IT专业英语UNIT9Database教材教学课件
Introduction to Database Management System
Definition
A Database Management System (DBMS) is a software application that provides users with an interface to manage and interact with databases. It allows users to create, modify, retrieve, and delete data from the database.
Database Normalization
The process of organizing the data in a database to minimize data redundancy and improve data integrity.
03
Data Independence
The ability of the data in the database to be accessed and used
IT Professional English Unit9 Database Textbook Teaching Courseware
• Introduction to Database • Relational database • Database design • Database security and maintenance • Development Trends and New
ogies of Database
01
Introduction to Database
Definition and role of databases
计算机专业英语的第四版课后习题翻译
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 subsystem is used to store program being executed by the CPU, along with the program’s 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 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 register 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, printer, 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 resolve 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 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 –primary 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. Optical 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 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 anything else that might hinder light reflectivity on the disc’s surface.Unit 3(a) A program is a list of instructions or statements for directing the computer to perform arequired 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 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) 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, 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 component 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’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 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 installation’s utility software consists of programs for performing activities that are fundamental to computer installations 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 computer’s 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 are valid and processed in an orderly fashion. It also manages the computer system’s 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 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 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 a single building or campus of up to a few kilometers in size. They are widely used to connect personal computers and workstations incompany 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 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 connecting 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 W AN spans a large geographical area that may comprise a country, a continent, or even the world. It provides long-distance transmission of data, voice, image, and video information over large geographical area.In contrast to LANs, W ANs 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 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, 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.Wireless 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 computers, 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 transmission 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, 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 user’s interactions with the system: physical level, logical level, and view 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 query 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 otherobjects. For example, each person is an entity, and bank 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 information——gathered from many different operational databases——that 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 differs 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 projected—typically at a rate of 30 frames per second—the effect is a smooth reconstruction of the original continuous stream 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 data—like audio data—is often compressed. A variety of compression standards exist. 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 video 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 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, which 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 of 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, also 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 portion of the problem, but the manager is responsible for the unstructured portion——applying 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 next link. The last cell’s 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 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 pessimistic, 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 element 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.figure 1figure 2figure 3Unit 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 grammar consists 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（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 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 object x. The set defined by P(x) written {x | P(x)}, is just a collection of all the objects for whichP 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 even 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, manufacturing 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 subjects, 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 organization-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 tests.(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 documents. You can easily insert, delete, and move words, sentences, and paragraphs——without ever using an eraser.