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[单选题]
A computer can only do______ you have instructed it to do.
A.how
B.after
C.what
D.when
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A.how
B.after
C.what
D.when
答案
更多“A computer can only do______ you have instructed it to do.”相关的问题
第1题
A．Not only
B．Unless
C．Except
D．Besides
第2题
从下面提供的答案中选出应填入下列英文语句中______内的正确答案。
The computer itself does not do all the work on its own. The work is done by a(1)of the computer, called hardware, and(2)ofinstructions, called software or computer programs. Inside the machine, the instructions are(3)and carried out to do the work you want to do. A computer without software is nothing more than a mass of metal and plastic. On the other hand, software without a computer is simply wasted(4)because only the computer can use the software and put it to work. When you talk about a computer's being able to do this or that, you are really refemng to the(5)that accepts your commands and the computer that carries them out.
第3题
从供选择的答案中，选出最确切的解答。
Most computer systems are(1)to two different groups of attacks: Insider attacks and outsider attacks. A system that is known to be(2)to an outsider attack by preventing(3)from outside can still be vulnerable to the insider attacks accomplished by abusive usage of(4)users. Detecting such abusive usage as well as attacks by outsides not only provides information on damage assessment, but also helps to prevent future attacks. These attacks are usually(5)by tools referred to as Intrusion Detection Systems.
第4题
1.The 2008 Beijing Olympic Games were such a good _____________ the world to know more about China.
2.Sorry, I can't give you an answer _____________ .I need to think about it further.
3.The professor encourages us to ____________ opportunities instead of waiting for good luck.
4.The organizer has ____________ a number of famous singers to perform. at the opening ceremony (开幕式).
5.The great progress they have made comes from their good ____________ work.
6.Exercise will always give you a good ____________.
7.The computer can easily get stuck, so you must ____________ of computer viruses.
8.Before it got dark the campers ____________ their tent in a field.
9.When I ____________ a new word, I write it down in my notebook.
10.Chatting with friends over the Internet in the dead of night is probably my only ___________.
第5题
Distributed Systems
分布系统
Computer systems are undergoing a revolution. From 1945, when the modern computer era began, until about 1985, computers were large and expensive. Even minicomputers normally cost tens of thousands of dollars each. As a result, most organizations had only a handful of computers, and for lack of a way to connect them, they operated independently from one another.
Starting in the mid 1980s, however, two advances in technology began to change that situation. The first was the development of powerful microprocessors. Initially, these were 8 bit machines, but soon 16, 32, and even 64 bit CPUs became common. Many of these had the computing power of a decent-sized mainframe (i. e. large) computer, but for a fraction of the price.
The amount of improvement that has occurred in computer technology in the past half century is truly staggering and totally unprecedented in other industries. From a machine that cost 10 million dollars and executed 1 instruction per second, we have come to machines that cost 1,000 dollars and execute 10 million instructions per second, a price/ performance gain of 1011. If cars had improved at this rate in the same time period, a Roll Royce would now cost 10 dollars and get a billion miles per gallon. (Unfortunately, it would probably also have a 200 page manual telling how to open the door.) The second development was the invention of high speed computer networks. The local area networks, or LANs, allow dozens, or even hundreds, of machines within a building to be connected in such a way that small amounts of information can be transferred between machines in a millisecond or so. Larger amounts of data can be moved between machines at rates of 10 to 100 million bits/sec and sometimes more. The wide area networks, or WANs, allow millions of machines all over the earth to be connected at speeds varying from 64Kbps (kilobits per second) to gigabits per second for some advanced experimental networks.
The result of these technologies is that it is now not only feasible, but easy, to put together computing systems composed of large numbers of CPUs connected by a high speed network. They are usually called distributed systems, in contrast to the previous centralized systems (or single processor systems) consisting of a single CPU, its memory, peripherals, and some terminals.
There is only one fly in the ointment[1]: software. Distributed systems need radically different software than centralized systems do. In particular, the necessary operating systems are only beginning to emerge. The first few steps have been taken, but there is still a long way to go. Nevertheless, enough is already known about these distributed operating systems that we can present the basic ideas.
What Is a Distributed System？
Various definitions of distributed systems have been given in literature, none of them satisfactory and none of them in agreement with any of the others. For our purposes it is sufficient to give a loose characterization.
A distributed system is a collection of independent computers that appear to the users of the system as a single computer.
This definition has two aspects. The first one deals with hardware: the machines are autonomous. The second one deals with software: the users think of the system as a single computer. Both are essential.
