While and Do-While Loops in C++

While and Do-While Loops in C++

📘 Overview A while loop tests its condition before executing its body; a do-while loop tests its condition after executing its body. Both repeat while the condition evaluates to true, but only do-while guarantees an initial execution of the body.

🧠 Key Idea Choose while when the body may need to be skipped entirely. Choose do-while when the body must execute before the first condition check, such as displaying a menu before checking whether to repeat it.

⚔️ Core Details: - Pre-test loop: while (condition) { body } checks the condition before each execution of the body. - Post-test loop: do { body } while (condition); checks the condition after each execution of the body. - A loop condition is contextually converted to bool. - Normal termination requires the condition eventually to evaluate to false. - break exits the innermost enclosing loop immediately. - continue skips the remaining body statements and proceeds to the condition check in both loop types.

🎯 Why It Matters: - Pre-test loops support processing that may have no work available, such as reading input with while (std::cin >> value). - Post-test loops naturally express menu interactions and input validation that require an initial action. - Missing condition updates can cause unintended infinite loops. - An accidental semicolon after while (condition) creates an empty loop body and can leave the following block outside the loop.

🧠 Quick Recall: - while - Pre-test loop with a minimum of zero body executions. - do-while - Post-test loop with a minimum of one body execution when the loop is reached. - Trailing semicolon - Required after the closing condition in do { body } while (condition); - continue - Transfers control to the condition check, not to any update statement remaining in the body. - Condition conversion - Zero converts to false; a nonzero arithmetic value converts to true.