do while loop with examples in C++

The provided C++ code demonstrates the use of do-while loops, a variant of loop that ensures the loop’s body is executed at least once before the condition is checked.

Code

#include <iostream>
using namespace std;

/**
 * Demonstrates various uses of the do-while loop in C++.
 *
 * This program includes examples of basic do-while loops, and do-while loops with control
 * flow statements such as break, continue, and return to manage loop execution.
 */
int main() {
    int i = 0;

    // Basic do-while loop example
    // This loop will execute the block at least once and then check the condition at the end.
    i = 0;
    do {
        cout << i << endl; // Prints numbers from 0 to 9
        i++;
    } while (i < 10);
    cout << "Done" << endl; // Indicates the end of the loop

    // Do-while loop with break statement
    // This loop demonstrates how to exit the loop prematurely using a break statement.
    i = 0;
    do {
        if (i == 5) {
            break; // Exits the loop when i equals 5
        }
        cout << i << endl; // Prints numbers from 0 to 4
        i++;
    } while (i < 10);
    cout << "Done" << endl; // Indicates the end of the loop

    // Do-while loop with continue statement
    // This loop shows how to skip the rest of the loop body for the current iteration using continue.
    i = 0;
    do {
        if (i == 5) {
            i++; // Increment before continue to avoid infinite loop
            continue; // Skips printing 5
        }
        cout << i << endl; // Prints numbers from 0 to 9, skipping 5
        i++;
    } while (i < 10);
    cout << "Done" << endl; // Indicates the end of the loop

    // Do-while loop with return statement
    // This loop demonstrates using return within a loop to exit the program based on a condition.
    i = 0;
    do {
        if (i == 5) {
            return 0; // Exits the program when i equals 5
        }
        cout << i << endl; // Prints numbers from 0 to 4
        i++;
    } while (i < 10);
    cout << "Done" << endl; // This line is never reached due to the return statement

    return 0;
}

Explanation

The provided C++ code demonstrates the use of do-while loops, a variant of loop that ensures the loop’s body is executed at least once before the condition is checked. This characteristic differentiates do-while loops from the more common while loops, where the condition is evaluated before the loop body is executed.

The first example in the code is a basic do-while loop that prints numbers from 0 to 9. The loop starts with i initialized to 0 and increments i in each iteration. The condition i < 10 is checked after the loop body is executed, ensuring that the loop runs at least once.

do {
    cout << i << endl;
    i++;
} while (i < 10);

Next, the code demonstrates how to use a break statement within a do-while loop to exit the loop prematurely. In this example, the loop is designed to break when i equals 5, thus it prints numbers from 0 to 4 before exiting.

do {
    if (i == 5) {
        break;
    }
    cout << i << endl;
    i++;
} while (i < 10);

Following that, a do-while loop with a continue statement is shown. This loop skips the current iteration when i equals 5 by using continue, which causes the loop to immediately proceed to the next iteration. To prevent an infinite loop, i is incremented before the continue statement.

do {
    if (i == 5) {
        i++;
        continue;
    }
    cout << i << endl;
    i++;
} while (i < 10);

Lastly, the code includes a do-while loop with a return statement. This loop exits not just the loop but the entire program when i equals 5. This demonstrates how a return statement can be used within a loop to control the flow of the program based on certain conditions.

do {
    if (i == 5) {
        return 0;
    }
    cout << i << endl;
    i++;
} while (i < 10);

Each of these examples illustrates different ways to control the execution flow within do-while loops, showcasing their flexibility and utility in scenarios where at least one iteration of the loop is required.

Output

0
1
2
3
4
5
6
7
8
9
Done
0
1
2
3
4
Done
0
1
2
3
4
6
7
8
9
Done
0
1
2
3
4

Process finished with exit code 0