//   
// Example 6.9. Program to print the digits of a    
// nonnegative input integer in reverse order   
//    
   
#include <iostream>

using namespace std;
   
int main()   
{   
   int readNum();   
   void printReverse(int num);   
   
   int num;             // nonnegative input integer 
   
   num = readNum();   
   printReverse(num);   
   
   return 0;
}   
   
//   
// Function to print instructions and repeatedly read   
// integers until the user enters a nonnegative integer,   
// which the function returns   
// Pre:  none   
// Post: A nonnegative integer has been returned.   
//    
   
int readNum()   
{   
   int num;             // nonnegative input integer 
   
   cout << "This program prints a nonnegative integer backwards." << endl << endl;
   
   do   
   {   
      cout << "Enter a nonnegative integer: ";
      cin  >> num;
   }   
   while (num < 0);   
   
   return num;   
}   
   

//
// Function to print the digits of a nonnegative integer
// in reverse order
// Pre:  num is a nonnegative integer.
// Post: The digits of num have been displayed in reverse order.
//

void printReverse(int num)
{
   int rightmostDigit; // rightmost digit of num

   cout << num << " backwards is ";
   do
   {
	rightmostDigit = num % 10;
	cout << rightmostDigit;
	num /= 10;   // move next digit into rightmost position
   }
   while (num > 0);

   cout << endl;
}