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The Definition of Computer Network
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There are many definitions of what the computer networks are. The definitions starting with phrase of the system of linked computers are misled because you could make a network without the linked computers. This network is characterized by people running back and forth between computers with floppy disks in their hands. Under this network, the computers are not linked physically but they still communicate data each other. Therefore, I would like to define it as follows： the computer network is the communication of data from one computer to one or more computers by any means such as people, wires, cables, or a telecommunications system.
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In the early 1980s, personal computer was developed with the concept of independent operation. With personal computer on your desktop, you could enter the information yourself, manipulate it, and produce the report you really wanted. While personal computer had become more powerful and applications for the computers included simple spreadsheet, databases, and word processors, the market for the computers exploded. So, many hardware and software venders joined in the market and it resulted competition.
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The competition pressed intense technological development, which led to increased power on the desktop and lower prices.Small businesses inDesktop computers were soon outperforming older, slowermainframe. Small businesses in particular were able to benefit from information management services that, a few years earlier, had been available only to wealthy corporations.
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For all its speed and power, the desktop computing environment had a difficulty in communicating among the users as computing information had became large and complicated.However, business information is useful only when it is communicated between human beings.The obvious solution was to link the desktop computers together. So, the idea of a Local Area Network (LAN) was developed.
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A local area network (LAN) is the communication of a number of computers by cable connecting to each one in a single location, usually a single floor of a building or all the computers in a small company. LANs may be contrasted with wide area networks (WANs). Stated simply, WANs are the communication between LANs by telephone lines leased from the various telephone companies, satellite links, packet radio, or microwave transceivers. The Internet has emerged as both the largest and the least expensive WAN in the world. Many companies take advantage of it now by forming private WANs, known as VPNs, or Virtual Private Networks, through encrypted communications over the Internet.
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对于计算机网络是什么有许多定义。因为没有连接的计算机你也可以建立一个网络，所以用连接的计算机的系统一词来定义会产生误解。这种网络可以被描述为手中拿着软盘的人们在计算机之间跑来跑去传递信息。在这种网络中，计算机之间物理上没有连接，但是它们仍然能够相互传递数据。因此，我喜欢这样定义网络：计算机网络就是可以通过任何一种方式，例如人、导线、电缆或电通信系统，在一台计算机与另一台或多台计算机之间进行的数据通信。
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在20世纪80年代初，个人计算机是依据独立操作的思想而开发的。通过桌面上的个人计算机，你可以自己输入信息、操纵它，并且生成你真正想要的报告。当个人计算机变得功能更强，并且计算机的应用开始包括简单的电子表格、数据库和字处理软件时，计算机市场开始蓬勃发展。因此，许多硬件和软件商加入计算机市场中，从而导致了竞争。
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竞争压力导致了技术的迅猛发展，从而导致了台式机功能的增强和价格的降低。台式机很快战胜了老式的、速度慢的大型机。特别是小型企业能够从信息管理服务中获益，而这种服务在几年前，只有有实力的公司才能获得。
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限于台式机的速度和功能，当计算信息变得大而复杂的时候，台式机计算环境在用户之间进行通信方面遇到了困难。然而，只有当商业信息在人们之间相互传递时，它才能起作用。一种显而易见的解决方法就是将多台台式机连接在一起。于是，局域网的思想就形成了。
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一个局域网（LAN）实现在某个单一区域中，通常是某个建筑物中的一层或者是一家小型公司的全部计算机，通过电缆彼此连接的多台计算机之间的数据通信。局域网可以与广域网（WAN）形成对比，简单地说，广域网就是通过从各电话公司租用的电话线、卫星链路、分组无线网以及微波收发装置，在各局域网之间进行通信。Internet已经成为世界上最大、最便宜的广域网。许多公司现在利用Internet构成被称作"虚拟专用网"（VPN）的专用广域网，在Internet上进行加密通信。
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