Rather than going further with definitions, it is probably more helpful to give several examples of distributed systems. As a first example, consider a network of workstations in a university or company department. In addition to each user's personal workstation, there might be a pool of processors in the machine room that are not assigned to specific users but are allocated dynamically as needed. Such a system might have a single file system, with all files accessible from all machines in the same way and using the same path name. Furthermore, when a user typed a command, the system could look for the best place to execute that command, possibly on the user's own workstation, possibly on an idle workstation belonging to someone else, and possibly on one of the unassigned processors in the machine room. If the system as a whole looked and acted like a classical single processor timesharing system, it would qualify as a distributed system.
As a second example, consider a factory full of robots, each containing a powerful computer for handling vision, planning, communication, and other tasks. When a robot on the assembly line notices that a part it is supposed to install is defective, it asks another robot in the parts department to bring it a replacement. If all the robots act like peripheral devices attached to the same central computer and the system can be programmed that way, it too counts as a distributed system.
As a final example, think about a large bank with hundreds of branch offices all over the world. Each office has a master computer to store local accounts and handle local transactions. In addition, each computer has the ability to talk to all other branch computers and with a central computer at headquarters. If transactions can be done without regard to where a customer or account is, and the users do not notice any difference between this system and the old centralized mainframe that it replaced, it too would be considered a distributed system.
Advantages of Distributed Systems over Centralized Systems
The real driving force behind the trend toward decentralization is economics. A quarter of a century ago, computer pundit and gadfly Herb Grosch stated what later came to be known as Grosch's law: the computing power of a CPU is proportional to the square of its price. By paying twice as much, you could get four times the performance. This observation fit the mainframe technology of its time quite well, and led most organizations to buy the largest single machine they could afford.
With microprocessor technology, Grosch's law no longer holds. For a few hundred dollars you can get a CPU chip that can execute more instructions per second than one of the largest 1980s mainframes. If you are willing to pay twice as much, you get the same CPU, but running at a somewhat higher clock speed. As a result, the most cost effective solution is frequently to harness a large number of cheap CPUs together in a system. Thus, the leading reason for the trend toward distributed systems is that these systems potentially have a much better price/performance ratio than a single large centralized system would have. In effect, a distributed system gives more bang for the buck[2].
A slight variation on this theme is the observation that a collection of microprocessors cannot only give a better price/performance ratio than a single mainframe, but may yield an absolute performance that no mainframe can achieve at any price. For example, with current technology it is possible to build a system from 10,000 modern CPU chips, each of which runs at 50 MIPS (Millions of Instructions Per Second), for a total performance of 500,000MIPS. For a single processor (i. e. CPU) to achieve this, it would have to execute an instruction in 0. 002 nsec (2 picosec). No existing machine even comes close to this, and both theoretical and engineering considerations make it unlikely that any machine ever will. Theoretically, Einstein's theory of relativity dictates that nothing can travel faster than light, which can cover only 0.6 mm in 2 picosec. Practically, a computer of that speed fully contained a 0.6 mm cube would generate so much heat that it would melt instantly. Thus, whether the goal is normal performance at low cost or extremely high performance at greater cost, distributed systems have much to offer.
As an aside, some authors make a distinction between distributed systems, which are designed to allow many users to work together, and parallel systems, whose only goal is to achieve maximum speedup on a single problem, as our 500,000 MIPS machine might. We believe that this distinction is difficult to maintain because the design spectrum is really a continuum. We prefer to use the term "distributed system" in the broadest sense to denote any system in which multiple interconnected CPUs work together.
A next reason for building a distributed system is that some applications are inherently distributed. A supermarket chain might have many stores, each of which gets goods delivered locally (possibly from local farms), makes local sales, and makes local decisions about which vegetables are so old or rotten that they must be thrown out. It therefore makes sense to keep track of inventory at each store on a local computer rather than centrally at corporate headquarters. After all, most queries and updates will be done locally. Nevertheless, from time to time, top management may want to find out how many rutabagas it currently owns. One way to accomplish this goal is to make the complete system look like a single computer to the application programs, but implement decentrally, with one computer per store as we have described. This would then be a commercial distributed system.
