Loop Exercises
C program to find sum of even numbers between 1 to n
Write a C program to input number from user and find 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.
Example
Input
Input upper limit of even number: 10
Output
Sum of even numbers between 1 to 10: 30
Required knowledge
Basic C programming, Relational operators, For loop
Logic to find sum of even numbers
Step by step descriptive logic to find sum of even numbers.
1.Input upper limit to find sum of even number. Store it in some variable say N.
2.Initialize another variable to store sum with 0 say sum = 0.
3.To find sum of even numbers we need to iterate through even numbers from 1 to n. 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 previous value of sum with i i.e. sum = sum + i.
5.After loop print 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;
/* Input 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;
}
Note: Do not confuse with the shorthand assignment operator sum += i. It is equivalent to sum = sum + i.
Output
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;
/* Input 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;
}
Output
Enter lower limit: 6
Enter upper limit: 10
Sum of all even number between 6 to 10 = 24
