计算机英语论文

学号09710128

计算机英语论文

书名：计算机网络（第四版）

作者：AndrewS.T anenbaum

出版社：清华大学出版社

出版时间：2004年8月

学生姓名袁璇

班级计算机1班

成绩

指导教师(签字)

电子与信息工程系

2011年10月8日

Uses of Computer Networks

Before we start to examine the technical issues in detail, it is worth devoting some time to pointing out why people are interested in computer networks and what they can be used for. After all, if nobody were interested in computer networks, few of them would be built. We will start with traditional uses at companies and for individuals and then move on to recent developments regarding mobile users and home networking.

1．Business Applications

Many companies have a substantial number of computers. For a example,a company may have separate computers to monitor production, keep track of inventories, and do the payroll. Initially, each of these computers may have worked in isolation from the others, but at some point, management may have decided to connect them to be able to extract and correlate information about the entire company.

Put in slightly more general form, the issue here is resource sharing, and the goal is to make all programs, equipment, and especially data available to anyone on the network without regard to the physical location of the resource and the user. An obvious and widespread example is having a group of office workers share a common printer. None of the individuals really needs a private printer, and a high-volume networked printer is often cheaper, faster, and easier to maintain than a large collection of individual printers.

However, probably even more important than sharing physical resources such as printers, scanners, and CD burners, is sharing information. Every large and medium-sized company and many small companies are vitally dependent on computerized information. Most companies have customer records, inventories, accounts receivable, financial statements, tax information, and much more online. If all of its computers went down, a bank could not last more than five minutes.

A modern manufacturing plant, with a computer-controlled assembly line, would not last even that long. Even a small travel agency or three-person law firm is now highly dependent on computer networks for allowing employees to access relevant information and documents instantly.

For smaller companies, all the computers are likely to be in a single office or perhaps a single building, but for larger ones, the computers and employees may be scattered over dozens of offices and plants in many countries. Nevertheless, a sales person in New Y ork might sometimes need access to a product inventory database in Singapore. In other words, the mere fact that a user happens to be 15,000 km away from his data should not prevent him from using the data as though they were local. This goal may be summarized by saying that it is an attempt to end the ''tyranny of geography.''

In the simplest of terms, one can imagine a company's information system as consisting of one or more databases and some number of employees who need to access them remotely. In this model, the data are stored on powerful computers called servers. Often these are centrally housed and maintained by a system administrator. In contrast, the employees have simpler machines, called clients, on their desks, with which they access remote data, for example, to include in spreadsheets they are constructing. (Sometimes we will refer to the human user of the client machine as the ''client,'' but it should be clear from the context whether we mean the computer or its user.) The client and server machines are connected by a network, as illustrated in Fig. 1-1. Note that we have shown the network as a simple oval, without any detail. We will use this form when we mean a network in the abstract sense. When more detail is required, it will be provided.

This whole arrangement is called the client-server model. It is widely used and forms the basis of much network usage. It is applicable when the client and server are both in the same building (e.g., belong to the same company), but also when they are far apart. For example, when a person at home accesses a page on the World Wide Web, the same model is employed, with the remote Web server being the server and the user's personal computer being the client. Under most conditions, one server can handle a large number of clients.

If we look at the client-server model in detail, we see that two processes are involved, one on the client machine and one on the server machine. Communication takes the form of the client process sending a message over the network to the server process. The client process then waits for a reply message. When the server process gets the request, it performs the requested work or looks up the requested data and sends back a reply. The client-server model involves requests and replies.

A second goal of setting up a computer network has to do with people rather than information or even computers. A computer network can provide a powerful communication medium among employees. Virtually every company that has two or more computers now has e-mail (electronic mail), which employees generally use for a great deal of daily communication. In fact, a common gripe around the water cooler is how much e-mail everyone has to deal with, much of it meaningless because bosses have discovered that they can send the same message to all their subordinates at the push of a button.

But e-mail is not the only form of improved communication made possible by computer networks. With a network, it is easy for two or more people who work far apart to write a report together. When one worker makes a change to an online document, the others can see the change immediately, instead of waiting several days for a letter. Such a speedup makes cooperation among far-flung groups of people easy where it previously had been impossible.

Y et another form of computer-assisted communication is videoconferencing. Using this technology, employees at distant locations can hold a meeting, seeing and hearing each other and even writing on a shared virtual blackboard. V ideoconferencing is a powerful tool for eliminating the cost and time previously devoted to travel. It is sometimes said that communication and transportation are having a race, and whichever wins will make the other obsolete.

