网上图书购销系统的设计 外文翻译.docx
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网上图书购销系统的设计 外文翻译.docx
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网上图书购销系统的设计外文翻译
毕业设计(论文)
外文翻译
题目网上图书购销系统的设计
专业信息管理与信息系统
班级09信管
(2)
学生张倩炜(20907234)
指导教师胡元义
高科学院
2013年
C#andDatabaseDevelopment
一、TheIntroduceofC#
Inonesense,C#canbeseenasbeingthesamethingtoprogramminglanguagesas.NETistotheWindowsenvironment.JustasMicrosofthasbeenaddingmoreandmorefeaturestoWindowsandtheWindowsAPIoverthepastdecade,VisualBasicandC++haveundergoneexpansion.AlthoughVisualBasicandC++haveendedupashugelypowerfullanguagesasaresultofthis,bothlanguagesalsosufferfromproblemsduetothelegaciesofhowtheyhaveevolved.
InthecaseofVisualBasic6andearlier,themainstrengthofthelanguagewasthefactthatitwassimpletounderstandanddidn’tmakemanyprogrammingtaskseasy,largelyhidingthedetailsoftheWindowsAPIandtheCOMcomponentinfrastructurefromthedeveloper.ThedownsidetothiswasthatVisualBasicwasnevertrulyobject-oriented,sothatlargeapplicationsquicklybecomedisorganizedandhardtomaintain.Aswellasthis,becauseVisualBasic’ssyntaxwasinheritedfromearlyversionsofBASIC(which,inturn,wasdesignedtobeintuitivelysimpleforbeginningprogrammerstounderstand,ratherthantowritelargecommercialapplications),itdidn’treallylenditselftowell-structuredorobject-orientedprograms.
C++,ontheotherhand,hasitsrootsintheANSIC++languagedefinition.Itisn’tcompletelyANSIcompliantforthesimplereasonthatMicrosoftfirstwroteitsC++compilerbeforetheANSIdefinitionhadbecomeofficial,butitcomesclose.Unfortunately,thishasledtotwoproblems.First,ANSIC++hasitsrootsinadecade-oldstateoftechnology,andthisshowsupinalackofsupportformodernconcepts(suchasUnicodestringsandgeneratingXMLdocumentation),andinsomearchaicsyntaxstructuresdesignedforthecompilersofyesteryear(suchastheseparationofdeclarationfromdefinitionofmemberfunctions).Second,MicrosofthasbeensimultaneouslytryingtoevolveC++intoalanguagethatisdesignedforhigh-performancetasksonWindows,andinordertoachievethatthey’vebeenforcedtoaddahugenumberofMicrosoft-specifickeywordsaswellasvariouslibrariestothelanguage.
TheresultisthatonWindows,thelanguagehasbecomeacompletemess.JustaskC++developershowmanydefinitionsforastringtheycanthinkof:
char*,LPTSTR,string,CString(MFCversion),CString(WTLversion),wchar_t*,OLECHAR*,andsoon.
Nowenter.NET—acompletelynewenvironmentthatisgoingtoinvolvenewextensionstobothlanguages.MicrosofthasgottenaroundthisbyaddingyetmoreMicrosoft-specifickeywordstoC++,andbycompletelyrevampingVisualBasicintoVisualBasic.NET,alanguagethatretainssomeofthebasicVBsyntaxbutthatissodifferentindesignthatwecanconsiderittobe,forallpracticalpurposes,anewlanguage.
It’sinthiscontextthatMicrosofthasdecidedtogivedevelopersanalternative—alanguagedesignedspecificallyfor.NET,anddesignedwithacleanslate.VisualC#.NETistheresult.Officially,MicrosoftdescribesC#asa“simple,modern,object-oriented,andtype-safeprogramminglanguagederivedfromCandC++.”Mostindependentobserverswouldprobablychangethatto“derivedfromC,C++,andJava.”Suchdescriptionsaretechnicallyaccuratebutdolittletoconveythebeautyoreleganceofthelanguage.Syntactically,C#isverysimilartobothC++andJava,tosuchanextentthatmanykeywordsarethesame,andC#alsosharesthesameblockstructurewithbraces({})tomarkblocksofcode,andsemicolonstoseparatestatements.ThefirstimpressionofapieceofC#codeisthatitlooksquitelikeC++orJavacode.Behindthatinitialsimilarity,however,C#isaloteasiertolearnthanC++,andofcomparabledifficultytoJava.Itsdesignismoreintunewithmoderndevelopertoolsthanbothofthoseotherlanguages,andithasbeendesignedtogiveus,simultaneously,theeaseofuseofVisualBasic,andthehigh-performance,low-levelmemoryaccessofC++ifrequired.SomeofthefeaturesofC#are:
❑Fullsupportforclassesandobject-orientedprogramming,includingbothinterfaceandimplementationinheritance,virtualfunctions,andoperatoroverloading.
❑Aconsistentandwell-definedsetofbasictypes.
❑Built-insupportforautomaticgenerationofXMLdocumentation.
❑Automaticcleanupofdynamicallyallocatedmemory.
❑Thefacilitytomarkclassesormethodswithuser-definedattributes.Thiscanbeusefulfordocumentationandcanhavesomeeffectsoncompilation(forexample,markingmethodstobecompiledonlyindebugbuilds).
