嵌入式LINUX操作系統(tǒng)原理：chp1-2 嵌入式Linux操作系統(tǒng)

Chp1-2EmbeddedLinuxOperationSystemOperationSystem:1.Definition:

Operatingsystem(OS)isthesystemsoftwareresponsibleforsupportingtherunningenvironmentofapplicationprogramandsupportingtheoperatingenvironmentofusersincomputersystem,anditisalsothecoreandcornerstoneofcomputersystem.

操作系統(tǒng)是電子計(jì)算機(jī)系統(tǒng)中負(fù)責(zé)支撐應(yīng)用程序運(yùn)行環(huán)境及用戶操作環(huán)境的系統(tǒng)軟件，同時(shí)也是計(jì)算機(jī)系統(tǒng)的核心與基石。OperationSystem:2.Responsibilitiesandfunctions:Itsresponsibilitiesincludedirectsupervisionofhardware,managementofvariouscomputingresources(suchasmemory,processortime,etc.),andapplication-orientedservicessuchasjobmanagement.

它的職責(zé)包括對(duì)硬件的直接監(jiān)管、對(duì)各種計(jì)算資源（如內(nèi)存、處理器時(shí)間等）的管理，以及提供諸如作業(yè)管理之類的面向應(yīng)用程序的服務(wù)等。

OperationSystem:Operatingsystemisabridgebetweentheunderlyinghardwareandusers.Userscaninputcommandsthroughtheuserinterfaceoftheoperatingsystem,whiletheoperatingsystem

interpretscommands,driveshardwaredevices,andachievesuser’srequirements.

操作系統(tǒng)的主要功能簡單總結(jié)為：

操作系統(tǒng)位于底層硬件與用戶之間，是兩者溝通的橋梁。用戶可以通過操作系統(tǒng)的用戶界面輸入命令，操作系統(tǒng)則對(duì)命令進(jìn)行解釋，驅(qū)動(dòng)硬件設(shè)備，實(shí)現(xiàn)用戶要求。

OperationSystem:3.Types:

Threebasictypes:

Batchprocessingsystem

(批處理操作系統(tǒng))Time-sharingsystem(分時(shí)操作系統(tǒng))Real-timesystem(實(shí)時(shí)操作系統(tǒng))Somenewkindsofoperatingsystems:

Embeddedoperatingsystem(嵌入式操作系統(tǒng))Personaloperatingsystem(個(gè)人操作系統(tǒng))Networkoperating(網(wǎng)絡(luò)操作系統(tǒng))Distributedoperatingsystem(分布式操作系統(tǒng))HistoryofLinux:Linux:

LinuxreferstoasetofUNIX-like(類unix)operatingsystemthatarefreetouseandspread(免費(fèi)使用，自由傳播).1990,LinusTorvalds(studentofUniversityofHelsinki)softwaresourcecode

Linux–Linus’sMinix1991,onlinecommunities,

thefirstLinuxsoftwaredistributions(version0.0.2)(containingDiskdriver,filesystem,gcccompiler…)1993,version1.0–thefirstformalversionComplywithGPL

GPL

–

General

Public

License(通用公共許可證)

1994,thefirstcommercialversion1.01996,version1.2.13meetthePOSIX

standardSince1998,widely

used

This“babyversion”operatingsystemhasgrownrapidlywithanaverageoftwoweeksofupdates.

Today,Linuxhasmorethan250distributions,andcansupportprocessorsofallarchitectures,suchasX86,PowerPC,ARM,XSCALE,aswellasprocessorswithorwithoutMMU.

Sofar,itskernelversionhasevolvedfrom0.0.1to2.6.xx.1.Freesoftware–自由軟件

Free:freedom(自由);freeofcharge(免費(fèi))區(qū)分:”freesoftware”（自由軟件）”freeware”（免費(fèi)軟件）Definitionof“freesoftware”(RichardStallman):“freesoftware”isamatterofliberty,notprice.Tounderstandtheconcept,youshouldthinkof“free”asin“freespeech,”notasin“freebeer”.自由軟件的重點(diǎn)在于自由權(quán)，而非價(jià)格。要了解其所代表的概念：你應(yīng)該將“free”想成是“freespeech”（言論自由）中的“free”（自由），而不是“freebeer”（免費(fèi)啤酒）中的“free”（免費(fèi)）

。Freesoftware–自由軟件Freesoftware

referstoakindofsoftwarethatfollowsthegeneralPubliclicensingrules(GPL),guaranteesthefreedomofuse,thefreedomofobtainingsourceprogram,thefreedomofmodifying,thefreedomofcopyingandspreading,andcanalsohavethefreedomofcharging.

