C++第八章

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1.#include <iostream>#include <cmath>using namespace std;double s(double,double,double);void main(){ double a,b,c,d,x1,x2; cout<<"输入a,b,c:"; cin>>a>>b>>c; d=-b/(2*a); x1=d+s(a,b,c); x2=d-s(a,b,c); cout<<"x1="<<x1<<endl; cout<<"x2="<<x2<<endl;}double s(double a,double b,double c){ double k; k=b*b-4*a*c; if(k<0) cout<<"此方程无实数根！"<<endl; else return sqrt(k)/(2*a);}

<img src="http://img.blog.csdn.net/20150618135138031" alt="" /><pre name="code" class="html">2. #include <iostream>#include <string>using namespace std;class Student{public:Student(int n,string nam){num=n;name=nam;}~Student(){cout<<"destructor"<<endl;}void show_data();private:int num;string name;};void Student::show_data(){ cout<<"num:"<<num<<endl; cout<<"name:"<<name<<endl;}void fun(){ Student s1(3907,"xiongxian"); s1.show_data();}int main(){cout<<"main begin"<<endl;cout<<"call fun()"<<endl;fun();cout<<"main end"<<endl;return 0;}

3. #include <iostream>#include <string>using namespace std;class Student{public:Student(int n,string nam,int a,string addr,char s,float sco){num=n;name=nam;age=a;address=addr;sex=s;score=sco;}void show_data();private:int num;string name;int age;string address;char sex;float score;};void Student::show_data(){ cout<<"num:"<<num<<endl; cout<<"name:"<<name<<endl; cout<<"age:"<<age<<endl; cout<<"address:"<<address<<endl; cout<<"sex:"<<sex<<endl; cout<<"score:"<<score<<endl;}int main(){ Student s1(1,"xiongxian",18,"nanchang",'F',100); s1.show_data();}

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