example

// *************************
//HW4prj5.cpp
//
//Author: Evan Anderson
//Created: 9/03/2013
//*************************

#include <iostream>
using namespace std;

double calcInflationRate(double, double);
double calcFutureCost(double, double);

int main() {
    double oldPrice, newPrice, inflationRate, futurePrice; //Define the variables
    char doAgain = 'y';

    while(doAgain == 'y' || doAgain == 'Y') {

        cout << "Enter the price of the item from 1 year ago: ";
        cin >> oldPrice;
        cout << "Enter the current price of the item: ";
        cin >> newPrice;

        inflationRate = calcInflationRate(oldPrice, newPrice);
        futurePrice = calcFutureCost(newPrice, inflationRate);

        cout.setf(ios::fixed);
        cout.setf(ios::showpoint);
        cout.precision(1);
        cout << "\nThe inflation rate was calculated to be " << inflationRate * 100 << "%";
        cout.precision(2);
        cout << "\nThe item will cost $" << futurePrice << " in one year";
        cout << "and $" << calcFutureCost(futurePrice, inflationRate) << " in two years";

        cout << "\n\nWould you like to repeat the calculation? (y or n): ";
        cin >> doAgain;
    }
        return 0;
}

double calcInflationRate(double oldPrice, double newPrice) {
        return ((newPrice-oldPrice) / oldPrice);
}

double calcFutureCost(double currentPrice, double inflationRate) {
        return (inflationRate * currentPrice) + currentPrice;
}