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+12 votes
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System calls are usually invoked by using

  1. a software interrupt
  2. polling
  3. an indirect jump
  4. a privileged instruction
asked in Operating System by Veteran (59.7k points) | 3.5k views
+3
Ans A

2 Answers

+25 votes
Best answer
Software interrupt is the answer.

Privileged instruction cannot be the answer as system call is done from user mode and privileged instruction cannot be done from user mode.
answered by Veteran (367k points)
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+2
what about polling and indirect jump?
0

System calls are Virtual Instructions. Instructions can be invoked by Interrupts.

Explanations are already given for options (A) and (D).

(C) is wrong.It is jump to fixed locations.

http://www.cs.princeton.edu/courses/archive/spr01/cs217/slides/21.os.pdf.

(B) is wrong.polling is the approach where the CPU repeatedly checks the status of a device for exchanging data.

http://www.cse.iitm.ac.in/~chester/courses/15o_os/slides/5_Interrupts.pdf

0

Note: Implementing system calls requires a transfer of control from user space to kernel space, which involves some sort of architecture-specific feature. A typical way to implement this is to use a software interrupt or trap. Interrupts transfer control to the operating system kernel, so software simply needs to set up some register with the system call number needed, and execute the software interrupt.

https://en.wikipedia.org/wiki/System_call#Typical_implementations

+14 votes
answered by Active (4.8k points)
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