Notes
[1] There is only one fly in the ointment. 美中不足。
[2] gives more bang for the buck: buck，俚语，表示—美元。这句的意思是“小钱办大事”。
第6题
It is difficult to imagine what life would be like without memory. (79)The meanings of thousands of everyday perceptions, the bases for the decisions we make, and the roots of our habits and skills are to be found in our past experiences, which are brought into the present by memory. Memory can be defined as the capacity to keep information available for later use. It includes not only "remembering" things like arithmetic or historical facts, but also involving any change in the way an animal typically behaves. (80)Memory is involved when a rat gives up eating grain because he has sniffed something suspicious in the grain pile.Memory is also involved when a six-year-old child learns to swing a baseball bat. Memory exists not only in humans and animals but also in some physical objects and machines. Computers, for example, contain devices for storing data for later use. It is interesting to compare the memory-storage capacity of a computer with that of a human being. The instant-access memory of a large computer may hold up to 100,000 "words"—ready for instant use. An average U. S. teenager probably recognizes the meaning of about 100,000 words of English. However, this is but a fraction of the total amount of information which the teenager has stored. Consider, for example, the number of faces and places that the teenager can recognize on sight. The use of words is the basis of the advanced problem-solving intelligence of human beings. A large part of a persons memory is in terms of words and combinations of words.
According to the passage, memory is considered to be______.
A．the basis for decision making and problem solving
B．an ability to store experiences for future use
C．an intelligence typically possessed by human beings
D．the data mainly consisting of words and combinations of words
第7题
Computer Security
计算机安全
The techniques developed to protect single computers and network-linked computer systems from accidental or intentional harm are called computer security. Such harm includes destruction of computer hardware and software, physical loss of data, and the deliberate invasion of databases by unauthorized individuals.
Data may be protected by such basic methods as locking up terminals and replicating data in other storage facilities. More sophisticated methods include limiting data access by requiring the user to have an encoded card or to supply an identification number or passworＤ. Such procedures can apply to the computer data system as a whole or may be pinpointed for particular information banks or programs. Data are frequently ranked in computer files according to degree of confidentiality.
Operating systems and programs may also incorporate built in safeguards, and data may be encoded in various ways to prevent unauthorized persons from interpreting or even copying the material. The encoding system most widely used in the United States is the Data Encryption Standard (DES), designed by IBM and approved for use by the National Institute of Standards and Technology in 1976. DES involves a number of basic encrypting procedures that are then repeated several times. Very large scale computer systems, for example, the U. S. military Advanced Research Project Agency Network (ARPANET), may be broken up into smaller subsystems for security purposes, but smaller systems in government and industry are more prone to system-wide invasions. At the level of personal computers, security possibilities are fairly minimal.
Most invasions of computer systems are for international or corporate spying or sabotage, but computer hackers[1]may take the penetration of protected databanks as a challenge, often with no object in mind other than accomplishing a technological feat. Of growing concern is the deliberate implantation in computer programs of worms or viruses[2]that, if undetected, may progressively destroy databases and other software. Such infected programs have appeared in the electronic bulletin boards available to computer users. Other viruses have been incorporated into computer software sold commercially. No real protection is available against such bugs except the vigilance of manufacturer and user.
Anti-Virus Programs to the Rescue
There is a wide range of virus protection products available to combat the 11,000 known viruses that currently plague personal computers. These products range in technology from virus scanners to terminate and stay resident monitors, to integrity checkers to a combination of the three. Each of these techniques has its associated strengths and weaknesses.[3]
The most fundamental question that must be asked when considering and evaluating automated anti-virus tools is "how well does the product protect against the growing virus threat？" When developing a security program, companies must think long term. Not only must you choose a form of protection that can detect and safely eliminate today's varieties, but you must consider tomorrow's gully wash as well.[4]The real challenge lies in securing against the 38,000 new species that are expected to appear within the next two years. The 11,000 known viruses that have been documented to date represent what is only the tip of the iceberg in terms of what tomorrow will bring.
Virus Protection Methods
Today there exists three broad based categories of anti-virus techniques: scanners, memory resident monitors (TSRs), and integrity checkers.
Virus Scanners
Virus scanners are programs designed to examine a computer's boot block, system memory, partition table, and executable files,[5]looking for specific code patterns that are typical to known virus strains. Generally, a virus scanner is able to identify a virus by name and indicate where on the hard drive or floppy drive the infection has occurreＤ. Virus scanners are also able to detect a known virus before it is executeＤ. Virus scanners do a good job of detecting known viruses. They are generally able to find a virus signature if it is present and will identify the infected file and the virus. Some are faster than others, which is an advantage when checking a hard disk with thousands of files. But virus scanners have several major weaknesses.
First and foremost, scanners are completely ineffective against any virus whose code pattern is not recognizeＤ. In other words, scanners cannot identify a virus if they don't have a signature for it. Also, many of today's viruses are designed specifically to thwart scanners. These so-called stealth viruses know the correct file size and date for a program (i. e. , what they were before the virus infected them). They will intercept operations that ask for that information and return the pre-infection values, not the actual ones during a disk reaＤ. Some viruses can mutate slightly so that the original signature will be rendered ineffective against the new strain and can even result in file damage if recovery is based off virus signature assumptions. A new wave in virus authorship is the creation of self mutating viruses. These viruses infect a file in a different way each time, so it cannot be identified by a simple pattern search, rendering virus scanners ineffective.
