While vs Do-While Loop: Key Differences & When to Use
A while loop checks its condition first; the body may never run. A do-while loop runs the body once, then checks, guaranteeing at least one execution.
Developers pick the wrong loop when they forget about the “first-run guarantee.” It’s like trying to sip from a coffee mug before pouring—do-while ensures the mug exists; while waits for permission.
Key Differences
while: condition-then-body, possibly zero runs. do-while: body-then-condition, always one run. Use while for zero-or-more, do-while for one-or-more.
Which One Should You Choose?
Need user input at least once? do-while. Want to skip work entirely on empty data? while. Match the guarantee to the task.
Examples and Daily Life
ATM PIN retry: do-while—ask once before checking. Playlist shuffle: while—skip if queue empty.
Can a do-while loop run zero times?
No. The body executes once before the condition is tested.
Is while faster than do-while?
Speed is identical; choose based on logic, not performance.