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SOFTWARE:DEVELOPMENT
ProgramPlanningandDevelopment StructuredDesign ProgrammingParadigm ProgrammingLanguage CompilersandInterpreters
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FiveStagesinProgramDevelopmentDefiningtheproblemDesigningasolutionWritingtheprogramCompiling,Debugging,andTestingtheprogramDocumentingtheprogram
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1st Stage:DefiningtheProblemrecognizetheneedforinformationdefinewhatoutputsarerequiredfromtheprogram
2nd Stage:DesigningaSolutionbreakingtheproblemintodiscretestepsknownasalgorithmuseflowcharttoillustratethesequenceofsteps
flowchart agraphicalrepresentationofthesequenceofoperationsacomputeristoperform
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FlowchartingTerminalGeneralInput/Output OperationProcessComparisonConnectorPredefinedProcessDocumentManualInput
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Example:PayrollFlowchartStart
Readhoursworkedandpayscale
Endofdata?
1
YES
CalculateEmployeesPay
Printcheck
1 Printreports Stop
NO
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PseudocodeA versionoftheinstructionsdescribingeachstepthecomputermustfollowExample:PayrollPseudocodeStartRead employee's hours worked and hourly wageDo until end of items
Multiply hours worked by hourly wage to get gross payIf gross pay is greater than 70KThen tax rate is 20%
Else tax rate is 15%Multiply tax rate by gross pay to give taxSubtract tax and union dues from gross to get net payPrint checkRead next employee's hours worked and hourly wage
End loop (no more data)Print reports
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3rd Stage:WritingaProgramWritetheprograminaspecificprogramminglanguageTypesofProgrammingStatements
CommentsDeclarationsInput/outputstatementsComputationsTransferofcontrolComparison
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QualitiesofaProgramEasytoreadandunderstandEfficientReliableRobustMaintainable
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4th Stage:Compiling,Debugging,andTestingtheProgram
A compilerisaspecialprogramforeachprogramminglanguageloadedintothecomputerwhenthatlanguageisusedCommonCompilationErrors
SpellingerrorsSyntaxerrorsImproperlysequencedstatementsImproperlylabeledstatementsConflictinvariablenamesIllegalnamesorstatementsMissingpunctuations
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LogicalerrorsaredetectedbytheprogrammerinadebuggingprocessTobesurethattheprogramwillgivethecorrectoutput,theprogramhastobetestedbyrunningtheprogramandinputtingdatawithknownoutputs
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5th Stage:DocumentationoftheProgramConsistsofwrittendescriptionsandexplanationsofprogramsandothermaterialsassociatedwithanorganizationsdataprocessingsystemServesasaguidetoprogrammersandanalystswhomustmodifyorupdateexistingprogramsandsystemproceduresOtherDescriptions
Acompletedescriptionofthecontentsandformatsofalldatainputs,outputsandfilestobeusedA statementofthehardwarerequirementsforrunningtheprogramaswellasestimatedprocessingtimeandstoragerequirementsA statementofsoftwarerequirementssuchasutilityprogramsandlibraryprograms
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EachmajorstepintheprogrammustbedevelopedasindependentmoduleandrepresentedintheflowchartasaseparateblockProgramcodeswillbeeasiertounderstandandmoremaintainableifyoubreakthelogicintosteps,andencompasseachstepinitsownsubroutineorfunctionBenefits
EarlydetectiondesignflawsProgramscanbeeasilymodifiedClearandcompletedocumentationModulardesigntoimprovetesting
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Topdownvs BottomupTopdown
Donebyrecognizingthemajorcomponentsofthesolution,expressingthesolutionasasequenceofthesemajorcomponents,andthenexpandingthemajorcomponentssimilarly
BottomupStartsbyidentifyingsmallfunctionsandsubroutinespresentinthedesignandmovinguptowardsmorecomplexprocedures
