/*
 * SelfTest2.question6.c
 * Chapter 9
 * By: John Stile
 * Purpose: Write a program named whatnum.c that reads a positive 
 *          integer from the keyboard and then determines if it 
 *          is a prime number.
 *          Have the program also print out the number of factors.
 *          Use a for loop and modulus operator.
 *          The input and output should have the following format:
 *
 * Enter a positive integer: 12
 *  12 has 5 factors including 1.
 *
 * Enter a positive integer: 13
 *  13 is a prime number.
 */
#include <stdio.h>

int main(void)
{
  int aa, bb; // declare two ints
  int factors=0; // declare int and initialize to zero

  printf("Enter a positive integer: "); // prompt for input
  
  scanf("%d", &aa); // read from stdin, 
                   // interpret as digit, 
                   // assign to aa
  
  for( bb=aa-1; bb>0 ; bb--) // initialzie bb to one less than aa
                             // if bb larger than zero, do block
                             // next round, decrement bb by one 
  {
    if( !(aa%bb) ) // divide aa by bb, 
                   // if there is no remainder, do block 
                   // Effectively, aa is divisable by bb, or one factorial
    {
      factors++; // increment number of factors
    }
  }
  
  if ( factors==0 )
  {
    printf(" %d is a prime number.\n", aa); // print resutl
  }
  else 
  {
    printf("%d has %d factors including 1.\n", aa, factors); // print resutl
  }
  
  return 0; // return 0 to calling program
}