首先我们知道任何变量都有左值和右值，分别对应变量的内存区域和内存区域中的值

引用其实就是变量的别名，其实是一个东西有两个名吧

定义方式 类型 &引用名 = 变量名 而且必须定义的时候就初始化，不然是错误的

看个例子吧

1 #include
     
       2 using namespace std; 3  4 int main() 5 { 6     int i = 9; 7     int *p = &i; 8     int &ir = i; 9     cout << &i << " " << &ir << " " << p << endl;10     11     cout << i << " " << *p << " " << ir << endl;12     cout << &i << " " << &ir << " " << p << endl;13     14     *p = 3;15     cout << i << " " << *p << " " << ir << endl;16     cout << &i << " " << &ir << " " << p << endl;17     18     ir = 8;19     cout << i << " " << *p << " " << ir << endl;20     cout << &i << " " << &ir << " " << p << endl;21     22     i = 99;23     cout << i << " " << *p << " " << ir << endl;24     cout << &i << " " << &ir << " " << p << endl;25     26     int *p2 = &ir;27     cout << i << " " << *p << " " << ir << " " << *p2 << endl;28     29     *p2 = 666;30     cout << &i << " " << &ir << " " << p << " " << p2 << endl;31     cout << i << " " << *p << " " << ir << " " << *p2 << endl;32     cout << &i << " " << &ir << " " << p << " " << p2 << endl;33     return 0;34 }