C++面向对象程序设计双语教程（第3版）课件 class 1-Introduction

ObjectivesTounderstandwhatacomputerprogrammingisToknowhowtowriteaprogramTorecognizetwoprogrammingmethodologies01HowtoWriteaProgram?02Two

ProgrammingMethodologies01HowtoWriteaProgram?WhatisProgramming?Problem(orTask):Abouta

student’sgradesRequirements:Astudentlearnstwocoursesatthisterm,thatis,OOP,math.Youneedtoinputtwogradesdisplaytwogradesdisplaymessagescondition:agrade<60,displaymessages“youfailedxxx”;otherwise,displaymessage“youpassedxxx”Calculatethesumoftwogradesandaverage,anddisplayresultsCaseStudy1ComputerProgramming–planningorschedulingtheperformanceofataskoraproblem,thatis,itisaprocessthatleadsfromoriginalcomputingproblemtoexecutablecomputerprogram.HowtoWriteaProgram?Phase1:Problem-solving-planningtheprocessoftask(1)Inputtwogrades;(2)Displaythesetwogrades;(3)Ifoneoftwogradesislessthan60,display“youfailedxxx”,otherwisedisplay“youpassedxxx”(4)Calculatethesumoftwogradesandaverage;(5)Displaytheresults.PseudocodeStep1.AnalysisandspecificationHowtoWriteaProgram?Step2.Generateanalgorithmbyusingaflowchart

gradeOfOPP<60yesnoinputgradeOfOPP,gradeOfMathoutputsum,averageStartEndgradeOfMath<60sum=gradeOfOPP+gradeOfMathoutputgradeOfOPP,gradeOfMathoutput“youpassedOPP”yesnooutput“youfailedOOP”output“youfailedMath”output“youpassedMath”average=sum/2Algorithm:astep-by-stepprocedureforsolvingaproblem.Step3.VerifyHowtoWriteaProgram?Step1.Youmightconsidersomequestionsinthecontextofprogramming.1.WhatdoIhavetoworkwith–thatis,whatismydata?gradeOfOOP,gradeOfMath,sum,average2.Whatdothedataitemslooklike?–data

types,int,double3.HowwillIknowwhenIhaveprocessedallthedata?–algorithm4.Howmanytimesistheprocessgoingtoberepeated?-structure5.Whatshouldmyoutput

looklike?6.Whatspecialerrors

mightcomeup?Phase2:Implementation–writeaprogramHowtoWriteaProgram?Step2.TranslatethealgorithmtoaprogramwithCStep3.Testtheprogram#include

<stdio.h>intmain(){intgradeOfOOP,gradeOfMath,sum;floataverage;scanf("%d%d",&gradeOfOOP,&gradeOfMath);printf("OOP:%dMath:%d\n",gradeOfOOP,gradeOfMath);if(gradeOfOOP<60) printf("youfailedOOP\n");else printf("youpassedOOP\n");if(gradeOfMath<60) printf("youfailedMath\n");else printf("youpassedMath\n");sum=gradeOfOOP+gradeOfMath;average=(float)sum/2;printf("sum%daverage%6.2f\n",sum,average);return0;}(1)Input:50,69(2)Input:85,55(3)Input:80,69HowtoWriteaProgram?Phase3:Maintenance(维护)–Modifytheprogramtomeetchangingrequirementsorcorrecterrors.#include

<stdio.h>intmain(){intgradeOfOOP,gradeOfMath,sum;floataverage;scanf("%d%d",&gradeOfOOP,&gradeOfMath);printf("OOP:%dMath:%d\n",gradeOfOOP,gradeOfMath);if(gradeOfOOP<60) printf("youfailedOOP\n");else printf("youpassedOOP\n");if(gradeOfMath<60) printf("youfailedMath\n");else printf("youpassedMath\n");sum=gradeOfOOP+gradeOfMath;average=(float)sum/2;printf("sum%daverage%6.2f\n",sum,average);return0;}Whaterrorsmightcomeup？

Formanystudents?Practice-orientedHowtoWriteaProgram?Phase1:Problem-solving:(1)analysisandspecification(2)generatesolution(algorithm)(3)verificationPhase2:Implementation:(1)concretesolution(writingprogram)(2)testPhase3:Maintenance:

(1)reuse

(2)maintainWritingaprogramhasthethree-phaseprocess02ProgrammingMethodologiesProgrammingMethodologies1.thestructuredprogramming(modular,procedural)e.g.C/C++,Pascal2.theobject-orientedprogramming(OOP)e.g.C++,Java,C#Abstractioniscrucialtobuildingthecomplexsoftwaresystems.Dataabstractioncanbesummedupasconcentratingontheaspectsrelevanttotheproblemandignoringthosethatarenotimportantatthemoment.DataAbstractionTwopopularmethodologiestoprogrammingStructuredProgrammingProblem:solveaquadraticequationDatavariables:a,b,c,root1,root2Datatype:float/doubleInputdata:a,b,cOutputdata:root1,root2Algorithm:

