📅 Date: Jan 5, 2026
🔥 Topic: While Loop, Do-While Loop & Comparison

🔄 The Other Loops

Yesterday I used the for loop because I knew the exact count. But what if we don't know when to stop? Like waiting for a user to enter the correct password?

That's where While and Do-While come in.

1️⃣ The While Loop (Entry Control)

Checks the condition first, then runs the code. If the condition is false initially, the code never runs. 

while (condition) {
    // Code runs as long as true
}

2️⃣ The Do-While Loop (Exit Control)

Runs the code first, then checks the condition. This guarantees the code runs at least once. 

do {
    // Runs at least once
} while (condition);

⚔️ Battle of Loops: When to use what?

Loop Type Best Use Case
For Loop When you know the number of iterations (e.g., Array traversal).
While Loop When iterations are unknown (e.g., Reading a file until end).
Do-While When code must run once (e.g., Menu driven programs).

💻 Day 5 Code: Input Validation

I used a do-while loop to force the user to enter a positive number. It won't let you escape until you obey! 

#include <iostream>
using namespace std;

int main() {
    int number;

    do {
        cout << "Enter a positive number: ";
        cin >> number;

        if(number <= 0) {
            cout << "Invalid! Try again." << endl;
        }

    } while (number <= 0);

    cout << "Finally! You entered: " << number << endl;
    return 0;
}

💭 Thoughts

The do-while loop is perfect for game menus ("Play Again?"). Next, I am excited to learn about Functions to modularize my code.