// Compound Interest Calculator
// By: Chris Benard
// Free to distribute, delete, change, anything

// Including Libs

#include <stdio.h>
#include <stdlib.h>

// Defining all needed number variables as floating

float inter, compinter, x, princ, yrs, orig, temp, realint;

// Defining enters as a string

char *enters="";

void main(int argc, char *argv[]) {

// Checks to see if one of the arguments is a form of help...if so
// give help and exit.

  if (argc==2) {
    if (strcmp(argv[1],"help") || strcmp(argv[1],"h") || strcmp(argv[1],"-h") || strcmp(argv[1],"/h") || strcmp(argv[1],"--help") || strcmp(argv[1],"/help"))
    {
      printf("\n");
      printf("By typing %s, you will be prompted for numbers.\n",argv[0]);
      printf("If you wish, on the commandline, you may specify three\n");
      printf("  arguments, the principle, the number of years, and\n");
      printf("  the percent interest which will be less than one.\n");
      printf("i.e.-- %s 5000 5 .08 will calculate $5000 for 5 years\n", argv[0]);
      printf("  at 8%% interest.");
      printf("\n\nBy: Chris Benard\n");
      exit(0);
    }
  }

// checks for command line args and assigns them their respective values
// in the program if found...also decides if four lines of skipping
// is needed

  if (argc==4) {
    princ = atof(argv[1]);
    yrs = atof(argv[2]);
    inter = atof(argv[3]);
  }
  else {

// if not cmdline args, interactively prompt

    printf("What is the principle? ");
    scanf("%f",&princ);
    printf("\nWhat is the number of years? ");
    scanf("%f",&yrs);
    printf("\nWhat is the interest rate[<1.0]? ");
    scanf("%f",&inter);

// assign 4 line skip after prompting to separate output from input

    enters="\n\n\n\n";
  }

// keep the value for the original input to show later

  orig = princ;

  for(x=0; x<yrs; x++) {
    temp=princ * inter;
    princ=princ + temp;
  }

// computer the total interest and mult the rate by 100 so it will
// be human readable

  compinter = princ - orig;
  realint = inter * 100;

// give human readable output

  printf("%s",enters);
  printf("Your original principle was: %.2f.\n",orig);
  printf("At the rate of %.1f%% compounded yearly,\n",realint);
  printf("Your compounded interest was %.2f.\n",compinter);
  printf("That gives you a total of %.2f.\n",princ);
}