A third goal for increasingly many companies is doing business electronically with other companies, especially suppliers and customers. For example, manufacturers of automobiles, aircraft, and computers, among others, buy subsystems from a variety of suppliers and then assemble the parts. Using computer networks, manufacturers can place orders electronically as needed. Being able to place orders in real time reduces the need for large inventories and enhances efficiency.

A fourth goal that is starting to become more important is doing business with consumers over the Internet. Airlines, bookstores, and music vendors have discovered that many customers like the convenience of shopping from home. Consequently, many companies provide catalogs of their goods and services online and take orders on-line. This sector is expected to grow quickly in the future. It is called e-commerce (electronic commerce).

2．Home Applications

In 1977, Ken Olsen was president of the Digital Equipment Corporation, then the number two computer vendor in the world (after IBM). When asked why Digital was not going after the personal computer market in a big way, he said: ''There is no reason for any individual to have a

computer in his home.'' History showed otherwise and Digital no longer exists. Why do people buy computers for home use? Initially, for word processing and games, but in recent years that picture has changed radically. Probably the biggest reason now is for Internet access. Some of the more popular uses of the Internet for home users are as follows:

Access to remote information.

Person-to-person communication.

Interactive entertainment.

Electronic commerce.

Access to remote information comes in many forms. It can be surfing the World Wide Web for information or just for fun. Information available includes the arts, business, cooking, government, health, history, hobbies, recreation, science, sports, travel, and many others. Fun comes in too many ways to mention, plus some ways that are better left unmentioned.

Many newspapers have gone on-line and can be personalized. For example, it is sometimes possible to tell a newspaper that you want everything about corrupt politicians, big fires, scandals involving celebrities, and epidemics, but no football, thank you. Sometimes it is even possible to have the selected articles downloaded to your hard disk while you sleep or printed on your printer just before breakfast. As this trend continues, it will cause massive unemployment among 12-year-old paperboys, but newspapers like it because distribution has always been the weakest link in the whole production chain.

The next step beyond newspapers (plus magazines and scientific journals) is the on-line digital library. Many professional organizations, such as the ACM (https://www.wendangku.net/doc/3f960102.html,) and the IEEE Computer Society (https://www.wendangku.net/doc/3f960102.html,), already have many journals and conference proceedings on-line. Other groups are following rapidly. Depending on the cost, size, and weight of book-sized notebook computers, printed books may become obsolete. Skeptics should take note of the effect the printing press had on the medieval illuminated manuscript.

All of the above applications involve interactions between a person and a remote database full of information. The second broad category of network use is person-to-person communication, basically the 21st century's answer to the 19th century's telephone. E-mail is already used on a daily basis by millions of people all over the world and its use is growing rapidly. It already routinely contains audio and video as well as text and pictures. Smell may take a while.

Any teenager worth his or her salt is addicted to instant messaging. This facility, derived from the UNIX talk program in use since around 1970, allows two people to type messages at each other in real time. A multiperson version of this idea is the chat room, in which a group of people can type messages for all to see.

Worldwide newsgroups, with discussions on every conceivable topic, are already commonplace among a select group of people, and this phenomenon will grow to include the population at large. These discussions, in which one person posts a message and all the other subscribers to the newsgroup can read it, run the gamut from humorous to impassioned. Unlike chat rooms, newsgroups are not real time and messages are saved so that when someone comes back from vacation, all messages that have been posted in the meanwhile are patiently waiting for reading. Another type of person-to-person communication often goes by the name of peer-to-peer communication, to distinguish it from the client-server model (Parameswaran et al., 2001). In this form, individuals who form a loose group can communicate with others in the group. Every person can, in principle, communicate with one or more other people; there is no fixed division

into clients and servers.

In a peer-to-peer system there are no fixed clients and servers. Peer-to-peer communication really hit the big time around 2000 with a service called Napster, which at its peak had over 50 million music fans swapping music, in what was probably the biggest copyright infringement in all of recorded history (Lam and Tan, 2001; and Macedonia, 2000). The idea was fairly simple. Members registered the music they had on their hard disks in a central database maintained on the Napster server. If a member wanted a song, he checked the database to see who had it and went directly there to get it. By not actually keeping any music on its machines, Napster argued that it was not infringing anyone's copyright. The courts did not agree and shut it down.

