/* primes.c - calculate the first twenty prime numbers */
/* Analog Devices, 1993 */

main()
{
    int index = 0;
    int n_primes = 1;
    int primes[20] = {2};
    int testnum = 3;

    while (n_primes < 20)
    {
        /* find a number that is indivisible by known primes. */
        while (index < n_primes)
            if (!(testnum % primes[index++]))
            {

                /* if a number is divisible by a known prime, it
                   cannot be prime.  Start over with the next
                   odd number */
                testnum += 2;
                index = 0;
            }
        
        /* this number is prime, add it to the list. */
        primes[n_primes++] = testnum;

        /* start checking at the next odd number */
        testnum += 2;
        index = 0;
    }
    exit(0);
}