So, I felt that many times people need a function to tell if a number is prime or not. Especially students. I have seen some relevant code in the forum to.

But, I saw that people of my level and even higher provided algorithms that were not so efficient in my mind. Probably they didn't try enough to improve their implementations.

So, I decided to write my function isPrime. If someone sees some way of improvement, then I would very glad˛ if he or she let me know!!

I have uploaded the function to my corner of the web.

But, for those that do not really like the css of my corner, I post the code here as well :)

Code:`#include <stdio.h>`

#include <math.h>

int isPrime(const int);

int main(void)

{

int i;

for (i = 1 ; i <= 15 ; ++i)

printf("%d is %sprime\n", i, isPrime(i) ? "" : "NOT ");

return 0;

}

int isPrime(const int number)

{

int i, r, prime = 1;

if (number != 2 && number % 2 == 0)

prime = 0;

else

for (i = 3, r = sqrt(number) ; i <= r && prime ; i += 2)

if (number % i == 0)

prime = 0;

return prime;

}