Secondly, virus scanners are quickly rendered obsolete and require frequent, costly and time-consuming updates—which may be available only after serious damage has been done. The burden of constantly updating virus scanners, even if provided free of charge, can be a huge burden. In a corporate environment, where thousands of personal computers must be protected, simply distributing scanner updates in a timely and efficient manner and making sure they are installed is an enormous task.
I ntegrity Checkers
This is a relatively new approach, compared to scanners and monitors. Integrity checkers incorporate the principle modification detection. This technique safeguards against both known and unknown viruses by making use of complex file signatures and the known state of the computer environment rather than looking for specific virus signatures.
Each file has a unique signature (which is like a fingerprint-a unique identifier for that particular file) in the form of a CRC or a checksum. Changes in any character within the file will probably change the file's checksum. For a virus to spread, it must get into system memory and change some file or executable code.
An integrity checker will fingerprint and register all program files and various system parameters, such as the boot block, partition table, and system memory, storing this information in an on-line database. By recalculating the files checksum and comparing it to the original, integrity checkers can detect file changes that are indicative of a virus infection.
Industry experts agree that integrity checking is currently the only way to contend with tomorrow's growing virus threat. Since this methodology is non-reliant on virus signatures, it offers protection against all potential viruses, today's and tomorrow's.
Additionally, stealth viruses have historically been able to bypass integrity checkers. The only way users can be certain that their computer is 100 percent clean is to boot the system from a clean, DOS based disk and check the integrity of the information stored on this disk with the current state of the hard drive. Called the "Golden Rule" in virus protection, most integrity checkers fail to follow this security principle.
System Administrator
System Administrator, in computer science, is the person responsible for administering Use of a multiuser computer system, communications system, or both. A system administrator performs such duties as assigning user accounts and passwords, establishing security access levels, and allocating storage space, as well as being responsible for other tasks such as watching for unauthorized access and preventing virus or Trojan Horse[6]programs from entering the system. A related term, sysop (system operator), generally applies to a person in charge of a bulletin board system, although the distinction is only that a system administrator is associated with large systems owned by businesses and corporations, whereas a sysop usually administers a smaller, often home- based, system.
Hacker
Hacker, in computer science, originally, is a computerphile, a person totally engrossed in computer programming and computer technology. In the 1980s, with the advent of personal computers and dial up[7]computer networks, hackers acquired a pejorative connotation, often referring to someone who secretively invades others computers, inspecting or tampering with the programs or data stored on them. (More accurately, though, such a person would be called a cracker.) Hacker also means someone who, beyond mere programming, likes to take apart operating systems and programs to see what makes them tick.
Notes
[1]computer hackers：电脑黑客，指非法侵入他人计算机进行浏览或篡改程序或计算机上所存数据的人。
[2]Of growing concern is the deliberate implantation in computer programs of worms or viruses．越来越令人担心的是蓄意地把蠕虫程序或病毒植入计算机程序。
[3]These products range in technology from virus scanners to terminate and stay resident monitors，to integrity checkers to a combination of the three．Each of these techniques has its associated strengths and weaknesses．这些防病毒的产品从技术上有病毒扫描到内存驻留监督程序，从完整性检查到三者的结合程序，每一种有其相关的优点和缺点。
[4]gully wash：gully冲沟，檐槽。此处字面意义是“冲水槽”，可翻译成“但必须从长计议”或“考虑到未来的问题”。
[5]to examine a computer's boot block，system memory，partition table，and executable files：检查计算机的引导块、系统内存、分区表和可执行文件。
[6]Trojan Horse：特洛伊木马，一种欺骗程序。在计算机安全学中，一种计算机程序，表面上或实际上有某种有用功能，而含有附加的(隐藏的)可能利用了调用进程的合法特许来危害系统安全的功能。
[7]dial up：拨号呼叫，访问计算机的一种方法。计算机通过调制解调器连接到电话线路上，拨号上网。
Choose the best answer for each of the following:
第8题
Does this sound familiar？ You have probably read something like it in magazines or books, or seen it in a film. Why is it so popular？ One of the reasons is that it reflects the fears of many people; fear of the unknown fear of what is not understood or, at least, fear of something that is not completely understood.
