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CPU Scheduling PYQs for GATE CS

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Question 1

2026 Slot Set2 PYQ

Which one of the following CPU scheduling algorithms cannot be preemptive?

Question 2

2026 Slot Set1 PYQ

Consider a CPU that has to execute two types of processes. The first type, Actuators (A), requires a CPU burst of 6 seconds. The second type, Controllers (C), requires a CPU burst of 8 seconds. A new process of type A arrives at time t = 10, 20, 30, 40, and 50 (in seconds). Similarly, a new process of type C arrives at time t = 11, 22, 33, 44, and 55 (in seconds). The CPU scheduling policy is First Come First Serve (FCFS). The first process of type A starts running at t = 10 seconds. The average waiting time (in seconds) for the 10 processes is ___________. (rounded off to one decimal place)

Question 3

2025 Slot Set2 PYQ

Processes P_{1}, P_{2}, P_{3}, P_{4} arrive in that order at times 0, 1, 2, and 8 milliseconds respectively, and have execution times of 10, 13, 6, and 9 milliseconds respectively. Shortest Remaining Time First (SRTF) algorithm is used as the CPU scheduling policy. Ignore context switching times. Which ONE of the following correctly gives the average turnaround time of the four processes in milliseconds?

Question 4

2025 Slot Set1 PYQ

A computer has two processors, M_{1} and M_{2} . Four processes P_{1}, P_{2}, P_{3}, P_{4} with CPU bursts of 20, 16, 25, and 10 milliseconds, respectively, arrive at the same time and these are the only processes in the system. The scheduler uses non-preemptive priority scheduling, with priorities decided as follows: • M_{1} uses priority of execution for the processes as, P_{1} > P_{3} > P_{2} > P_{4}, i.e., P_{1} and P_{4} have highest and lowest priorities, respectively. • M_{2} uses priority of execution for the processes as, P_{2} > P_{3} > P_{4} > P_{1}, i.e., P_{2} and P_{1} have highest and lowest priorities, respectively. A process P_{i} is scheduled to a processor M_{k}, if the processor is free and no other process P_{j} is waiting with higher priority. At any given point of time, a process can be allocated to any one of the free processors without violating the execution priority rules. Ignore the context switch time. What will be the average waiting time of the processes in milliseconds?

Question 5

2024 Slot Set2 PYQ

Consider a single processor system with four processes A, B, C, and D, represented as given below, where for each process the first value is its arrival time, and the second value is its CPU burst time. A (0, 10), B (2, 6), C (4, 3), and D (6, 7). Which one of the following options gives the average waiting times when preemptive Shortest Remaining Time First (SRTF) and Non-Preemptive Shortest Job First (NP-SJF) CPU scheduling algorithms are applied to the processes?

Question 6

2023 PYQ

Which one or more of the following CPU scheduling algorithms can potentially cause starvation?

Question 7

2022 PYQ

Consider four processes P, Q, R, and S scheduled on a CPU as per round robin algorithm with a time quantum of 4 units. The processes arrive in the order P, Q, R, S, all at time t = 0 . There is exactly one context switch from S to Q, exactly one context switch from R to Q, and exactly two context switches from Q to R. There is no context switch from S to P. Switching to a ready process after the termination of another process is also considered a context switch. Which one of the following is <b>NOT</b> possible as CPU burst time (in time units) of these processes?

Question 8

2021 Slot Set2 PYQ

Which of the following statement(s) is/are correct in the context of CPU scheduling?

Question 9

2021 Slot Set1 PYQ

Three processes arrive at time zero with CPU bursts of 16, 20 and 10 milliseconds. If the scheduler has prior knowledge about the length of the CPU bursts, the minimum achievable average waiting time for these three processes in a non-preemptive scheduler (rounded to nearest integer) is __________ milliseconds.

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CPU Scheduling PYQs for GATE CS

Solve 9+ CPU Scheduling previous year questions for GATE CS with answers and detailed solutions. Free sample questions below.

Chapter Roadmap: CPU Scheduling

The CPU Scheduling Journey

Foundations & Metrics: Arrival, Burst, Completion, Turnaround, Waiting, Response.

SJF & SRTF: Optimal algorithms for minimizing average waiting time.

Scheduling Properties: Preemption overhead, starvation, convoy effect.

Round Robin (RR): Time-slicing, quantum selection, context switches.

Priority & Multiprocessor: Diverse workloads and multi-CPU distribution.

Topic Hero: The Core Philosophy of SJF and SRTF

The primary objective of any scheduling algorithm is to optimize system metrics. For batch systems, the most critical metric is average waiting time.

The Mathematical Truth: To minimize the sum of waiting times, you must execute the shortest jobs first. If you execute a long job first, all subsequent short jobs are forced to wait for the entire duration of that long job.

Shortest Job First (SJF): Non-preemptive. Once a process gets the CPU, it runs to completion.
Shortest Remaining Time First (SRTF): Preemptive. If a newly arrived process has a burst time strictly less than the remaining time of the currently running process, the CPU is snatched away.

Note: Both algorithms are mathematically proven to give the minimum average waiting time for a given set of processes.

CPU Scheduling: Solved Questions with Step-by-Step Explanations (9 Problems)

Question 1 · Operating System · 2026_Set2 MCQ

Which one of the following CPU scheduling algorithms cannot be preemptive?