(d) What is a spreadsheet? Spreadsheet software takes its name from the accountant’s columnar worksheet, which it imitates. A spreadsheet is a worksheet consisting of a collection of cells formed 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 simplest 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 compute 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 world. Most current virtual reality environments areprimarily 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 development 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 CMM 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 CMM’s third key role is to serve as a blueprint for software process improvement.(c) The UML offers a standard way to write a system’s blueprints, including conceptual things such as business processes and system functions as well as concrete things such as programming language statements, database schemas, and reusable software components. The UML represents a collection of the best engineering practices that have proven successful in the modeling of large and complex systems.(d) Object modeling is a technique for identifying objects within the system environment and the relationships between those objects. The object-oriented approach to system development is based on several concepts, such as object, attribute, behavior, encapsulation, class, inheritance, polymorphism, persistence, etc.Unit 16“Security” is an all-encompassing term that describes all the concepts, techniques, and technologies to protect information from unauthorized access. There are several requirements for information security.Confidentiality: hiding data, usually with encryption, to prevent unauthorized viewing and access.Authenticity: the ability to know that the person or system you are communicating with is who or what you think it is.Access control: once a person or system has been authenticated, their ability to access data and use systems is determined by access controls.Data integrity: providing assurance that an information system or data is genuine.Availability: making sure that information is available to users in a secure way.To prevent unauthorized access, some type of identification procedure must be used. These vary from passwords to physical access object (access cards, etc.) to biometric devices that verify some type of personal characteristic, such as a fingerprint.Some of the most secure access control systems address both identification and authentication. Identification involves verifying that the person’s name or other identifying feature is listed as an authorized user; authentication refers to determining whether or not the person is actually who he or she claims to be.Unit 17A distributed system is a collection of independent computers which appear to the users of system as a single computer. Nearly all large software systems are distributed. For example, enterprise-wide business systems must support multiple users running common applications across different sites.A distributed system encompasses a variety of applications, their underlying support software, the hardware they run on, and the communication links connecting the distributed hardware. The largest and best-known distributed system is the set of computers, software, and services comprising the World Wide Web, which is so pervasive that it coexists with and connects to most other existing distributed systems. The most common distributed systems are networked client/server systems. Distributed systems share the general properties described below.●Multiple nodes●Message passing or communication●Resource sharing●Decentralized control●Concurrency or parallelism●Fault tolerance●Heterogeneity●OpennessDistributed systems have many inherent advantages, especially over centralized systems. Some applications are inherent distributed as well. In general, distributed systems:●Yield higher performance●Allow incremental growth●Allow one user to run a program on many different machines in parallel●Provide higher reliability。
第九单元课文译文 计算机英语 吕云翔
第九单元参加面试第一部分听说A. 对话：面试（Kevin对Expansion公司技术部门程序员职位的申请已经得到公司人力资源部门的回复。
今天，Kevin来到公司进行面试。
）Smith先生：早上好，欢迎申请我们公司的空缺职位。
我叫Smith，是人力资源部经理。
请问怎么称呼你？Kevin：早上好，Smith先生。
我叫Kevin，我是来申请技术部门程序员职位的。
Smith先生：好的，现在我们来谈谈关于你的资格和条件。
能介绍一下你自己吗?Kevin：我是一个积极负责的人，即使在追求目标的途中会碰上无数的障碍挫折，我也不会放弃对成功的追求。
我喜欢团队工作，因为我相信，为获得最好的结果，分享彼此的意见和主张是很重要的。
我对科学技术的最新进展很感兴趣，并且具备很好的理论背景和动手能力。
我热爱IT行业，并希望从事IT职业。
Smith先生：能不能谈谈你的教育背景？Kevin：我于2008年7月从北京航空航天大学软件学院毕业，并获得了软件工程的学士学位。
Smith先生：你为什么想申请我们公司的职位呢？Kevin：众所周知，Expansion公司是中国成立时间最长和最主要的软件外包产品、服务和解决方案提供商之一，并且具有世界知名度。
因此，我相信在这里工作可以提升我的专业能力，而且我认为我也可以为公司的发展做出自己的贡献。
Smith先生：你是否曾参加过能帮助你准备这类工作的实习呢？Kevin：是的。
在本科的时候，作为程序员，我曾在我们学校与微软合作的实验室中，参加了几个实际项目。
作为项目经理，我曾参与了为四季酒店开发的管理信息系统和为Giant公司财务部开发的管理信息系统。
此外，我还为国内一家领先的IT公司做过关于全球软件市场的研究和分析，并用英语完成了商业报告。
我认为以上所有这些对于我准备这份工作都是非常宝贵的实习经历。
.Smith先生：好，听起来不错！关于你的工作你还有什么想要知道的吗？Kevin：我想知道，您认为要从事这个职位还需要什么其他必要条件呢？Smith先生：好，据我所知，软件开发的工作量有时候会很大，因此，负责这项工作的人可能必须承担很大的压力，而且必须精力充沛，并很能干。
unit9-徐娜
Task I
Careers in IT
• Dialogue: Practice With Your Partner
Tom: Jerry, long time no see. How are you doing today? Jerry: So far so good, how about you? I think you must be busy these days. Tom: Yes, I am. Our bank decided to set a new branch in Wenzhou, so there are many preparations need to be done. Jerry: Pretty fair. So you guys are going to buy a great many new computers for that branch? Tom: Partly, but I am not responsible for this part, I am in the charge of setting the new cipher machine. Jerry: Cipher machine, it sounds so mystical. Tom: Ha-ha that is because you are not major in computer science. Jerry: Probably, but for me, it is really a big problem to deal with the computer things. Tom: Really? If you hit this kind of problems next time feel free to call me, it will be my pleasure to give you a hand. Jerry: Wow, it is really good news for me, thank you very much. Oops, its 6pm now. I need to go, my husband is waiting me for dinner, see you next time. Tom: All right, see you.