The fact is that every day it seems that computers take control of another area of our lives. Some
factory jobs are now done by robots and the robots are controlled by computers. Our bank accounts are managed by computers. At the airport, our tickets are sold by a computer. Certainly, many of these operations are made more
efficient by computers, but our admiration is sometimes mixed with unsafe feelings. And this lack of safety is caused by the fact that we do not know how computers do these things, and we really don't know what they might do next. But we can find out how computers work, and once we understand them, we can use computers instead of worrying about being used by them. Today, there is a new generation of computer wizards who know exactly how computers get things done. These young men and women, usually university students, are happy to sit for hours, sometimes for days, designing programs, not eating, not sleeping, but discovering what can be done by these wonderful slaves which they have learned to control. These computer wizards have learned to use the computer and search for new tasks for their machines.
(1)、According to the passage, our present world is under the control of ______ .
A：mad scientists
B：men and women
C：the unknown fear
D：some super-inventions
(2)、The reason why many people are afraid of computers is that ______ .
A：they don't know anything about computers
B：they haven't really understood computers
C：there are so many computer games
D：computers are often down
(3)、The author mentions computer wizards in order to point out that ______ .
A：computers can be controlled by man
B：there should be more people devoted to computers
C：only young people are interested in computers
D：more time and energy is required to control computers
(4)、This passage is probably written to suggest that ______ .
A：some day computers can deal with all human problems
B：computers can be used in place of traveling to our jobs
C：people should not fear computers
D：computer technology will not meet people's needs in various situations
(5)、The author's attitude towards widely used computers is __.
A：positive
B：anxious
C：worried
D：serious
第9题
The study of computer architecture involves ______.
A．hardware organization only B．programming requirement only
C．both D．neither
第10题
Turing Award & ACM
图灵奖与美国计算机学会
Turing, Alan. M. (1912—1954) is famous as a British theorist of computer science. In 1936 he invented a machine, later called Turing Machine, which has become a crucial part of the foundation of modern computer science. Turing discussed his ideas for the future of machines in mechanizing mental processes: not only chess playing but also the possibility of machines capable of learning.
Turing's plan for the ACE[1]was approved in March 1946. Its main foree, however, was in programming ideas. Turing stressed, that the machine would require no reengineering—only new programming—for a wide range of acti.vities. Turing withdrew from the test in 1948, when nothing had actually been built. The Pilot ACE was later completed in 1950, and was in the vanguard of computing.
Turing' s progress lay in advancing computing ideas rather than practice. His underlying goals for computation, in which program modification played a vital part, appeared in his philosophical paper of 1950. This, including the imitation game operational definition of intelligence now known as the Turing test, is still regarded as the foundation of the philosophy of artificial intelligence[2].
Turing Award[3]
Turing Award was named for Alan M. Turing. Turing Award is the most prestigious technical recognition in the computer science field. It is sometimes referred to as[4]the "Nobel Prize" of computer science. The Association for Computing Machinery started bestowing this honor in 1966 to persons selected for their contributions to[5]computing. The Association for Computing Machinery is a New York-based scientific and educational organization of computer science professionals, with a worldwide membership of about 80,000.
Turing Machine[6]
The Turing machine isa mathematical construct, devised by Turing to specify precisely what should he understood by a mechanical process, what would nowadays generally be called an algorithm.
Turing's paper gave an analysis of what could be done by people acting mechanically. The key idea is that a machine may have finitely many configurations or states. A table of behavior then lays down precisely what the machine is to do in response to what it has read. Given[7]the general formalism, any particular Turing machine simply is the table of behavior.
Turing defined the term computable numbers[8]for those numbers that can be computed by a Turing machine. Turing's analysis picked out what is now known as the halting problem[8], which refers to predicting what an arbitrary Turing machine will do. It is shown that there is no Turing machine that can perform the required prediction.
Turing observed in his analysis that reading a table of behavior and interpreting the entries is itself a mechanical operation. This gave rise to his idea of the universal Turing machine, which is a particular kind of Turing machine that has a table of instructions that it will read the table of instructions of any other Turing machine and do what that Turing machine would have done. In modern terms, this is the function of a digital computer. Turing himself later extended this idea into the discussion of the possible mechanization of all mental processes. Turing machine is now an important concept in the cognitive sciences[10].
Turing Test
Turing test is an operational criterion for intelligence introduced by Turing in the paper "Computing Machinery and Intelligence", which is generally regarded as a founding contribution to the philosophy of artificial intelligence. The test, which Turing called the imitation game, is its most famous aspect.
The interrogator, a human, can communicate with two sources, one human and one machine. The interrogator mus decide which is which[11].
Figure 1 Turing Test
His proposal was as follows: Imagine you have a person able to communicate with two others, B and C, only through a teletype or computer link. This person must try to distinguish B from C simply by asking questions, while those being questioned try to fool the interrogator about their gender. In the Turing test, one of the human participants is replaced by a computer. If the computer is able to convince the interrogator it is the human, Turing argued, it can be said to be intelligent.
