Round Robin MCQ Quiz - Objective Question with Answer for Round Robin - Download Free PDF

Last updated on Jun 6, 2025

Latest Round Robin MCQ Objective Questions

Round Robin Question 1:

Comprehension:

Consider the following set of processes with the arrival time and length of CPU burst time given in milli secends (ms)
Process Arrival Time Burst Time
P1 0 5
P2 2 3
P3 2 2
P4 5 3
P5 6 1

Calculate the average response time for these processes with a nonpreemptive priority Scheduling algorithm? Priority of the process are as follows and consider that all the processes came at zero (0) time. (Note low numbers represent high priority).

Process Arrival Time Burst Time
P1 5 3
P2 3 1
P3 2 5
P4 3 4
P5 1 2

  1. 5.8 ms
  2. 5.2 ms
  3. 4.7 ms
  4. 3.8 ms

Answer (Detailed Solution Below)

Option 1 : 5.8 ms

Round Robin Question 1 Detailed Solution

Scheduling Algorithm: Non-preemptive Priority Scheduling (Low number = High Priority)

Gantt chart:

P5

P3

P2

P4

P1

0    2    7    8    12    15

Process Table:

Process Priority Arrival Time (AT) Burst Time (BT) Start Time (ST) Completion Time (CT) Response Time (RT)
P1 5 0 3 12 15 12
P2 3 0 1 7 8 7
P3 2 0 5 2 7 2
P4 3 0 4 8 12 8
P5 1 0 2 0 2 0

Average response time = ​​​​​\(\frac{{12 + 7 + 2 + 8 + 0}}{5} = 5.8\) ms

Answer: The corrected average response time is 5.8 ms.

Note: The Priority column is essential to justify the scheduling order. The correct formula for response time is Response Time = Start Time − Arrival Time.

Round Robin Question 2:

Comprehension:

Consider the following set of processes with the arrival time and length of CPU burst time given in milli secends (ms)
Process Arrival Time Burst Time
P1 0 5
P2 2 3
P3 2 2
P4 5 3
P5 6 1

When we apply Shortest Job First (SJF) scheduling Policy/algorithm, Process (P2) faces partial starvation and waits for the longer time to execute. Which one of the following algorithms addresses this problem?

  1. Round Robin
  2. Priority
  3. Highest Response ratio Next
  4. Least Completed next

Answer (Detailed Solution Below)

Option 3 : Highest Response ratio Next

Round Robin Question 2 Detailed Solution

The correct answer is Highest Response Ratio Next.

Key Points

  • Shortest Job First (SJF) scheduling algorithm selects the process with the smallest execution time. This can lead to issues such as starvation, where longer processes keep getting delayed by shorter processes.
  • The Highest Response Ratio Next (HRRN) algorithm addresses the starvation problem by considering the waiting time of the processes. It calculates the response ratio for each process using the formula:
    • Response Ratio = (Waiting Time + Burst Time) / Burst Time
  • The process with the highest response ratio is selected next for execution. This ensures that even processes with longer burst times get a chance to execute after waiting for a sufficient period.
  • By considering both the waiting time and the burst time, HRRN balances the needs of both short and long processes, mitigating the risk of starvation.

Additional Information

  • The HRRN algorithm dynamically adjusts the priority of processes based on their waiting time, making it more flexible and fair compared to static scheduling algorithms.
  • This algorithm is particularly useful in systems where processes have varying burst times, as it ensures a more equitable distribution of CPU time.
  • Other scheduling algorithms like Round Robin and Priority Scheduling also aim to address different aspects of process scheduling, but HRRN specifically targets the starvation problem in SJF.
  • HRRN is a non-preemptive scheduling algorithm, meaning once a process starts executing, it runs to completion before the next process is selected.

Round Robin Question 3:

Comprehension:

Consider the following set of processes with the arrival time and length of CPU burst time given in milli secends (ms)
Process Arrival Time Burst Time
P1 0 5
P2 2 3
P3 2 2
P4 5 3
P5 6 1

What is the average waiting time for these processes with non-preemptive Shortest Job First (SJF) scheduling Algorithm?

  1. 3.0 ms
  2. 2.1 ms
  3. 4.6 ms
  4. 3.2 ms

Answer (Detailed Solution Below)

Option 4 : 3.2 ms

Round Robin Question 3 Detailed Solution

Scheduling Algorithm: Non-preemptive Shortest Job First (SJF)

Gantt chart:

P₁

P₃

P₅

P₂

P₄

0       5       7       8       11       14

Process Table:

Process

Arrival Time (AT)

Burst Time (BT)

Completion Time (CT)

Turn Around Time (TAT)

Waiting Time (WT)

P₁

0

5

5

5

0

P₃

2

2

7

5

3

P₅

6

1

8

2

1

P₂

2

3

11

9

6

P₄

5

3

14

9

6

 

Average waiting time = \(\frac{{0 + 3 + 1 + 6 + 6}}{5} = 3.2\)

Important Points:

WT = TAT - BT

Round Robin Question 4:

Comprehension:

Consider the following set of processes with the arrival time and length of CPU burst time given in milli secends (ms)
Process Arrival Time Burst Time
P1 0 5
P2 2 3
P3 2 2
P4 5 3
P5 6 1

What is the average turnaround time for these Processes with First Come First Serve (FCFS) scheduling Algorithm?

