C Program - Check whether a Number is Even or Odd

A number is known as an even number if it is a natural number and divisible by 2. On the other hand, an odd number is a natural number which not divisible by 2. Examples:

• Even Number: -10, -4, 0, 6, 18, 50
• Odd Number: -11, -5, -1, 9, 21, 99

Method 1: Using conditional statements

In the example below, the number called MyNum is checked for even number by dividing it by 2 and checking the remainder. For even number, the remainder is 0 and for odd number, the remainder is 1.

#include <stdio.h>

int main() {
  int MyNum = 17;
  if (MyNum % 2 == 0) {
    printf("%i is an even number.", MyNum);
  } else if (MyNum % 2 == 1) {
    printf("%i is an odd number.", MyNum);
  }
}

The above code will give the following output:

17 is an odd number.

Method 2: Using function

In the example below, a function called CheckEven() is created which takes a number as argument and checks it for even number.

#include <stdio.h>

static void CheckEven(int);

static void CheckEven(int MyNum) {
  if (MyNum % 2 == 0){
    printf("%i is an even number.", MyNum);
  } else if (MyNum % 2 == 1) {
    printf("%i is an odd number.", MyNum);
  }
}

int main() {
  CheckEven(42);
}

The above code will give the following output:

42 is an even number.

Method 3: Using bitwise operators

When bitwise operator is used, the last bit of the given number is checked. If the last bit is 1, the number will be odd and if the last bit is 0, the number will be even.

Even Number:  50 ->    110010
                     & 000001
                     ---------
                       000000

Odd Number:   99 ->   1100011
                    & 0000001
                     ---------
                      0000001

#include <stdio.h>

static void CheckEven(int);

static void CheckEven(int MyNum) {
  if ((MyNum & 1) == 1) {
    printf("%i is an odd number.\n", MyNum);
  } else {
    printf("%i is an even number.\n", MyNum);
  }
}

int main() {
  CheckEven(50);
  CheckEven(99);
}

The above code will give the following output:

50 is an even number.
99 is an odd number.