C program to check even or odd using functions

Write a C program to input a number from user and check whether given number is even or odd using functions. How to check even or odd using functions in C programming. Write a function in C programming to check even or odd.



Input any number: 10


10 is even

Required knowledge

Basic C programming, Functions, Returning value from function

Declare function to find even odd

In my previous posts I have explained various ways to check even numbers. You can embed the logic to check even numbers using any of the following approaches in a function.

Must know – Program to check even number using conditional operator.

Let us define a function to check even or odd.

  1. First give a meaningful name to our function, say isEven().
  2. Next, the function must accept one integer which is to be validated for even condition, say isEven(int num).
  3. Finally as per name, the function must return true if given integer is even otherwise false. However, C does not supports boolean values. In C programming, 0 is represented as false and 1 (any non-zero integer) as true. Hence, isEven() we must return an integer from function.

So the function declaration to check even number is int isEven(int num);

Program to check even or odd

 * C program to check even or odd using functions

#include <stdio.h>

 * Function to check even or odd
 * Returns 1 is num is even otherwise 0
int isEven(int num)
    return !(num & 1);

int main()
    int num;
    /* Input number from user */
    printf("Enter any number: ");
    scanf("%d", &num);
    /* If isEven() function returns 0 then the number is even */
        printf("The number is even.");
        printf("The number is odd.");
    return 0;

In the above program I have used bitwise operator & to check even or odd numbers. However you can also use if else statement to check even or odd numbers.


Enter any number: 22
The number is even.

Happy coding 😉