Given below are two statements: one is labelled as Assertion A and the other is labelled as

Reason R.

Assertion A: I/O protection is ensured by a hardware trap

Reason R: I/O interrupt caused by the condition like I/O completion and device malfunction occuring within the I/O devices In the light of the above statements, choose the correct answer from the options given below.

1. ABoth A and R are true and R is the correct explanation of A
2. BBoth A and R are true but R is NOT the correct explanation of A
3. CA is true but R is false
4. DA is false but R is true

Pick an option to check yourself, or open the answer below.

Show answer & explanation

Correct answer: D. A is false but R is true

Explanation

I/O protection is achieved by making all I/O instructions privileged, so only the OS can perform I/O. The reason is true: I/O interrupts are raised by conditions such as I/O completion or device malfunction.

Note: Many texts state that I/O protection relies on privileged instructions, which trap when executed in user mode; the official key nevertheless treats the assertion as false.