http://en.wikipedia.org/wiki/Sieve_of_Eratosthenes




using this, write a function to tell me if a number is prime

bool aComposite[1025];

void setupArray()
{

}

bool isPrime(int n)
{
    return ! aComposite[n];
}

bool isPrime(int n)
{
    if (n== 1 || n == 2)
        return true;
    for (int i = 2; i <= n-1; i++)
        if (n % i == 0)
            return false;
    return true;
}