Do While Loop

The do-while Loop in C++:

The do-while loop in C++ is similar to the while loop, but with a key difference: the do-while loop guarantees that the loop body is executed at least once, even if the condition is initially false. The syntax of a do-while loop is as follows:

do {
    // Code to be executed
} while (condition);

Here's an example of a simple do-while loop that prints the numbers from 1 to 5:

#include <iostream>

int main() {
    int i = 1;

    do {
        std::cout << i << " ";
        ++i;  // Increment the loop control variable
    } while (i <= 5);

    return 0;
}

In this example, the loop will print the numbers 1 to 5, just like the while loop. The key difference is that the condition i <= 5 is checked after the first execution of the loop body, ensuring that the loop body is executed at least once.

The output of this program will be:

1 2 3 4 5

Here's another example that demonstrates the use of do-while in a menu-driven program:

#include <iostream>

int main() {
    char choice;

    do {
        std::cout << "1. Print Hello\n";
        std::cout << "2. Print Goodbye\n";
        std::cout << "3. Exit\n";
        std::cout << "Enter your choice: ";
        std::cin >> choice;

        switch (choice) {
            case '1':
                std::cout << "Hello!\n";
                break;

            case '2':
                std::cout << "Goodbye!\n";
                break;

            case '3':
                std::cout << "Exiting the program.\n";
                break;

            default:
                std::cout << "Invalid choice. Please try again.\n";
        }

    } while (choice != '3');

    return 0;
}

In this example, the menu is displayed, and the user is prompted to enter a choice. The loop continues to display the menu and process choices until the user chooses to exit by entering '3'.

Use do-while when you want to ensure that a certain block of code is executed at least once, regardless of the initial condition.