tests for prime

prime.c

/*
 * file: prime.c
 * Asks user to input an integer number, checks if
 * given number is prime or not and prints result of check.
 *
 */


#include <stdio.h>

/* checks if argument is a prime number
 * returns 1 if it is, return 0 otherwise */
int prime(int x)
{
	/* handle special cases */
	if(x<=2)
		return 1;
	int i;
	
	/* largest number to take into account is sqrt x */
	for(i=2; i*i<=x; i++)
	{
		/* if there is a number that divides x */
		if((x%i) == 0)
			return 0;
	}
	return 1;
}

int main()
{
	int x;
	
	/* ask user for input */
	printf("Please enter a number: ");
	scanf("%i", &x);

	/* check if users number is a prime number */
	if(prime(x)) 
		printf("%i is a prime number\n", x);
	
	/* check if users number is not a prime number */
	if(!prime(x))
		printf("%i is not a prime number\n", x);
	
	return 0;
}