Introduction to Linux1.1 History1.1.1 UNIXInordertounderstandthepopularityofLinux,weneedtotravelbackintime,about30yearsago.Imaginecomputersasbigashouses,evenstadiums.Whilethesizesofthosecomputersposedsubstantialproblems,therewasonethingthatmadethisevenworse:everycomputerhadadifferentoperatingsystem.Softwarewasalwayscustomizedtoserveaspecificpurpose,andsoftwareforonegivensystemdidntrunonanothersystem.Beingabletoworkwithonesystemdidntautomaticallymeanthatyoucouldworkwithanother.Itwasdifficult,bothfortheusersandthesystemadministrators.Computerswereextremelyexpensivethen,andsacrificeshadtobemadeevenaftertheoriginalpurchasejusttogettheuserstounderstandhowtheyworked.ThetotalcostofITwasenormous.Technologicallytheworldwasnotquitethatadvanced,sotheyhadtolivewiththesizeforanotherdecade.In1969,ateamofdevelopersintheBellLabslaboratoriesstartedworkingonasolutionforthesoftwareproblem,toaddressthesecompatibilityissues.Theydevelopedanewoperatingsystem,whichwassimpleandelegantwrittenintheCprogramminglanguageinsteadofinassemblycodeabletorecyclecode.TheBellLabsdevelopersnamedtheirprojectUNIX.Thecoderecyclingfeatureswereveryimportant.Untilthen,allcommerciallyavailablecomputersystemswerewritteninacodespecificallydevelopedforonesystem.UNIXontheotherhandneededonlyasmallpieceofthatspecialcode,whichisnowcommonlynamedthekernel.ThiskernelistheonlypieceofcodethatneedstobeadaptedforeveryspecificsystemandformsthebaseoftheUNIXsystem.Theoperatingsystemandallotherfunctionswerebuiltaroundthiskernelandwritteninahigherprogramminglanguage,C.ThislanguagewasespeciallydevelopedforcreatingtheUNIXsystem.Usingthisnewtechnique,itwasmucheasiertodevelopanoperatingsystemthatcouldrunonmanydifferenttypesofhardware.Thesoftwarevendorswerequicktoadapt,sincetheycouldselltentimesmoresoftwarealmosteffortlessly.Weirdnewsituationscameinexistence:imagineforinstancecomputersfromdifferentvendorscommunicatinginthesamenetwork,orusersworkingondifferentsystemswithouttheneedforextraeducationtouseanothercomputer.UNIXdidagreatdealtohelpusersbecomecompatiblewithdifferentsystems.ThroughoutthenextcoupleofdecadesthedevelopmentofUNIXcontinued.MorethingsbecamepossibletodoandmorehardwareandsoftwarevendorsaddedsupportforUNIXtotheirproducts.UNIXwasinitiallyfoundonlyinverylargeenvironmentswithmainframesandminicomputers(notethataPCisamicrocomputer).Youhadtoworkatauniversity,forthegovernmentorforlargefinancialcorporationsinordertogetyourhandsonaUNIXsystem.Butsmallercomputerswerebeingdeveloped,andbytheendofthe80s,manypeoplehadhomecomputers.Bythattime,therewereseveralversionsofUNIXavailableforthePCarchitecture,butnoneofthemweretrulyfree.1.1.2 CurrentapplicationofLinuxsystemsTodayLinuxhasjoinedthedesktopmarket.Linuxdevelopersconcentratedonnetworkingandservicesinthebeginning,andofficeapplicationshavebeenthelastbarriertobetakendown.WedontliketoadmitthatMicrosoftisrulingthismarket,soplentyofalternativeshavebeenstartedoverthelastcoupleofyearstomakeLinuxanacceptablechoiceasaworkstation,providinganeasyuserinterfaceandMScompatibleofficeapplicationslikewordprocessors,spreadsheets,presentationsandthelike.Ontheserverside,Linuxiswell-knownasastableandreliableplatform,providingdatabaseandtradingservicesforcompanieslikeAmazon,thewell-knownonlinebookshop,USPostOffice,theGermanarmyandsuch.EspeciallyInternetprovidersandInternetserviceprovidershavegrownfondofLinuxasfirewall,proxy-andwebserver,andyouwillfindaLinuxboxwithinreachofeveryUNIXsystemadministratorwhoappreciatesacomfortablemanagementstation.ClustersofLinuxmachinesareusedinthecreationofmoviessuchasTitanic,Shrekandothers.Inpostoffices,theyarethenervecentersthatroutemailandinlargesearchengine,clustersareusedtoperforminternetsearches.Theseareonlyafewofthethousandsofheavy-dutyjobsthatLinuxisperformingday-to-dayacrosstheworld.ItisalsoworthtonotethatmodernLinuxnotonlyrunsonworkstations,mid-andhigh-endservers,butalsoongadgetslikePDAs,mobiles,ashiploadofembeddedapplicationsandevenonexperimentalwristwatches.ThismakesLinuxtheonlyoperatingsystemintheworldcoveringsuchawiderangeofhardware.1.2Theuserinterface1.2.1 IsLinuxdifficult?WhetherLinuxisdifficulttolearndependsonthepersonyoureasking.