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UsingFlowchartsGenerallyinvolvesatopdownanalysisoftheproblemBasedontheassumptionthattherearefourbasiclogicpatterns
SimplesequenceSelectionpatternLooppatternBranchpattern
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SimpleSequence SelectionPattern
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LoopPattern BranchPattern
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DoWhileStructure CaseStructure
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ParadigmAnexample,model,orpatternAnidealizedpatternofusageunderwhichsomeagentcanoperate
ProgrammingParadigmA wayofthinkingaboutproblemsandtheirsolutions,oranapproachonhowtouseacomputertoimplementthosesolutions
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MajorProgrammingParadigmsImperativeLogicalFunctionalObjectOriented
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ImperativeParadigmCharacterizedbyprogrammingwithstatesandcommandsthatmodifythestatesImpliesprocedures(orprograms)ordirectionsforperforminganactionAnabstractionofrealcomputers,whicharebasedontheVonNeumannmachineAssumesthatacomputercanmaintain,throughenvironmentvariables,anychangeinthecomputationprocess
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AdvantageCanbeeasilytranslatedtoanefficientmachinecode,sotheyareconsideredhighlyefficient
DisadvantageSomeproblemsarehardtomodelusingthisparadigm
Example:ImperativeprogramthatwillcomputethefactorialofagivennumberFunction factorial(n){ var x = 1;
while(n>0) {x = x*n;n = n-1; }
return x;}
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LogicalParadigmTakesadeclarativeapproachtoproblemsolvingCanbedividedintothree(3)steps1. Aseriesofdefinitions/declarationsthatdefinethe
problemdomain2. Statementsofrelevantfacts3. StatementsofgoalsintheformofqueriesAdvantagesThesystemsolvestheproblemsoprogrammingstepsarekepttoaminimumSinceitislargelybasedonmathematicallogic,provingthevalidityofagivenprogrambecomessimple
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Example:Anillustrationofalogicalparadigm
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FunctionalParadigmBasedonfunctionalexpressionsandtheevaluationoftheseexpressionViewsallprogramsasfunctionsinamathematicalsenseAdvantages
Provideahighlevelofabstraction;theprogrammingbecomesmodularandremovesthepossibilityofcreatingseveralerrorsNotheavilydependentontheassignmentoperation,sotheprogramscanbeevaluatedwithmanydifferentordersMuchmoreamenabletomathematicalproofandanalysisthanimperativeones
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DisadvantagesHardtoimplementefficiently,becauseitishardtodetermineifdatastoragecanbereusableDifficulttosolveproblemsinvolvingmanyvariablesoralotofsequentialactivity
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Example:FactorialfunctionFactorial n = If n = 1 then 1Else
n * Factorial(n-1);
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Example:FunctionforcomputingtheaverageoftwonumbersFunction for computing the average of two
numbers:
(defun avg(X Y) (/ (+ X Y) 2.0))
Function is called by:> (avg 10.0 20.0)
Function returns:15.0
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ObjectOrientedParadigmA paradigminwhichrealworldobjectsareviewedasseparateentitieshavingtheirownstateandexhibitingtheirownbehaviorFocusesontheobjectsthattheprogrammerisrepresenting
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Illustratesobjectsandhowtheyareencapsulatedintomodules
Object interface
DATA Methods
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Canbedividedintofoursteps1. Identifytheproblem2. Identifytheobjectsneededforthesolution3. Identifymessagestobesenttotheobjects4. Createasequenceofmessagestotheobjectsthat
solvetheproblem
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Example:1. Problemidentification:Computerthesumoftwo
numbersandprintouttheresult2. Objectidentification:
Num1 firstnumber(object)Num2 secondnumber(object)Sum resultoftheadditionofthetwonumbers
