GATE - 2008 | OS | Which of the following statements about synchronous and asynchronous

GATE - 2008 [Operating System]

Question:

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 (Interrupt Service Routine) is invoked after completion of the I/O
C	A process making a synchronous I/O call waits until I/O is complete, but a process making an asynchronous I/O call does not wait for completion of the I/O
D	In the case of synchronous I/O, the process waiting for the completion of I/O is woken up by the ISR that is invoked after the completion of I/O

     

Solution:

Option (B) is Correct.

Synchronous I/O mean that some flow of execution (such as a process or thread) is waiting for the operation to complete.

Asynchronous I/O means that nothing is waiting for the operation to complete and the completion of the operation itself causes something to happen.

Synchronous I/O -- some execution vehicle (like a process or thread) that initiates the I/O also waits for the I/O to complete (and perhaps completes it).

When the I/O completes, that same execution vehicle goes on to do something else, perhaps using the results of the I/O.

Asynchronous I/O -- no execution vehicle waits for the I/O to complete.

When the I/O completes, whatever execution vehicle happens to complete the I/O may arrange for later things to happen.

Option B is not true, because both synchronous and asynchronous I/O, an ISR (Interrupt Service Routine) is not invoked after completion of the I/O.

Thank You