const修饰指针

   int b = 10; 
   int c = 15; 
   const int *p1 = &b; 
   //*p1 = 12; /* 错误 */
   p1 = &c; /* 正确 */
   cout << *p1 << endl;

   int * const p2 = &b; 
   *p2 = c; /* 正确 */                                                                      
   //p2 = &c; /* 错误 */
   cout << *p2 << endl;