C program to find sum of even numbers between 1 to n using loop

Write a C program to enter any number from user and find the sum of all even numbers between 1 to n. How to find sum of even numbers in a given range using loop in C programming. Logic to find sum of even numbers in a given range in C program.

Input upper limit of even number: 10

Sum of even numbers between 1 to 10: 30

Required knowledge

Basic C programming, For loop

Logic to find sum of even number

Logic of finding sum of even numbers is almost similar to printing even number in range. In case you are in doubt about printing even numbers, here it is.

• Program to print even numbers in a given range.

Below is the step by step descriptive logic to find sum of even numbers.

1. Read upper limit to find sum of even number. Store it in some variable say N.
2. Initialize another variable that will hold our sum with 0. Which is sum = 0.
3. Initialize a loop from 2 to N and increment 2 on each iteration. The loop structure should look like for(i=2; i<=N; i+=2).
4. Inside the loop body add the previous value of sum with i. Store the sum back in sum. Which is sum = sum + i.
5. After the loop print the final value of sum.

Program to find sum of even numbers

/**
 * C program to print sum of all even numbers between 1 to n
 */

#include <stdio.h>

int main()
{
    int i, n, sum=0;

    /* Read upper limit from user */
    printf("Enter upper limit: ");
    scanf("%d", &n);

    for(i=2; i<=n; i+=2)
    {
        /* Add current even number to sum */
        sum += i;
    }

    printf("Sum of all even number between 1 to %d = %d", n, sum);

    return 0;
}

Enter upper limit: 10
Sum of all even number between 1 to 10 = 30

Program to find sum of even numbers in given range

/**
 * C program to print sum of all even numbers in given range
 */

#include <stdio.h>

int main()
{
    int i, start, end, sum=0;

    /* Read lower and upper limit from user */
    printf("Enter lower limit: ");
    scanf("%d", &start);
    printf("Enter upper limit: ");
    scanf("%d", &end);


    // If start is not even then make it even
    if(start%2!=0)
    {
        start++;
    }

    for(i=start; i<=end; i+=2)
    {
        /* Add current even number to sum */
        sum += i;
    }

    printf("Sum of all even number between %d to %d = %d", start, end, sum);

    return 0;
}

Enter lower limit: 6
Enter upper limit: 10
Sum of all even number between 6 to 10 = 24

Happy coding ;)