先看代码：

#include 
     
      using namespace std;int _tmain(int argc, _TCHAR* argv[]){    const  int a = 1;    int *p = const_cast
      
       (&a);    *p = 2;    cout << "value a="<< a << endl;    cout << "value *p=" <<*p << endl;    cout << "address a=" <<&a << endl;    cout << "address p=" <
       
<< endl;    return 0;}
      
     

输出结果：

value a=1

value *p=2

address a=0022FBC8

address p=0022FBC8

请按任意键继续. . .

采用volatile关键字，修改为：

#include 
     
      using namespace std;int _tmain(int argc, _TCHAR* argv[]){    const volatile int a = 1;    int *p = const_cast
      
       (&a);    *p = 2;    cout << "value a="<< a << endl;    cout << "value *p=" <<*p << endl;    cout << "address a=" <<&a << endl;    cout << "address p=" <
       
<< endl;    return 0;}
      
     

结果为：

value a=2

value *p=2

address a=1

address p=0042FDB8

请按任意键继续. . .