C++ Do While Loop Control Structure

Introduction

The do-while loop in C++ is similar to the while loop, but with one key difference:
👉 The loop body executes at least once, even if the condition is false initially.

That’s why it’s called an exit-controlled loop.

Syntax

do {
    // statements
} while (condition);

do {
    // statements
} while (condition);

• Loop executes body first.
• Then condition is tested.
• If true → repeat body. If false → exit.

Working of Do-While Loop

1. Run loop body once.
2. Test the condition.
3. If true → repeat body → step 2.
4. If false → exit loop.

Example: Menu-driven program using Do-While

#include <iostream>
using namespace std;

int main() {
    int choice;
    do {
        cout << "Menu:\n";
        cout << "1. Say Hello\n";
        cout << "2. Say Bye\n";
        cout << "3. Exit\n";
        cout << "Enter choice: ";
        cin >> choice;

        switch (choice) {
            case 1: cout << "Hello!\n"; break;
            case 2: cout << "Bye!\n"; break;
            case 3: cout << "Exiting...\n"; break;
            default: cout << "Invalid choice!\n";
        }
    } while (choice != 3);

    return 0;
}

#include <iostream>
using namespace std;

int main() {
    int choice;
    do {
        cout << "Menu:\n";
        cout << "1. Say Hello\n";
        cout << "2. Say Bye\n";
        cout << "3. Exit\n";
        cout << "Enter choice: ";
        cin >> choice;

        switch (choice) {
            case 1: cout << "Hello!\n"; break;
            case 2: cout << "Bye!\n"; break;
            case 3: cout << "Exiting...\n"; break;
            default: cout << "Invalid choice!\n";
        }
    } while (choice != 3);

    return 0;
}

Key Points

• Exit-controlled loop → executes at least once.
• Condition is tested after the body.
• Useful in menu-driven programs or situations where the first run must always happen.

Differences Between While and Do-While

Tips

• Always terminate the do…while with a semicolon (;) after the condition.
• Don’t confuse it with while — the placement of condition is the key difference.