Problem-solvingCaseStudy2StructuredProgrammingImplementation#include

<stdio.h>#include

<math.h>intmain(){floata,b,c;floatroot1,root2;printf("Enterthevaluesofa,bandc:\n");scanf("%f%f%f",&a,&b,&c);if(fabs(a)<=1e-6||fabs(b)<=1e-6) printf("theequationhasnorealroots!\n");else{floatdisc=b*b-4*a*c;if(disc<0)printf("theequationhasnorealroots\n");if(disc==0){root1=root2=-b/(2*a);printf("therootis%6.2f",root1);}if(disc>0){root1=(-b+sqrt(disc))/(2*a);root2=(-b-sqrt(disc))/(2*a);printf("therootis%6.2fand%6.2f",root1,root2); }}return0;}StructuredProgramming#include

<stdio.h>#include

<math.h>>boolquadratic(float

a,float

b,float

c,float*root1,float*root2){if(fabs(a)<=1e-6||fabs(b)<=1e-6)return

false;else{floatdisc=b*b-4*a*c;if(disc<0)return

false;if(disc==0){*root1=*root2=-b/(2*a);return

true;}if(disc>0){*root1=(-b+sqrt(disc))/(2*a);*root2=(-b-sqrt(disc))/(2*a);return

true;}}}intmain(){float_a,_b,_c;float_root1,_root2;printf("Enterthevaluesofa,bandc:\n");scanf("%f%f%f",&_a,&_b,&_c);if(quadratic(_a,_b,_c,&_root1,&_root2))printf("therootsare%6.2fand%6.2f",_root1,_root2);elseprintf("theequationhasnorealroot.\n");return0;}Dividingaproblemintosmallersub-problemsiscalledstructureddesign.Thisprocessofimplementingastructureddesigniscalledstructuredprogramming.StructuredProgrammingStructuredProgrammingDividingaproblemintosmallersub-problems.Eachsub-problemisthenanalysed,andasolutionisobtainedtosolvethesub-problem.Thesolutionstoallsub-problemsarecombinedtosolvetheoverallproblem.Characteristics:Top-downdesign,stepwiserefinementandmodularprogrammingBenefit:improvingtheclarity,quality,anddevelopmenttimeofa

computerprogram.StructuredProgrammingquadratic(…){a,b,c,root1,root2}intmain(){……}(function)(function1)(function2)float_a,_b,_c,_root1,root2StructuredProgrammingProblem:Student’sgrades(1)Inputtwogrades;(2)Displaythesetwogrades;(3)Ifoneoftwogradesislessthan60,display“youfailedxxx”,otherwisedisplay“youpassedxxx”(4)Calculatethesumoftwogradesandaverage;(5)Displaytheresults.MainfunctionInputgradeoutputgradeDisplaypassMCalculationsum_averageoutputsum_averageCaseStudy1Object-OrientedProgramming(OOP)#include

<stdio.h>#include

<math.h>class

quadratic_equation{public:quadratic_equation(float

aa,float

bb,float

cc):a(aa),b(bb),c(cc){}boolquadratic(float*root1,float*root2){if(fabs(a)<=1e-6||fabs(b)<=1e-6)return

false;else{floatdisc=b*b-4*a*c;if(disc<0)return

false;if(disc==0){*root1=*root2=-b/(2*a);return

true;}if(disc>0){*root1=(-b+sqrt(disc))/(2*a);*root2=(-b-sqrt(disc))/(2*a);return

true;}}}private:floata,b,c;};class,auser-defineddatatypeintmain(){float_a,_b,_c;float_root1,_root2;printf("Enterthevaluesofa,bandc:\n");scanf("%f%f%f",&_a,&_b,&_c);quadratic_equationqe(_a,_b,_c);if(qe.quadratic(&_root1,&_root2))printf("therootsare%6.2fand%6.2f",_root1,_root2);elseprintf("theequationhasnorealroot.\n");return0;}Themethodofobjectqeintmain(){float_a,_b,_c;float_root1,_root2;printf("Enterthevaluesofa,bandc:\n");scanf("%f%f%f",&_a,&_b,&_c);if(quadratic(_a,_b,_c,&_root1,&_root2))printf("therootsare%6.2fand%6.2f",_root1,_root2);elseprintf("theequationhasnorealroot.\n");return0;}Usingobjectsandtheirinteractions(methods)todesignprogramsiscalledOOdesign.ThisprocessofimplementinganOOdesigniscalled

OOprogramming.ObjectsObject-OrientedProgramming(OOP)qe1qe2qe4qe3MainfunctionObject-OrientedProgramming(OOP)Object-orientedprogramming(OOP