However, the next generation of peer-to-peer systems eliminates the central database by having each user maintain his own database locally, as well as providing a list of other nearby people who are members of the system. A new user can then go to any existing member to see what he has and get a list of other members to inspect for more music and more names. This lookup process can be repeated indefinitely to build up a large local database of what is out there. It is an activity that would get tedious for people but is one at which computers excel.

Legal applications for peer-to-peer communication also exist. For example, fans sharing public domain music or sample tracks that new bands have released for publicity purposes, families sharing photos, movies, and genealogical information, and teenagers playing multiperson on-line games. In fact, one of the most popular Internet applications of all, e-mail, is inherently peer-to-peer. This form of communication is expected to grow considerably in the future. Electronic crime is not restricted to copyright law. Another hot area is electronic gambling. Computers have been simulating things for decades. Why not simulate slot machines, roulette wheels, blackjack dealers, and more gambling equipment? Well, because it is illegal in a lot of places. The trouble is, gambling is legal in a lot of other places and casino owners there have grasped the potential for Internet gambling. What happens if the gambler and the casino are in different countries, with conflicting laws? Good question.

Other communication-oriented applications include using the Internet to carry telephone calls, video phone, and Internet radio, three rapidly growing areas. Another application is telelearning, meaning attending 8 A.M. classes without the inconvenience of having to get out of bed first. In the long run, the use of networks to enhance human-to-human communication may prove more important than any of the others.

Our third category is entertainment, which is a huge and growing industry. The killer application here is video on demand. A decade or so hence, it may be possible to select any movie or television program ever made, in any country, and have it displayed on your screen instantly. New films may become interactive, where the user is occasionally prompted for the story direction with alternative scenarios provided for all cases. Live television may also become interactive, with the audience participating in quiz shows, choosing among contestants, and so on.

On the other hand, maybe the killer application will not be video on demand. Maybe it will be game playing. Already we have multiperson real-time simulation games, like hide-and-seek in a virtual dungeon, and flight simulators with the players on one team trying to shoot down the players on the opposing team. If games are played with goggles and three-dimensional real-time, photographic-quality moving images, we have a kind of worldwide shared virtual reality.

Our fourth category is electronic commerce in the broadest sense of the term. Home shopping is already popular and enables users to inspect the on-line catalogs of thousands of companies.

Some of these catalogs will soon provide the ability to get an instant video on any product by just clicking on the product's name. After the customer buys a product electronically but cannot figure out how to use it, on-line technical support may be consulted. Another area in which e-commerce is already happening is access to financial institutions. Many people already pay their bills, manage their bank accounts, and handle their investments electronically. This will surely grow as networks become more secure.

One area that virtually nobody foresaw is electronic flea markets (e-flea?). On-line auctions of second-hand goods have become a massive industry. Unlike traditional e-commerce, which follows the client-server model, on-line auctions are more of a peer-to-peer system, sort of consumer-to-consumer. Some of these forms of e-commerce have acquired cute little tags based on the fact that ''to'' and ''2'' are pronounced the same. The most popular ones are listed in Fig. 1-4. Some forms of e-commerce.

No doubt the range of uses of computer networks will grow rapidly in the future, and probably in ways no one can now foresee. After all, how many people in 1990 predicted that teenagers tediously typing short text messages on mobile phones while riding buses would be an immense money maker for telephone companies in 10 years? But short message service is very profitable.

Computer networks may become hugely important to people who are geographically challenged, giving them the same access to services as people living in the middle of a big city. Telelearning may radically affect education; universities may go national or international. Telemedicine is only now starting to catch on, but may become much more important. But the killer application may be something mundane, like using the webcam in your refrigerator to see if you have to buy milk on the way home from work.

3．Mobile Users

Mobile computers, such as notebook computers and personal digital assistants (PDAs), are one of the fastest-growing segments of the computer industry. Many owners of these computers have desktop machines back at the office and want to be connected to their home base even when away from home or en route. Since having a wired connection is impossible in cars and airplanes, there is a lot of interest in wireless networks. In this section we will briefly look at some of the uses of wireless networks.

Why would anyone want one? A common reason is the portable office. People on the road often want to use their portable electronic equipment to send and receive telephone calls, faxes, and electronic mail, surf the Web, access remote files, and log on to remote machines. And they want to do this from anywhere on land, sea, or air. For example, at computer conferences these days, the organizers often set up a wireless network in the conference area. Anyone with a notebook computer and a wireless modem can just turn the computer on and be connected to the Internet, as though the computer were plugged into a wired network. Similarly, some universities have installed wireless networks on campus so students can sit under the trees and consult the library's card catalog or read their e-mail.

