大学教学课件：计算机英语

COMPUTINGESSENTIALSContentsChapter1IntroductiontoInformationTechnologyChapter2SystemUnitChapter3InputDevicesChapter4OutputDevicesChapter5SecondaryStorageChapter6SystemSoftwareChapter7ApplicationSoftwareChapter8CommunicationSystemChapter9ComputerNetworkChapter10InternetChapter11ElectronicCommerceandSecurityChapter12ProfessionalCertificationandCareersinInformationSystemsChapter1IntroductionInformationTechnologyObjectiveAfterreadingthischapter,youshouldbeableto:Definewhatthedigitalcomputeris.Knowtheevolutionofcomputer.Describethefivetypesofcomputer.Knowtheseveraltypesofdata.Explainthefivepartsofaninformationsystem.1.1DigitalComputer

Digitalcomputerisalsocalledelectroniccomputerorcomputer—atoolthatisaprogrammable,electronicdevicethatacceptsinput,performsoperationsorprocessingonthedata,andoutputsandstorestheresults.1.1DigitalComputerTherelationshipsbetweenthesefourmaincomputeroperationsareshowninFigure1-1.1.1DigitalComputerAllgeneral-purposecomputersrequirethefollowinghardwarecomponents:Centralprocessingunit(CPU).

Memory(fast,expensive,short-termmemory).Massstoragedevice(slower,cheaper,long-termmemory).

Inputdevice.

Outputdevice.

1.2EvolutionofComputerFromthefirstlarge-scaleelectroniccomputerwasbuilt,computershavedevelopedthroughfivegenerations.1.2.1FirstGeneration(1944-1958):VacuumTubes1.2.2SecondGeneration(1959-1964):Transistor1.2.3ThirdGeneration(1964-1970):IntegratedCircuits1.2.4FourthGeneration(1971-Present):VLSIintegratedcircuits1.2.5FifthGeneration(PresentandBeyond):ArtificialIntelligenceFifthgenerationcomputingdevices,basedonartificialintelligence,arestillindevelopment.1.3TypesofComputers1.3.1SupercomputersThesupercomputeristhetopoftheheapinpowerandexpense.Thistypeofcomputerusuallycostshundredsofthousandsorevenmillionsofdollars.Asupercomputerisacomputerthatisatthefrontlineofcurrentprocessingcapacity,particularlyspeedofcalculation.1.3.1SupercomputersThetermsupercomputeritselfisratherfluid,andtoday'ssupercomputertendstobecometomorrow'sordinarycomputer.1.3.1SupercomputersSupercomputersareusedforhighlycalculation-intensivetaskssuchasproblemsinvolvingweatherforecasting,climateresearch,molecularmodeling(computingthestructuresandpropertiesofchemicalcompounds,biologicalmacromolecules,polymers,andcrystals),physicalsimulations(suchassimulationofairplanesinwindtunnels.),cryptanalysis,andthelike.1.3.2MainframeComputersThemainframecomputerisapowerfulmulti-usercomputercapableofsupportingmanyhundredsorthousandsofuserssimultaneously.1.3.2MainframeComputersTodayinpractice,thetermusuallyreferstocomputerscompatiblewiththeIBMSystem/360line,firstintroducedin1965.