  1. 5.3 ms
  2. 6.4 ms
  3. 7.0 ms
  4. 8.2 ms

Answer (Detailed Solution Below)

Option 3 : 7.0 ms

Round Robin Question 4 Detailed Solution

The correct answer is : Option 3

key-point-imageKey Points

Scheduling Algorithm: First Come First Serve (FCFS)

Gantt chart:

P1

P2

P3

P4

P5

0 5 8 10 13 14

Process Table:

Process Arrival Time (AT) Burst Time (BT) Completion Time (CT) Turn Around Time (TAT)
P1 0 5 5 5
P2 2 3 8 6
P3 2 2 10 8
P4 5 3 13 8
P5 6 1 14 8

Average Turnaround Time: \({{5+6+8+8+8} \over 5} = 7.0\)

 Important Points:

TAT = CT - AT

Round Robin Question 5:

Comprehension:

Consider the following set of processes with the arrival time and length of CPU burst time given in milli secends (ms)
Process Arrival Time Burst Time
P1 0 5
P2 2 3
P3 2 2
P4 5 3
P5 6 1

Find the average weighted turnaround time for these process using Highest Response Ratio Next (HRN) Algorithm?

  1. 3.2 ms
  2. 2.834 ms
  3. 1.632 ms
  4. 6.721 ms

Answer (Detailed Solution Below)

Option 2 : 2.834 ms

Round Robin Question 5 Detailed Solution

The correct answer is option 2.

CONCEPT:

Highest Response Ratio Next (HRN):

HRN is a non-preemptive scheduling algorithm where the process with the highest response ratio is selected next. The response ratio is calculated as:

Response Ratio = (Waiting Time + Burst Time) / Burst Time

Formula:

Turnaround Time (TAT) = Completion Time (CT) - Arrival Time (AT)

Weighted TAT = Turnaround Time / Burst Time

Steps:

  1. Select the process with the highest response ratio among all arrived processes.
  2. Compute completion time, TAT, and weighted TAT.
  3. Repeat until all processes are scheduled.

Calculated weighted turnaround times:

Process AT BT CT TAT WTAT
P1 0 5 5 5 1.00
P3 2 2 7 5 2.5
P2 2 3 10 8 2.67
P4 5 3 13 8 2.67
P5 6 1 14 8 8.0

Average Weighted Turnaround Time = \({{1+ 2.5+2.67+2.67+8} \over 5 } = 2.834\)

∴ Hence, the correct answer is 2.834 ms

Top Round Robin MCQ Objective Questions

Round Robin Scheduling is most suitable for _____.

  1. Batch OS
  2. Hard RTOS
  3. Soft RTOS
  4. Time Sharing OS

Answer (Detailed Solution Below)

Option 4 : Time Sharing OS

Round Robin Question 6 Detailed Solution

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  • The round-robin (RR) scheduling algorithm is designed especially for timesharing systems.
  • It is similar to FCFS scheduling, but preemption is added to enable the system to switch between processes.
  • A small unit of time, called a time quantum or time slice, is defined.
  • The ready queue is treated as a circular queue. The CPU scheduler goes around the ready queue, allocating the CPU to each process for a time interval of up to 1-time​ quantum.

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

  1. Round robin
  2. First come first serve
  3. Pre-emptive
  4. Random scheduling 

Answer (Detailed Solution Below)

Option 3 : Pre-emptive

Round Robin Question 7 Detailed Solution

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Pre-emptive is the most suitable scheduling scheme for the real-time operating system 

Key Points

  • 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 Kernel-mode process will run for arbitrarily long periods before relinquishing the processor to the waiting process.
  • Real-time systems require that results be produced within a specified deadline. One of the key features of a Real-time system is its ability to respond to real-time processes as soon as the process requires CPU.
  • As a result, the scheduler for the real-time system must support a priority-based algorithm with preemption.

Additional Information

  • The round-robin (RR) scheduling algorithm is designed especially for timesharing systems.
  • It is similar to FCFS scheduling, but preemption is added to enable the system to switch between processes.
  • A small unit of time, called a time quantum or time slice, is defined.
  • The ready queue is treated as a circular queue. The CPU scheduler goes around the ready queue, allocating the CPU to each process for a time interval of up to 1-time​ quantum.

