Check if prime

Giovanny Gongora

Check whether an integer entered by the user is a prime number or not. A prime number is a positive integer that is divisible only by 1 and itself. For example: 2, 3, 5, 7, 11, 13, 17

#include <stdio.h>

int ifPrime() {
  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;
}