(IBMSystemz10isthelatestincarnation.)1.3.2MainframeComputersMainframesarecomputersusedmainlybylargeorganizationsforcriticalapplications,typicallybulkdataprocessingsuchascensus,industryandconsumerstatistics,ERP,andfinancialtransactionprocessing.1.3.3MinicomputersItisamidsizecomputer.Theterm"minicomputer"evolvedinthe1960stodescribethe"small"thirdgenerationcomputersthatbecamepossiblewiththeuseoftransistorandcorememorytechnologies.1.3.3MinicomputersAndalthoughtoday’sPCsandserversareclearlymicrocomputersphysically,architecturallytheirCPUsandoperatingsystemshaveevolvedlargelybyintegratingfeaturesfromminicomputers.1.3.4MicrocomputersMicrocomputersaretheleastpowerful,yetarethemostwidelyusedandfastest-growingtypeofcomputer.Amicrocomputerisacomputerwithamicroprocessorasitscentralprocessingunit.Anothergeneralcharacteristicofthesecomputersisthattheyoccupyphysicallysmallamountsofspacewhencomparedtomainframeandminicomputers.1.3.4MicrocomputersCategoriesofmicrocomputerincludedesktop,notebook,andpersonaldigitalassistant.1.4DataTypeDataisusedtodescribefactsaboutsomething.1.5InformationSystemsChapter2SystemUnitObjectiveAfterreadingthischapter,youshouldbeableto:Describethebasictypesofpersonalcomputer.Explainthefunctionsofthehardwarecomponentscommonlyfoundinsidethesystemunit.KnowthetwounitsofCPU.Nameseveralexamplesofbothinternalandexternalbuses.2.1SystemUnitAsystemunit,alsoknownasabaseunit,isthemainbodyofadesktopcomputer,typicallyconsistingofaplasticenclosurecontainingthemotherboard,powersupply,coolingfans,internaldiskdrives,andthememorymodulesandexpansioncardsthatarepluggedintothemotherboard,suchasvideoandnetworkcards.2.1SystemUnitForpersonalcomputers,therearethreebasictypes.Desktopsystemunits.Notebooksystemunits.PDAsystemunits.2.2SystemBoardThesystemboardisalsoknownasthemainboardormotherboard.Thesystemboardisthemainprintedcircuitboardthatcontainsthecentralprocessingunitforthecomputer,memory,andsometimesprinterportsorotherdevices.2.2SystemBoard2.3MicroprocessorAmicroprocessorincorporatesmostorallofthefunctionsofacentralprocessingunit(CPU)onasingleintegratedcircuit(IC).2.3MicroprocessorTheCPUhastwobasiccomponents:Controlunit.ThecontrolunitcanbethoughtofasthebrainoftheCPUitself.Ittellstherestofthecomputersystemhowtocarryoutaprogram’sinstructions.Arithmetic-logicunit.Thearithmetic-logicunit,usuallycalledtheALU,performstwotypesofoperations—arithmeticandlogical.2.3MicroprocessorThreebasiccharacteristicsdifferentiatemicroprocessors:Instructionset.Wordsize.Clockspeed.

