C PROGRAM TO CHECK WHETHER A NUMBER IS PRIME OR NOT

#include <stdio.h>

int main() {

    int n, i, flag = 0;

    printf("Enter a positive integer: ");

    scanf("%d", &n);

    for (i = 2; i <= n / 2; ++i) {

        // The condition for non-prime

        if (n % i == 0) {

            flag = 1;

            break;

        }

    }

    if (n == 1) {

        printf("1 is neither prime nor composite.");

    }

    else {

        if (flag == 0)

            printf("%d is a prime number.", n);

        else

            printf("%d is not a prime number.", n);

    }

    getch();

}