1.1 History of Computer Development
Nothing epitomizes modern life better than the computer. For better or worse， computers have infiltrated every aspect of our society. Today computer do much more than simply computer： computerized telephone switching centers play traffic cop to millions of calls and keep lines of communication untangled； and automatic teller machines （ATM） let us conduct banking transactions from virtually anywhere in the world. But where did all this technology come from and where is it heading？ To fully understand and appreciate the impact computers have on our lives and promises they hold for the future， it is important to understand their evolution. The advancement in computer technology is divided into four time periods called generations.
First Generation Computers
The first generation of computers lasted from 1951 until 1958. They were large， costly to buy， expensive to power， and often unreliable. It was during this period that symbolic language was developed. Symbolic language use symbols made up of letters and numbers to stand for the 0s and 1s of machine languages. For example， ADD may stand for addition. Computer instructions written in symbolic languages were easier for people to use than machine languages.
Second Generation Computers
The second generation of computers spanned the years from 1959 to 1964. The most notable change was that transistors replaced vacuum tubes. As a result， computers became much smaller， faster， and more reliable and efficient. Next， second generation computers were given auxiliary storage， sometimes called external or secondary storage ended the limitation on how much data the computer could store and reduced the use of punched cards. Using magnetic tapes for input and output operations increased the speed of the computer. Finally， improvements were made in the symbolic programming languages. New languages were more like English than the earlier ones， making programming the computer much easier.
Third Generation Computers
The third generation of computers lasted from 1965 to 1970. During this time， technology continued to improve and computers became even smaller， while their memory capacities became larger. The third generation is marked chiefly by the development of integrated circuits， which replaced transistors. With integrated circuits， hundreds of electronic components could be included on one silicon chip less than one eighth inch square. A number of other developments characterized this period. For example， minicomputers were introduced. These machines had many of the same capabilities as large computers， but they were much smaller， had more storage space， and cost less. Another development was the use of remote terminals， so input/output devices can be electronically linked to a main computer but located at some distance from it.
Fourth Generation Computers
The period for the fourth generation of computers is given from 1971 to the present. Chip circuit has become increasingly miniaturized in fourth generation machines circuits. Large scale integration （LSI） circuits， featuring thousands of electronic components on a single silicon chip， became common during the 1970s. From large scale integration （LSI） technology， comes the microprocessor， the small “computer on a chip”. Microprocessor chips can manage the functions of the computer， perform calculations， and control other devices just as large computers can. The combination of the microprocessor and other densely packed chips used for storage and input/output operations forms a microcomputer. Modern microcomputers have more powers than the large computers of earlier generations. LSI has already progressed into VLSI （very large scale integration）， which means even more capabilities in even smaller packages.
【Vocabulary】
epitomize
vt. 摘要，概括，称为…缩影
infiltrate
vt. 渗透
computerize
vt. 用计算机处理，使计算机化
electronic
adj. 电子的
evolution
n. 发展，进化，演变
generation
n. 代
auxiliary
adj. 辅助的，补助的
install
vt. 安装，安置
instruction
n. 指示，指令，用法说明书
span
vt. 跨越 n. 跨度，范围
efficient
adj. 高效率的
media
n. 媒体，媒介
capacity
n. 容量
program
n. 程序 vt. 编程序
silicon chip
n. 硅片
characterize
n. 表现…的特色，展现个性
minicomputer
n. 小型计算机
microcomputer
n. 微型计算机
memory
n. 内存，存储器
dense
adj. 密集的，浓厚的
package
n. 组件，包裹
miniaturize
vt. 使小型化
integrated circuit
集成电路
vacuum tube
真空管
remote terminal
远程终端
LSI（large scale integration）
n. 大规模集成电路
VLSI（very large scale integration） n. 超大规模集成电路
【参考译文】
计算机发展历史
没有任何东西比计算机更能够称为现代生活的缩影了。不论好与坏，计算机渗透在我们社会的每一个方面。今天的计算机并不是一台机器那么简单：计算机电话转换中心对数以百万的电话起着交通中转的作用，并且维持交流线路的畅通；自动取款机让我们在世界上任何地方进行银行交易操作。可是所有的这些技术从何而来，又将怎样发展？为了充分认识和理解计算机对我们生活的影响，和它们所预示的未来，了解计算机的发展是重要的。计算机技术的发展进程被划分为四个时代。
第一代计算机
第一代计算机从1951年发展到1958年。这一代计算机的体积大、价格昂贵、耗电量大而且可靠性差。在这个时期，符号语言得到了发展。用字母和数字组成的符号语言来代表机器语言的0和1状态。例如，ADD代表加法。用符号语言写的计算机指令比用机器语言写的指令对人们来说要方便得多。
第二代计算机
第二代计算机经过了1959年到1964年。最显著的变化是晶体管代替了真空管。其结果使计算机变得更小、更快、更可靠、更有效了。其次，第二代计算机有了辅助存储器，有的时候也叫做外存或二级存储器。辅助存储器的使用结束了在计算机上存储数据量的限制并减少了使用穿孔卡的次数。用磁带来进行输入和输出的方式提高了计算机的运行速度。后来，符号程序设计语言也得到了改善。新的语言比以前任何一种都更像英语，从而用计算机进行程序设计就变得更加容易了。
第三代计算机
第三代计算机从1965年到1970年。在此期间，技术继续得到改善，同时计算机体积变得更小了，而其存储容量变得更大了。第三代计算机的主要标志是集成电路的发展，集成电路取代了晶体管。集成电路使成百上千的电子元件可以被集成在一块不到 1/8 平方英寸的硅片上。一些其他的发展也称为这个时期的特色。例如，产生了小型计算机，这些机器与大型机相比有着许多相同的功能，但是它的体积更小，存储容量更大而且更便宜。另外一个发展是远程终端的使用，即把一些远离主机的输入输出设备通过电子线路与主机连接在一起。
第四代计算机
第四代计算机所处的阶段是从 1971 年至今。在第四代计算机中，芯片电路已日益小型化。20世纪70年代，在单个硅片上集成成百上千个电子元件的大规模集成电路已变得很普及了。由大规模集成技术而产生了微处理机，即“在一块芯片上的小型计算机”。微处理器芯片能像大型机那样管理计算机的操作，执行运算，控制其他设备。微处理器和其他用于存储和输入输出操作的高密组件组成了微机。现在的微机比早期的大型机有更强的功能。大规模集成电路已发展成了超大规模集成电路，这意味着在更小的组件里有更强大的能力。
【Reading Materials】
Types of Computers
1．Microcomputer
