专业英语3

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我是靠谱客的博主清秀黄豆，最近开发中收集的这篇文章主要介绍专业英语3，觉得挺不错的，现在分享给大家，希望可以做个参考。

概述

The Evolution of Computer

The first large-scale electronic computer was the Electronic Numerical Integrator and Computer(ENIAC),which became operational in 1946. From that start, computer has developed through four so-called generations, or stages, each one characterized by smaller size ,and less expense than its predecessor.

1.First Generation(1944-1958)

In the eariest general-purpose computer, most input and output media wre punched cards and magnetic tape .Main memory was almost exclusively made up of hundreds of vacuum tubes——although one computer used a magnetic drum for main memory .These computers wre somewhat unreliable because the vacuumtubes failed frequently.They wre also slower than any microcomputer used today ,produced a tremendous amount of heat, and wre very large .They could run only one program at a time.

2.Second Generation(1959-1963)

By the early 1960s, transistors and soe other solid-state devices that were much smaller than vacuum tubes were being used for much of the computer .Magnetic cores,which looked like very small metal washers strung together by wires that carrid electricity, became the most widely used type of main memory. Removable magnetic disk packs, stacks of disks connected by a common spindle , were introduced as storage devices. Second-generation machines tended to be smaller, more reliabe, and significantly faster than first-generation computers.

3.Third Generation(1964-1970)

In the third period, the integrated circuit(IC)——a complete electronic circuit that packages transistors and other electronic components on a small silicon chip_——replaced traditional transistorized circuitry. Integrated circuits are cost-effective because individual components don’t need to be wired directly to to the computer’s system board.

The use of magnetic disks for secondary data storage became widespread, and computers began to support such capabilities as multiprogramming (processing several programs simultaneously) and timesharing (people using the same computer simultansly). Minicomputers wre being widely used by the early 1970s and were taking some of the business away from the established mainframe market. Processing that formerly required the processing power of a mainframe could now be done on a minicomputer.

4.Fourth Generation(1971-Now)

Large-scale integrated(LSI) and very-large-scale integrated(VLSI) circuits were developed that containedhundreds to millions of transistors on a tiny chip.In 1971, Ted Hoff of Intel developed the microprocessor, which pakaged an entire CPU, complete with memory, logic, and control circuits,on a single chip. The microprocessor and VLSI circuit technology caused radical changes in computers——in their size , appearance ,cost ,availability and capability ,and they started the process of miniaturization——the development of smoller and smaller computers.

Also during this time ,computer’s main memory capacity increased, and its cost decreased, which directly affected the types and usefulness of software that could be used. Software applications like word processing, electronic spreadsheets, database management programs ,painting and drawing programs, desktop publishing ,and so forth became commercially available, giving more people reasons to use a computer.