Unit-9-Machining-Center-机电专业英语-图文课件
Text & Translation
Two new trends are observed in the development of machining centers. One is the growing interest in smaller，more compact machining centers and the other is the emphasis on extended shift or even unmanned operations. Modern machining centers have contributed significantly to improved productivity in many companies. They have eliminated the time lost in moving workpieces from machine to machine and the time needed for workpiece loading and unloading for separate operations. In addition，they have minimized the time lost in changing tools，carrying out gauging operations，and aligning workpieces on the machine.
Text & Translation
加工中心有两个发展趋势：一是更小、更紧凑 的加工中心的兴起；二是对扩展轴或无人操作 的重视。现代的加工中心对很多公司提高生产 率有着重要的作用，节省了把工件从一台机床 移向另一台机床与对工件的单个加工所需的装 卸时间。此外，更换刀具、测量和工件定位的 时间也缩短至最低限度。
计算机英语教程unit 9
Notes
[4] For example, when a user is working on a slide with the bulleted list layout applied and then he inserts a table, PowerPoint automatically changes the layout to the Text and Object layout so that the table and text are side by side.
本 句 中 ， that lets you move objects along a path simultaneously or slide transitions effects 是一定语从句， 修饰the new 'path animation'。 本句意为： 最后， Custom Animation 面板含有 PowerPoint 必须提供的非常强 大的动画效果。如新的“路径动画”可使你同时沿着一个路径移 动多个目标或具有滑动过渡效果。
本句中，so that引导了一个结果状语从句。
本句意为： 例如，当用户在制作使用项目符列表布局的幻灯片、然后插入一个表 格时，PowerPoint自动将该布局变为Text和Object布局。这样，表格 和文本就并列了。
Exercises
请做课后练习
司爱侠其他部分著作
《计算机英语教程》，北京，人民邮电出版社：国家级十五规划教材 《电脑英语掌中宝》，南京，东南大学出版社：获“华东地区大学出版社教材专著二等奖” 《计算机专业英语教程》，北京，高等教育出版社 《电子商务专业英语教程》，北京，高等教育出版社 《计算机专业英语教程》，北京，机械工业出版社 《电脑英语词汇通》，北京，人民邮电出版社 《计算机实用英语》，西安，世界图书出版公司 《计算机专业英语教程》，北京，清华大学出版社 《电子商务专业英语教程》，北京，清华大学出版社 《信息管理专业英语教程》，北京，清华大学出版社 《电气工程专业英语教程》，北京，清华大学出版社 《电子商务专业英语实用教程》，杭州，浙江大学出版社 《计算机专业英语教程》，北京，科学出版社 《饭店酒店管理专业英语教程》，北京，清华大学出版社 《法律专业英语教程》，北京，清华大学出版社 《旅游专业英语教程》，北京，清华大学出版社 《大学英语听说新体验（带mp3光盘）》，杭州，浙江大学出版社 《大学英语学习指南》，北京，外语教学与研究出版社 《大学体验英语学与练》（丛书，四册），天津，南开大学出版社 《大学体验英语词汇通》，天津，南开大学出版社
《计算机英语》第九单元
9.1
主要内容
• 正文 • 生词
— 4—
9.1 Internet Security
Anyone responsible for the security of a trusted network will be concerned when connecting it to a distrusted network. In the case of connections to the Internet this concern may be based largely on anecdotal evidence gleaned from widespread media coverage of security breaches. A closer inspection of the facts and statistics behind some of the media coverage will, however, only serve to deepen that concern. For example, the US National Computer Security Agency (NCSA) asserts that most attacks to computer systems go undetected and unreported, citing attacks made against 9000 Department of Defense computers by the US Defense Information Systems Agency (DISA). These attacks had an 88 percent success rate and went undetected by more than 95 percent of the target organizations. Only 5 percent of the 5 percent that detected an attack, a mere 22 sites, reacted to it.
