Loops

Loops repeat a block of code while a condition holds, letting you process collections of data or repeat an action a set number of times without duplicating code.

for and while Loops

A for loop is ideal when you know how many times you want to repeat something — it bundles initialisation, condition, and increment in one line. A while loop is better when the number of iterations depends on a condition that changes inside the loop body.

for (int i = 1; i <= 5; i++) {
    std::cout << "Count: " << i << std::endl;
}

int attempts = 0;
while (attempts < 3) {
    std::cout << "Attempt " << attempts + 1 << std::endl;
    attempts++;
}

do-while, break, and continue

A do-while loop guarantees the body runs at least once before checking its condition — useful for menus that must display before validating input. break exits a loop immediately, and continue skips to the next iteration.

int num = 0;
do {
    std::cout << "Enter a number (0 to stop): ";
    std::cin >> num;
    if (num < 0) continue;   // skip negative numbers
    if (num == 0) break;     // stop the loop
    std::cout << "You entered: " << num << std::endl;
} while (true);

Common Mistakes

• Writing a loop condition that never becomes false, creating an infinite loop.
• Forgetting to update the loop variable inside a while loop.
• Using = instead of == or <= instead of <, causing off-by-one errors.
• Confusing break (exits the loop entirely) with continue (skips to the next iteration).