2.3MicroprocessorMicroprocessorsareclassifiedasbeingeitherRISC(reducedinstructionsetcomputer)orCISC(complexinstructionsetcomputer).

RISC.ARISCmicroprocessorrecognizesarelativelylimitednumberofinstructions.CISC.ACISCmicroprocessorcontainsamorecomplexsetofinstructionsthatitrespondsto.2.4MemoryMemoryisaholdingareafordata,instructions,andinformation.2.4MemoryTherearetwomaintypesofmemory:VolatileandNon-volatile.Volatilememory,alsoknownasvolatilestorageorprimarystoragedevice,iscomputermemorythatrequirespowertomaintainthestoredinformation.Non-volatilememory,NVMornon-volatilestorage,iscomputermemorythatcanretainthestoredinformationevenwhennotpowered.2.4.2Read-OnlyMemory(ROM)InmodernPCs,"ROM"isusedtostorethebasicbootstrappingfirmwareforthemainprocessor,aswellasthevariousfirmwareneededtointernallycontrolselfcontaineddevicessuchasgraphiccards,harddisks,DVDdrives,TFTscreens,etc,inthesystem.UnlikeRAM,ROMcannotbewrittento.2.4.3ComplementaryMetal-OxideSemiconductor(CMOS)Itcontainsessentialinformationthatisrequiredeverytimethecomputersystemisturnedon.CMOSchipsrequirelesspower,whichmakesthemparticularlyattractiveforuseinbattery-powereddevices,suchasportablecomputers.2.5SystemClockThesystemclockisacircuitthatemitsacontinuousstreamofprecisehighandlowpulsesthatareallexactlythesamelength.Oneclockcycleisthetimethatpassesfromthestartofonehighpulse,untilthestartofthenext.Clockspeedsareexpressedinmegahertz(MHz)orgigahertz(GHz).2.6BuslinesAbusisasubsystemthattransfersdatabetweencomputercomponentsinsideacomputerorbetweencomputers.Mostcomputershavebothinternalandexternalbuses.2.6.1ExamplesofinternalcomputerbusesIndustryStandardArchitecture(ISA).ItwasacomputerbusstandardforIBMcompatiblecomputers.2.6.1ExamplesofinternalcomputerbusesPeripheralComponentInterconnect(PCI).Itisacomputerbusforattachinghardwaredevicesinacomputer.2.6.1ExamplesofinternalcomputerbusesAcceleratedGraphicsPort(AGP).Itisahigh-speedpoint-to-pointchannelforattachingagraphicscardtoacomputer'smotherboard,primarilytoassistintheaccelerationof3Dcomputergraphics.2.6.1ExamplesofinternalcomputerbusesPCIExpress.PCIExpress(PeripheralComponentInterconnectExpress),officiallyabbreviatedasPCIe,isacomputerexpansioncardstandarddesignedtoreplacetheolderPCI,PCI-X,andAGPstandards.IntroducedbyIntelin2004,2.6.2ExamplesofexternalcomputerbusesUniversalSerialBus(USB).USBisaserialbusstandardtoconnectdevicestoahostcomputer.TheUSB3.0specificationwasreleasedonNovember17,2008bytheUSB3.0PromoterGroup.2.6.2ExamplesofexternalcomputerbusesSerialAttachedSCSI.Incomputing,thedata-transfertechnologySerialAttachedSCSI(SAS)movesdatatoandfromcomputerstoragedevicessuchasharddrivesandtapedrives.2.6.2ExamplesofexternalcomputerbusesSerialATA.TheSerialATA(SATA)computerbusisastorage-interfaceforconnectinghostbusadapterstomassstoragedevices.Chapter3InputDeviceObjectiveAfterreadingthischapter,youshouldbeableto:Explaintheroleofinputdevices.Knowwhatthecommoninputdevicesare.Knowtheuseofthecommoninputdevice.3.1InputDeviceInputdevicesarehardwareusedtoprovideinputtothecomputer.Thepurposeofinputdevicesistocollectdataandconvertitintoaformsuitableforcomputerprocessing.Thewidelyusedinputdevicesincludekeyboards,mice,touch

screens,scanners,andaudioinputdevices.3.2KeyboardAkeyboardisaninputdevice.3.3MouseAmouse(pluralmouses,mice,ormousedevices)isapointingdevicethatfunctionsbydetectingtwo-dimensionalmotionrelativetoitssupportingsurface.Therearetwobasictypesofmice:Mechanicalmouse.Opticalmouse

3.3Mouse3.3Mouse3.4TouchScreenAtouchscreen(SeeFigure3-4.)isatypeofdisplayscreenthathasatouch-sensitivetransparentpanelcoveringthescreen.3.5ScannerIncomputing,ascannerisadevicethatopticallyscansimages,printedtext,handwriting,oranobject,andconvertsittoadigitalimage.3.6AudioinputdeviceAudioinputdevicesallowausertosendaudiosignalstoacomputerforprocessing,recording,orcarryingoutcommands.Therearetwomajorcategoriesofaudioinputdevices:Microphone.MIDIkeyboardorotherdigitalmusicalinstrument.

Chapter4OutputDevicesObjectiveAfterreadingthischapter,youshouldbeableto:Identifyseveraltypesofoutputdevicesandexplaintheirfunctions.Describethecharacteristicsoftheoutputequipmentthatmostusersencounterregularly-namely,displaydevicesandprinters.Discussseveraltypesofmultimediaoutputequipment.4.1OutputDevicesOutputequipmentallowspeopletocommunicatewithcomputers.Outputdevicesconverttheprocessed0sand1sbackintoaformunderstandabletohumans.Outputdevicesproduceresultsineitherhard-copyorsoft-copyform.4.2MonitorsAmonitoristhemostcommonformofoutputdevice.Tocreatethecolors,threephosphorcoatingsfortheprimarycolorsred,greenandblueareprovided.4.2MonitorsAnimportantcharacteristicofallscreensistheirresolution.Eachpointoflightonthescreeniscalledapixel.Theresolutionofascreenisthemaximumnumberofpixelsthatthescreencandisplay.4.2MonitorsMonitorsuseacathode-raytube(CRT)orliquid-crystaldisplay

