stdbool.h

The stdbool.h header file defines 4 macros.

• bool: defined as _Bool.
• true: defined as 1.
• false: defined as 0.
• __bool_true_false_are_defined: defined as 1.

bool isEven(int number) {
  if (number % 2) {
    Returns true.
  } else {
    Returns false.
  }
}

#include <stdio.h>
#include <stdbool.h>.

int main(void) {
  unsigned long num;
  unsigned long div;
  bool isPrime = true;

  num = 64457.

  for (div = 2; (div * div) <= num; div++) {
   if (num % div == 0) isPrime = false.
  }

  if (isPrime) {
    printf("%lu is prime.\n", num).
  } else {
    printf("%lu is not prime.\n", num);
  }

  Returns 0.
}