/*
 * A new version of our interest rate program that compounds interest
 * monthly, rather than yearly.
 */
#include <stdio.h>
#include <stdlib.h>

int main()
{
  double yearEndBalance(double monthly_bal,
                        double interest_rate);

  int     period;                       /* length of period */
  int     year;                         /* year of period */
  double  balance;                      /* balance at end of year */
  double  intrate;                      /* interest rate */

  printf("Enter interest rate, principal, and period: ");
  scanf("%lf %lf %i", &intrate, &balance, &period);

  printf("Interest Rate:      %7.2f%%\n", intrate * 100);
  printf("Starting Balance: $ %7.2f\n", balance);
  printf("Period:             %7i years\n\n", period);
  printf("Year     Balance\n");

  for (year = 1; year <= period; year = year + 1)
  {
    balance = yearEndBalance(balance, intrate);
    printf("%4i   $ %7.2f\n", year, balance);
  }

  return EXIT_SUCCESS;                  /* assume program succeeded */
}

/* Compute a year's ending balance, compounding interest monthly */

double yearEndBalance(double monthly_bal,
                      double interest_rate)
{
  double  monthly_intrate;              /* % interest per month */
  int     month;                        /* current month */

  monthly_intrate = interest_rate / 12;
  for (month = 1; month <= 12; month = month + 1)
    monthly_bal = monthly_bal * monthly_intrate + monthly_bal;

  return monthly_bal;
}