Determining if a number is a prime

/* prime1.c  It prompts the user to enter an integer N. It prints out
*           if it is a prime or not. If not, it prints out a factor of N.
*/

#include <stdio.h>

int main(void) {
int n;
int i;
int flag;

printf("Enter value of N > ");
scanf("%d", &n);
flag = 1;
for (i=2; (i<(n/2)) && flag; ) { /* May be we do not need to test
values of i greater than the square root of n? */
if ((n % i) == 0) /* If true n is divisible by i */
flag = 0;
else
i++;
}

if (flag)
printf("%d is prime\n", n);
else
printf("%d has %d as a factor\n", n, i);
return 0;
}