小编use*_*112的帖子

class Student{
public:
Student(int test)
:key(705)
{
    if(test == key)
    {cout << "A student is being verified with a correct key: "<< test << endl;
    allow=1;
    }
    else
    {
        cout << "Wrong key" ;
    }
}

friend void printResult();


private:
const int key;
int allow;


};

void printResult()
{
 if(allow==1)
 {
   cout<< " Maths: 75 \n Science:80 \n English: 75" << endl;
  }
}

int main()
{
int testkey;
cout << "Enter key for Bob: ";
cin >> testkey;

Student …

为什么这没有任何错误？

int array[2];
array[5] = 21;
cout << array[5];

打印出21就好了.但看看这个!我改变了5到46,它仍然有效.但是当我放47时,它没有打印任何东西.在任何地方都没有显示任 那是怎么回事!？!？