[Solved] Which of the following statements about context switching is INCORRECT? - Ans: The scheduler directly saves and restores CPU registers during a context switch | Operating Systems

Operating Systems - Context Switch - Cost & Causes

Which of the following statements about context switching is INCORRECT?

AContext switching involves saving the current process's CPU state into its PCB

BThe scheduler directly saves and restores CPU registers during a context switch

CContext switches can be triggered by interrupts or system calls

DFrequent context switches increase CPU overhead and reduce throughput

Step-by-Step Solution

Step 1: Verify saving CPU state
Saving CPU state to PCB is true and essential for context switching.
Step 2: Scheduler role
The scheduler decides which process runs next but does not perform register saving/restoring; this is done by the OS kernel and hardware mechanisms.
Step 3: Triggers for context switch
Interrupts and system calls can trigger context switches, so this is correct.
Step 4: Overhead of frequent switches
Frequent context switches increase overhead and reduce throughput, which is true.
Final Answer:
Option B -> Option B
Quick Check:
Scheduler does not directly save/restore registers; it manages process selection.

Quick Trick: Scheduler selects process, kernel saves/restores registers [OK]

Common Mistakes:

MISTAKES

Trap Explanation:

PITFALL

Option B sounds plausible but misattributes register saving to the scheduler, which is incorrect.

Interviewer Note:

CONTEXT

Tests ability to spot subtle misconceptions about OS component responsibilities.

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Which of the following statements about context switching is INCORRECT?