Turing's test presents the question "Can a machine think？" in a form amenable to experiment. It is intended to circumvent philosophical problems about the nature of mind by introducing an operational definition based on a materialist view[12]in which minds are identified with the functioning of the brain[13].
Turing's test is based entirely on observable output, avoiding the discussion of consciousness. However, many philosophers have continued to hold that human beings have an intrinsic quality that cannot be possessed even by a machine that successfully imitates human behavior. Other critics wonder whether digital information can be a satisfactory guide to intelligence. But Turing's game does have the merit of taking seriously the word intelligence.
The imitation game is only one aspect of Turing's paper, which has more constructive elements that put the ancient mind-matter problem in the scientific arena of the digital machine. Turing holds that computability is fundamental, argues that the action of the brain is computable, and that[14]a computer, as a universal machine[15]can do anything computable. He describes approaches to artificial intelligence through explicit programming and through implicit methods of teaching. Turing vividly illustrates the potential scope of machines as going beyond the mechanical in the everyday sense.
An Overview of ACM
The Association for Computing Machinery (ACM) is a major force in advancing the skills of information technology professionals and students. Founded in 1947, ACM is the largest and oldest international scientific and educational computer society in the industry todaY. Organized only a year after the unveiling of ENIAC, the first general-purpose[16]electronic computer, ACM was established by mathematicians and electrical engineers to advance the science and application of information technology. John Mauchly, co-inventor of the ENIAC, was one of ACM's founders. Since its inception, ACM has provided its members and the world of computer science a forum for the sharing of knowledge on developments and achievements necessary to the fruitful interchange of ideas. Over the years, ACM has flourished along with the industry itself[17], playing a major role in enriching the quality, form and function of computer usage.
The Importance of ACM.
Over the past 45 years ACM has played a vital role in disseminating the fruits of scientific efforts within and throughout the scientific and electronic engineering community. ACM' s founders understood the potential of the computer and were responsible for forming the early gathering points for exchange of data and ideas, and most of all, for stimulating others with their enthusiasm to learn and follow this exciting new endeavor.
ACM answered the need for a scientific and educational society to publish the latest scholarly opinions and briefs, to provide a forum for the interaction of ideas and concepts, and to consolidate the leadership of a new profession. Its Journal tied together the pioneering efforts on university and college campuses.
Much of the discussion after the earliest machines centered on programming—could a way better than basic binary machine code be found to instruct these new marvels？ And out of this, with help from ACM members, came FORTRAN and COBOL. ACM was the organization which provided the conferences, committee meetings and publications which gave impetus to these monumental efforts and provided the stimulus for integrity and high academic standards which have remained today as the guiding light and hallmark in computer science.
Nearly all the giants[18]of software development have been personally influenced by ACM membership—ACM publications—ACM Special Interest Groups—ACM Chapters and Student Chapters—ACM conferences... and virtually all academic computer science curricula used today stem from ACM's involvement in curricula creation and their efforts to maintain a consistently high level of content in computer science instruction.
Awards: ACM sponsors awards to recognize individuals for their technical and professional contributions to the field.
Turing Award. It is ACM's most prestigious technical award. It is given to an individual selected for contributions considered to be of lasting and major technical importance to the computer field.
Distinguished Service Award:The award is on the basis of value and degree of services to the computing community. The contribution is not limited to service to ACM itself, but includes activities in other organizations and emphasizes contributions to the computing profession at large.
Doctoral Dissertation[19]Award:This award is presented annually to the author(s) of the best doctoral dissertation(s) in computer science and engineering. The award includes ＄1000 plus royalties from sales of the published version.
Software System Award:It is awarded to an institution or individual(s) recognized for developing a software system that has had a lasting influence, reflected in contributions to concepts, in commercial acceptance, or both.
Outstanding Educator Award: Presented annually to an outstanding educator who is appointed to a recognized educational baccalaureate insti.tution and is recognized for advancing new teaching methodologies, effecting new curriculum development or expansion in Computer Science and Engineering, or making a significant contribution to the educational mission of the ACM. Those who have been teaching for ten years or less are given special consideration.
ACM Student Research Competition: Students from universities across the US and around the world can participate in this competition. ACM Special Interest Group, namely SIG[20]conferences offer additional opportunities for undergraduate students to demonstrate their research contributions and receive recognition for their work while encouraging graduate students to participate in computing research. They also enable students to interact with researchers in their respective fields and raise the profile of computing research within the IT community.
