WHILE Loops - Advanced

When to Use WHILE Loops

Use WHILE loops when you DON'T know how many times to repeat.

Perfect for: User keeps entering data until they quit, password attempts until correct, searching until found, game loops, processing until condition changes.

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Example 1: Login System - Keep Asking Until Correct Password

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string correctPassword = "abc123";
string userInput = "";

while (userInput != correctPassword)
{
    Console.Write("Enter password: ");
    userInput = Console.ReadLine();

    if (userInput != correctPassword)
        Console.WriteLine("Incorrect! Try again.");
}
Console.WriteLine("Access granted!");

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Example 2: ATM System - Withdraw Until Balance is Low

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float balance = 100.00f;

while (balance >= 20)  // Keep allowing withdrawals while balance allows
{
    Console.WriteLine($"Current balance: ${balance}");
    Console.Write("Withdraw $20? (y/n): ");
    string response = Console.ReadLine();

    if (response == "y")
        balance = balance - 20;
    else
        break;  // Exit loop if user says no
}
Console.WriteLine($"Final balance: ${balance}");

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Example 3: Inventory Search - Find Item in Stock

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string[] inventory = { "Laptop", "Mouse", "Keyboard", "Monitor", "Printer" };
string searchItem = "Keyboard";
int index = 0;
bool found = false;

while (index < inventory.Length && !found)
{
    if (inventory[index] == searchItem)
    {
        found = true;
        Console.WriteLine($"Found {searchItem} at position {index + 1}");
    }
    index++;
}

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Example 4: Game Menu - Keep Playing Until User Quits

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bool playing = true;
int score = 0;

while (playing)
{
    Console.Write("Roll dice? (y/n): ");
    string input = Console.ReadLine();

    if (input == "y")
    {
        Random rand = new Random();
        int roll = rand.Next(1, 7);
        score = score + roll;
        Console.WriteLine($"You rolled: {roll} | Score: {score}");
    }
    else
    {
        playing = false;
    }
}
Console.WriteLine($"Game over! Final score: {score}");

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Example 5: Shopping Cart - Add Items Until Finished

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List<string> cart = new List<string>();
bool shopping = true;

while (shopping)
{
    Console.Write("Add item (or type 'done'): ");
    string item = Console.ReadLine();

    if (item == "done")
    {
        shopping = false;
    }
    else
    {
        cart.Add(item);
        Console.WriteLine($"Added to cart. Total items: {cart.Count}");
    }
}
Console.WriteLine($"Checkout complete with {cart.Count} items");

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Assessment Use Cases

When to Use in Your Software Module

• Login systems with retry
• ATM withdrawals until balance low
• Search functions
• Add items to cart until "done"
• Game scoring until user quits