自由軟件是指遵循通用許可證規(guī)則，保證使用上的自由，獲得源程序的自由，可以自行修改的自由，可以復(fù)制和推廣的自由，也可以有收費(fèi)自由的一種軟件。自由軟件的精神領(lǐng)袖（自由軟件之父）

—

RichardStallman（理查德·斯托曼）RichardStallman）。2.

FSF

–FreeSoftwareFundation

(自由軟件基金會(huì),一個(gè)致力于推廣自由軟件、促進(jìn)計(jì)算機(jī)用戶自由的美國民間非盈利性組織)

EstablishedbyRichardStomaninOctober19853.

GNU

–

GNU‘sNotUnix!

(遞歸縮寫

)GNUisasoftwaresystemplan,developedbyRichardStallmanin1984.ItsmaingoalistodevelopanoperatingsystemcompatiblewithUNIXandit’salsoafreesoftware.ItssoftwarewillbereleasedcompletelyinGPLmode.4.

GPL

–

GNUGeneral

Public

License

(通用公共許可證)Definitions

aboutLinux：1）What

is

Linux？

Linux

kernelLinuxsystemLinuxdistributions2）What

is

EmbeddedLinux？

EmbeddedLinuxsystemsorEmbeddedLinuxdistributions

shorterform:

hostsystem/hosttargetsystem/target

developmentdistributionstargetdistributions3）What

is

Real-TimeLinux？Initially,real-timeLinuxdesignatedtheRTLinuxprojectreleasedin1996byMichaelBarabanov.

ThegoaloftheprojectwastoprovidedeterministicresponsetimesunderaLinuxenvironment.Mainly,itisusedtosaythatthesystemoroneofitscomponentsissupposedtohavefixedresponsetimesRTLinux,2007seldtoWindRiverTypesofEmbeddedLinuxSystems1)Size

small,medium,large

small

low-poweredCPU,

≥4MBROM(NORorNANDFlash)8~16MBRAM

medium

medium-poweredCPU,

≥32MBROM(NORorNANDFlash)64~128MBRAMMostconsumer-orienteddevices:PDAs,MP3players,entertainmentsystems,networkappliance,etc.

largeapowerfulCPUorcollectionofCPUspermanentstorage(持久性存儲(chǔ)器)largeamountsofRAM

Largetelecomswitchesandflightsimulators2)Timeconstraints

stringent(嚴(yán)格的),mild(寬松的)

stringent

requirethesystemreactinapredefinedtimeframe;otherwise,catastrophic(災(zāi)難性的)eventshappen.hardreal-timesystem:

forinstance,clargeequipmentofcuttingmaterialssoftreal-timerequirement:MP3players,cellphones

mild

applytosystemswheretimelyresponsivenessisn’tnecessarilycritical3)Networkability

NetworkabilitydefineswhetherasystemcanbeconnectedtoanetworkchooseLinuxasanembeddedOS-----itsprovennetworkingcapabilities.4)Userinteraction

ThedegreeofuserinteractionvariesgreatlyfromonesystemtoanotherReasonsforChoosingLinux1)QualityandreliabilityofcodePropertiesof“qualitycode”

Modularityandstructure

Readability

ExtensibilityConfigurabilityPropertiesof“reliablecode”

PredictabilityErrorrecovery

Longevity(?)-----LinuxfitthisdescriptionofqualityandreliabilityReasonsforChoosingLinux2)Availabilityofcode3)Hardwaresupport4)Communicationprotocolandsoftwarestandards5)Availabletools

6)Communitysupport7)Licensing8)Vendorindependence9)Costsomeofthebetterknownvendors1)MontaVistaaleaderintheembeddedLinuxmarketCont