2023.4.12

//c++语言程序设计第二章习题
//2-4
#include <iostream>
using namespace std;
int main()
{
    const double PI = 3.1416;
    double a;
    a = PI;
    cout<<"a的值为："<<a<<endl;
    return 0;
}

 1 //c++语言程序设计第二章习题
 2 //2-11
 3 #include <iostream>
 4 using namespace std;
 5 int main()
 6 {
 7     int n =100;
 8     for(int n=100;n<=200;n+=2){}
 9     do{int n=100;n+=2;}while(n!=200);
10     while(n!=200){n+=2;}
11     return 0;
12 }

 1 //c++语言程序设计第二章习题
 2 //2-13
 3 #include <iostream>
 4 using namespace std;
 5 int main()
 6 {
 7     int x;
 8     int y;
 9     cout<<"请输入x,y的值"<<endl;
10     cin>>x>>y;
11     int temp;
12     if(x>y||x<y)
13     {
14         temp = y;
15         y = x;
16         x = temp;
17     }
18     cout<<"x = "<<x<<endl;
19     cout<<"y = "<<y<<endl;
20     return 0;
21 }

 1 //c++语言程序设计第二章习题
 2 //2-16
 3 #include <iostream>
 4 using namespace std;
 5 int main()
 6 {
 7     cout<<"int字节数为："<<sizeof(int)<<endl;
 8     cout<<"char字节数为："<<sizeof(char)<<endl;
 9     cout<<"float字节数为："<<sizeof(float)<<endl;
10     cout<<"double字节数为："<<sizeof(double)<<endl;
11     return 0;
12 }

 1 //c++语言程序设计第二章习题
 2 //2-17
 3 #include <iostream>
 4 using namespace std;
 5 int main()
 6 {
 7     int num = 0;
 8     for(int i=32;i<=127;i++)
 9     {
10         cout<<(char)i<<"\t";
11         num++;
12         if(num == 4)
13         {
14             num = 0;
15             cout<<endl;
16         }
17     }
18     return 0;
19 }