Q20

MCQ1 mark, −0.25

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 instruction 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?

(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

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