2023年北航软院复试笔试和面试准备

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46szᵨᡝ◤Ḅ⌕ᵨ!☢ᔣḄ$%&'()஺*+,-Ḅᔜ/▤12ᨵ45Ḅ67&'8ᕒ:;<=>&'஺ᐸ*+:
@$%⚗B&'ᦔ᳛⁚ḕ&'〉H☢ᔣḄ$%&'()஺I◍,ᵫᙠᔜ/&'▤1MḄNOᙠ&'()P◤⌕ᜧRḄ&'8ᕒNOSᑭ⚗BḄUᳮ஺O᜜XYZ[\Uᳮᦻ᫏_`a᪶Ḅcdeᜧᱯg☢hijeᐭᔜlmஹ◤opᧇḄrs஺WaterfallmodelThewaterfallmodelisasequentialdesignprocess,oftenusedinsoftwaredevelopmentprocesses,inwhichprogressisseenasflowingsteadilydownwards(likeawaterfall)throughthephasesofConception,Initiation,Analysis,Design,Construction,Testing,Production/Implementation,andMaintenance.Thewaterfalldevelopmentmodeloriginatesinthemanufacturingandconstructionindustries;highlystructuredphysicalenvironmentsinwhichafter-the-factchangesareprohibitivelycostly,ifnotimpossible.Sincenoformalsoftwaredevelopmentmethodologiesexistedatthetime,thishardware-orientedmodelwassimplyadaptedforsoftwaredevelopment.111ThefirstknownpresentationdescribinguseofsimilarphasesinsoftwareengineeringwasheldbyHerbertD.BeningtonatSymposiumonadvancedprogrammingmethodsfordigitalcomputerson29June1956.ফThispresentationwasaboutthedevelopmentofsoftwareforSAGE.In1983thepaperwasrepublished131withaforewordbyBeningtonpointingoutthattheprocesswasnotinfactperformedinastricttop-downfashion,butdependedonaprototype.Thefirstformaldescriptionofthewaterfallmodelisoftencitedasa1970articlebyWinston

47W.Royce,(4115)althoughRoycedidnotusetheterm"waterfair'inthisarticle.Roycepresentedthismodelasanexampleofaflawed,non-workingmodel.161This,infact,ishowthetermisgenerallyusedinwritingaboutsoftwaredevelopment-todescribeacriticalviewofacommonlyusedsoftwaredevelopmentpractice.171Theearliestuseofthetermnwaterfall"mayhavebeena1976paperbyBellandThayerJ81prototypefproto,taip]n.uvw,yz;|ᦪ,prototypesprohibitively[prohibitivli]adv.[Ἥᙢ;(@ᙢ(dᙢOperatingsystemAnoperatingsystem(OS)isacollectionofsoftwarethatmanagescomputerhardwareresourcesandprovidescommonservicesforcomputerprograms.Theoperatingsystemisanessentialcomponentofthesystemsoftwareinacomputersystem.Applicationprogramsusuallyrequireanoperatingsystemtofunction.Time-sharingoperatingsystemsscheduletasksforefficientuseofthesystemandmayalsoincludeaccountingsoftwareforcostallocationofprocessortime,massstorage,printing,andother

48resources.Forhardwarefunctionssuchasinputandoutputandmemoryallocation,theoperatingsystemactsasanintermediarybetweenprogramsandthecomputerhardware,পফalthoughtheapplicationcodeisusuallyexecuteddirectlybythehardwareandwillfrequentlymakeasystemcalltoanOSfunctionorbeinterruptedbyit.Operatingsystemscanbefoundonalmostanydevicethatcontainsacomputer-fromcellularphonesandvideogameconsolestosupercomputersandwebservers.ExamplesofpopularmodernoperatingsystemsincludeAndroid,BSD,iOS,Linux,OSX,QNX,MicrosoftWindows,বWindowsPhone,andIBMz/OS.Allthese,exceptWindows,WindowsPhoneandz/OS,sharerootsinUNIX.schedulevt.᣸ᑜ;ᑴB...ᑡᐭᑜ⊤n.⊤ᑜ⊤⊤[(scheduled(ᑖscheduledᙠᑖscheduling]memoryallocation[i+]ᘤᑖᑖintermediaryadj.P8ḄḄḄḄn.P8;8P▤1;

49HypertextTransferProtocolTheHypertextTransferProtocol(HTTP)isanapplicationprotocolfordistributed,collaborative,hypermediainformationsystems.111HTTPisthefoundationofdatacommunicationfortheWorldWideWeb.Hypertextisstructuredtextthatuseslogicallinks(hyperlinks)betweennodescontainingtext.HTTPistheprotocoltoexchangeortransferhypertext.ThestandardsdevelopmentofHTTPwascoordinatedbytheInternetEngineeringTaskForce(IETF)andtheWorldWideWebConsortium(W3C),culminatinginthepublicationofaseriesofRequestsforComments(RFCs),mostnotablyRFC2616(June1999),whichdefinesHTTP/1.1,theversionofHTTPincommonuse.HTTPfunctionsasarequest-responseprotocolintheclient-servercomputingmodel.Awebbrowser,forexample,maybetheclientandanapplicationrunningonacomputerhostingawebsitemaybetheserver.TheclientsubmitsanHTTPrequestmessagetotheserver.Theserver,whichprovidesresourcessuchasHTMLfilesandothercontent,orperformsotherfunctionsonbehalfoftheclient,returnsaresponsemessagetotheclient.Theresponsecontainscompletionstatusinformationabouttherequestandmayalsocontainrequestedcontentinitsmessagebody.Awebbrowserisanexampleofauseragent(UA).Othertypesofuseragentincludetheindexingsoftwareusedbysearchproviders(webcrawlers),voicebrowsers,mobileappsandothersoftwarethataccesses,consumesordisplayswebcontent.hypermedia]haipo/mldiiin.collaborativefkslaebaretiv]adj.ᔠ¡Ḅ¢¡Ḅcoordinaled[ko'ordn,etid]adj.¢Ḅv._¢_£(coordinateḄ(£(ᑖ)¢