A scheduling algorithm assigns priority proportional to the waiting time of a process. Every process starts with priority zero (the lowest priority). The scheduler re-evaluates the process priorities everyT time units and decides the next process to schedule. Which one of the following is TRUE if theprocesses have no I/O operations and all arrive at time zero?

  1. This algorithm is equivalent to the first-come-first-serve algorithm.
  2. This algorithm is equivalent to the round-robin algorithm.
  3. This algorithm is equivalent to the shortest-job-first algorithm.
  4. This algorithm is equivalent to the shortest-remaining-time-first algorithm.

Answer (Detailed Solution Below)

Option 2 : This algorithm is equivalent to the round-robin algorithm.

Round Robin Question 8 Detailed Solution

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Concepts:

  • First come first serve automatically executes queued requests and processes in order of their arrival.
  •  Round robin: In RR, each ready task runs turn by turn only in a cyclic queue for a limited time slice.
  • Shortest –job-first: In which the process having the smallest execution time present in ready queue is chosen for the next execution.
  • Shortest-remaining-time-first: In this scheduling algorithm, the process with the smallest amount of time remaining until completion is selected to execute next.


Data:

The given scheduling algorithm assigns priority proportional to the waiting time of a process and every process starts with priority zero (the lowest priority). The scheduler re-evaluates the process priorities every T.

Explanation

With options elimination method

  • The scheduler re-evaluates the process priorities every T time units and decides the next process to schedule means here the algorithm using- pre-emptive approach. By this analogy we can eliminate the option 1(FCFS) and 3(SJF).
  • This means there must be a time quantum T exists without time quantum scheduler cannot re-evaluates the process priorities and the scheduling algorithm assigns priority proportional to the waiting time of a process instead the less service time.
  • From this it is quite clear that the algorithm cannot be Shortest-remaining-time-first and it will equivalent to Round-robin algorithms. 

Consider the following.

Process ID CPU Burst Arrival Time

P1

5

0

P2

7

2

P3

3

3

 

The completion order of the three processes under the policies FCFS and RR (with CPU quantum of 2 time units) are:

  1. FCFS: P1, P2, P3 and RR: P3, P1, P2
  2. FCFS: P1, P2, P3 and RR: P1, P2, P3
  3. FCFS: P1, P2, P3 and RR: P3, P2, P1
  4. FCFS: P1, P3, P2, and RR: P1, P2 P3

Answer (Detailed Solution Below)

Option 1 : FCFS: P1, P2, P3 and RR: P3, P1, P2

Round Robin Question 9 Detailed Solution

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Process

Arrival time

Burst time

P1

0

5

P2

2

7

P3

3

3

 

FCFS:

Gantt chart

0                   5                   12                  15

P1

P2

P3

 

Round – robin with time quantum = 2:

Gantt chart

0        2          4          6         8         10        11       12       14      15

P1

P2

P3

P1

P2

P3

P1

P2

P2

Suppose a system contains n processes and system uses the round-robin algorithm for CPU scheduling then which data structure is best suited ready queue of the processes  

  1. stack
  2. queue
  3. circular queue
  4. tree

Answer (Detailed Solution Below)

Option 3 : circular queue

Round Robin Question 10 Detailed Solution

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The correct answer is "option 3".

CONCEPT:

The circular queue is best known for the Round Robin CPU scheduling algorithm.

A circular Queue is a linear data structure based on the FIFO principle and the last position of the queue is connected back to the first position.

In Round Robin scheduling, when the timer goes off the process then swapped out & goes to the end of the ready queue.

Hence, the correct answer is "option 3".

Circular Queue

F1 R.S Deepak 09.12.2019 D3

 Additional Information

1. Queue is a linear data structure used to store data on the basis of the FIFO (First In First Out) principle.

2. Stack is a linear data structure based on the LIFO (Last In First Out) principle.

3. A tree is a non-linear data structure that store data in hierarchical form.

4. LIFO means the data entered last in the data structure will be removed first. 

5. FIFO means the data entered first in the data structure will be removed first. 

Consider the following set of processes, assumed to have arrived at time 0. Consider the CPU scheduling algorithms Shortest Job First (SJF) and Round Robin (RR). For RR, assume that the processes are scheduled in the order P1, P2, P3, P4.

Processes

P1

P2

P3

P4

Burst time (in ms)

8

7

2

4

 

If the time quantum for RR is 4 ms, then the absolute value of the difference between the average turnaround times (in ms) of SJF and RR (round off to 2 decimal places) is ______.

