计算机导论答案 1.docx

计算机导论答案 1.docx

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计算机导论答案1

Chapter5

TheSystemUnit

LectureGuide

∙LearningObjectives

oDifferentiatebetweenthefourbasictypesofsystemunits.

oDescribesystemboards,includingsockets,slots,andbuslines.

oRecognizedifferentmicroprocessors,includingmicroprocessorchipsandspecialtyprocessors.

oComparedifferenttypesofcomputermemoryincludingRAM,ROM,andflashmemory.

oExplainexpansionslotsandcards.

oDescribebuslines,buswidths,andexpansionbuses.

oDescribeportsincludingstandardandspecializedports.

oIdentifypowersuppliesfordesktop,laptop,tablets,andmobiledevices.

oExplainhowacomputercanrepresentnumbersandencodecharacterselectronically.

ChapterOutline

∙TheSystemUnit

oAlsoknownasthesystemchassis,thesystemunithousesmostoftheelectroniccomponentsthatmakeupacomputersystem.

oTherearefourbasictypesofpersonalcomputers:

▪Desktops-Thisisthemostpowerfultypeofpersonalcomputer.Manydesktopshavetheirsystemunitinaseparatecase.Thiscasecontainsthesystem’selectroniccomponentsandselectedsecondarystoragedevices.Inputandoutputdevicessuchasamouse,keyboard,andmonitor,arelocatedoutsidethesystemunit.

∙Desktopsystemunitthatareplacedverticallyaresometimesreferredtoasatowerunitortowercomputer.Somedesktopcomputers,likeApple'siMac,havetheirmonitorandsystemunithousedtogetherinthesamecase.Thesecomputersareknownasall-in-one.

▪Laptops,alsocalledlaptops,areportableandmuchsmaller.Thesesystemunitsarehousedwith,selectedsecondarystoragedevicesandinputdevices.Themonitorisattachedbyhinges.

∙Ultrabooks,ormininotebooksareatypeofaveryportablelaptop.Theyarelighter,smallerandgenerallyhavealongerbatterylifethanalaptop.

▪Tablets-arethenewestandoneofthemostpopulartypesofcomputer.Theyareeffectivelyathinslabthatisallmonitorwiththesystemunitlocatedbehindthemonitor.Tabletsaresmaller,lighter,andgenerallylesspowerfulthanlaptopcomputers.Tabletstypicallyuseavirtualkeyboardthatappearsonthescreenandistouchsensitive.

▪Mobiledevices–mobiledevicesarethesmallestandaredesignedtofitcomfortablyintothepalmofonehand.Thesesystemscontainanentirecomputersystem,includingtheelectroniccomponents,secondarystorage,andinputandoutputdevices.

∙Mostpopularisthesmartphone.

∙Smartphonesextendthecapabilitiesofacellphonebyprovidingcomputingpower.Inadditiontocapturingandsendingaudioandvideo,smartphonesrunapps,connecttotheInternet,andmore.Theirsystemunitislocatedbehindthedisplayscreen.

oComponents

▪Personalcomputerscomeinavarietyofdifferentsizes,shapes,andcapabilities.

▪Eachtypeofsystemunithassimilarcomponents

∙theseincludeasystemboard,microprocessor,andmemory

∙ElectronicDataandInstructions

oComputersaredigitaldevicesasopposedtoanalogdevices.Therefore,computerscanonlyunderstandthingsasonoroff.

▪Binarysystem

∙Abinarycodingschemeassignsauniquesequenceofbitstoeachcharacter.

∙Byte–agroup8bits

▪Hexadecimalsystemuses16digitstorepresentbinarynumbers

oCharacterEncoding-howacomputerprovidesrepresentationtocommunicate

▪Characterencodingstandards–assignsauniquesequenceofbitstoeachcharacter

∙ASCII（AmericanStandardCodeforInformationInterchange）isasevenbitcodingscheme.

∙EBCDIC（ExtendedBinaryCodedDecimalInterchangeCode）isaneightbitcodingscheme

∙Unicodeisa16-bitcodingschemeoriginallydesignedtosupportinternationallanguageslikeChineseandJapanese.Theselanguageshavetoomanycharacterstoberepresentedbythesevenandeight-bitASCIIandEBCDICcodes.

oMostwidelyusedsincetheexplosionoftheInternet

∙SystemBoard

oAlsoknownasthemotherboardormainboard.

oItisthecommunicationsmediumfortheentirecomputersystembecauseeverycomponentofthesystemunitconnectstothesystemboard.

oAlargeflatcircuitboardcoveredwithavarietyofdifferentelectroniccomponentsincludingsockets,slots,andbuslines.

▪Socketsprovideaconnectionpointforsmallspecializedelectronicpartscalledchips.

▪Chipsconsistoftinycircuitboardsetchedontosquaresofsand-likematerialcalledsilicon.Alsocalledasiliconchip,semiconductor,orintegratedcircuit.

▪Chipcarriersareusedtomountmicrochips.Theyareeitherpluggeddirectlyintosocketsonthesystemboardorontocardsthatarethenpluggedintoslotsonthesystemboard.

▪Slotsprovideaconnectionpointforspecializedcardsorcircuitboards.Thesecardsprovideexpansioncapabilityforacomputersystem.