3. Messageidentification:+aNum senttothereceiverobjectwithparameteraNumprint displaysthevalueofthereceiverobject
4. Objectmessagesequences:(Num1+Num2)print
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OtherProgrammingParadigmsTree
ViewingcodeordatainahighlyhierarchicalmannerExpertSystem
Organizesdatabyusingalistorpoolofrulesthataresometimesrecycledthroughconstantly
StreamBasedontheideathatinputandoutputofsmallerprogramsorutilitiescanbelinkedtogether
NeuralNetworkBasedontheconceptsthatcomputersareprogrammedinthesamewayashowhumansthink
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LanguageDefinedasasystemforcommunicationWrittenlanguageusesymbols(characters)tobuildwords
VocabularyReferstoentiresetofwords
SyntaxandGrammarDefinethewayinwhichthewordscanbemeaningfulwhencombined
SemanticsActualmeaningofwordsandcombinationsofwords
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MachineLanguageThelowestlevelofprogramminglanguageOnlylanguageunderstoodbycomputersandconsistsofpurenumbers;takestheformof1or0Eachmachineinstructionhastwo(2)parts:
Opcode(operationcode)Operand
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LowLevelLanguageAlsocalledasassemblylanguageEasiertounderstandthanmachinelanguage
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Programmersmustbehighlyskilledintwoareas:Mustknowagreatdealabouttheinternalworkingsofthemicroprocessor,andabroadtechnicalknowledgeofthecomputerisneededMustbeverydetailoriented;everystepofthecomputermustbecoded,andtheactualnumericaladdressoftheinstructionsanddatamustbespecified
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Example:Usingassemblylanguagetomultiply87and243andsavingtheresultinthememory
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HighLevelLanguageEnablesaprogrammertowriteprogramsthataremoreorlessindependentofaparticulartypeofcomputerClosertohumanlanguagethanthemachinelanguageEasiertounderstandandallowstheprogrammertofocusonsolvingtheproblemratherthanknowinghowtoprogramthecomputerExamples:Ada,Algol,BASIC,COBOL,C,C++,FORTRAN,LISP,Pascal,Prolog
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BASICBeginnersAllpurposeInstructionCodeDevelopedbyJohn Kemeny andThomas Kurtz intheearly1960sIntendedasaneasytolearninteractivelanguageforthestudentsAdvantages
SimplicityandflexibilityAllowsbasicmanipulationoftextProvidesbuiltinfunctionssuchaslogarithms,squareroot,trigonometricfunctions,andrandomnumbergenerator
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Example:UsingBASICprogramtomultiply87and243andprintingtheresult
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FORTRANFormulaTranslatorTheoldesthighlevelprogramminglanguageDevelopedinthemid1950sbyJohnBackusPrimarilyintendedasahighlevellanguageusedforprogrammingscientific,mathematical,andengineeringapplications
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AdvantagesProcedureorientedlanguagewithexcellentmathematicalcapabilitiesItspatternissimilartotheBASIClanguage;aprogrammerwhoisfamiliarwithFORTRANcaneasilywriteprogramsinBASIC
DisadvantagesCloselyresemblesmathematicalnotations,itisverydifficultfornonprogrammertounderstandorfindtheerrorsinaprogramNotsuitedasabusinessapplicationlanguageforitdoesnothavethecapabilitytodevelopprogramsthatinvolvefilemaintenance,editingofdata,ordocumentproduction
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Example:UsingFORTRANprogramtomultiply87and243andprintingtheresult
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COBOLCommonBusinessOrientedLanguagethemostfrequentlyusedbusinessprogramminglanguageusedextensivelyinbusiness,education,andgovernmentstartedintheearly1960swhenacommitteeledbyUSDepartmentofDefenseandothercomputerusersandmanufacturersknownasCODASYL(ConferenceofDataSystemsLanguages)wantedtodevelopacommonbusinessprogramminglanguageDr.GrayMurrayHopperwasamajorcontributortothestructureanddevelopmentofthelanguage
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AdvantagesEasytounderstandevenfornonprogrammersSelfexplanatoryandwelldocumentingGoodliterarycapabilitywhichmeansthatitisgoodinmanipulatingwords,sentences,orparagraphsoftextmaterialStrongfilehandlingcapabilitiesMachineindependent
