program12-1.c

#include <stdio.h>

#define YES   1
#define NO    0

// Function to determine if an integer is even

int isEven(int number)
{
    int answer;

  if (number % 2 == 0)
      answer = YES;
  else
      answer = NO;

  return answer;
}

int main(void)
{
    int isEven(int number);

  if (isEven(17) == YES)
      printf("yes ");
  else
      printf("no ");

  if (isEven(20) == YES)
      printf("yes\n");
  else
      printf("no\n");

  return 0;
}