How to Calculate the Sum of Even Numbers Using While Loop and If Statement in C

Calculating the sum of even numbers using a while loop and an if statement is a common programming task that helps in understanding basic control structures and number operations. This article will guide you through the process with detailed explanations and examples.

Understanding the Basics

In C, the while loop runs as long as a specified condition remains true, and the if statement is used to execute a block of code only if a certain condition is met. Here’s how you can use these constructs to sum even numbers:

Steps to Calculate the Sum of Even Numbers

Initialize Variables: Create variables to store the sum and the current number being checked. Create a While Loop: Use a while loop to iterate through numbers until a specified condition is met. Use If Statement: Use an if statement within the loop to check if the current number is even. Add Even Numbers: If the number is even, add it to the sum. Increment the Number: Increment the current number by one in each iteration. Output the Result: Print the final sum once the loop is done.

Example: Sum of Even Numbers from 1 to 100

Let’s create a simple C program to sum all even numbers from 1 to 100:

#include iostreamint main() {    int number  1; // Starting number    int sum  0;    // Variable to store the sum    while (number  100) { // Loop until number is less than or equal to 100        if (number % 2  0) { // Check if the number is even            sum   number; // Add the even number to the sum        }        number  ; // Increment the number    }    std::cout 

Explanation:

Initialization: The variable number starts at 1, and sum is initialized to 0. While Loop: The loop continues as long as number is less than or equal to 100. If Statement: The if statement checks if number % 2 0 to determine if the number is even. Updating Sum: If the condition is true, the even number is added to sum. Incrementing: number is incremented by 1 in each iteration. Output: The sum is printed out.

Modifying the Range or Condition

Feel free to modify the range or the condition based on your requirements. For example, if you want to calculate the sum of the first 10 even numbers from 1 to 20, the following is an example:

#include iostream#include iomanipusing namespace std;int main() {    int number, sum  0;    for (number  1; number  20; number  ) {        if (number % 2  0) {            sum   number;        }    }    cout  "The sum of the first 10 even numbers from 1 to 20 is: "  sum  endl;    return 0;}

Similarly, you can calculate the sum of even numbers from 1 to 10:

#include iostreamusing namespace std;int main() {    int sum  0;    int i  1;    while (i  10) {        if (i % 2  0) {            sum   i;        }        i  ;    }    cout  "The sum of even numbers from 1 to 10 is: "  sum  endl;    return 0;}

These examples illustrate different ways to achieve the same goal using loops and if statements. Experimenting with different conditions and ranges helps in understanding the flexibility and power of these constructs.

Conclusion

Summing even numbers using a while loop and an if statement is a fundamental concept in C programming that enriches your understanding of loop and conditional control structures.