C++第八章

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();
}