Wireless networks are of great value to fleets of trucks, taxis, delivery vehicles, and repairpersons for keeping in contact with home. For example, in many cities, taxi drivers are independent businessmen, rather than being employees of a taxi company. In some of these cities, the taxis have a display the driver can see. When a customer calls up, a central dispatcher types in the pickup and destination points. This information is displayed on the drivers' displays and a beep

sounds. The first driver to hit a button on the display gets the call.

Wireless networks are also important to the military. If you have to be able to fight a war anywhere on earth on short notice, counting on using the local networking infrastructure is probably not a good idea. It is better to bring your own.

Although wireless networking and mobile computing are often related, they are not identical, as Fig. 1-5 shows. Here we see a distinction between fixed wireless and mobile wireless. Even notebook computers are sometimes wired. For example, if a traveler plugs a notebook computer into the telephone jack in a hotel room, he has mobility without a wireless network. Combinations of wireless networks and mobile computing.

On the other hand, some wireless computers are not mobile. An important example is a company that owns an older building lacking network cabling, and which wants to connect its computers. Installing a wireless network may require little more than buying a small box with some electronics, unpacking it, and plugging it in. This solution may be far cheaper than having workmen put in cable ducts to wire the building.

But of course, there are also the true mobile, wireless applications, ranging from the portable office to people walking around a store with a PDA doing inventory. At many busy airports, car rental return clerks work in the parking lot with wireless portable computers. They type in the license plate number of returning cars, and their portable, which has a built-in printer, calls the main computer, gets the rental information, and prints out the bill on the spot.

As wireless technology becomes more widespread, numerous other applications are likely to emerge. Let us take a quick look at some of the possibilities. Wireless parking meters have advantages for both users and city governments. The meters could accept credit or debit cards with instant verification over the wireless link. When a meter expires, it could check for the presence of a car (by bouncing a signal off it) and report the expiration to the police. It has been estimated that city governments in the U.S. alone could collect an additional $10 billion this way (Harte et al., 2000). Furthermore, better parking enforcement would help the environment, as drivers who knew their illegal parking was sure to be caught might use public transport instead.

Food, drink, and other vending machines are found everywhere. However, the food does not get into the machines by magic. Periodically, someone comes by with a truck to fill them. If the vending machines issued a wireless report once a day announcing their current inventories, the truck driver would know which machines needed servicing and how much of which product to bring. This information could lead to more efficient route planning.

Of course, this information could be sent over a standard telephone line as well, but giving every vending machine a fixed telephone connection for one call a day is expensive on account of the fixed monthly charge.

Another area in which wireless could save money is utility meter reading. If electricity, gas, water, and other meters in people's homes were to report usage over a wireless network, there would be no need to send out meter readers. Similarly, wireless smoke detectors could call the fire department instead of making a big noise. As the cost of both the radio devices and the air time drops, more and more measurement and reporting will be done with wireless networks.

A whole different application area for wireless networks is the expected merger of cell phones and PDAs into tiny wireless computers. A first attempt was tiny wireless PDAs that could display stripped-down Web pages on their even tinier screens. This system, called WAP 1.0 (Wireless Application Protocol) failed, mostly due to the microscopic screens, low bandwidth, and

poor service. But newer devices and services will be better with W AP 2.0.

One area in which these devices may excel is called m-commerce (mobile-commerce) (Senn, 2000). The driving force behind this phenomenon consists of an amalgam of wireless PDA manufacturers and network operators who are trying hard to figure out how to get a piece of the e-commerce pie. One of their hopes is to use wireless PDAs for banking and shopping. One idea is to use the wireless PDAs as a kind of electronic wallet, authorizing payments in stores, as a replacement for cash and credit cards. The charge then appears on the mobile phone bill. From the store's point of view, this scheme may save them most of the credit card company's fee, which can be several percent. Of course, this plan may backfire, since customers in a store might use their PDAs to check out competitors' prices before buying. Worse yet, telephone companies might offer PDAs with bar code readers that allow a customer to scan a product in a store and then instantaneously get a detailed report on where else it can be purchased and at what price.

Since the network operator knows where the user is, some services are intentionally location dependent. For example, it may be possible to ask for a nearby bookstore or Chinese restaurant. Mobile maps are another candidate. So are very local weather forecasts (''When is it going to stop raining in my backyard?''). No doubt many other applications appear as these devices become more widespread.

