职称英语理工类b级.doc

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1、阅读判断*第十一篇　　ComputerMouseThebasiccomputermouseisanamazinglycleverinventionwitharelativelysimpledesignthatallowsustopointatthingsonthecomputeranditisveryproductive.Thinkofallthethingsyoucandowithamouselikeselectingtextforcopyingandpasting1，drawing，andevenscrollingonthepagewiththenewermicewit

2、hthewheel.Mostofususethecomputermousedailywithoutstoppingtothink2howitworksuntilitgetsdirtyandwehavetolearnhowtocleanit.Welearntopointatthingsbeforewelearntospeak，sothemouseisaverynaturalpointingdevice.Qthercomputerpointingdevicesincludelightpens，graphicstabletsandtouchscreens，butthemousei

3、sstillourworkhorse.Thecomputermousewasinventedin1964byDouglasEnglehartofStanfordUniversity.Ascomputerscreensbecamemorepopularandarrowkeyswereusedtomovearoundabodyoftext，itbecameclearthatapointingdevicethatallowedeasiermotionthroughthetextandevenselectionoftextwouldbeveryuseful.Theintroduct

4、ionofthemouse，withtheAppleLisacomputerin1983，reallystartedthecomputerpublicontheroadtorelyingonthemouseforroutinecomputertasks.3Howdoesthemousework?Wehavetostartatthebottom，sothinkupsidedownfornow.Itallstartswiththemouseball.Asthemouseballinthebottomofthemouserollsoverthemousepad，itpresses

5、againstandturnstwoshafts.Theshaftsareconnectedtowheelswithseveralsmallholesinthem.Thewheelshaveapairofsmallelectroniclight-emittingdevicescalledlight-emittingdiodes(LED)mountedoneitherside4.OneLEDsendsalightbeamtotheLEDontheotherside.Asthewheelsspinandaholerotatesby，thelightbeamgetsthrough

6、totheLEDontheotherside.Butamomentlaterthelightbeamisblockeduntilthenextholeisinplace.TheLEDdetectsachangingpatternoflight，convertsthepatternintoanelectronicsignal，andsendsthesignaltothecomputerthroughwiresinacablethatgoesoutofthemousebody.Thiscableisthetailthathelpsgivethemouseitsname.Thec

7、omputerinterpretsthesignaltotellitwheretopositionthecursoronthecomputerscreen.Sofarwehaveonlydiscussedthebasiccomputermousethatmostofyouprobablyhaveorhaveused.5Oneproblemwiththisdesignisthatthemousegetsdirtyastheballrollsoverthesurfaceandpicksupdirt.Eventually