Notes
[1] ACE Automatic Computing Equipment自动计算机(装置)。
[2] ...the foundation of the philosophy of artificial intelligence人工智能基本原理的基础。
[3] Turing Award图灵奖(被誉计算机领域里的诺贝尔奖)。
[4] It is sometimes referred to as...有时它被誉为……。
[5] ...contributions to...对于……的贡献。注意：此处to为介词。
[6] Turing Machine图灵机(一种可不受存储容量限制的假想计算机)。
[7] given假设，假定。例如：
Given the condition of the engine,it is a wonder that it even starts.
倘若这台发动机能发动的话，可真是不可思议。
Given good health, I hope to finish the work this week.
倘若健康状况良好，我希望本周完成这项工作。
[8] computable numbers可计算数
[9] halting problem (of Turing machines)图灵机停机问题
[10] ...cognitive sciences认知科学。研究各种思维活动和过程，以及产生这些思维活动和过程的本质。
[11] The interrogator must decide which is which具体指The interrogator should be able to identify which one is human and which one is the machine.
[12] materialist view唯物主义观点。该理论认为物质实体是唯一现实存在。
[13] ...minds are identified with the functioning of the brain智力与大脑的作用有关。be identified with与……有关。例如：That politician is too closely identified with the former government to become a minister.
[14] ...and that... that为连接词，引导宾语从句，原文中相当于and argues that...。
[15] a universal machine通用机器。
[16] general purpose通用的。
[17] ACM has flourished along with the industry itself. ACM与(计算机)产业一样兴旺发达。
[18] giant此处应为名词，指“巨子、巨人”。
[19] doctoral dissertation博士论文。
[20] SIG：Special Interest Groups (of ACM)美国计算机协会的各类别专业组。
第11题
Computer Viruses
计算机病毒
Introduction
A computer virus is a piece of software programmed to perform one major task: to replicate. Viruses accomplish their reproductive task by preying on other computer files, requiring a host program[1]as a means of survival. Viruses gain control over their host in various ways, for example by attaching their infected code to the end of a host program and misguiding the header information at the beginning of the file so that it points toward itself rather than the legitimate program. Therefore, when an infected host program is run, the virus gets executed before the host. The host program can be almost anything: an application, part of the operating system's, part of the system boot code, or a device driver. The virus continues to spread, moving from file to file in this infectious manner.
In addition to its propagation mission, many viruses contain code whose purpose is to cause damage. In some viruses, this code is activated by a trigger mechanism.[2]A trigger condition may be linked to the number of times the host file is run, or it could be a response to a particular date, time or random number. In other cases, the damage could occur continuously or on a random basis. Of the 11,000 known viruses present today, more than 2,000 have been diagnosed as being data destructive.
Types of Viruses
Several types of viruses exist and are classified according to their propagation patterns.
1. Executable File Infectors
These viruses spread infection by attaching to an executable file, misdirecting the header information, and executing before the host file. It is very common for these viruses to load themselves into memory once their infected host file is launched. From there, they monitor access calls, infecting programs as executed.
2. Boot Sector Infectors
This type of virus overwrites the original boot sector, replacing this portion of code with itself, so it is the first to load and gain control upon system boot, even before DOS. In order for boot block viruses to replicate, it is usually necessary to boot the computer from an infected floppy disk. Upon system boot, the virus will jump from the infected floppy disk to the hard disks partition table.
3. Partition Table Infectors
These viruses attack the hard disk partition table by moving it to a different sector and replacing the original partition table with its own infectious code. These viruses will then spread from the partition table to the boot sector of floppy disks as floppies are accessed. 4. Memory Resident Infectors
Many viruses load themselves into memory while altering vital system services. For example, some viruses modify the operating system's Execute Program service in such a way that any executed program is immediately infected. Other viruses modify the operating system in order to camouflage their existence. These viruses are called Stealth Viruses.
Why Are Viruses Written？
Bulgaria is often referred to as the "Virus Factory" because the country accounts for the highest percentage of new virus creation. Several cultural factors attribute to this state. Primarily, the country offers no software copyright protection, so legitimate software programmers are not rewarded financially for their work. And there are no laws in place to prohibit the authorship of new viruses. In fact, virus source code is often posted on international bulletin boards for anyone to access. Certainly, this is not the case in the United States, so why do we maintain the second highest level of virus authorship？ Today's viruses are being written to attack a specific person, company or program. There are countless stories of disgruntled employees who seek vengeance by writing viruses to attack their former employer's computer system.
