C Program to Check Whether a Number is Prime or Not

A prime number is a positive integer which can be divided by only 1 and itself. For instance: 2 , 3, 5 , 7, 11, 13, 17 …

code of the program

#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) {
        // 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);
    }
    return 0;
}

Enter a positive integer: 29
29 is a prime number.