Passage Three The Advancement of the Computer. Training target: In this part ， you should try your best to form good reading habits. In order to avoid.

Passage Three Passage Three

The Advancement of The Advancement of the Computerthe Computer

Training target: Training target:

In this partIn this part ，， you should try your best to you should try your best to form good reading habits. In order to avoiform good reading habits. In order to avoid your ill habits such as regressiond your ill habits such as regression ，， yoyou should read with the card showed to you should read with the card showed to you in the preface of this book. Keep readinu in the preface of this book. Keep reading the paragraphs from the beginning to thg the paragraphs from the beginning to the end without stopping.e end without stopping.

Text. Text. The use of the The use of the transistortransistor in computers in the late1950s in computers in the late1950s

marked the coming of the second-generation computermarked the coming of the second-generation computers. The most notable change was that transistors replacs. The most notable change was that transistors replaced vacuum tubes. This meant that the advent of smalleed vacuum tubes. This meant that the advent of smallerr，， fasterfaster ，， more reliable and less expensive computemore reliable and less expensive computers was possible with transistor machines. In additionrs was possible with transistor machines. In addition ，，the second-generation computers were given the second-generation computers were given auxiliaryauxiliary storagestorage，， sometimes called external or secondary storsometimes called external or secondary storage. Data were stored outside the computer on either age. Data were stored outside the computer on either magnetic tapes or magnetic tapes or magneticmagnetic disks. Using magnetic tape disks. Using magnetic tapes or magnetic disks for input and output operations incrs or magnetic disks for input and output operations increased the speed of the computer. eased the speed of the computer.

RAM capacities increased from 8RAM capacities increased from 8 ，， 000 to 64000 to 64 ，，000words in commercially available machines b000words in commercially available machines by the1960sy the1960s ，， with access time of 2 to 3 mswith access time of 2 to 3 ms（（ millisecondsmilliseconds ）） .These machines were very .These machines were very expensive to purchase or even to rent and were expensive to purchase or even to rent and were particularly expensive to operate because of thparticularly expensive to operate because of the cost of expanding programming. Such compue cost of expanding programming. Such computers were mostly found in large computer centerters were mostly found in large computer centers operated by industriess operated by industries ，， governments and prgovernments and private laboratories—ivate laboratories—staffedstaffed with many program with many programmers and support personnel. mers and support personnel.

Late in the1960s the Late in the1960s the integrated circuitintegrated circuit ，， or ICor IC，，was introducedwas introduced ，， making it possible for many trmaking it possible for many transistors to be included on one ansistors to be included on one silicon chipsilicon chip. Th. Thereforeerefore ，， the computers became even smaller the computers became even smaller and cheaper while their memory capacities becand cheaper while their memory capacities became larger. The ame larger. The microprocessormicroprocessor became a reali became a reality in the midˉ1970s with the largeˉscale integratty in the midˉ1970s with the largeˉscale integrateded（（ LSILSI）） circuit. The earliest microcomputercircuit. The earliest microcomputer ，，the Altair8800the Altair8800 ，， was developed in1975by Ed Rwas developed in1975by Ed Roberts; This machine used the Intel microproceoberts; This machine used the Intel microprocessor and had less than1kilobyte of memory. ssor and had less than1kilobyte of memory.

In the1980sIn the1980s ，， very largeˉscale integratedvery largeˉscale integrated （（ VVLSILSI）） circuitscircuits ，， in which hundreds of thousanin which hundreds of thousands of electronic components were ds of electronic components were etched etched into a into a single silicon chipsingle silicon chip ，， became more and more cbecame more and more common. Many companiesommon. Many companies ，， some new to the some new to the computer fieldcomputer field ，， introduced in the1970s progrintroduced in the1970s programmable mini-computers supplied with softwarammable mini-computers supplied with software packages. The“shrinking”trend continued wite packages. The“shrinking”trend continued with the introduction of personal computersh the introduction of personal computers （（ PCPCss），）， which are programmable machines smalwhich are programmable machines small enough and inexpensive enough to be purchal enough and inexpensive enough to be purchased and used by individuals.sed and used by individuals.

By the late1980sBy the late1980s ，， some personal computers some personal computers were run by microprocessors thatwere run by microprocessors that ，， handling32handling32bits of data at a timebits of data at a time ，， could process about4could process about4 ，，000000，， 000instructions per second. Microproces000instructions per second. Microprocessors equipped with read-only memorysors equipped with read-only memory （（ ROROMM），）， which storage constantly usedwhich storage constantly used ，， unchaunchanging programsnging programs ，， now performed an increasinnow performed an increasing number of process-controlg number of process-control ，， testingtesting ，， monitmonitoringoring，， and and diagnosing diagnosing functionsfunctions ，， like like automautomobile ignitionobile ignition systems systems ，， automobile-engine diaautomobile-engine diagnosis and production-line inspection duties. gnosis and production-line inspection duties.