(LCD)toshowcharactersandgraphicsonatelevision-likescreen.4.3PrintersPrintersaredevicethatprintscharacters,symbols,andsometimesgraphicsonpaper.Thetwomaintypesofprinterareimpactandnon-impact:Impactprintersdohavecontact;non-impactprintersdonot.1.ImpactPrintersImpactPrintersuseaprintheadcontaininganumberofmetalpinsthatstrikeaninkedribbonplacedbetweentheprintheadandthepaper.2.Non-ImpactPrintersNon-impactprintersaremuchquieterthanimpactprintersastheirprintingheadsdonotstrikethepaper.4.4Audio-OutputDevicesAudio-Outputdevicestranslateaudioinformationfromthecomputerintosoundsthatpeoplecanrecognizeandunderstand.Themostwidelyusedaudio-outputdevicesarespeakersandheadphones.Chapter5SecondaryStorageObjectiveAfterreadingthischapter,youshouldbeableto:DistinguishthedifferencebetweenPrimarystorageandSecondarystorage.Explainwhatfunctionsthatsecondarystoragedevicesperforminthecomputersystem.Comprehendthecharacteristicsofcommonsecondarystoragedevices.5.1SecondaryStorageSecondarystorage(orsecondarymemory)iswhereprogramsanddataarekeptonalong-termbasis.Thethreetypesofsecondarystorage:harddisks,opticaldisks,andUSBflashdrives.5.2HardDisksAharddiskisoneofthemostimportantcomponentswithinthePC.Itisadevicewhereyoupermanentlystoreprogramsanddata.5.3OpticalDisksAnopticaldiscisaflat,circulardiscwhereindataisstoredinthepits(orbumps)initsflatsurface—sequentiallyonthecontinuous,spiraltrackextendingfromtheinnermosttracktotheoutermosttrack,coveringtheentirediscsurface.Therearethreebasictypesofopticaldisks:CD-ROM.CD-R.CD-RW.

5.3OpticalDisks5.4USBFlashDrivesAUSBflashdriveconsistsofaNAND-typeflashmemorydatastoragedeviceintegratedwithaUSBinterface.5.4USBFlashDrivesUSBflashdrivesofferpotentialadvantagesoverotherportablestoragedevices,particularlythefloppydisk.Theyhaveamorecompactshape,operatefaster,holdmuchmoredata,haveamoredurabledesign,andoperatemorereliablyduetotheirlackofmovingparts.Chapter6SystemSoftware

ObjectiveAfterreadingthischapter,youshouldbeableto:Definewhatthesystemsoftwareis.Describethefourcategoriesofsystemsoftware.Discussthebasicfunctionsandcategoriesofoperatingsystem.Discusstheadvantagesofutilities.Definedevicedrivers.Discussprogramminglanguageandtranslators.6.1SystemSoftware

Systemsoftwareisthepartofacomputersystemthatmakestherawcomputingpowerprovidedbythehardwareconvenientfortheuserandefficientfortheowner.Systemsoftwareissoftwarethatbasicallymakesthecomputerwork.Systemsoftwareisnotasingleprogram.Systemsoftwareisusuallydividedintofourcategories:Operatingsystem.Utilitysoftware.

Devicedrivers.Languagetranslators.6.2OperatingSystemsAnoperatingsystemisaninterfacebetweenhardwareanduser;itisresponsibleforthemanagementandcoordinationofactivitiesandthesharingofthelimitedresourcesofthecomputer.6.2OperatingSystemsOperatingsystems,suchasGNU,MicrosoftWindows,MacOSXorLinux,areprominentexamplesofsystemsoftware.6.2OperatingSystemsAccordingtothemodernunderstanding,anOSshouldbeabletodothefollowing:Programexecution.

Interrupts.

Protectedmodeandsupervisormode.Memorymanagement.Virtualmemory.

