C程序设计第七章函数.ppt

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1、Chapter7-FunctionsOutline7.1Introduction7.2ProgramModulesinC7.3MathLibraryFunctions7.4Functions7.5FunctionDefinitions7.6FunctionPrototypes7.7HeaderFiles7.8CallingFunctions:CallbyValueandCallbyReference7.9RandomNumberGeneration7.10Example:AGameofChance7.11StorageClasses7.12ScopeR

2、ules7.13Recursion7.14ExampleUsingRecursion:TheFibonacciSeries7.15Recursionvs.Iteration17.1IntroductionDivideandConquer——分而治之ConstructaprogramfromsmallerpiecesorcomponentsEachpiecemoremanageablethantheoriginalprogram函数是一段完成特定任务的程序。2模块化程序设计基本思想：将一个大的程序按功能分割成一些小模块特点：各模块相对独立、功能单一、结构

3、清晰、接口简单控制了程序设计的复杂性提高元件的可靠性缩短开发周期避免程序开发的重复劳动易于维护和功能扩充开发方法:自上向下，逐步分解，分而治之3C程序结构C是函数式语言必须有且只能有一个名为main的主函数C程序的执行总是从main函数开始，在main中结束函数不能嵌套定义,可以嵌套调用C是模块化程序设计语言47.2ProgramModulesinCFunctionsModulesinCProgramswrittenbycombininguser-definedfunctionswithlibraryfunctionsCstandardlibraryh

4、asawidevarietyoffunctionsMakesprogrammer'sjobeasier-avoidreinventingthewheel57.2ProgramModulesinC(II)Functioncalls——函数调用Invokingfunctions——调用函数Providefunctionnameandarguments(data)FunctionperformsoperationsormanipulationsFunctionreturnsresultsBossasksworkertocompletetaskWorkerge

5、tsinformation,doestask,returnsresultInformationhiding:bossdoesnotknowdetails67.3MathLibraryFunctionsMathlibraryfunctionsperformcommonmathematicalcalculations#includeFormatforcallingfunctionsFunctionName(argument);Ifmultiplearguments,usecomma-separatedlistprintf("%.2f",sq

6、rt(900.0));Callsfunctionsqrt,whichreturnsthesquarerootofitsargumentAllmathfunctionsreturndatatypedoubleArgumentsmaybeconstants,variables,orexpressions77.4FunctionsFunctionsModularizeaprogramAllvariablesdeclaredinsidefunctionsarelocalvariables（局部变量）KnownonlyinfunctiondefinedParam

7、etersCommunicateinformationbetweenfunctionsLocalvariablesBenefitsDivideandconquerManageableprogramdevelopmentSoftwarereusabilityUseexistingfunctionsasbuildingblocksfornewprogramsAbstraction-hideinternaldetails(libraryfunctions)Avoidscoderepetition87.5FunctionDefinitionsFunctiond

8、efinitionformatreturn-value-typefunction-name(p