🔁 C++ while Loop – Condition-Based Iteration

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🧲 Introduction – What Is a while Loop in C++?

The while loop in C++ is a pre-test loop that repeatedly executes a block of code as long as a given condition remains true. It is ideal when the number of iterations is not known beforehand and depends on dynamic input or calculations.

🎯 In this guide, you’ll learn:

• Syntax and flow of a while loop
• Real-world examples and use cases
• Infinite and controlled loops
• Best practices and pitfalls to avoid

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✅ Syntax of while Loop

while (condition) {
    // code block to execute
}

📌 The loop condition is evaluated before each iteration.

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✏️ Example – Basic while Loop

int count = 1;

while (count <= 5) {
    cout << count << " ";
    count++;
}

Output:

1 2 3 4 5

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🔄 Flow of Execution

1. Evaluate the condition
2. If true, execute the block
3. Update control variable (if needed)
4. Repeat until condition becomes false

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🔁 while Loop for User Input

int number;
cout << "Enter a number (0 to exit): ";
cin >> number;

while (number != 0) {
    cout << "You entered: " << number << endl;
    cin >> number;
}

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🔁 Infinite while Loop

while (true) {
    // executes forever unless manually broken
}

✅ Use break inside the loop to exit conditionally.

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🔁 Nested while Loops

int i = 1;
while (i <= 3) {
    int j = 1;
    while (j <= 2) {
        cout << "(" << i << "," << j << ") ";
        j++;
    }
    cout << endl;
    i++;
}

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⚠️ Common Mistakes

❌ Mistake	✅ Fix
Forgetting to update condition	Leads to infinite loop
Using = instead of ==	Use comparison == instead of assignment =
Condition never true	Ensure control variable is initialized properly

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🧠 Best Practices

• Always ensure the condition will eventually become false
• Use clear and meaningful loop control variables
• Favor while when the number of iterations is unknown

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📌 Summary – Recap & Next Steps

🔍 Key Takeaways:

• The while loop runs as long as the condition is true
• Ideal for input validation, dynamic iterations, and event-based logic
• Keep track of control variables to avoid infinite loops
• Prefer when condition checking must happen before execution

⚙️ Real-World Relevance:
Used in menus, interactive programs, file reading, and event polling where actions depend on run-time conditions.

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❓ FAQs – C++ while Loop

❓ What happens if the condition is initially false?
✅ The loop body will not execute at all.

❓ Can I use break in a while loop?
✅ Yes. break will immediately exit the loop.

❓ How is while different from do-while?
✅ while checks the condition before execution, do-while checks after.

❓ Can I use multiple conditions in while?
✅ Yes. Use logical operators:

while (x > 0 && y < 10)

❓ How can I prevent an infinite while loop?
✅ Ensure the control variable is updated inside the loop and the condition can become false.

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