How Are Viruses Transmitted？
Because a virus is nothing more than a piece of software, it can be acquired in the same way as legitimate programs. Viruses have reportedly been transmitted through shrink- wrapped retail software.[3]Unsuspecting sales representatives often act as carriers by demonstrating infected programs. Newly purchased computers, which had their hard disks formatted by service technicians, have been returned with viruses. These pests travel over phone lines through programs sent by modem. Bulletin boards do occasionally transmit viruses. The most common means of contracting a virus, however, is through the use ot floppy disks. Piracy of software, in particular, expedites viral spread, as do floppy disks traveling from one computer to another.
We Are All at Risk
All personal computer users are at risk for viral infection. Several events, trends and technological inroads have combined in the past few years to increase our vulnerability to infection. The proliferation of local area networks, the downloading of information from mainframes to desktop computers, our increased reliance on personal computers to store mission critical data, the arrival of electronic bulletin boards, the globalization of communications, the gained popularity of shareware, the growing use of remote communications, the increased sophistication of end users, the portability of data, the casual spread of software via piracy, and the staggering rate of new virus creation all contribute to increase our risk of virus infection.
A Special Threat to Networks
Viruses present a special threat to networks because of the inherent connectivity they provide and because of the potential for widespread data loss. Once a virus infects a single networked computer, the average time required for it to infect another workstation is anywhere from 10 to 20 minutes. With a propagation time of this magnitude, a virus can paralyze an entire network in several hours.
Virus Infection Symptoms
The most successful virus has no symptoms at all. Your computer may be infected, and you will notice no change in the normal behavior of your computer. The only way to be aware of such viruses is to use automated virus detection tools. Some less sophisticated viruses may exhibit "visible" symptoms such as:
1) Changes in program length
2) Changes in the data or time stamp
3) Longer program load times
4) Slower system operation
5) Unexplained disk activities
6) Unexplained reduction in memory or disk space
7) Bad sectors on your floppy
8) Disappearing programs
9) Unusual error messages
10) Unusual screen activity
11) Access lights turn on for non-referenced drive
12) Failed program execution
It is important to remember that some viruses may not exhibit any visible symptoms at all. Don't count on your intuition as your only tool for detecting viruses.
Anti-Virus Tools
In dealing with today's sophisticated viruses, intuition and strict employee policies are not enough. The more carefully engineered virus programs exhibit no visible symptoms at all until it is too late. Your computer may be infected with a virus without any noticeable alteration in functionality. Therefore, relying solely on visible side effects, such as slower system operation, longer program load time or unusual screen activity as a means of early detection, may not prove as reliable as it once did. You can no longer afford to count on your intuition as your only tool for detecting viruses. While information systems managers should establish employee guidelines and policies to lessen the potential for infection, strict rules alone will not insure complete protection. What about the shrink-wrapped software program purchased by your company that was later found to be infected by a virus？ Or what about the hard drive that was sent out for repair by a service technician, only to[4]have it returned with a virus？ The only way to prevent viruses from mysteriously entering your company is to reinforce the security programs already in place with automated virus detection tools.
Defending against Viruses
Following are some tips in helping to combat the growing threat of viral infection.
1) Use an automated virus detection tool, such as Fifth Generation Systems Untouchable virus protection software.
2) Regularly perform a backup of your data with a backup program, such as Fifth Generation Systems Fastback Plus.[5]
3) Prevent unauthorized access to your computer by using a security access program, such as Fifth Generation Systems Disklock.[6]
4) Use write-protected tabs on all program disks before installing any new software. If the software does not allow this, install it first, then apply the write-protected tabs.
5) Do not install new software unless you know it has come from a reliable source. For instance, service technicians and sales representatives are common carriers of viruses. Scan all demonstration or repair software before use.
6) Scan every floppy disk before use and check all files downloaded from a bulletin board or acquired from a modem.
7) Educate employees. As the adage goes, an ounce of prevention is worth a pound of cure.
8) Do not boot from any floppy disk[7], other than a clean, DOS based disk.
9) Avoid sharing software and machines.
10) Store executable and other vital system parameters on a bootable DOS based disk and regularly compare this information to the current state of your hard drive.
Notes
[1]requiring a host program：host表示“主人”、“东道主”。此处a host program可译成“主机程序”。
[2]a trigger mechanism：触发装置。
[3]shrink-wrapped retail software：用收缩塑料薄膜包装的零售软件。
[4]only to：不定式短语表示结果；翻译成“结果……”，如：He made a long speech only to show his ignorance of the subject．他讲一大段话，结果只暴露出他对这门学科一无所知。
[5]Fifth Generation Systems Fastback Plus：第五代生成系统快速备份。
[6]Fifth Generation Systems Disklock：第五代生成系统磁盘锁。
[7]Do not boot from any floppy disk. boot意指“引导”、“启动”。此句译为“不要直接从软盘启动计算机”。
Choose the best answer for each of the following:
