/* cintrest.c - lasketaan korkoa korolle */
#include <stdio.h>
 
void prn_instructions();
void prn_results(double amount, double interest_rate,
                 int nyears, double principal);
double compute(double interest_rate,
               int nyears, double principal);
 
main()
{
  int nyears;
  double amount,
         interest_rate,
         principal;
 
  prn_instructions();
  printf(" Anna paaoma, korko, vuosien lukumaara: ");
  scanf("%lf%lf%d", &principal, &interest_rate, &nyears);
  amount = compute(interest_rate, nyears, principal);
  prn_results(amount, interest_rate, nyears, principal);
}
 
void prn_instructions()
{
  printf("\n%s\n%s\n%s\n%s\n%s\n%s\n%s\n",
     "Tama ohjelma laskee korkoa korolle vuosittain, kun",
     "paaoma, korko, vuosien lukumaara on annettu.",
     "Esimerkiksi kun halutaan laskea korko",
     "1000 euron talletuksella,",
     "jonka korko on 4.5% ja talletusaika 15 vuotta",
     "on annettava:",
     "  1000.0  0.045  15");
}
 
void prn_results(double amount, double interest_rate,
        int nyears, double principal)
{
  printf("\n%s%g%s\n%s%d%s\n\n",
    "       Korko: ", 100.0 * interest_rate, "%",
    "Talletusaika: ", nyears, " vuotta");
  printf("%s%9.2f\n%s%9.2f\n%s%9.2f\n\n",
    " Paaoma jakson alussa: ", principal,
    "        Paaoman kasvu: ", amount - principal,
    "Paaoma jakson lopussa: ", amount);
}
 
double compute(double interest_rate,
               int nyears, double principal)
{
  int i;
  double amount;
 
  amount = principal;
  for (i = 1; i <= nyears; ++i)
    amount *= 1.0 + interest_rate;
  return (amount);
}