From the integrated circuit to large-scale From the integrated circuit to large-scale integration and to very large-scale integraintegration and to very large-scale integrationtion，， this was the start of the microprocthis was the start of the microprocessor age. The microprocessor continued essor age. The microprocessor continued to improve from the 8086to improve from the 8086 ，， 80286 to the 80286 to the 8048680486，， then Pentiumthen Pentium ，， Pentium and ⅡPentium and Ⅱso onso on （（ equivalentequivalent to 80586 and 8068 to 80586 and 806866）） . .

Modern digital computers are all conceptModern digital computers are all conceptually similarually similar ，， regardless of the size. Thregardless of the size. They can be divided into several categories ey can be divided into several categories on the basis of cost and performance: the on the basis of cost and performance: the personal computer or personal computer or microcomputermicrocomputer ，， a a relatively lowˉcost machinerelatively lowˉcost machine ，， usually of usually of desktopdesktop size. size.

It also includes laptops which are small enough It also includes laptops which are small enough to fit in a briefcase and palmtops which can fit ito fit in a briefcase and palmtops which can fit into a pocket; thento a pocket; the workstation workstation ，， a microcomputa microcomputer with enhanced graphics and communications er with enhanced graphics and communications capabilities that make it especially useful for officapabilities that make it especially useful for office work; the ce work; the minicomputerminicomputer ，， generally too expgenerally too expensive for personal useensive for personal use ，， suitable for businesssuitable for businesseses，， schoolsschools ，， or laboratories; the or laboratories; the mainframemainframe computercomputer ，， a largea large ，， expensive machine whicexpensive machine which meets the needs of major business enterpriseh meets the needs of major business enterprisess，， government departmentsgovernment departments ，， scientific reseascientific research establishments; the rch establishments; the super-computersuper-computer ，， the lthe largest and fastest computer.argest and fastest computer.

A program is a A program is a sequencesequence of instructions that tell of instructions that tells the hardware of a computer what operations ts the hardware of a computer what operations to perform on data. Programs can be built into tho perform on data. Programs can be built into the hardware itselfe hardware itself ，， or they may exist independeor they may exist independently in a form known as software. In some specintly in a form known as software. In some specializedalized ，， or “or “dedicateddedicated” computers” computers ，， the operatithe operating instructions are ng instructions are embeddedembedded in their circuitries; in their circuitries; common examples are the microcomputers founcommon examples are the microcomputers found in calculatorsd in calculators ，， wristwatcheswristwatches ，， car enginescar engines ，，and microwave ovens. Software in widespread and microwave ovens. Software in widespread use includes a wide range of application progrause includes a wide range of application programs-instructions to the computer on how to perfoms-instructions to the computer on how to perform various tasks. rm various tasks.

Process in the area of software has not matcheProcess in the area of software has not matched the great advance in hardware. Software has d the great advance in hardware. Software has become the major cost of many systems becaubecome the major cost of many systems because programming productivity has not increased se programming productivity has not increased very quickly. New programming techniquesvery quickly. New programming techniques ，， ssuch as object-oriented programminguch as object-oriented programming ，， have behave been developed to help relieve this problem. Despen developed to help relieve this problem. Despite difficulties with softwareite difficulties with software ，， howeverhowever，， the cthe cost per calculation of computers is rapidly lesseost per calculation of computers is rapidly lesseningning，， and their convenience and efficiency arand their convenience and efficiency are expected to increase in the near future. e expected to increase in the near future.

One continuing trend in computer develoOne continuing trend in computer development is microminiaturizationpment is microminiaturization ，， the effort the effort to compress more circuit elements into sto compress more circuit elements into smaller and smaller chip space.maller and smaller chip space.

The “fifth-generation” computer is using new tecThe “fifth-generation” computer is using new technologies in very large integrationhnologies in very large integration ，， along with along with new programming languagenew programming language ，， and will be capaand will be capable of amazing feats in the area of ble of amazing feats in the area of artificial intellartificial intelligenceigence ，， such as voice such as voice recognitionrecognition. One import. One important parallel-processing approach is ant parallel-processing approach is neural neural netwnetworkork，， which which mimicsmimics the architecture of the nerv the architecture of the nervous system. Another ongoing trend is the increaous system. Another ongoing trend is the increase in computer networkingse in computer networking ，， electronic mailelectronic mail ，，and electronic publishing. Advances in technoloand electronic publishing. Advances in technologies continue to produce cheaper and more pogies continue to produce cheaper and more powerful computers. werful computers.