/* Filename:  pointers.cpp

   Author:  Br. David Carlson

   Date:  July 29, 1998

   Last Revised:  December 1, 2001

   This program places a few values into integer and pointer variables
   and then prints their values.  It illustrates simple uses of
   pointers.

   Tested with:
      Microsoft Visual C++ 6.0
      Microsoft Visual C++ .NET
      g++ under Linux
*/

#include <iostream>
using namespace std;


typedef int * IntPtrType;


int main(void)
   {
   IntPtrType NumPtr;
   int AgeOfMary, AgeOfBill; 

   AgeOfMary = 19;
   AgeOfBill = 21;

   NumPtr = &AgeOfMary;  // get address of the AgeOfMary variable
   cout << "After setting NumPtr to point to AgeOfMary, NumPtr is "
      << NumPtr << endl;
   cout << "NumPtr points to " << *NumPtr << endl;
   cout << "AgeOfMary is " << AgeOfMary << endl
      << "AgeOfBill is " << AgeOfBill << endl << endl;

   NumPtr = &AgeOfBill;
   cout << "After moving NumPtr to point to AgeOfBill, NumPtr is "
      << NumPtr << endl;
   cout << "NumPtr points to " << *NumPtr << endl;
   cout << "AgeOfMary is " << AgeOfMary << endl
      << "AgeOfBill is " << AgeOfBill << endl << endl;

   *NumPtr = 22;
   cout << "After changing *NumPtr, NumPtr is " << NumPtr << endl;
   cout << "NumPtr points to " << *NumPtr << endl;
   cout << "AgeOfMary is " << AgeOfMary << endl
      << "AgeOfBill is " << AgeOfBill << endl << endl;

   NumPtr = NULL;
   cout << "After changing NumPtr to NULL, NumPtr is " << NumPtr << endl;
   cout << "We cannot print *NumPtr as NumPtr is NULL" << endl;
   cout << "AgeOfMary is " << AgeOfMary << endl
      << "AgeOfBill is " << AgeOfBill << endl << endl;

   return 0;
   }