Loops (for, while, do-while)
Repeating actions without writing the same code again and again.
for Loop
Used when you know how many times to repeat in advance. It combines initialization, condition, and increment/decrement in one line, making it compact and readable for counting loops.
for (int i = 1; i <= 5; i++) {
printf("%d ", i);
} // prints 1 2 3 4 5while Loop
Checks the condition BEFORE each iteration — useful when the number of repetitions isn't known in advance, like reading input until the user types 'quit'.
int n = 5;
while (n > 0) {
printf("%d ", n);
n--;
}do-while Loop
Checks the condition AFTER each iteration, so the loop body always runs at least once — useful for menu-driven programs where you want to show the menu at least one time before checking whether to continue.
🌍 Real-World Use
Any repeated task — printing a multiplication table, processing every item in a shopping cart, or running a game loop that keeps checking for player input — relies on loops.
💡 Pro Tip
A classic bug is the 'infinite loop' — forgetting to update the loop variable (like forgetting n-- in a while loop) causes the condition to never become false. Always double-check your loop actually moves toward its exit condition.
🧪 Quick Self-Test
Check what you just learned — no pressure, just practice.
1. Which loop guarantees the body runs at least once?
2. What causes an infinite loop?