An even number is an integer that is exactly divisible by 2. For example: 0, 8, -24

An odd number is an integer that is not exactly divisible by 2. For example: 1, 7, -11, 15

Program to Check Even or Odd

#include <stdio.h>
int main(){
    int num;
    printf("Enter an integer: ");
    scanf("%d", &num);

    // True if num is perfectly divisible by 2
    if(num % 2 == 0)
        printf("%d is even.", num);
    else
        printf("%d is odd.", num);
    
    return 0;
}

Output

Enter an integer: -7
-7 is odd.

In the program, the integer entered by the user is stored in the variable num.

Then, whether num is perfectly divisible by 2 or not is checked using the modulus % operator.

If the number is perfectly divisible by 2, test expression number%2 == 0 evaluates to 1 (true). This means the number is even.

However, if the test expression evaluates to 0 (false), the number is odd.

Program to Check Odd or Even Using the Ternary Operator

#include <stdio.h>
int main(){
    int num;
    printf("Enter an integer: ");
    scanf("%d", &num);
    
    (num % 2 == 0) ? printf("%d is even.", num) : printf("%d is odd.", num);
    return 0;
}

Output

Enter an integer: 33
33 is odd.

In the above program, we have used the ternary operator ?: instead of the if...else statement.