/*
 **************************************************************************
 * Program name : 050_what_is_pointer (Version 1.00)                      *
 * Author       : Duck Wong                                               *
 * Language     : C / C++                                                 *
 * Compiler     : Boodshed Dec-C++ compiler Ver 3.95                      *
 * Computer     : PII350                                                  *
 * O/S          : Windows 98                                              *
 **************************************************************************
 * Version 1.00 : 2000/07/01 - first version                              *
 **************************************************************************
 * Description  : (a) Input an integer number (1-10)                      *
 *                (b) Output the memory address and the value of Number   *
 *                (c) Input the values of all element in the array Values *
 *                (d) Output the memory address and elements of Values    *
 *                (e) Try again ?                                         *
 **************************************************************************
*/
#include <iostream.h>
#include <stdlib.h>

int main()
{
 // part 1 : declaration
 int   Number;
 int   *NumPointer;                                                  // Note (1)
 float Values[10];
 float *ValuesPointer;
 int   Index;
 char  Again;

 do {
     do {
         // part 2 : Input an integer number (1-10)
         cout << "\n\nPlease input an integer number (1-10) : ";
         cin  >> Number;
         NumPointer = &Number;                                       // Note (2)

         // part 3 : Output the memory address and value of variables
         cout << "\n\tVariables      \tMemory address\tContains"
              << "\n\t---------------\t--------------\t------------"
              << "\n\tNumPointer\t"  << &NumPointer << "\t" << NumPointer
              << "\n\tNumber\t\t"    << &Number     << "\t" << *NumPointer
              << "\n\t---------------\t--------------\t------------\n\n";
        } while (Number<1 || Number>10);
        system("PAUSE");

     // part 4 : Input the values of all element in the array Values
     ValuesPointer = Values;                                         // Note (3)
     cout << "\n\n\tPlease input " << Number << " real numbers : ";
     for (Index=0; Index<=Number-1; Index++)
       {
        cout << "\n\tReal numbers [" << Index+1 << "] :";
        cin  >> ValuesPointer[Index];    // same as "cin  >> Values[Index];"
       }


     // part 5 : Output the memory address and all elements of array Values
     cout << "\n\n\tMemory addresses:\tValues: ";
     for (Index=0; Index<=Number-1; Index++)
       {
        cout << "\n\n\t" << ValuesPointer
             << "\t\t" << *ValuesPointer;
        ValuesPointer++;                                             // Note (4)
       }

     // part 6 : try another number ?
     cout << "\n\n\tTry another number (Y/N) : ";
     cin  >> Again;
     cout << "\n";
    } while (Again=='Y' || Again=='y');
 cout << "\n" << endl;

 system("PAUSE");
 return 0;
}

/* Notes
   (1) A pointer is a variable that holds a memory address. Most comonly this
       address is the location of another variable in memory. A pointer
       declaration consists of a basic type , an *, and the variable name.

       syntex  :  type  *name
       example :  int   *NumPointer

   (2) (a) There are two pointer operators.

       Operator |Sample                |Function
       ---------|----------------------|----------------------------------------
       &        |&Number               |Returns the memory address of the
                |                      |variable Number
       ---------|----------------------|----------------------------------------
       *        |*NumPointer           |Returns the value of the variable locate
                |                      |at the address as stated by NumPointer
       ---------|----------------------|----------------------------------------

       (b) Since the pointer Numpointer is assigned to the memory location of
           the variable Number, therefore the result may be (if Number == 3):

           Variables       Memory address           Contains
           --------------- -----------------------  -------------------------
           NumPointer      0x254fda0 (&NumPointer)  0x254fda4 (NumPointer)
           Number          0x254fda4 (&Number)      3 (*NumPointer or Number)
           --------------- -----------------------  -------------------------

   (3) The pointer ValuesPointer is assigned to the memory location of the first
       element in the array Values (since refer to an array, so does not use &).
       For example :

         Memory addresses:       Values:
         0x254fdb8               12.3

   (4) Each time ValuePointer is incremented, it will point to the memory
       location of the next element in the array Values. For example :

         Memory addresses:       Values:
         0x254fdb8               12.3
         0x254fdbc               -6.356
         0x254fdc0               2.979
*/