Check whether a number is 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 */
    if (isEven(num))
    {
        printf("The number is even.");
    }
    else
    {
        printf("The number is odd.");
    }

    return 0;
}

Output

Enter any number : 5
The number is odd.