Which of the following statements about synchronous and asynchronous I/O is NOT true?
- A. An ISR is invoked on completion of I/O in synchronous I/O but not in asynchronous I/O
- B. In both synchronous and asynchronous I/O, an ISR is invoked after completion of the I/O
- C. A process making a synchronous I/O call waits until I/O is complete
- D. In the case of synchronous I/O, the process waiting for the completion of I/O is woken up by the ISR
Answer: B. In both synchronous and asynchronous I/O, an ISR is invoked after completion of the I/O
Explanation: This question phrasing is tricky. Usually, interrupts (and ISRs) are used in both to signal completion. However, in synchronous I/O, the process waits. In asynchronous, it doesn't. The option claiming ISR is invoked in both is actually TRUE physically. ISRO key suggests (b), likely implying there's a difference in how the user process perceives it, or referring to polling vs interrupt.