Multitasking.

Diskaccessandfilesystems.

Devicedrivers.

Networking.

Security.

Graphicaluserinterfaces.

6.2OperatingSystemsThethreebasiccategoriesofoperatingsystems:EmbeddedNetworkStand-alone6.2.1EmbeddedOperatingSystemsAnembeddedoperatingsystemisaspecial-purposecomputersystemthatisusedforaparticulartask.Someofthemostcommonembeddedsystemsusedineverydaylifeare:RefrigeratorsMicrowaveovensTV,VCR,DVDplayersCamerasCarsPersonaldigitalassistantsPrinters6.2.2NetworkOperatingSystemAnetworkoperatingsystem(NOS)issoftwarethatcontrolsanetworkanditsmessage(e.g.packet)trafficandqueues,controlsaccessbymultipleuserstonetworkresourcessuchasfiles,andprovidesforcertainadministrativefunctions,includingsecurity.

ANOSisanOSthathasbeenspecificallywrittentoimplementandmaintainnetworks.6.2.2NetworkOperatingSystem

Theexamplesofnetworkoperatingsystemsare:6WINDGate.6WINDsoftwarepackagesthatturnLinuxdistributionsintorouters'controlplaneanddataplane.CiscoIOS.CiscoIOS(formerly"CiscoInternetworkOperatingSystem")isaNOShavingafocusontheinternetworkingcapabilitiesofnetworkdevices.ItisusedonCiscoSystemsroutersandsomenetworkswitches.BSD.BSD,alsousedinmanynetworkservers.6.2.3Stand-aloneOperatingSystemsStand-aloneoperatingsystemsalsocalleddesktopoperatingsystemscontrolasingledesktopornotebookcomputer.Theseoperatingsystemsarelocatedonthecomputer’sharddisk.6.3UtilitysoftwareUtilitysoftwarealsoknownasserviceprogramsperformspecifictasksrelatedtomanagingcomputerresources.Theexamplesofutilitysoftwaresare:DiskstorageutilitiesSystemprofilersprovidedetailedinformationaboutthesoftwareinstalledandhardwareattachedtothecomputer.Anti-virusutilitiesscansforcomputerviruses.Datacompressionutilitiesoutputashorterstreamorasmallerfilewhenprovidedwithastreamorfile.Cryptographicutilitiesencryptanddecryptstreamsandfiles.RegistrycleanerscleanandoptimizetheWindowsregistrybyremovingoldregistrykeysthatarenolongerinuse.Networkmanagerscheckthecomputer'snetwork,logeventsandcheckdatatransfer.6.4DeviceDriversAdevicedriverisacomputerprogramallowinghigher-levelcomputerprogramstointeractwithahardwaredevice.6.5ProgrammingLanguagesandTranslatorsProgramminglanguagesareavocabularyandsetofgrammaticalrulesforinstructingacomputertoperformspecifictasks.Thetermprogramminglanguageusuallyreferstohigh-levellanguages,suchasBASIC,C++,C,COBOL,FORTRAN,Ada,andPascal.6.5ProgrammingLanguagesandTranslatorsTraditionally,computerprogramminglanguagesaredividedintofivegenerations.6.5.1CompilerAcompilerisaspecialprogramthattakeswrittensourcecodeandturnsitintomachinelanguage.Whenacompilerexecutes,itanalyzesallofthelanguagestatementsinthesourcecodeandbuildsthemachinelanguageobjectcode.Afteraprogramiscompiled,itisthenaformthattheprocessorcanexecuteoneinstructionatatime.6.5.1CompilerInsomeoperatingsystems,anadditionalstepcalledlinkingisrequiredaftercompilation.Linkingresolvestherelativelocationofinstructionsanddatawhenmorethanoneobjectmoduleneedstoberunatthesametimeandbothmodulescross-referenceeachothersinstructionsequencesordata.6.5.2AssemblerAnassemblertranslatesassemblylanguageintomachinelanguage.Itusescomputer-specificcommandsandstructuresimilartomachinelanguage,butassemblylanguageusesnamesinsteadofnumbers.6.5.3InterpreterItconvertsprogramsintomachine-executableformeachtimetheyareexecuted.Itanalyzesandexecuteseachlineofsourcecode,inorder,withoutlookingattheentireprogram.Insteadofrequiringastepbeforeprogramexecution,aninterpreterprocessestheprogramasitisbeingexecuted.Chapter7ApplicationSoftwareObjectiveAfterreadingthischapter,youshouldbeableto:Identifythesystemsoftwarefromtheapplicationsoftware.Discusscommonfeaturesofmostapplicationsoftware.Givesomeexamplesofcommonlyusedapplicationsoftware.7.1ApplicationSoftwareApplicationsoftwareisalooselydefinedsubclassofcomputersoftwarethatemploysthecapabilitiesofacomputerdirectlytoataskthattheuserwishestoperform.Applicationsoftwareincludesavarietyofprogramsthatcanbesegregatedintogeneral-purposeandapplication-specificcategories.7.1ApplicationSoftwareGeneral-purposeprogramsperformcommoninformationprocessingjobsforendusers.Examplesarebrowsers,wordprocessors,spreadsheets,databasemanagementsystems,andpresentationprograms.Special-purposeprogramsaccomplishinformationprocessingtasksthatsupportspecificbusinessfunctionsorprocesses,scientificorengineeringapplications,andothercomputerapplicationsinsociety.Someofthebestknownaremultimedia,graphics,virtualreality,andartificialintelligence