新编计算机英语教程Chapter 09
Data Structure - Data Structure Fundamentals
• Abstraction
• Static Versus Dynamic Structures • An important distinction in constructing abstract data structures is whether the structure being simulated is static or dynamic, that is, whether the shape or size of the structure changes over time. For example, if the abstract tool is a list of names, it is important to consider whether the list will remain a fixed size throughout its existence, expand and shrink as names are added and deleted.
Data Structure - Data Structure Fundamentals
• Basic Data Structures- heterogeneous array
• In contrast to a homogeneous array, a heterogeneous array is a block of data items that might be of different types. The items within the block are usually called components.
计算机专业英语翻译及课后答案
计算机专业英语翻译及课后答案Unit Nine: The InternetUnit Nine/Section AI. Fill in the blanks with the information given in the text:1. research2. ICANN或the Internet Corporation for Assigned Names and Numbers3. router; gateway4. temporary/dial-up; permanent/dedicated5. ISP或Internet service provider6. network; host7. decimal8. mnemonicII. Translate the following terms or phrases from English into Chinese and vice versa:1. cell phone 蜂窝电话，移动电话，手机2. IP address 网际协议地址，IP地址3. autonomous system 自主系统4. dial-up connection 拨号连接5. network identifier 网络标识符6. binary notation 二进制记数法7. mnemonic name 助记名，缩写名8. Internet-wide directory system 因特网范围的目录系统9. name server 名称服务器10. Internet infrastructure 因特网基础结构11. 助记地址mnemonic address12. 网吧cyber cafe13. 宽带因特网访问broadband Internet access14. 顶级域名top-level domain (TLD)15. 因特网编址Internet addressing16. 点分十进制记数法dotted decimal notation17. 因特网服务提供商Internet service provider (ISP)18. 专用因特网连接dedicated Internet connection19. 主机地址host address20. 硬件与软件支持hardware and software supportIII. Fill in each of the blanks with one of the words given in the following list, making changes if necessary:Early computer networks used leased telephone company lines for their connections. Telephone company systems of that time established a single connection between sender and receiver for each telephone call, and that connection carried all data along a single path. Whena company wanted to connect computers it owned at two different locations, the company placed a telephone call to establish the connection, and then connected one computer to eachend of that single connection.The U. S. Defense Department was concerned about the inherent risk of thissingle-channel method for connecting computers, and its researchers developed a differentmethod of sending information through multiple channels. In this method, files and messagesare broken into packets that are labeled electronically with codes for their origins, sequences,and destinations. In 1969, Defense Department researchers in the Advanced Research ProjectsAgency (ARPA) used this network model to connect four computers into a network called theARPANET. The ARPANET was the earliest of the networks that eventually combined to become what we now call the Internet. Throughout the 1970s and 1980s, many researchers in the academic community connected to the ARPANET and contributed to the technological developments that increased its speed and efficiency.IV. Translate the following passage from English into Chinese: 因特网只是提供了将许许多多的计算机连接在一起的物理与逻辑基础结构。
《信息技术英语》-unit9
Unit 9Serial CommunicationsChapter Three&Part4 Extensive Reading @Part 1 Notes to Text@Part5Notes to Passage & Part 2 Word Study@Part3 Practice on Text @Part6 Practice on Passage@Part 1 Notes to TextSerial Communications1)serial communications 串口通讯简介：串口通讯是指在一个时间内传输一位数字数据。
从19世纪的二进位电报编码，发展到现在的RS-232(EIA-232)，主要用于连接终端和大型主机。
串口通讯在过去的40年里，大大推动了通讯技术的发展。
本文主要阐述了关于串口通讯的串口按位（bit）发送和接收字节的基本概念。
2) On the other hand, when communicating with a timesharingsystem over a modem, only a single channel is available,and bit-serial transmission is required. 另一方面，如果通过调制解调器与分时系统进行通讯，就只有一条通道可行，此时就需要用到位串行传输了。
注释：该句是并列句。
现在分词短语when communicating with…作时间状语。
