#include <iostream>
using namespace std;

int main()
{
	int *p = new int;   // allocate memory pointed by p
	*p = 3;
	cout << "address:" << p << "  content:" << *p << endl;

	delete p;   // delete it, memory area returned to the heap, 
                // but p still points to it. 
	*p = 20;    // however you can still manipulate the deleted memory area
	cout << "address:" << p << "  content:" 
         << *p << endl; // and this statement may display 20
	                    // but after deletion the pointer p is an address in available heap, 
	                    // so it should not be used

	p = NULL;           // however, if you make it NULL (zero)
	delete p;
	*p = 6;
	cout << *p << endl; // then you cannot access. That gives a run-time error.

	return 0;
}