C Even Number Program

What Is an Even Number?

An even number is an integer divisible by 2 with remainder 0. In math form: n = 2 * k for some integer k.

n is even  ↔  n % 2 == 0

Examples:
  10 % 2 == 0  → even
  11 % 2 == 1  → odd
   0 % 2 == 0  → even
  -4 % 2 == 0  → even

How to Check an Even Number in C

Four clear steps — then pick modulo, bitwise, or a step-by-two range loop.

1. Read the integer n (positive, negative, or zero).
2. Compute n % 2 (or check the least significant bit with n & 1).
3. If the remainder is 0 (or the LSB is 0), n is even.
4. To list evens in a range, test each value — or start at the first even and add 2.

Pseudocode

function IsEven(n):
    return (n mod 2) == 0

function PrintEvens(start, end):
    for i from start to end:
        if IsEven(i):
            output i

// Faster range listing:
function PrintEvensStep(start, end):
    i = start
    if i is odd:
        i = i + 1
    while i <= end:
        output i
        i = i + 2

Cheat Sheet

Keep these facts handy while writing the program.

Live Preview

Enter any integer to see the remainder and the even/odd verdict.

n = 10
n % 2 = 0
(n & 1) = 0
Verdict: EVEN

Worked Walkthrough — n = 10

Apply the modulo rule, then confirm with the bitwise check.

Step 1: Compute 10 % 2
        10 = 2 * 5 + 0
        remainder = 0

Step 2: Remainder is 0 → even

Step 3: Bitwise check
        10 in binary ends with 0
        (10 & 1) = 0 → same answer

Verdict: 10 is even

C Programs

Start with the modulo helper — it is the clearest interview answer. Then reuse it for a range, and finish with the bitwise shortcut.

#include <stdio.h>

int is_even(int n)
{
    return n % 2 == 0;
}

int main(void)
{
    int number = 10;
    if (is_even(number))
        printf("%d is an even number.\n", number);
    else
        printf("%d is not an even number.\n", number);
    return 0;
}

10 is an even number.

#include <stdio.h>

int is_even(int n)
{
    return n % 2 == 0;
}

int main(void)
{
    int start = 1;
    int end = 10;
    int i;

    printf("Even numbers from %d to %d:\n", start, end);
    for (i = start; i <= end; i++)
    {
        if (is_even(i))
            printf("%d ", i);
    }
    printf("\n");
    return 0;
}

Even numbers from 1 to 10:
2 4 6 8 10

#include <stdio.h>

int is_even_bitwise(int n)
{
    return (n & 1) == 0;
}

int main(void)
{
    int samples[] = { 10, 11, 0, -4 };
    int i;

    for (i = 0; i < 4; i++)
    {
        int n = samples[i];
        printf("%d: %s\n", n, is_even_bitwise(n) ? "even" : "odd");
    }
    return 0;
}

10: even
11: odd
0: even
-4: even

Time and Space Complexity

A single parity test is constant time. Range printers grow with how many integers you visit.

Key Takeaways