#include <iostream>
using namespace std;

void main(){
   int x = 3, y;

   // show address of x
   cout << &x << endl;

   // declare a pointer
   int *p;
   p = &x;
   cout << p << endl;

   // access x via pointer
   // "*p" is said to be a dereference
   cout << *p << endl;

   // change x via the pointer
   *p = 42;
   cout << x << endl;

   // put x into y
   y = *p;
   cout << y << endl;

   // declare a second pointer
   int *q;
   q = p;
   cout << q << endl;
   cout << *q << endl;

   // type mismatch
   // int z = p;  will not compile
   // int *z = p; // z gets the address of x
   // int z = *p; // z gets the value of x

   // create a pointer to the address of p
   int **z = &p;
   cout << z << endl; // address of p
   cout << &p << endl;
   cout << *z << endl; // address x
   cout << **z << endl; // value of x

   // create an invalid pointer
   p = 0;

   // not allowed
   //cout << *p << endl;

   // reinitialize pointer p to a heap location
   p = new int(9);
   if(p != 0)
	   cout << "successful allocation\n";
   cout << p << endl; // address very different
   cout << *p << endl;// p points to heap
   delete(p); 
   // do not dereference deleted memory
   cout << *p << endl;// bad idea
   p = 0;// invalidate pointer
   //cout << *p << endl;
   p = new int(77);// do a new allocation
   cout << *p << endl;
   delete(p);

   // allocate infinite memory
   for(int i=0; true; i++)
	   p = new int();// memory leak - no delete
}