Answer (Detailed Solution Below) 5.25

Round Robin Question 11 Detailed Solution

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Turnaround time = completion time – arrival time

Since arrival time = 0

∴ Turnaround time = completion time

Average Turnaround time = (sum of completion time) ÷ (number of process)

Gantt chart for SJF

P3

P4

P2

P1

0              2                6                13          21

\({\rm{Average\;turnaround\;time}} = \frac{{2 + 6 + 13 + 21}}{4} = 10.5\)

Gantt chart for RR with time quantum = 4

P1

P2

P3

P4

P1

P2

0              4                8                10          14          18          21

\({\rm{Average\;turnaround\;time}} = \frac{{21 + 18 + 14 + {\rm{\;}}10}}{4} = \frac{{63}}{4} = 15.75\)

absolute value of the difference between the average turnaround = |15.75 – 10.5| = 5.25

Which of the following algorithms defines time quantum?

  1. shortest job scheduling algorithm
  2. round robin scheduling algorithm
  3. priority scheduling algorithm
  4. multilevel queue scheduling algorithm

Answer (Detailed Solution Below)

Option 2 : round robin scheduling algorithm

Round Robin Question 12 Detailed Solution

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Concept:

Time quantum is defined in round robin scheduling algorithm.

Explanation:

  • The period of time for which a process is allowed to run in a pre-emptive multitasking system is generally called the time slice or quantum.
  • Each process is assigned a fixed time (Time Quantum/Time Slice) in cyclic way. It is designed especially for the time-sharing system. The ready queue is treated as a circular queue.
  • The CPU scheduler goes around the ready queue, allocating the CPU to each process for a time interval of up to 1-time quantum.
  • If time quantum for Round Robin scheduling is very large, then it behaves same as FCFS scheduling.

In Round Robin CPU scheduling, as the time quantum is increased, the average turn around time

  1. increases
  2. decreases
  3. remains constant
  4. varies irregularly

Answer (Detailed Solution Below)

Option 4 : varies irregularly

Round Robin Question 13 Detailed Solution

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The correct answer is varies irregularly.

Key Points

  • The Round-Robin is known as a CPU scheduling algorithm.
  • The Round-Robin method mainly used the time-sharing method. The time frame for which a method or task is permitted to run in a pre-emptive technique is known as time quantum.
  • In Round Robin CPU scheduling, as the time quantum is increased, the average turn-around time varies irregularly.

Thus the correct answer is varies irregularly.

Additional Information

  • The main characteristics of the Round-Robin method are-
    • It is very easy to implement in the system.
    • In this process, time is shared equally for each process.
  • The main advantage of the Round Robin Scheduling is time slicing. If any new process is created, then it is always added at the end of the queue.
  • The main disadvantage of the Round Robin Scheduling is waiting time is more than the response time. It has very low throughput.

 

If the time quantum size is 2 units of time and there is only one job of 14 time units in a ready queue, the round-robin scheduling algorithm will cause ______context switches.

  1. 5
  2. 7
  3. 6
  4. 8

Answer (Detailed Solution Below)

Option 3 : 6

Round Robin Question 14 Detailed Solution

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Concept:

Round - robin scheduling uses time slices for each process. Each process will be assigned a time quantum to execute. If time quantum is too large, then it will behave as FCFS.

Explanation:

Given time quantum = 2 units

There is only one job that requires 14-time units to execute completely.

So, the job queue will be :

P

P

P

P

P

P

P

0     2     4      6     8     10   12    14

Context switches at 2, 4, 6, 8, 10, 12

In this, there is a total of 6 context switches, as first and last will not be the context switch.

At time 0, an OS with round-robin scheduling (time quantum = 5 units) has 5 processes P1, P2, P3, P4, P5 with burst times 15, 10, 20, 5, 15 respectively. What is the average turn-around time?

  1. 40 units
  2. 46 units
  3. 56 units
  4. 65 units

Answer (Detailed Solution Below)

Option 2 : 46 units

Round Robin Question 15 Detailed Solution

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Concept:

The round-robin (RR) scheduling algorithm is designed especially for timesharing systems.

It is similar to FCFS scheduling, but preemption is added to enable the system to switch between processes.

A small unit of time, called a time quantum or time slice, is defined.

The ready queue is treated as a circular queue. The CPU scheduler goes around the ready queue, allocating the CPU to each process for a time interval of up to 1-time​ quantum.

Time quantum = 5 units

Gantt Chart:

P1

P2

P3

P4

P5

P1

P2

P3

P5

P1

P3

P5

P3

0       5        10     15       20      25      30      35     40       45      50      55      60      65

Calculation

Process

Arrival Time (AT)

Burst Time (BT)

Completion Time (CT)

Turnaround time =

CT – AT

P1

0

15

50

50

P2

0

10

35

35

P3

0

20

65

65

P4

0

5

20

20

P5

0

15

60

60

 

Average turn around time = \(\frac{50 + 35 + 65 + 20 + 60}{5} = 46\)

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