In this blog post, we learn C Program to find the sum of even numbers from 1 to n.  We will take the help of iterative statements like for, while or do-while loop to find the sum of even numbers from 1 to n.

What are Natural numbers?

Natural numbers are the positive integers or non-negative integers which starts from 1 and ends at infinity, such as:

1,2,3,4,5,6,7,8,9,10,……,∞

C Program to find the sum of even numbers 1 to n using if and for Loop

In the below program, we will ask the user to enter the value of ‘n’. After entering the value of ‘n’ we will calculate the sum of even natural numbers 1 to n terms with the help of for loop.

#include<stdio.h>
int main()
{
    int num, i;
    unsigned long int sum = 0;

    printf("Please Enter any Integer number = ");
    scanf("%d", &num);
    //Validate positive number
    if(num >0)
    {
        for(i = 1; i <= num; i++)
        {
            if((i%2) == 0)
            {
                sum += i;
            }
        }
        printf("Sum = %ld\n",sum);
    }
    else
    {
        printf("Enter Valid number\n");
    }
    return 0;
}

Output:

Please Enter any Integer number = 10
Sum = 30

C Program to find the sum of even numbers 1 to n without using if

In the below program, we will ask the user to enter the value of ‘n’. After entering the value of ‘n’ we will calculate the sum of even natural numbers 1 to n terms without using the if condition.

#include<stdio.h>

int main()
{
    int num, i;
    unsigned long int sum = 0;

    printf("Please Enter any Integer number = ");
    scanf("%d", &num);
    //Validate positive number
    if(num >0)
    {
        for(i = 2; i <= num; i+=2)
        {
            //calculating sum
            sum += i;
        }
        printf("Sum = %ld\n",sum);
    }
    else
    {
        printf("Enter Valid number\n");
    }
    return 0;
}

Output:

Please Enter any Integer number = 20
Sum = 110

C Program to find the sum of even numbers within a range

The mentioned C Program to find the sum of even numbers in a given range. The minimum and maximum value of the range ask by users.

#include<stdio.h>
int main()
{
    int rangeMinValue,rangeMaxValue, i;
    unsigned long int sum = 0;
    
    printf("Please Enter the rangeMinValue of natural number = ");
    scanf("%d",&rangeMinValue);
    
    printf("Please Enter the rangeMaxValue of natural number = ");
    scanf("%d",&rangeMaxValue);
    
    if((rangeMinValue > 0) && (rangeMaxValue > 0) && (rangeMaxValue > rangeMinValue ))
    {
        printf("List of Natural Numbers from %d to %d are \n",rangeMinValue,rangeMaxValue);
        for(i = rangeMinValue; i <= rangeMaxValue; i++)
        {
            if((i%2) == 0)
            {
                sum += i;
            }
        }
        printf("Sum = %ld\n",sum);
    }
    else
    {
        printf("Enter Valid numbers\n");
    }
    return 0;
}

Output:

Please Enter the rangeMinValue of natural number = 1
Please Enter the rangeMaxValue of natural number = 10
List of Natural Numbers from 1 to 10 are
Sum = 30