C PROGRAM

#include <stdio.h>

int main() {

int n, i, flag = 0;
printf("Enter a positive integer: ");
scanf("%d", &n);

// 0 and 1 are not prime numbers
// change flag to 1 for non-prime number
if (n == 0 || n == 1)
flag = 1;

for (i = 2; i <= n / 2; ++i) {

// if n is divisible by i, then n is not prime
// change flag to 1 for non-prime number
if (n % i == 0) {
  flag = 1;
  break;
}

}

// flag is 0 for prime numbers
if (flag == 0)
printf("%d is a prime number.", n);
else
printf("%d is not a prime number.", n);

return 0;
}