/* Prime number calculator V. 2 (with functions) */

#include <stdio.h>

void test_prime(int number);
int is_prime(int test_number);

void main(void) {

  int input;
  
  do {
    
    printf("Input number for testing: ");
    
    scanf("%i", &input);
    
    if(input > 1)
      test_prime(input);
    
  } while(input > 1);
  
}

void test_prime(int number) {

  printf("%i ", number);
  
  if(is_prime(number))
    printf("is ");
  else
    printf("is not ");
  
  printf("a prime number.\n\n");
}

int is_prime(int test_number) {

  int counter = test_number-1;

  while ( test_number % counter )
    counter--;

  if(counter <= 1)
    return(1);

  return(0);
}