cpp/CPrimerPlus6E/Ch07/divisors.c

// divisors.c -- nested ifs display divisors of a number
#include <stdio.h>
#include <stdbool.h>
int main(void)
{
    unsigned long num;          // number to be checked
    unsigned long div;          // potential divisors
    bool isPrime;               // prime flag
    
    printf("Please enter an integer for analysis; ");
    printf("Enter q to quit.\n");
    while (scanf("%lu", &num) == 1)
    {
        for (div = 2, isPrime = true; (div * div) <= num; div++)
        {
            if (num % div == 0)
            {
                if ((div * div) != num)
                    printf("%lu is divisible by %lu and %lu.\n",
                           num, div, num / div);
                else
                    printf("%lu is divisible by %lu.\n",
                           num, div);
                isPrime= false; // number is not prime
            }
        }
        if (isPrime)
            printf("%lu is prime.\n", num);
        printf("Please enter another integer for analysis; ");
        printf("Enter q to quit.\n");
    }
    printf("Bye.\n");
    
    return 0;
}