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A processor needs software interrupt to

  1. test the interrupt system of the processor
  2. implement co-routines
  3. obtain system services which need execution of privileged instructions
  4. return from subroutine
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Software interrupt ex - System Call.
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1 Answer

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Best answer

Answer is (C).

(A) and (B) are obviously incorrect. In (D) no need to change mode while returning from any subroutine. therefore software interrupt is not needed for that. But in (C) to execute any privileged instruction processor needs software interrupt while changing mode.

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is think

A processor needs software interrupt to

should be 

A process needs software interrupt to

0
copy from above link

Privileged mode==kernel mode
Non privileged mode==user mode
 From kernel to user mode, a non privileged instruction is required.
From user to kernel mode., a software interrupt is required.
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