DisadvantagesProgramstendtobewordyandquitelongLimitedcomputationalcapabilitieswhichmakesitinappropriateforapplicationsthatrequirecomputations
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Example:UsingCOBOLprogramtomultiply87and243andprintingtheresult
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PASCALThelanguagenamedaftertheseventeenthcenturyFrenchmathematicianBlaisePascalwhoconstructedoneofthefirstaddingmachinesA highlevellanguagedevelopedbyNiklaus WirthofZurich,Switzerlandinthelate1960sOneofthefirstlanguagesdevelopedusingastructuredprogrammingapproach
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CharacteristicsPascalprogramsconsistofmodules,andeachmoduleperformsaspecificfunctionThestatementsinthemodulecanbeorganizedintolevels,andthelevelofthestatementisshownbyitsdegreeofindentionfromthemargintofollowtheprogramlogiceasilyStatementsinaPascalprogramarecomposedofreservedwords,symbols,andidentifiersReservedwordsarewordsthathaveaspecialmeaningtothePascalcompilerSymbolsusedinPascalincludemathematicalsymbolsandpunctuationmarksIdentifiersarenamesthatrepresentvariousconstants,variables,procedures,orfunctions
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AdvantagesRelativelyeasytolearnPowerfulandefficientlanguageStronggraphicscapabilities
DisadvantagesNotasstandardasCOBOLorBASICPoorinputandoutputcapabilitiesLimitedfilehandlingcapabilitiesDoesnotpossesstheabilitytomanipulatelargecollectionofnumbersorwords
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Example:UsingPASCALprogramtomultiply87and243andprintingtheresult
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CLanguageA highlevelprogramminglanguagedevelopedbyDennisRitchieattheBellLaboratoriesin1972NamedC,becauseitwasinfluencedbyanotherlanguagecalledBdevelopedbyKenThompsonOriginallydesignedasasystemsprogramminglanguageusedtowriteoperatingsystemsprograms
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AdvantagesAllowsdirectmanipulationofbits,bytesandwordsthataresimilartoassemblylanguageUsefulfornumerical,textprocessing,anddatabaseprogramsVerygoodgraphicsprogrammingcapabilities
DisadvantagesNotintendedasalanguagefornonprogrammers,unlikeBASICandCOBOL;ifyouarenotfamiliarwiththelanguage,youwillnotunderstandthestructure
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Example:UsingCprogramtomultiply87and243andprintingtheresult
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C++LanguageDevelopedbyBjarne Stroustrup whileworkingattheBellLaboratoriesConsideredasupersetofC,andhasthesamecapabilitiesasCwithaddedobjectorientedfeaturesExample:UsingC++programtomultiply87and243andprintingtheresult
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JAVALanguagepopularprogramminglanguageforcreatingapplicationsontheWebOak,wasdevelopedinDecember1990bySunMicrosystemsReasonstoUseJava
SimpleandfamiliarObjectorientedArchitectureneutralPortableDistributedSecure
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CompilerA programthattranslatesaprogramwritteninahighlevellanguageandtranslatesitintomachinelanguageAdvantages
CompiledmachinecodesrunmuchfasterthaninterpretedonesCompiledcodesoccupylessmemoryduringexecutionOnceaprogramiscompileditcanbererunanytime
DisadvantagesTheprogramcanonlybeexecutedoncethetranslationiscompleteAnychangetothesourcecoderequiresacompleterecompilation
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InterpreterTranslatesandexecutestheprogramlinebylineTranslateshighlevelinstructionsintoanintermediateform,whichitthenexecutesAdvantages
FasterandeasiertodetecterrorsintheinterpretedprogramthanthecompiledprogramEasierandfastertomakechangestotheprogramwhichreducesdevelopmenttimeespeciallyforlargeprograms
DisadvantagesUsesmorememoryandmuchslowerthancompiledcodesNocopyofthetranslatedcodeexist;ifyouwanttoreruntheprogramitmustbeinterpretedalloveragain
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