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C++ Program: Summing Even Numbers Within a User-Defined Limit

Welcome to the exciting world of C++ programming! Today, we'll embark on a journey into the heart of coding by exploring a simple yet powerful program that captures the essence of logic and iteration. Our quest: to sum even numbers up to a user-specified limit.

This program prompts the user to enter a positive integer. It then validates the input and calculates the sum of all even numbers from 2 up to the entered value using a 

 loop. The result is displayed to the user.

#include <iostream>

int main() {
    // Declare variables
    int userInput, sum = 0;

    // Get user input
    std::cout << "Enter a positive integer: ";
    std::cin >> userInput;

    // Validate input
    if (userInput <= 0) {
        std::cout << "Please enter a positive integer.\n";
        return 1;  // Exit the program with an error code
    }

    // Add even numbers up to the user input
    for (int i = 2; i <= userInput; i += 2) {
        sum += i;
    }

    // Display the result
    std::cout << "The sum of even numbers up to " << userInput << " is: " << sum << std::endl;

    return 0;  // Exit the program successfully
}

Let's break down the C++ code step by step:

This line includes the iostream library, which is necessary for performing input and output operations.

This is the beginning of the main function, which is the entry point of any C++ program.

// Declare variables
    int userInput, sum = 0;

// Get user input
    std::cout << "Enter a positive integer: ";
    std::cin >> userInput;

This prints a message asking the user to enter a positive integer and then reads the user's input from the console into the 

// Validate input
    if (userInput <= 0) {
        std::cout << "Please enter a positive integer.\n";
        return 1;  // Exit the program with an error code
    }

This block checks if the entered value is less than or equal to 0. If it is, it prints an error message and exits the program with a return code of 1, indicating an error.

// Add even numbers up to the user input
    for (int i = 2; i <= userInput; i += 2) {
        sum += i;
    }

 loop iterates over even numbers from 2 up to the entered 

, incrementing by 2 in each iteration, and adds them to the 

// Display the result
    std::cout << "The sum of even numbers up to " << userInput << " is: " << sum << std::endl;

Finally, this line prints the result, showing the sum of even numbers up to the entered value.

return 0;  // Exit the program successfully
}

This line indicates that the program has run successfully, and the main function is returning 0, which conventionally indicates a successful execution.

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