#include <iostream>#include <iomanip>using namespace std;int main() //main函数可以不要void{    int a;    float b;    double c;    //最基本的输入，不需要 %d之类的转换说明    cin >> a >> b >> c;    cout << a << ‘ ‘ << b << ‘ ‘ << c << ‘\n‘;    //保留两位小数    a = 3;    b = 54.6f;    c = 1.67895;    cout << fixed << setprecision(2) << a << ‘ ‘ << b << ‘ ‘ << c << ‘\n‘;    //宽度    cout << setw(8) << a << ‘\n‘;    return 0;}

 1 #include <iostream> 2 #include <string> 3 using namespace std; 4 struct Student {           //声明结构体类型Student 5     string name; 6     int num; 7     char sex; 8 }; 9 10 int main()11 {12     Student *p; //定义指向结构体类型Student的数据的指针变量13     p = new Student; //用new运算符开辟一个存放Student型数据的空间14     p->name = "Wang Fun";  //向结构体变量的成员赋值15     p->num = 10123;16     p->sex = ‘m‘;17     cout << p->name << endl << p->num18          << endl << p->sex << endl; //输出各成员的值19     delete p;//撤销该空间20     return 0;21 }

 1 #include <iostream> 2 #include <iomanip> 3 using namespace std; 4  5 void swap(float &a, float &b) //此处的引用a 被认为是main函数a的别名 6 { 7     float temp; 8     temp = a; 9     a = b;10     b = temp;11 }12 13 int main(void)14 {15     float  a, b;16     cin >> a >> b;17     swap(a, b);18     cout << a << ‘ ‘ << b << endl;19     return 0;20 }