C语言程序设计现代方法课件.ppt

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1、Chapter5SelectionStatements1Copyright©2008W.W.Norton&Company.Allrightsreserved.StatementsSofar,we’veusedreturnstatementsandexpressionstatements.MostofC’sremainingstatementsfallintothreecategories:Selectionstatements:ifandswitchIterationstatements:while,do,andforJumpstatements:break

2、,continue,andgoto.(returnalsobelongsinthiscategory.)OtherCstatements:CompoundstatementNullstatementCopyright©2008W.W.Norton&Company.Allrightsreserved.2LogicalExpressionsSeveralofC’sstatementsmusttestthevalueofanexpressiontoseeifitis“true”or“false.”Forexample,anifstatementmightneedt

3、otesttheexpressioni

4、atorsC’srelationaloperators:greaterthan<=lessthanorequalto>=greaterthanorequaltoTheseoperatorsproduce0(false)or1(true)whenusedinexpressions.Therelationaloperatorscanbeusedtocompareintegersandfloating-pointnumbers,withoperandsofmixedtypesallowed.Copyright©2008W.W.Norton&Co

5、mpany.Allrightsreserved.4RelationalOperatorsTheprecedenceoftherelationaloperatorsislowerthanthatofthearithmeticoperators.Forexample,i+j

6、

7、rators:==equalto!=notequaltoTheequalityoperatorsareleftassociativeandproduceeither0(false)or1(true)astheirresult.Theequalityoperatorshavelowerprecedencethantherelationaloperators,sotheexpressioni

8、gicalOperatorsMorecomplica