Before start the program, see the recursion function of 'backwardNums' in Self-Test Exercise 3. Now need to convert from recursive function to iterative function.

Iterative function of 'backwardNums':

//Recursive function of backwardNums:
//It takes one parameter, which is a positive integer. 
//When called, the function writes its argument to the screen backward.
void backwardNums(int number)
{
    while (number >= 10)
    {
         cout << (number%10);
          number = number/10;
    }
    cout << number;
}

Complete program by using above Iterative method:

//Header section
#include <iostream>
using namespace std;
//Function prototype
void backwardNums(int n);

//main program
int main( )

{
    //Call the method
    cout<<"If the argument is 1234,then the output: ";
    backwardNums(1234);

    return 0;
}
//Iterative function of backwardNums:
//It takes one parameter, which is a positive integer. 
//When called, the function writes its argument to the screen backward.
void backwardNums(int number)
{
    while (number >= 10)
    {
         cout << (number%10);
          number = number/10;
    }
    cout << number;
}

Output of the program: