Chapter4-ControlStructures-Repetition.ppt

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1、Copyright©2012PearsonEducation,Inc.Chapter4ControlStructures:RepetitionCopyright©2012PearsonEducation,Inc.OutlineObjectivesAlgorithmDevelopmentRepetitionStructuresProblemSolvingApplied:GPSDataC++breakandcontinueStatementsStructuringInputLoopsProblemSolvingApplied:WeatherBalloonsCopyright©2

2、012PearsonEducation,Inc.ObjectivesDevelopproblem-solvingsolutionsinC++containing:Repetitionstructuresthatallowustorepeatasetofstepsaslongasaconditionistrue.ThreecommonformsofinputloopsAlgorithmdevelopmentanddescriptionsofloopsusingflowchartsandpseudocode.AlgorithmDevelopmentCopyright©2012

3、PearsonEducation,Inc.Example:ComputingVelocityoveraRangeofTime.Sequentialstructuresarenotwellsuitedforcomputingthesamequantitiesrepeatedly.Flowchartsandpseudocodeareusefultodescriberepetition.Copyright©2012PearsonEducation,Inc.RepetitionStructuresCopyright©2012PearsonEducation,Inc.Thewhile

4、StatementCopyright©2012PearsonEducation,Inc.Syntax:while(boolean_expression)statement;while(boolean_expression){statement1;…statement_n;}Exampleswhile(!isspace(ch))cin.get(ch);//statementrepeateduntila//spacecharacterisreadwhile(x>y){//statementblockexecuted//whilex>0++cl;--x;}InfiniteLoo

5、psAninfiniteloopisoneinwhichtheloopconditionisalwaystrue.Selectiveexecutionofabreakstatementoraborting/exitingtheprogrammethodsofescapinganinfiniteloop.Copyright©2012PearsonEducation,Inc.AvoidingBugsWhenprogramminglongerprograms,itisnotuncommontohavealargenumberoferrormessagesfromthecomp

6、iler.Asingleerroroftencausesseveralerrorsasthecompilergets‘confused’overwhatfollowsanerror.Startcorrectingerrorsfromthetopoftheerrorlist,NOTthebottom.Recompileyourprogramfrequently,limitingtheplaceswhereerrorsmayoccur.Useendlindebuggingoutputstatementstobesurewhatyousendisactuallyseenonscr

7、een.Copyright©2012PearsonEducation,Inc.Thedo-whileStatementCopyright©2012PearsonEducation,Inc.Syntax:dostatement;while(boolean_expression);do{statement1;…statement_n;}while(boolean_expression);Examplesdocin.get(ch);//statementrepeateduntilanwhile(ch!=‘’)//ne