Interrupts vs polling

Polling checks for data repeatedly. Interrupts react when a device signals that data is available.

Mechanism	Best use	Trade-off
Polling	simple tests, predictable short waits	wastes CPU when events are rare
Interrupts	normal interactive input	needs event-loop structure

Keyboard events are sporadic, so interrupts usually fit better. Polling is still useful for understanding the controller and for small deterministic experiments. Both versions exercise the same controller rules; only the decision about when to ask for data changes.

Timeout discipline

Polling loops need limits. A loop that waits forever for a key can hang a test, a demo, or a grading run.

Timer-driven limits make behavior observable. "Wait until ESC is released or until N seconds of idle time pass" is precise and testable. "Wait for some input" can easily become impossible to test.

TIP

Poll with a clear maximum number of attempts or a timer-driven timeout, then return an error the caller can handle.