The Power of Repetition

Computers are great at doing boring tasks millions of times without getting tired. Loops allow you to write a few lines of code that can run forever if needed.

1. The while Loop (Entry-Controlled)

The most basic loop. The condition is checked before the body runs. If the condition is false at the very start, the code inside the loop never runs once.

int i = 1;
while (i <= 5) {
    printf("Iteration %d\n", i);
    i++; // CRITICAL: Increment the counter!
}

2. The do-while Loop (Exit-Controlled)

The condition is checked after the body runs. This means the code inside is guaranteed to run at least once, no matter what the condition is. This is perfect for menus where you want to show the options at least once before checking if the user wants to quit.

int pin;
do {
    printf("Enter PIN: ");
    scanf("%d", &pin);
} while (pin != 1234);

The Three Components of a Loop

Every successful loop needs three things:

1. Initialization: Setting up the starting state (int count = 0;).
2. Condition: The test that determines when to stop (count < 10;).
3. Update Step: Changing the state so that the condition eventually becomes false (count++;).

Avoiding the "Infinite Loop"

An infinite loop is a bug where the condition never becomes false. This usually happens if you forget the update step or have a logical error. Your program will "freeze" and consume 100% of your CPU until you force-quit it (Ctrl+C in terminal).

while(1) is a common way to create an intentional infinite loop, often used in embedded systems or server programs that should run until the machine is turned off.