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The computer virus is an outcome of the computer overgrowth in the 1980s. The cause of the term computer virus is the likeness between the biological virus and the evil program infected with computers. The origin of this term came from an American science fiction The Adolescence of P－1written by Thomas J. Ryan,published in 1977. Human viruses invade a living cell and turn it into a factory for manufacturing viruses. However,computer viruses are small programs. They replicate by attaching a copy of themselves to another program.

　　Once attached to the host Program,the viruses then look for other programs to infect.In this way, the virus can spread quickly throughout a hard disk or an entire organization when it infects a LAN or a multi-user system. At some point,determined by how the virus was programmed the virus attacks. The timing of the attack can be linked to a number of situations,including a certain time or date, the presence of a particular file,the security privilege level of the user,and the number of times a file is used. Likewise,the mode of attack varies. So－called benign viruses might simply display a message,like the one that infected IBM''s main computer system last Christmas with a season''s greeting. Malignant viruses are designed to damage the system. The attack is to wipe out data, to delete flies, or to format the hard disk.

　　What Kind of Viruses Are There？There are two main types of viruses：shell,intrusive. Shell viruses wrap themselves around a host program and don''t modify the original program. Shell programs are easy to write,which is why about half of viruses are of this type. Intrusive viruses invade an existing program and actually insert a portion of themselves into the host program. Intrusive viruses are hard to write and very difficult to remove without damaging the host file.

　　参考译文：

　　计算机病毒是八十年代计算机飞速发展带来的结果，计算机病毒这一名词起因于在计算机上传染的有害程序与生物学中病毒的相似性，该名词起源于1977年出版的、由Thomas J. Ryan写的一本美国科幻小说《p-1的青春》。人体病毒入侵活的细胞后，就把它转变成制造病毒的工厂。而计算机病毒是一些小程序，它们把自己的一个副本附加到另一个程序上面进行复制。

　　病毒程序一旦附加到一个主程序上，就开始寻找其他可以进行“感染”的程序。这样，病毒就很快地布满整个硬盘，如果病毒感染了一个局域网或者一个多用户系统，那么就在整个组织内进行扩散。只有在某个点上病毒程序才会发作（这是由病毒程序的设计所决定的）。攻击的时间与多种情况有关，包括：某个时间或日期、特定用户识别符的出现、用户的安全保密等级和一个文件使用的次数。同样，攻击的方式也是各种各样的。所谓的“良性”病毒可能只是简单地显示一个消息，如在去年圣诞节时，受感染的IBM公司的主要计算机系统显示节日问候。恶性病毒被设计出来破坏系统。常见的攻击方式是消除数据、删除文件或者格式化硬盘。

　　病毒的种类有哪些？主要有两种病毒：shell病毒和instrusive病毒。Shell病毒把自己盘绕在主程序周围，它并不修改原程序。这种病毒容易复制，因此它的数量占了所有病毒的一半。Instrusive病毒入侵现有程序并且把自己的一部分插入主程序。这种病毒不易复制，但是很难在不损伤主程序的情况下被删除。

　　重点单词：

　　1、virus　病毒

　　2、outcome　结果

　　例句：I think there can be but one outcome to this affair.

　　我认为这件事只能有一种结局。

　　3、program 　[电脑]程序

　　4、replicate　复制，折叠，复制品

　　5、host 　[电脑]主机

　　6、at some point　某时，某种情况下

　　7、so-called　所谓的

　　8、malignant　邪恶的，极有害的

　　9、data　数据

　　10、wipe out　消灭；彻底摧毁

　　例句：They have wipe out the enemy‘s major military target.

　　他们已经彻底摧毁了敌人的主要军事目标。

　　句型分析：

　　1、The cause（of the term “computer virus”）is the likeness（between the biological virus and the evil program [infected with computers].）

　　2、The timing（of the attack）can be linked to a number（of situations），including [1]a certain time or date，[2]the presence of a particular file，[3]the security privilege level of the user，[4]and the number of times a file is used.

　　[1]、[2]、[3]、[4]是在including下的并列短句。