A.
Shortest Remaining Time First (SRTF) Scheduling
B.
First Come First Serve (FCFS) Scheduling
C.
Round Robin Scheduling
D.
Priority Scheduling

Question 2 · Operating System · 2026_Set1 NAT

Consider a CPU that has to execute two types of processes. The first type, Actuators (A), requires a CPU burst of 6 seconds. The second type, Controllers (C), requires a CPU burst of 8 seconds. A new process of type A arrives at time $t = 10, 20, 30, 40,$ and $50$ (in seconds). Similarly, a new process of type C arrives at time $t = 11, 22, 33, 44,$ and $55$ (in seconds). The CPU scheduling policy is First Come First Serve (FCFS). The first process of type A starts running at $t = 10$ seconds. The average waiting time (in seconds) for the 10 processes is ___________. (rounded off to one decimal place)

Question 3 · Operating System · 2025_Set2 MCQ

Processes

P_{1}

P_{2}

P_{3}

P_{4}

arrive in that order at times 0, 1, 2, and 8 milliseconds respectively, and have execution times of 10, 13, 6, and 9 milliseconds respectively. Shortest Remaining Time First (SRTF) algorithm is used as the CPU scheduling policy. Ignore context switching times.

Which ONE of the following correctly gives the average turnaround time of the four processes in milliseconds?

A.
22
B.
15
C.
37
D.
19

Question 4 · Operating System · 2025_Set1 MCQ

A computer has two processors,

M_{1}

and

M_{2}

. Four processes

P_{1}, P_{2}, P_{3}, P_{4}

with CPU bursts of 20, 16, 25, and 10 milliseconds, respectively, arrive at the same time and these are the only processes in the system. The scheduler uses non-preemptive priority scheduling, with priorities decided as follows:

•

M_{1}

uses priority of execution for the processes as,

P_{1} > P_{3} > P_{2} > P_{4}

, i.e.,

P_{1}

and

P_{4}

have highest and lowest priorities, respectively.
•

M_{2}

uses priority of execution for the processes as,

P_{2} > P_{3} > P_{4} > P_{1}

, i.e.,

P_{2}

and

P_{1}

have highest and lowest priorities, respectively.

A process

P_{i}

is scheduled to a processor

M_{k}

, if the processor is free and no other process

P_{j}

is waiting with higher priority. At any given point of time, a process can be allocated to any one of the free processors without violating the execution priority rules. Ignore the context switch time. What will be the average waiting time of the processes in milliseconds?

A.
9
B.
8.75
C.
6.5
D.
7.5

Question 5 · Operating System · 2024_Set2 MCQ

Consider a single processor system with four processes A, B, C, and D, represented as given below, where for each process the first value is its arrival time, and the second value is its CPU burst time.

A (0, 10), B (2, 6), C (4, 3), and D (6, 7).

Which one of the following options gives the average waiting times when preemptive Shortest Remaining Time First (SRTF) and Non-Preemptive Shortest Job First (NP-SJF) CPU scheduling algorithms are applied to the processes?

A.
SRTF = 6, NP-SJF = 7
B.
SRTF = 6, NP-SJF = 7.5
C.
SRTF = 7, NP-SJF = 7.5
D.
SRTF = 7, NP-SJF = 8.5

Question 6 · Operating System · 2023 MSQ

Which one or more of the following CPU scheduling algorithms can potentially cause starvation?

A.
First-in First-Out
B.
Round Robin
C.
Priority Scheduling
D.
Shortest Job First

Question 7 · Operating System · 2022 MCQ

Consider four processes P, Q, R, and S scheduled on a CPU as per round robin algorithm with a time quantum of 4 units. The processes arrive in the order P, Q, R, S, all at time $t = 0$ . There is exactly one context switch from S to Q, exactly one context switch from R to Q, and exactly two context switches from Q to R. There is no context switch from S to P. Switching to a ready process after the termination of another process is also considered a context switch. Which one of the following is <b>NOT</b> possible as CPU burst time (in time units) of these processes?

A.
P = 4, Q = 10, R = 6, S = 2
B.
P = 2, Q = 9, R = 5, S = 1
C.
P = 4, Q = 12, R = 5, S = 4
D.
P = 3, Q = 7, R = 7, S = 3

Question 8 · Operating System · 2021_Set2 MSQ

Which of the following statement(s) is/are correct in the context of CPU scheduling?

A.
Turnaround time includes waiting time.
B.
The goal is to only maximize CPU utilization and minimize throughput.
C.
Round-robin policy can be used even when the CPU time required by each of the processes is not known apriori.
D.
Implementing preemptive scheduling needs hardware support.

Question 9 · Operating System · 2021_Set1 NAT

Three processes arrive at time zero with CPU bursts of 16, 20 and 10 milliseconds. If the scheduler has prior knowledge about the length of the CPU bursts, the minimum achievable average waiting time for these three processes in a non-preemptive scheduler (rounded to nearest integer) is __________ milliseconds.

Try a question

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Built around you, not around a syllabus PDF

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Questions calibrated to the real exam

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Honest progress

Unlock the whole course

CPU Scheduling PYQs for GATE CS

Chapter Roadmap: CPU Scheduling

Topic Hero: The Core Philosophy of SJF and SRTF

CPU Scheduling: Solved Questions with Step-by-Step Explanations (9 Problems)

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