UGC NET CS 2011 Dec-Paper-2
December 4, 2023Question 8170 – Machine-Instructions
December 4, 2023GATE 2008
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Question 34
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Which of the following must be true for the RFE (Return From Exception) instruction on a general purpose processor?
- I. It must be a trap instruction
II. It must be a privileged instruction
III. An exception cannot be allowed to occur during execution of an RFE instruction
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I only
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II only
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I and II only
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I, II and III only
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Question 34 Explanation:
RFE is a privileged instruction that is performed explicitly by the Operating System to switch from kernel mode to user mode at the end of handling an exception. Hence it has to be a trap. We know when a trap/interrupt is in execution, till its completion all other trap/interrupts will not be allowed to execute. So option D is correct answer.
Correct Answer: D
Question 34 Explanation:
RFE is a privileged instruction that is performed explicitly by the Operating System to switch from kernel mode to user mode at the end of handling an exception. Hence it has to be a trap. We know when a trap/interrupt is in execution, till its completion all other trap/interrupts will not be allowed to execute. So option D is correct answer.