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
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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。