programs.7.2CommonFeaturesofApplicationSoftware1.Window.Awindowissimplyarectangularareaonadisplayscreen.7.2CommonFeaturesofApplicationSoftware2.Menus.Menusarealistofcommandsoroptionsfromwhichyoucanchoose.7.2CommonFeaturesofApplicationSoftware3.Help.Helpisanonlinedocumentation.7.2CommonFeaturesofApplicationSoftware4.Toolbar.ToolbarisaseriesofselectablebuttonsinaGUIthatgivetheuseraneasywaytoselectdesktop,applicationorWebbrowserfunctions.7.3BrowsersShortforWebBrowser,itisasoftwareapplicationwhichenablesausertodisplayandinteractwithtext,images,videos,music,gamesandotherinformationtypicallylocatedonaWebpageataWebsiteontheWorldWideWeboralocalareanetwork.Webbrowsersarethemost-commonly-usedtypeofHTTPuseragent.7.3BrowsersExamplesofWebBrowsersare:NetscapeNavigatorMicrosoftInternetExplorerOperaSafariFirefox7.3Browsers7.4WordProcessorsAwordprocessorisacomputerapplicationusedfortheproduction(includingcomposition,editing,formatting,andpossiblyprinting)ofanysortofprintablematerial.Mostwordprocessorsarepowerfulsystemsconsistingofoneormoreprogramsthatcanproduceanyarbitrarycombinationofimages,graphicsandtext,thelatterhandledwithtype-settingcapability.7.4WordProcessorsMicrosoftWordisthemostwidelyusedcomputerwordprocessingsystem;Therearealsomanyothercommercialwordprocessingapplications,suchasKingsoftWPS.7.4WordProcessorsWordprocessorsvaryconsiderably,butallwordprocessorssupportthefollowingbasicfeatures:Inserttext.

Deletetext.Cutandpaste.Copy.Pagesizeand

margins.Searchand

replace.Wordwrap.Print.