One huge thing that m-commerce has going for it is that mobile phone users are accustomed to paying for everything (in contrast to Internet users, who expect everything to be free). If an Internet Web site charged a fee to allow its customers to pay by credit card, there would be an immense howling noise from the users. If a mobile phone operator allowed people to pay for items in a store by using the phone and then tacked on a fee for this convenience, it would probably be accepted as normal. Time will tell.

A little further out in time are personal area networks and wearable computers. IBM has developed a watch that runs Linux (including the X11 windowing system) and has wireless connectivity to the Internet for sending and receiving e-mail (Narayanaswami et al., 2002). In the future, people may exchange business cards just by exposing their watches to each other. Wearable wireless computers may give people access to secure rooms the same way magnetic stripe cards do now (possibly in combination with a PIN code or biometric measurement). These watches may also be able to retrieve information relevant to the user's current location (e.g., local restaurants). The possibilities are endless.

Smart watches with radios have been part of our mental space since their appearance in the Dick Tracy comic strip in 1946. But smart dust? Researchers at Berkeley have packed a wireless computer into a cube 1 mm on edge (Warneke et al., 2001). Potential applications include tracking inventory, packages, and even small birds, rodents, and insects.

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计算机英语论文(中英双语)

稀疏表示计算机视觉和模式识别 从抽象技术的现象已经可以开始看到稀疏信号在电脑视觉产生重大影响，通常在非传统的应用场合的目标不仅是要获得一个紧凑的高保真度表示的观察信号，而且要提取语义信息。非常规词典在字典的选择中扮演了重要的角色，衔接的差距或学习、训练样本同来获得自己提供钥匙，解出结果和附加语义意义信号稀疏表示。理解这种非传统的良好性能要求词典把新的算法和分析技术。本文强调了一些典型例子：稀疏信号的表现如何互动的和扩展计算机视觉领域，并提出了许多未解的问题为了进一步研究。 稀疏表现已经被证明具有非常强大的工具，获取、表示、压缩高维信号的功能。它的成功主要是基于这个事实，即重要类型的信号(如声音和图像，稀疏表示很自然地就固定基地或串连这样的基地。此外，高效、大概有效算法说明基于凸优化一书提供了计算这样的陈述。 虽然这些应用在经典信号处理的铺垫下,已经可以在电脑视觉上形成一个我们经常更感兴趣的内容或语义，而不是一种紧凑、高保真的表示。一个人可能会理所当然地知道是否可以有用稀疏表示为视觉任务。答案很大程度上是积极的：在过去的几年里，变化和延伸的最小化已应用于许多视觉任务。 稀疏表示的能力是揭示出语义信息，大部分来自于一个简单但重要的性质数据：虽然照片所展示的图像是在非常高自然的空间，在许多同类应用中图像属于次级结构。也就是说他们在接近低维子空间或层次。如果发现一个收集的样本分布，我们理应期望一个典型的样品有一个稀疏表示理论的基础。 然而，想要成功地把稀疏表示应用于电脑视觉，我们通常是必须面对的一个额外的问题，如何正确选择依据。这里的数据选择不同于在信号处理的传统设置，基于指定的环境具有良好的性能可以被假定。在电脑视觉方面，我们经常要学习样本图像的任务词典，我们不得不用一个连贯的思想来贯穿工作。因此，我们需要扩展现有的理论和稀疏表示算法新情况。 自动人像识别仍然是最具有挑战性的应用领域和计算机视觉的难题。在理论基础实验上，稀疏表示在近期获得了显著的进展。 该方法的核心是选择一个明智的字典作为代表，用来测试信号稀疏线性组合信号。我们首先要简单的了解令人诧异的人脸识别途径是有效的解决办法。反过来，人脸识别实例在稀疏表示光曝光之前揭示了新的理论现象。 之前稀疏表示的部分用机器检查并且应用，在一个完全词典里组成的语义信息本身产生的样品。对于许多数据不是简单的应用，这是合乎情理的词典，使用一个紧凑的数据得到优化目标函数的一些任务。本节概述学习方法那种词典，以及这些方法应用在计算机视觉和图像处理。 通过近年来我们对稀疏编码和优化的应用的理解和启发，如面部识别一节描述的例子，我们提出通过稀疏数据编码构造，利用它建立了受欢迎的机器学习任务。在一个图的数据推导出研究学报。2009年3月5乘编码每个数据稀疏表示的剩余的样本，并自动选择最为有效的邻居为每个数据。通过minimization稀疏表示的计算自然的性能满足净水剂结构。此外，我们将会看到描述之间的关系进行了实证minimization线性数据的性能，可以显著提高现有的基于图论学习算法可行性。 摘自：期刊IEEE的论文- PIEEE ，第一卷

