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嵌入式Linux应用：概述文献翻译题目基于Linux的拼音输入法设计学生姓名####专业班级信息工程11-01学号541107070104院（系）计算机与通信工程学院指导教师###########完成时间2015年06月01日嵌入式Linux应用：概述译文题目：嵌入式Linux应用：概述原文题目：EmbeddedLinuxapplications:Anoverview原文出处：Internetsource::AnoverviewLinuxnowspansthespectrumofcomputingapplications,includingIBM'stinyLinuxwristwatch,hand-helddevices(PDAsandcellphones),Internetappliances,thinclients,firewalls,industrialrobotics,telephonyinfrastructureequipment,andevencluster-basedsupercomputers.Let'stakealookatwhatLinuxhastoofferasanembeddedsystem,andwhyit'sthemostattractiveoptioncurrentlyavailable.One.EmergenceofembeddedsystemsThecomputersusedtocontrolequipment,otherwiseknownasembeddedsystems,havebeenaroundforaboutaslongascomputersthemselves.Theywerefirstusedbackinthelate1960sincommunicationstocontrolelectromechanicaltelephoneswitches.Asthecomputerindustryhasmovedtowardeversmallersystemsoverthepastdecadeorso,embeddedsystemshavemovedalongwithit,providingmorecapabilitiesforthesetinymachines.Increasingly,theseembeddedsystemsneedtobeconnectedtosomesortofnetwork,andthusrequireanetworkingstack,whichincreasesthecomplexitylevelandrequiresmorememoryandinterfaces,aswellas,youguessedit,theservicesofanoperatingsystem.Off-the-shelfoperatingsystemsforembeddedsystemsbegantoappearinthelate1970s,andtodayseveraldozenviableoptionsareavailable.Outofthese,afewmajorplayershaveemerged,suchasVxWorks,pSOS,Neculeus,andWindowsCE.Two.Advantages/disadvantagesofusingLinuxforyourembeddedsystemAlthoughmostLinuxsystemsrunonPCplatforms,Linuxcanalsobeareliableworkhorseforembeddedsystems.Thepopularback-to-basicsapproachofLinux,whichmakesiteasierandmoreflexibletoinstallandadministerthanUNIX,isanaddedadvantageforUNIXguruswhoalreadyappreciatetheoperatingsystembecauseithasmanyofthesamecommandsandprogramminginterfacesastraditionalUNIX.Thetypicalshrink-wrappedLinuxsystemhasbeenpackagedtorunonaPC,withaharddiskandtonsofmemory,muchofwhichisnotneededonanembeddedsystem.AfullyfeaturedLinuxkernelrequiresabout1MBofmemory.However,theLinuxmicro-kernelactuallyconsumesverylittleofthismemory,only100KonaPentiumCPU,2includingvirtualmemoryandallcoreoperatingsystemfunctions.Withthenetworkingstackandbasicutilities,acompleteLinuxsystemrunsquitenicelyin500KofmemoryonanIntel386microprocessor,withan8-bitbus(SX).Becausethememoryrequiredisoftendictatedbytheapplicationsneeded,suchasaWebserverorSNMPagent,aLinuxsystemcanactuallybeadaptedtoworkwithaslittleas256KBROMand512KBRAM.Soit'salightweightoperatingsystemtobringtotheembeddedmarket.AnotherbenefitofusinganopensourceoperatingsystemlikeEmbeddedLinuxoveratraditionalreal-timeoperatingsystem(RTOS),isthattheLinuxdevelopmentcommunitytendstosupportnewIPandotherprotocolsfasterthanRTOSvendorsdo.Forexample,moredevicedrivers,suchasnetworkinterfacecard(NIC)driversandparallelandserialportdrivers,areavailableforLinuxthanforcommercialoperatingsystems.ThecoreLinuxoperatingsystemitselfhasafairlysimplemicro-kernelarchitecture.Networkingandfilesystemsarelayeredontopofthemicro-kernelinmodularfashion.Driversandotherfeaturescanbeeithercompiledinoraddedtothekernelatrun-timeasloadablemodules.Thisprovidesahighlymodularbuilding-blockapproachtoconstructingacustomembeddablesystem,whichtypicallyusesacombinationofcustomdriversandapplicationprogramstoprovidetheaddedfunctionality.Anembeddedsystemalsooftenrequiresgenericcapabilities,which,inordertoavoidre-inventingthewheel,arebuiltwithoff-the-shelfprogramsanddrivers,manyofwhichareavailableforcommonperipheralsandapplications.Linuxcanrunonmostmicroprocessorswithawiderangeofperipheralsandhasareadyinventoryofoff-the-shelfapplications.Linuxisalsowell-suitedforembeddedInternetdevices,becauseofitssupportofmultiprocessorsystems,whichlendsitscalability.Thiscapabilitygivesadesignertheoptionofrunningareal-timeapplicationonadualprocessorsystem,increasingtotalprocessingpower.SoyoucanrunaLinuxsystemononeprocessorwhilerunningaGUI,forexample,simultaneouslyonanotherprocessor.TheonedisadvantagetorunningLinuxonanembeddedsystemisthattheLinuxarchitectureprovidesreal-timeperformancethroughtheadditionofreal-timesoftwaremodulesthatruninthekernelspace,theportionoftheoperatingsystemthatimplementstheschedulingpolicy,hardware-interruptsexceptionsandprogramexecution.Sincethesereal-timesoftwaremodulesruninthekernelspace,acodeerrorcanimpacttheentiresystem'sreliabilitybycrashingtheoperatingsystem,whichcanbeaveryserious3vulnerabilityforreal-timeapplications.Anoff-the-shelfRTOS,ontheotherhand,isdesignedfromthegroundupforreal-timeperformance,andprovidesreliabilitythroughallocatingcertainprocessesahigherprioritythanotherswhenlaunchedbyauserasopposedtobysystem-levelprocesses.Processesareidentifiedbytheoperatingsystemasprogramsthatexecuteinmemoryorontheharddrive.TheyareassignedaprocessIDoranumericalidentifiersothattheoperatingsystemmaykeeptrackoftheprogramscurrentlyexecutingandoftheirassociatedprioritylevels.Suchanapproachensuresahigherreliability(predictability)withtheRTOStimetha