ISRO CSE 2016 | Question: 51

Question

For the real time operating system, which of the following is the most suitable scheduling scheme?

• A. Round robin
• B. First come first serve
• C. Pre-emptive
• D. Random scheduling

Comments

Random scheduling is directly out of consideration 

Same for FCFS as it is non-preemptive scheduling algo

Now, RR sometimes fits but what if high priority/urgent process came then too it will have to wait and process one by one when it's turn came.

But if we are using preemptive scheduling, then we can remove the current executing process with the high priority process and let it finish first.

Hence, ANS (C)

Answer 1

Answer C :

Preemptive Scheduling is suitable for Real-Time Programming, as it will allow a real-time process to preempt a process currently running in the Kernel. A preemptive Kernel may be more responsive, since there is less risk that a Kernal-mode process will run for arbitrarily long period before relinquishing the processor to waiting proces. Real-time systems requires that results be produced within a specified deadline.One of the key feature of Real-time system is its ability to respond to real-time process as soon as process requires CPU .As a result the scheduler for real-time system must support priority-based algorithm with preemption.

Round Robin Scheduling is used in Time Sharing Systems . (Refer Galvin)

Comments

But these cases also possible with pre-emptive scheduling like a important or urgent process may starve .

so on this way we can also reject c option

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Real time implies any new process must get immediate priority. This should be given in any standard text book.

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So in context of this question with pre-emptive you mean a system where a currently running program could be pre-empted to serve an urgent process.

whereas in round robin it will go until time quantum or process completion so we are not getting immediate response ..

Answer 2

Real-time systems need to meet strict deadlines. Some tasks are more urgent than others (like handling sensors or controlling motors), so they must:

• Interrupt lower-priority tasks when needed

• Respond immediately to time-critical events

• Guarantee predictable timing behavior

Only pre-emptive scheduling allows high-priority tasks to interrupt lower-priority ones as soon as they arrive.

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Why others don’t fit:

Scheme	Why it’s not suitable
Round Robin	Fair but not priority-aware — bad for critical deadlines
First Come First Serve (FCFS)	No preemption — critical tasks may wait
Random Scheduling	Unpredictable, no guarantee on deadlines

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Answer 3

https://en.wikipedia.org/wiki/Real-time_operating_system

nice explanation.