▪Connectinglinescalledbuslinesprovidepathwaysthatsupportcommunicationamongthevariouselectroniccomponentsthatareeitherlocatedonthesystemboardorattachedtothesystemboard.

oLaptop,tablets,andmobilesystemboards

▪Smallerthanthedesktopsystemboards

▪Performthesamefunctionsasdesktopsystemboards

∙Microprocessor

oThecentralprocessingunit（CPU）orprocessoriscontainedonasinglechipcalledthemicroprocessor.

oThemicroprocessoristhe“brains”ofthecomputersystem.

oIthastwobasiccomponents:

▪Thecontrolunittellstherestofthecomputersystemhowtocarryoutaprogram’sinstructions.Itdirectsthemovementofelectronicsignals.

▪Thearithmetic-logicunit,usuallycalledtheALU,performstwotypesofoperations:

∙Arithmeticoperations–fundamentalmathoperations

∙Logicaloperations–consistsofcomparisons

∙Microprocessorchips

▪Chipprocessingcapacitiesareoftenexpressedinwordsizes.

▪Awordisthenumberofbits（suchas16,32,or64）thatcanbeaccessedatonetimebytheCPU.

▪TheprocessingspeedofamicroprocessoristypicallyrepresentedbyitsclockspeedwhichisrelatedtothenumberoftimestheCPUcanfetchandprocessdataorinstructionsinasecond.

▪Newerpersonalcomputersaremuchfasterandprocessdataandinstructionsinbillionthsofasecond,ornanoseconds.

▪Supercomputers,bycontrast,operateatspeedsmeasuredintrillionthsofasecond,orpicoseconds-1,000timesfasterthanpersonalcomputers.

▪Untilrecently,64-bitprocessorswereprimarilyusedinlargemainframesandsupercomputers.However,64-bitprocessorsarebecomingcommonplaceintoday’smorepowerfulpersonalcomputers.

▪ThemulticorechipcanprovidetwoormoreseparateandindependentCPUstherebyallowingasinglecomputertoruntwoormoreoperationsatthesametime.

▪Formulticoreprocessorstobeusedeffective,computersmustunderstandhowtodividetasksintopartsthatcanbedistributedacrosseachcore—anoperationcalledparallelprocessing.

oSpecialtyprocessors

▪Coprocessorsarespecialtychipsdesignedtoimprovespecificcomputingoperations.

∙Oneofthemostwidelyusedisthegraphicscoprocessor,alsocalledagraphicsprocessingunit（GPU）.Theseprocessorsarespecificallydesignedtohandletheprocessingrequirementsrelatedtodisplayingandmanipulating3-Dgraphicsimagesandencryptingdata.

▪Smartcardsareplasticcardsthesizeofaregularcreditcardthathaveanembeddedspecialtychip.

▪Luxurycarshavemorethan70separateprocessors.

∙Memory

oMemoryisaholdingareafordata,instructions,andinformation.

oMemoryiscontainedonchipsconnectedtothesystemboard.

oTherearethreewell-knowntypesofmemorychips:

random-accessmemory（RAM）,read-onlymemory（ROM）,andflashmemory

oRAM

▪Random-accessmemory（RAM）chipsholdtheprogram（sequenceofinstructions）anddatathattheCPUispresentlyprocessing.

▪RAMistemporaryorvolatilestoragebecauseeverythinginmosttypesofRAMislostassoonasthepersonalcomputeristurnedoff.

▪Cachememoryimprovesprocessingbyactingasatemporaryhigh-speedholdingareabetweenthememoryandtheCPU.ComputerdetectswhichinformationinRAMismostfrequentlyusedandthencopiesthatinformationintothecache.

▪Memorycapacityisexpressedinbytes.SeechartinFigure5-12.

▪HavingenoughRAMisimportant

▪RAMcanbeaddedbyinsertinganexpansionmodule–DIMM（dualin-linememorymodule）.OthertypesofRAMincludeDRAM,SDRAM,DDR,andDirectRDRAM.

▪Virtualmemoryisspaceutilizedonasecondarystoragedevicebytheoperatingsystemwhenthereisn’tenoughRAMtoprocessallapplications.ItisaswapareawhereeachpartisreadintoRAMonlywhenneeded.

∙FormoreinformationonhowvirtualmemoryworksvisitselectStudentEdition,thenExplore,andthenMemory.

oROM

▪Read-onlymemory（ROM）chipshaveinformationandprogramsbuiltintothematthefactory.

▪ROMchipsarenotvolatileandcannotbechangedbytheuser.

▪Notlongago,ROMchipsweretypicallyusedtocontainalmostallinstructionsforbasiccomputeroperations.

▪Recently,however,flashmemorychipshavereplacedROMchipsformanyapplications.

oFlashMemory

▪OffersacombinationofthefeaturesofRAMandROM.

▪Flashmemorycanbeupdatedtostorenewinformation

▪Flashmemorychipscanretaindataevenifpowerisdisrupted.

▪Usedforawidevarietyofapplicationssuchasstartupinstructionsforacomputer.Thisinformationiscalledthesystem'sBIOS（basicinput/outputsystem）.

∙ExpansionSlotsandCards

oExpansioncardsplugintoexpansionslotslocatedonthesystemboard.

oPortsonthecardsallowcablestobeconnectedfromtheexpansioncardstodevicesoutsidethesystemunit.

oSomeofthemorecommondevicesare

▪Graphicscards–providehigh-quality3Dgraphicsandanimationforgamesandsimulations

▪Soundcards,acceptaudioinputfromamicrophoneandconvertitintoaformthatcanb