C++二级指针

#include<iostream>
using namespace std;
int main(void) {
  int room0 = 666;
  cout << "room0: " << room0 << endl;
  cout << "&room0: " << &room0 << endl;
  int *room1 = &room0;//room1=&room0
  cout <<"room1: " << room1 << endl;//room1=&room0=666
  cout << "&room1: " << &room1 << endl;//&room1
  cout<<"*room1:" << *room1 << endl;//*room1=room0
  int *room2 = room1;
  cout<<"room2: " << room2 << endl;//room2=room1;
  cout << "&room2: " << &room2 << endl;//&room2
  cout<<"*room2: " << *room2 << endl;//*room2=*room1=room=666
  int** room3 = &room2;//room2=&room1 
  cout << "room3: " << room3 << endl;//room3=&room2
  cout << "&room3: " << &room3 << endl;//&room3
  cout << "*room3: " << *room3 << endl;//*room3=room2=room1=&room0
  cout << "**room3: " << **room3 << endl;//**room3=&room2
                                         //*room3=room2=&room1
                                         //room3=room1=&room0=666
                                         //room3=666
  system("pause");
  return 0;
}