3) The popular Centronics printer interface is a case where byte-serial transmission is used. 广为流行的并行打印机接口就是一个使用字节串行传输的例子。
简介：Cenronics,称并口，也有称之为IEEE1284，是目前外部设备与电脑连接常见的接口类型之一，另外还有其他接口类型包括：串口（也有称之为RS-232接口的）和USB接口。
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Unit 9 Computer VirusText 1 Virus IntroductionExercises1. Multiple choices.(1) A virus is a ( A ).A. programB. computerC. bad manD. beast(2) A virus is a program that reproduces its own code by ( ABC ).A. adding to the end of a fileB. inserting into the middle of a fileC. simply placing a pointerD. replacing another program(3)( AD )is a type of executable file .A. COM fileB. TXT fileC. JPG fileD. EXE file(4)Similar to viruses, you can also find malicious code in ( ABC ).A. Trojan HorsesB. wormsC. logic bombsD. Microsoft Word Documents2. Fill in the blanks.(1) A virus is a program that reproduces its own code by attaching itself to otherexecutable files in such a way that the virus code is executed when the infectedexecutable file is executed .(2)To attach might mean physically adding to the end of a file, inserting into the middle ofa file, or simply placing a pointer to a different location on the disk somewhere wherethe virus can find it.(3)Similar to viruses, you can also find malicious code in Trojan Horses, worms, andlogic bombs.3. Translate and analyze the following sentences.(1)These self-replicating codes, when caused by some event, may do a potentially harmfula ct to your computer.句子组成：when引导时间状语从句做插入语，当…的时候.翻译：当这些自复制代码被一些事件触发时，或许会做出一些对你的计算机有潜在危害的行为.(2)M ore recently, scripts written for Internet web sites and/or included in E-mail can alsob e executed and infected.句子组成：scripts written…省略的定语从句完整形式scripts which were writtened….翻译：现在，为网站编写的或者包括在E-mail中的脚本也能够被执行和感染。
4. Reading comprehension.Unit 9Computer Virus2 Viruses can infect any type of executable code, not just the files that are commonly called―program files‖. Viruses can be spread by:∙Executable code in the boot sector of infected floppy disks∙Executable code in the system area of infected hard drives∙Word processing and spreadsheet documents that use infected macros Infected HTML documents that contain JavaScript or other types of executable codeSince virus code must be executed (run) to have any effect, files that the computer treats as pure data are safe. This includes graphics and sound files such as .gif, .jpg, .mp3, .wav, etc., as well as plain text in .txt files. For example, just viewing picture files won't infect your computer with a virus. The virus code has to be in a form, such as an .exe program file or a Word .doc file, that the computer will actually try to execute.Answer the following questions according to the article above.(1)What kind of files can be infected by a virus?A virus can infect the executable files such as .exe or .com or .doc files,etc.(2)How about viruses can be spread?Executable code in the boot sector of infected floppy disks or in the system area ofinfected hard drives, word processing and spreadsheet documents that use infectedmacros Infected HTML documents that contain JavaScript or other types of executablecode.Text 2 Virus Behavior – Infection Phase Exercises1. Multiple choices.(1)V iruses all have two phases to their execution, the ( A )and the ( C ).A. infection phaseB. delete phaseC. attack phaseD. create phase(2)( ABCD ) maybe a certain cause that some viruses infect upon.A. a dayB. a timeC. an external event on your PCD. a counter within the virus(3)Many viruses go resident in the memory like a ( C ).A. .exe fileB. .com fileC. tsr programD. data file(4)Y ou want to ( ABC ) maybe wake up a virus that has residented in memory.A. copy a fileB. access a disketteC. execute a programD. delete a file(5)Some viruses use ( A ) and ( B ) techniques to hide their existence.A. stealthB. polymorphicC. quickly spreadD. replace a part of system softwareVirus Behavior – Infection Phase32. Fill in the blanks.(1) Viruses come in a great many different forms, but they all potentially have two phases to their execution, the infection phase and the attact phase.(2) For those not old enough to remember tsr, they were programs that executed under system but stayed in memory instead of ending.(3) Note that worms often take the opposite approach and spread as fast as possible.3. Translate and analyze the following sentences.(1) When the virus executes it has the potential to infect other programs.句子组成：when 引导时间状语从句 当,,,时 .翻译：病毒在执行时，能够感染其他程序 .(2) Some viruses infect other programs each time they are executed; other viruses infectonly upon a certain cause.句子组成：some …other …引导两个并列句子，一些…其他….。