计算机专业英语报告

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学号09710128 计算机英语论文 书名：计算机网络（第四版） 作者：AndrewS.T anenbaum 出版社：清华大学出版社 出版时间：2004年8月 学生姓名袁璇 班级计算机1班 成绩 指导教师(签字) 电子与信息工程系 2011年10月8日

Uses of Computer Networks Before we start to examine the technical issues in detail, it is worth devoting some time to pointing out why people are interested in computer networks and what they can be used for. After all, if nobody were interested in computer networks, few of them would be built. We will start with traditional uses at companies and for individuals and then move on to recent developments regarding mobile users and home networking. 1．Business Applications Many companies have a substantial number of computers. For a example,a company may have separate computers to monitor production, keep track of inventories, and do the payroll. Initially, each of these computers may have worked in isolation from the others, but at some point, management may have decided to connect them to be able to extract and correlate information about the entire company. Put in slightly more general form, the issue here is resource sharing, and the goal is to make all programs, equipment, and especially data available to anyone on the network without regard to the physical location of the resource and the user. An obvious and widespread example is having a group of office workers share a common printer. None of the individuals really needs a private printer, and a high-volume networked printer is often cheaper, faster, and easier to maintain than a large collection of individual printers. However, probably even more important than sharing physical resources such as printers, scanners, and CD burners, is sharing information. Every large and medium-sized company and many small companies are vitally dependent on computerized information. Most companies have customer records, inventories, accounts receivable, financial statements, tax information, and much more online. If all of its computers went down, a bank could not last more than five minutes. A modern manufacturing plant, with a computer-controlled assembly line, would not last even that long. Even a small travel agency or three-person law firm is now highly dependent on computer networks for allowing employees to access relevant information and documents instantly. For smaller companies, all the computers are likely to be in a single office or perhaps a single building, but for larger ones, the computers and employees may be scattered over dozens of offices and plants in many countries. Nevertheless, a sales person in New Y ork might sometimes need access to a product inventory database in Singapore. In other words, the mere fact that a user happens to be 15,000 km away from his data should not prevent him from using the data as though they were local. This goal may be summarized by saying that it is an attempt to end the ''tyranny of geography.'' In the simplest of terms, one can imagine a company's information system as consisting of one or more databases and some number of employees who need to access them remotely. In this model, the data are stored on powerful computers called servers. Often these are centrally housed and maintained by a system administrator. In contrast, the employees have simpler machines, called clients, on their desks, with which they access remote data, for example, to include in spreadsheets they are constructing. (Sometimes we will refer to the human user of the client machine as the ''client,'' but it should be clear from the context whether we mean the computer or its user.) The client and server machines are connected by a network, as illustrated in Fig. 1-1. Note that we have shown the network as a simple oval, without any detail. We will use this form when we mean a network in the abstract sense. When more detail is required, it will be provided.

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计算机专业英语论文--硬件概述

题目：计算机硬件概述（Overview of the computer hardware based） 学院：信息技术学院 班级：XXXXXX 学号：XXXXXXXXXX 姓名：XXXX

A computer is a fast and accurate symbol processing system. It can accept, store, process data and produce output results. A computer can automatically process data without human intervention. However, it must be given a set of instruction to guide it, step by step, through processes. The set of instructions is called a program, The program is stored physically inside the machine, making it a program. All computer systems of interest to us are similar. They contain hardware components for input, central processing unit and output. The system on the small-scale is called a microcomputer or minicomputer. Continuing up the size scale, the mainframe computer is one that may offer a faster processing speed and a greater storage capacity than a typical mini. Finally comes the supercomputer, designed to process complex scientific applications，which is the largest and fastest. Although the capacity of computers' storage locations is varied，every computer stores numbers，letters，and other characters in a coded form. Every character in the storage is represented by a string of 0s and 1s，the only digits founded in the binary numbering system. BCD and ASCII are popular computer codes. So, what part of computer hardware that contains it? Computer hardware has four parts: the central processing unit (CPU) and memory, storage hardware, input hardware, and output hardware. The Central Processing Unit Pronounced as separate letters it is the abbreviation for central processing unit. The CPU is the brains of the computer. Sometimes referred to simply as the central processor, but more commonly called processor, the CPU