計算機的歷史

History of Computers 
 
　　The first general-purpose electronic computer to operate suclearcase/" target="_blank" >ccessfully was the Electronic Numerical Integrator and Computer (ENIAC)．Its construction was proposed in 1942 by John Mushily and J.Presser Eckert of the Moore School of Engineering, University of Pennsylvania. Work started on its development in June 1943 and the computer was completed by late 1945.It occupied 1500 ft2（140M2） of floor space, weighed over 30 tons, consisted of approximately 18000 vacuum tubes, 70000 resistors，10000 capacitors and 6000 switches and consumed150 kW of power. It was used to generate ballistic tables and weather forecasts．In principle it was programmable but this could only be done with consider--able difficulty by rewiring parts of the machine.   
　　With the development of the ENIAC, the computer became a useful scientific and business tool The ENIAC could operate without human intervention, depending only upon stored instructions．This development marked the beginning of the modern computer era. Since then, many refinements in computers speed, size, and cost have been made．Many advancements in computer technology are divided into four time periods called generations．

1 ．First Generation of Computers   
　　The first generation of computers lasted from•1951 to 1958. They were large, costly to buy, expensive to power, and often unreliable. Their internal operations were controlled through the use of vacuum tubes．These tubes were fairly large, and they generated so much heat that special air-conditioning had to be installed to handle it.
　　It was during this period that symbolic languages were developed. Symbolic languages use symbols made up of letters and numbers to stand for Os and 1 soft machine language. For example, ADD may stand for addition. Computer instructions written in symbolic languages were easier for people to use than machine language but symbolic language had to be translated into machine code before the computer could follow the instructions. The machine codes we restored on the outer surface of ma.netic drum.

2. Second Generation of Computers   
　　The second generation of computers spanned the years from 1959 to 1964.It was during this time that the technology race really began．   
　　The most notable change was that transistors replaced vacuum tubes．As a result, computers be-came much smaller，faster，and more reliable. They also became more efficient. Also at this time, magnetic cores replaced magnetic drums as storage media.
　　Next, the second generation of computers were given auxiliary storage, sometimes called external or secondary storage．Data was stored outside the computer on either magnetic tapes or magnetic disks．The use of auxiliary storage ended the limitation on how much data the computer could store and reduce these of punched cards．Using magnetic tapes for input and output operations increased the speed of computer.   
　　Finally, improvements were made in the symbolic programming languages．New languages were more like English than the earlier ones, making progranuning the computer much easier.

3. Third Generation of Computers   
　　The third generation of computers lasted from1965 to 1970 During the 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 electrum 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 less storage space, and cost less．Another development was the use of remote terminals; in-put/output devices that are electronically linked to the main computer but located at some distance from it. A popular innovation was the introduction of families of computers that could support as many as forty different external devices，such as printer and remote terminals．Each computer in the family contained a different main storage capacity. A company could easily move up a machine with more storage while continuing to use the same external devices．

4 ．Fourth Generation of Computers   
　　The period for the fourth generation of computers is given as 1971 to the present. Chip circuit has become increasingly miniaturized in the fourth generation of computers．Large-scale Integration (LSI)circuit, featuring thousands of electronic components on a single silicon chip became common during the1970s．From LSI technology came the microcomputer, 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 power than the large computers of earlier generations．LSI has al-ready progressed into VLSI (Very Large Scale Integration), which means even more capabilities in even smaller packages．

翻譯：

計算機的歷史     

　　第一臺成功運行的通用電子計算機是ENIAC電子數值積分計算機）亡的結構是賓夕法尼亞大學牧爾工程學院的約翰，莫奇菜（John MaUChIN）與?？颂兀↗. PresperEckert ）于1942年提出的。該工程于1943年6月萬始研制。它占地1500平方英尺（140M2），重量超過30噸。它由約18000只真空管，70000只電阻，10000只電容及6000只開關組成，耗電150KW o被用于編制彈道表及天氣預報。從原理說，它是可編程的，但是。要做到這一點相當困難，因為要對機器的部件重新接線。
　　隨著ENIAC的開發，計算機成為有用的科學和商業工具。ENIAC能夠不需要人的干預而只依靠存儲的指令進行操作。這個發展標志著現代化計算機時代的開端。從那以后，進行了許多對計算機在速度、大小、價格等方面的改進，被分為四個階段，稱為“代”。

1.第一代計算機   
　　第一代計算機從1951年持續至1958年?！詡凅w積大，價格昂貴，啟動費力且常常不可靠。它們的內部操作是通過真空管來控敘的。這些真空管很大，并且它們聚集了如此多的熱量以至于不得不靠安裝專門的空調來進行處理。    正是是這個時期，符號語言得到了開發。符號語言是用字母和數字組成的符號來代表機器語言的0和1。例如，ADD代表加法，用符號語言寫的計算機指令比用機器語言寫的指令對人來說要好用一些。但在計算機能執行這些指令之前，符號語言必須被翻譯成機器代碼，機器代碼被存儲在磁鼓的外表面。

2.第二代計算機   
　　第二代計算機跨越了1959年，直到1964年。正是在這段時間里，技術競爭真正開始了。   
　　最顯著的變化是晶體管代替了真空管，它導致計算機的體積變得更小，更快，更可靠。同時也變得更高效了。也就是在這個時期，磁芯代替了磁鼓作為存儲媒介。   
　　其次，第二代計算機有了輔助存儲器（有時一也稱為外存或二級存儲器）。數據被存儲在計算機外部的磁帶或磁盤上。輔助存儲器的使用結束了計算機主存容量對程序和數據的規模的限制，減少了穿孔紙帶的使用，采用磁帶來進行輸入與輸出，提高了計算機的速度。   
最后，在符號程序設計語言上也得到了改善。新的語言比以前更加接近英語，從而，為計算機設計程序變得更加容易了。

3.第三代計算機
　　第三代計算機從1965年持續至1970年。在此期間，技術繼續得到了提高，同時計算機的體積變得更小，而其存儲能力卻更大了。
　　第三代計算機的主要標志是集成電路的發展，集成電路代替了晶體管。有了集成電路，成百上千的電子元件可以被集成到一塊不到l／8平方英寸的硅片上。   
　　另一些發展也成為這個時期的特色，例如產生了小型計算機。這些機器有許多大型機相同的能力。但它體積更小，存儲容量更大而且更便宜。另一個發展是使用遠程終端，即是一個遠離主機但通過電子線路與主機聯系在一起的輸入輸出設備。一個很受歡迎的改進是產生了能夠支持多達40多個不同外部設備（這些設備的例子是打印機和遠程終端等）的計算機系列中的每一種計算機都有不同的主存容量。計算機公司能夠在使用原有的外部設備的情況下，通過增加存儲容量輕易地將計算機升級。

4．第四代計算機
   第四代計算機所處的階段是1971年至今。第四代計算機的芯片電路已日益縮小化。70年代，以在單個硅片上集成成千上萬電子元件為特色的大規模集成電路己變得很普及了。由于大規模集成技術而產生了微處理機，即“在一塊芯片上的小型計算機”。微處理機芯片能管理計算機的功能，執行運算，控制其它設備，像大型機那樣。微處理機和其它的用于存儲和輸入輸出操作的緊密結合在一起的部件組合而產生了微機?，F代的微機比早期的微機具有更強的能力。大規模集成電路己發展成為超大規模集成電路，這意味著更小的組件具有更大的能力。

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