## C Program To Print Sum Of All Odd Numbers Between 1 to n Using While Loop

In this tutorial, you will learn how to write a program to print sum of all odd numbers between 1 to n using a while loop in C. Here, we will see examples, algorithms, logics and program explanation for your better understanding in C programming language.

## Problem Statement

You have to write a C program that should take a positive integer ‘n’ as input. After taking the input it should print the sum of all odd numbers between 1 and n using a while loop. The program provides a solution to find the sum of odd numbers using a while loop in the C programming language. You can refer to the below example to understand better what we have to achieve. The first value and n will be not included in the operation.

Example

``````Input:
Enter the value of n: 7

Output:
The sum of odd numbers between 1 and 7 is: 8``````

In the above example, user given input is 7. So the odd number between 1 to 7 is 1, 3, 5 and 7. So the output is 16.

## Algorithm

1. Start the program.
2. Declare the variables: `n` to store the input value, `num` to represent the current number, and `sum` to store the sum of odd numbers.
3. Read the value of `n` from the user.
4. Initialize `num` to 1 and `sum` to 0.
5. Enter the while loop with the condition `num <= n`.
• Check if the current number `num` is odd using the modulo operator (`num % 2 != 0`).
• If it is odd, add `num` to `sum`.
• Increment `num` by 1.
6. Exit the while loop.
7. Print the sum of odd numbers as: “The sum of odd numbers between 1 and n is: sum”.
8. End the program.

## Logic used to solve this problem

• Declare a variable to hold the input number.
• Prompt the user to enter a number.
• Read and store the entered number in the variable.
• Initialize a variable to hold the sum of odd numbers and set it to 0.
• Initialize a num variable to 1.
• Use a while loop that runs as long as the num is less than or equal to the given number (n).
• Inside the loop, check if the num is an odd number using the modulo (%) operator.
• If the num is odd, add it to the sum variable.
• Increment the num by 1 in each iteration.
• Continue the loop until the counter reaches the given number (n).
• Print the sum of odd numbers.
• Finish the program.

## Print the sum of all odd numbers between 1 to n

``````#include <stdio.h>
int main() {
int n, num = 1, sum = 0;
printf("Enter the value of n: ");
scanf("%d", &n);
while (num <= n) {
if (num % 2 != 0) {
sum += num;
}
num++;
}
printf("The sum of odd numbers between 1 and %d is: %d\n", n, sum);
return 0;
}``````

Output

``````Enter the value of n: 12
The sum of odd numbers between 1 and 12 is: 36``````

### Program Explanation

• The program takes input for the value of n from the user.
• It initializes a variable `num` to 1, which represents the first odd number to be considered for summation.
• It also initializes a variable `sum` to 0, which will hold the running sum of odd numbers.
• The program enters a while loop with the condition `num <= n` to iterate through numbers from 1 to n.
• Inside the while loop, it checks if `num` is an odd number.
• If `num` is odd, it adds the value of `num` to `sum`.
• It then increments the value of `num` by 2 since the next odd number will be 2 greater than the current one.
• The loop continues until `num` exceeds the value of n.
• Once the while loop is complete, the program prints the value of `sum`, which represents the sum of all odd numbers between 1 and n.
• The program ends.

## Conclusion

The C program successfully calculates and prints the sum of all odd numbers between 1 and the given input `n` using a while loop. By iterating through the numbers and checking their divisibility by 2, it identifies the odd numbers, calculates their sum, and displays the result on the screen.