7.5SpreadsheetsSpreadsheetprogramsorganize,analyze,andgraphnumericdatasuchasbudgetsandfinancialreports.Thereareanumberofspreadsheetapplicationsonthemarket,Lotus1-2-3andExcelbeingamongthemostfamous.7.5Spreadsheets7.6DatabaseManagementSystemsToaccessinformationfromadatabase,youneedadatabasemanagementsystem(DBMS).Thisisasetofcomputerprogramsthatcontrolsthecreation,maintenance,andutilizationofthedatabasesofanorganization.ThreeofthemostwidelyusedDBMSareMicrosoftAccess,CorelParadox,andLotusApproach.7.6DatabaseManagementSystemsTherelationaldatabaseisthemostwidelyuseddatabasestructure.Therelationaldatabasesareorganizedbyfields,records,andtables.7.7PresentationGraphicsPresentationgraphicsisatypeofbusinesssoftwarethatenablesuserstocreatehighlystylizedimagesforslideshowsandreports.ThreeofthemostwidelyusedpresentationgraphicsprogramsareMicrosoftPowerPoint,CorelPresentations,andLotusFreelanceGraphics.7.7PresentationGraphics7.8SoftwareSuitesAsoftwaresuiteisacombinationofindividualsoftwarepackageswhichshareacommongraphicaluserinterfaceandaredesignedforeasytransferofdatabetweenapplications.Itissignificantlylessexpensivetobuyasuiteofapplicationsthantobuyeachapplicationseparately.7.8SoftwareSuitesMicrosoftOfficeisapopularsoftwaresuite.Chapter8CommunicationSystemObjectiveAfterreadingthischapter,youshouldbeableto:Definethetermofcommunicationsystem.Givesomeexamplesofcommunicationmediaandconnectiondevices.Graspsomeknowledgeaboutpopularnewcommunicationtechnologies.Definethetermofdatatransmissionandknowfactorsofdatatransmission.8.1CommunicationSystemCommunicationsystemisasystemorfacilitycapableofprovidinginformationtransferbetweenpersonsandequipment.Thesystemusuallyconsistsofsendingandreceivingdevices,communicationmedium,connectiondevices,anddatatransmissionspecifications.8.1CommunicationSystem8.2CommunicationMediaThecommunicationmediaincludestwistedpaircables,coaxialcables,fibercables,radiowaves,infraredtransmissions,microwaves,andcommunicationsatellites.8.2CommunicationMedia1.TwistedpairCable8.2CommunicationMedia2.CoaxialCables8.2CommunicationMedia3.FiberCables8.2CommunicationMedia4.RadioWave6.Microwave5.Infraredtransmission8.2CommunicationMedia7.CommunicationSatellites8.3ConnectionDevicesConnectionDevicesarehardwarecomponentsusedtoconnectvariouspartsofanetwork.8.4CommunicationTechnologyCommunicationTechnologyisbasicallytheuseoftechnologiestocommunicatewithotherpeople,thus,everythingfromthepostalservicetowirelessphonesandInternet.Therearesomepopulardatacommunicationnewtechnologies,suchasISDN,ADSL,GSM,Bluetooth,andCDMA.8.4CommunicationTechnology1.ISDN

Abbreviationofintegratedservicesdigitalnetwork,itisaninternationalcommunicationsstandardforsendingvoice,video,anddataoverdigitaltelephonelinesornormaltelephonewires.

8.4CommunicationTechnology2.ADSL

Shortforasymmetricdigitalsubscriberline,itisanewtechnologythatallowsmoredatatobesentoverexistingcoppertelephonelines(POTS).ProvidersusuallymarketADSLasaserviceforconsumerstoconnecttotheInternetinarelativelypassivemode:abletousethehigherspeeddirectionforthe"download"fromtheInternetbutnotneedingtorunserversthatwouldrequirehighspeedintheotherdirection.8.4CommunicationTechnology3.GSM

ShortforGlobalSystemforMobileCommunications,itisoneoftheleadingdigitalcellularsystems.8.4CommunicationTechnology4.Bluetooth

Bluetooth

isanopenwirelessprotocolforexchangingdataovershortdistancesfromfixedandmobiledevices,creatingpersonalareanetworks(PANs).ItaimedatsimplifyingcommunicationsamongInternetdevicesandbetweendevicesandtheInternet.

8.4CommunicationTechnology4.Bluetooth8.4CommunicationTechnology5.CDMAShortforCode-DivisionMultipleAccess,itisadigitalcellulartechnologythatusesspread-spectrumtechniques.

8.5DataTransmissionDatatransmissionisthetransferofdataorinformationbetweenasourceandareceiver.Severalfactorsaffecthowdataistransmitted.Theyincludebandwidth,serial

or

parallel

transmission,direction

ofdataflow,andprotocols.8.5DataTransmission1.Bandwidth

Bandwidth