❑Fullaccesstothe.NETbaseclasslibrary,aswellaseasyaccesstotheWindowsAPI(ifyoureallyneedit,whichwon’tbeallthatoften).
❑Pointersanddirectmemoryaccessareavailableifrequired,butthelanguagehasbeendesignedinsuchawaythatyoucanworkwithouttheminalmostallcases.
❑SupportforpropertiesandeventsinthestyleofVisualBasic.
❑Justbychangingthecompileroptions,youcancompileeithertoanexecutableortoalibraryof.NETcomponentsthatcanbecalledupbyothercodeinthesamewayasActiveXcontrols(COMcomponents).
❑C#canbeusedtowriteASP.NETdynamicWebpagesandXMLWebservices.
Mostoftheabovestatements,itshouldbepointedout,doalsoapplytoVisualBasic.NETandManagedC++.ThefactthatC#isdesignedfromthestarttoworkwith.NET,however,meansthatitssupportforthefeaturesof.NETisbothmorecomplete,andofferedwithinthecontextofamoresuitablesyntaxthanforthoseotherlanguages.WhiletheC#languageitselfisverysimilartoJava,therearesomeimprovements:
inparticular,Javaisnotdesignedtoworkwiththe.NETenvironment.
Beforeweleavethesubject,weshouldpointoutacoupleoflimitationsofC#.Theoneareathelanguageisnotdesignedforistime-criticalorextremelyhighperformancecode—thekindwhereyoureallyareworriedaboutwhetheralooptakes1,000or1,050machinecyclestorunthrough,andyouneedtocleanupyourresourcesthemillisecondtheyarenolongerneeded.C++islikelytocontinuetoreignsupremeamonglow-levellanguagesinthisarea.C#lackscertainkeyfacilitiesneededforextremelyhighperformanceapps,includingtheabilitytospecifyinlinefunctionsanddestructorsthatareguaranteedtorunatparticularpointsinthecode.However,theproportionsofapplicationsthatfallintothiscategoryareverylow.
二、databasedevelopmentprocess
Basedoninformationengineeringinformationsystemsplanningdatabaseisasourceofdevelopmentprojects.Thesenewdatabasedevelopmentprojectsisusuallyinordertomeetthestrategicneedsoforganizations,suchasimprovingcustomersupport,improveproductandinventorymanagement,oramoreaccuratesalesforecast.However,manymoredatabasedevelopmentprojectisthebottom-upapproachemerging,suchasinformationsystemuserneedsspecificinformationtocompletetheirwork,thusbeginningaprojectrequest,andasotherinformationsystemsexpertsfoundthatorganizationsneedtoimprovedatamanagementandbeginnewprojects.Bottom-upeveninthecircumstances,tosetupanenterprisedatamodelisalsonecessarytounderstandtheexistingdatabasecanprovidethenecessarydata,otherwise,thenewdatabase,dataentitiesandattributescanbeaddedtothecurrentdataresourcestotheorganization.
Boththestrategicneedsoroperationalinformationneedsofeachdatabasedevelopmentprojectsnormallyconcentratedinadatabase.Someprojectsonlyconcentratedinthedatabasedefinition,designandimplementationofadatabase,asafollow-uptothebasisofthedevelopmentofinformationsystems.However,inmostcases,thedatabaseandassociatedinformationprocessingfunctionasacompleteinformationsystemsdevelopmentprojectwaspartofthedevelopment.
1、SystemDevelopmentLifeCycle
Guidemanagementinformationsystemdevelopmentprojectsisthetraditionalprocessofsystemdevelopmentlifecycle(SDLC).SystemdevelopmentlifecycleisanorganizationofthedatabasedesignersandprogrammersinformationsystemcomposedofthePanelofExpertsdetaileddescription,development,maintenanceandreplacementoftheentireinformationsystemsteps.ThisprocessisbecauseWaterfallthanforeverystepintotheadjacentthenextstep,thatis,theinformationsystemisaspecificationdevelopedbyapieceofland,everypieceoftheoutputisunderaninput.Howevershowninthefigure,thesestepsarenotpurelylinear,eachofthestepsoverlapintime(andthuscanmanageparallelsteps),butwhentheneedtoreconsiderpreviousdecisions,butalsotorollbacksomestepsahead.(Andthereforewatercanbeputbackinthewaterfall!
)
Figure4onthesystemdevelopmentlifecycleandthepurposeofeachstageoftheproductcanbedeliveredconcisenotes.Thesystemdevelopmentlifecycleincludingeachstageanddatabasedevelopment-relatedactivities,therefore,thequestionofdatabasemanagementsystemsthroughouttheentiredevelopmentprocess.InFigure5werepeatofthesystemdevelopmentlifecyclestageoftheseven,andoutlinesthecommondatabaseateachstageofdevelopmentactivities.Pleasenotethatthesystemsdevelopmentlifecyclestagesanddatabasedevelopmentsteps一一existsbetweentherelationshipbetweentheconceptofmodelingdatainbothsystemsdevelopmentlifecyclestagesbetween.
EnterpriseModeling
Databasedevelopmentprocessfromtheenterprisemodeling(systemdevelopmentlifecyclestageoftheprojectfeasibilitystudies,andtochooseapart),Organizationssetthescopeandgeneraldatabasecontent.Enterprisemodelingininformationsystemsplanningandother
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