翻译：一些病毒会在每次被执行时，都感染其他程序；另一些病毒只是在一些特定的触发原因下才能感染其他程序.(3) Resident viruses frequently take over portions of the system software on the PC to hidetheir existence.句子组成：to hide their existence 不定式做目的状语 take over 代替.翻译：驻留内存病毒常常代替PC 系统文件的一部分来掩饰它的存在 .4. Reading comprehension.Polymorphic viruses use encryption (密码术) or other methods to change how they look. This strategy of changing their appearance helps to defeat antivirus scanning software. Stealth viruses attempt to hide any modifications they have made from antivirus scanning software. For example, stealth viruses sometimes substitute unaltered files and directory table entries for the virus-altered ones, in an attempt to fool antivirus scanning software. Fast infector viruses are capable of infecting any file which is opened, rather than only executed files. Slow infectors only modify files as the files are being created or altered for legitimate reasons, a practice which fools some antivirus software. Sparse infectors only infect at certain intervals dictated by their programming, lessening their chance of creating suspicion on the part of the user.Choose the best answer.(1) How can polymorphic viruses defeat antivirus scanning software?(B)A. resident in memoryB. use encryptionC. hide in other programsD. use the unaltered files to replace the virus-altered ones(2) How can stealth viruses fool antivirus scanning software?(C)A. resident in memoryB. use encryptionC. hide in other programsUnit 9Computer Virus4 D. use the unaltered files to replace the virus-altered ones(3)Which kind of virus can only alter files, as the files are being created or altered forlegitimate reasons?(D)A. polymorphic virusB. stealth virusC. fast virusD. slow virus(4) A few of viruses only infect at certain intervals dictated by their programming, becauseof ___?(A)A. Don’t let user notice them.B. They wait for some special programs to infect.C. No special reason.D. They want to change how they look.Text 3 Virus Behavior－Attack PhaseExercises1. Multiple choices.(1)Many viruses do harmful things such as ( ABCD ).A. deleting filesB. changing random data on your diskC. simulating typosD. slowing your PC down(2)Viruses can delay their attack for ( ABCD ).A. daysB. weeksC. monthsD. years(3)If a virus simply reproduce and have no cause for an attack phase, but it will still( AB ) without your permission.A. stealing storageB. pilfer CPU cyclesC. delete files C. play music(4)Some viruses, with no attack phase, often damage the programs or disks they infectbecause they ( AB ).A. have bugs in themB. contain poor quality codeC. steal storageD. show messages on your screen2. Fill in the blanks.(1)Many viruses do unpleasant things such as deleting files or changing random data onyour disk.(2)Most viruses have bugs in them and these bugs often cause unintended negative sideeffects.(3)In addition, even if the virus is perfect, it still steals system resources.(4)The attack phase is optional, many viruses simply reproduce and have no cause for anattack phase.(5)An example, one of the most common past viruses, Stoned, is not intentionally harmful.3. Translate and analyze the following sentences.Number of Viruses5(1) Just as the infection phase can be caused by some event, the attack phase also has itsown cause.句子组成：as 引导状语从句. 翻译：如同感染阶段需要一些事件触发一样，攻击阶段也有它自己的触发条件.(2) In addition, even if the virus is perfect, it still steals system resources.句子组成：even if 即使，引导条件状语从句；in addition 另外. 翻译：此外，即使病毒设计完美，它仍会盗用系统资源。