50¢;ᡂ;§InternetEngineeringTaskForceNᱯ¨©)[ª«]culminating[kAl'mineitn]]adj.ᑮ¯⚔Ḅ±᩽Ḅᨬ´ḄaseriesofRequestsforCommentsµᑡḄ¶·¸ᦻ᫏indexingn.᪗Zᢣᦪ»ᙬ᪗½;¾½Thispapermainlystudiestheacquirementofinformationfrominternetwebcrawlerstechnology.zᦻ⌕ẆÀÁ¨ÃÄᢕÆlmḄ¨ÃÇÈᢈÊ஺voicebrowsersËÌÍᘤuseragentᵨᡝÎᳮTCP/IPÏУISOÑÐÒὃTCP/IPÔ᪀ÖHOSITCP/IPOSIHᵨÐHᵨÐᦪ×⊤ØÐÙÚÐÛÜᑮÛÜÐÝTCPáÝâãäåÐáᦪᒹäåШÃÐÝIPáÝâãçὶÐáᦪ"¨ÃÐᦪéêëШÃì×ÐÝâãêëÐá#ᱯᱥᳮÐTCP/IP¢îSTCP£IPXï/¢îḄᔠãðᢣNᱯ¨᦮/TCP/IP¢îò஺¢îᑖÐó☢ᩭõTCP/IPᵫÏ/Ðö÷ᡂ,¨Ãì×Ðஹ¨ÃÐஹäåÐஹHᵨÐ஺TCP/IP¢îøSùᐰûᔠOSIḄÑÐÒὃOSIOpenSystemInterconnect

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le&m1234n3ᑮp12$q᝞X.25%ᣚ1ᡈIEEE802tu1஺=ᵨFTPஹTELNET.HTTPSNMPஹTFTP.NTP6᝶TCPUDP12%nIP802.2HDLC,PPPஹFRAME-RELAYwxᑮ12802.3EIA/TIA-232.449.V.35ஹV.21InternetprotocolsuiteTheInternetprotocolsuiteisthenetworkingmodelandasetofcommunicationsprotocolsusedfortheInternetandsimilarnetworks.ItiscommonlyknownasTCP/IP,becauseitsmostimportantprotocols,theTransmissionControlProtocol(TCP)andtheInternetProtocol(IP),werethefirstnetworkingprotocolsdefinedinthisstandard.ItisoccasionallyknownastheDoDmodel,becausethedevelopmentofthenetworkingmodelwasfundedbyDARPA,anagencyoftheUnitedStatesDepartmentofDefense.TCP/IPprovidesend-to-endconnectivityspecifyinghowdatashouldbeformatted,addressed,transmitted,routedandreceivedatthedestination.Thisfunctionalityhasbeenorganizedintofourabstractionlayerswhichareusedtosortallrelatedprotocolsaccordingtothescopeofnetworking

52involved.111121Fromlowesttohighest,thelayersarethelinklayer,containingcommunicationtechnologiesforasinglenetworksegment(link),theinternetlayer,connectingindependentnetworks,thusestablishinginternetworking,thetransportlayerhandlingprocess-to-processcommunication,andtheapplicationlayer,whichinterfacestotheuserandprovidessupportservices.TheTCP/IPmodelandrelatedprotocolsaremaintainedbytheInternetEngineeringTaskForce(IETF).DARPAz{{■}~DẆYᑜtUnitedStatesDepartmentofDefense.z{{■}connectivity[,kan£k'tiviti]n.n&ឋspecifying['spesifaij]v.ᢣ(specifyḄᙠᑖ);M…Ḅᩩᐹᨵᱯឋ;process-to-processcommunication&InternetEngineeringTaskForceᱯ1[]}OSImodel

53TheOpenSystemsInterconnection(OSI)model(ISO/IEC7498-1)isaconceptualmodelthatcharacterizesandstandardizestheinternalfunctionsofacommunicationsystembypartitioningitintoabstractionlayers.ThemodelisaproductoftheOpenSystemsInterconnectionprojectattheInternationalOrganizationforStandardization(ISO).Themodelgroupssimilarcommunicationfunctionsintooneofsevenlogicallayers.Alayerservesthelayeraboveitandisservedbythelayerbelowit.Forexample,alayerthatprovideserror-freecommunicationsacrossanetworkprovidesthepathneededbyapplicationsaboveit,whileitcallsthenextlowerlayertosendandreceivepacketsthatmakeupthecontentsofthatpath.Twoinstancesatonelayerareconnectedbyahorizontalconnectiononthatlayer.OSIModelDataunitLayerFunction7.ApplicationNetworkprocesstoapplicationDatarepresentation,encryptionanddecryption,convertmachine6.PresentationHostDatadependentdatatomachineindependentdatalayers5.SessionInterhostcommunication,managingsessionsbetweenapplicationsSegments4.TransportReliabledeliveryofpacketsbetweenpointsonanetwork.Addressing,routingand(notnecessarilyreliable)deliveryofPacket/Datagram3.Networkdatagramsbetweenpointsonanetwork.MedialayersBit/Frame2.DatalinkAreliabledirectpoint-to-pointdataconnection.Bit1.PhysicalA(notnecessarilyreliable)directpoint-to-pointdataconnection.

54partitioning[pQ(hig]n.ᑖᒘ,ᑖᢈᑖᒘ;ᑖ;ᑖᙽ;error-free¡¢┯hostlayerswxmedialayers¤¥