What is the difference between a polling loop and an interrupt-driven design?

• A. Polling checks status periodically; interrupts trigger actions as events occur to reduce latency.
• B. Polling checks status less often than interrupts.
• C. Polling uses interrupts in place of polling.
• D. They are functionally identical.

Answer: (C)

The key difference is how the system learns about events: polling versus interrupts. In a polling loop, the program keeps checking the device’s status over and over, wasting CPU cycles if nothing has changed and potentially adding delay because you only notice the event when the next poll happens. In an interrupt-driven design, the device signals the CPU with an interrupt as soon as the event occurs, allowing the CPU to handle the event promptly and then resume other work. This typically reduces wasted cycles and lowers latency for event handling.

The idea that polling uses interrupts in place of polling isn’t accurate—polling and interrupts are two different mechanisms for detecting events. They are not functionally identical, and describing polling as inherently checking status less often misses the core distinction: how the event is detected and how the CPU is alerted.