Operating Systems | Input Output Systems | Question 4

Normally user programs are prevented from handling I/O directly by I/O instructions in them. For CPUs having explicit I/O instructions, such I/O protection is ensured by having the I/O instructions privileged. In a CPU with memory mapped I/O, there is no explicit I/O instruction. Which one of the following is true for a CPU with memory mapped I/O? (GATE CS 2005)
(A) I/O protection is ensured by operating system routine(s)
(B) I/O protection is ensured by a hardware trap
(C) I/O protection is ensured during system configuration
(D) I/O protection is not possible

Answer: (A)
Explanation: See question 1 of https://www.geeksforgeeks.org/operating-systems-set-16/amp/