Operating System Tutorial

Operating System Tutorial Types of Operating System Evolution of Operating System Functions of Operating System Operating System Properties Operating System Services Components of Operating System Needs of the Operating System

Operating Systems

Linux Operating System Unix Operating System Ubuntu Operating System Chrome Operating Systems Fedora Operating System MAC Operating System MS Windows Operating System Solaris Operating System Cooperative Operating System CorelDRAW Operating System CentOS FreeBSD Operating Systems Batch Operating System MS-DOS Operating System Commercial Mobile Operating Systems


Difference Between Multi-programming and Multitasking Difference between C-LOOK and C-SCAN Difference between Rotational Latency and Disk Assess Time Trap vs Interrupt Difference between C-SCAN and SSTF Difference between SCAN and FCFS Difference between Seek Time and Disk Access Time Difference between SSTF and LOOK Difference between Process and Program in the Operating System Difference between Protection and Security in Operating System

How To

How to implement Monitors using Semaphores How to Install a Different Operating System on a PC


What is Kernel and Types of Kernel What is DOS Operating System What is Thread and Types of Thread What is Process Scheduler and Process Queue What is Context Switching What is CPU Scheduling What is Producer-Consumer Problem What is Semaphore in Operating System Monitors in Operating System What is Deadlock What is Paging and Segmentation What is Demand Paging What is Virtual Memory What is a Long term Scheduler What is Page Replacement in Operating System What is BSR Mode What is Convoy Effect What is Job Sequencing in Operating System Why is it critical for the Scheduler to distinguish between I/O-bound and CPU-bound programs Why is there a Need for an Operating System


Process Management Process State Scheduling Algorithm FCFS (First-come-First-Serve) Scheduling SJF (Shortest Job First) Scheduling Round-Robin CPU Scheduling Priority Based Scheduling HRRN (Highest Response Ratio Next) Scheduling Process Synchronization Lock Variable Mechanism TSL Mechanism Turn Variable Mechanism Interested Variable Mechanism Deadlock Avoidance Strategies for Handling Deadlock Deadlock Prevention Deadlock Detection and Recovery Resource Allocation Graph Banker’s Algorithm in Operating System Fixed Partitioning and Dynamic Partitioning Partitioning Algorithms Disk Scheduling Algorithms FCFS and SSTF Disk Scheduling Algorithm SCAN and C-SCAN Disk Scheduling Algorithm Look and C-Look Disk Scheduling Algorithm File in Operating System File Access Methods in Operating System File Allocation Method Directory Structure in Operating System N-Step-SCAN Disk Scheduling Feedback Queue in Operating System Contiguous Memory Allocation in Operating System Real-time Operating System Starvation in Operating System Thrashing in Operating System 5 Goals of Operating System Advantages of Operating System Advantages of UNIX Operating System Bit Vector in Operating System Booting Process in Operating System Can a Computer Run Without the Operating System Dining Philosophers Problem in Operating System Free Space Management in Operating System Inter Process Communication in Operating System Swapping in Operating System Memory Management in Operating System Multiprogramming Operating System Multitasking Operating Systems Multi-user Operating Systems Non-Contiguous Memory Allocation in Operating System Page Table in Operating System Process Scheduling in Operating System Segmentation in Operating System Simple Structure in Operating System Single-User Operating System Two Phase Locking Protocol Advantages and Disadvantages of Operating System Arithmetic operations in binary number system Assemblers in the operating system Bakery Algorithm in Operating System Benefits of Ubuntu Operating System CPU Scheduling Criteria in Operating System Critical Section in Operating System Device Management in Operating System Linux Scheduler in Operating System Long Term Scheduler in Operating System Mutex in Operating System Operating System Failure Peterson's Solution in Operating System Privileged and Non-Privileged Instructions in Operating System Swapping in Operating System Types of Operating System Zombie and Orphan Process in Operating System 62-bit operating system Advantages and Disadvantages of Batch Operating System Boot Block and Bad Block in Operating System Contiguous and Non - Contiguous Memory Allocation in Operating System Control and Distribution Systems in Operations Management Control Program in Operating System Convergent Technologies in Operating System Convoy Effect in Operating System Copy Operating Systems to SSD Core Components of Operating System Core of UNIX Operating System Correct Value to return to the Operating System Corrupted Operating System Cos is Smart Card Operating System Cosmos Operating Systems Examples Generation of Operating System Hardware Solution in Operating System Process Control Block in Operating System Function of Kernel in Operating System Operating System Layers History of Debian Operating Systems Branches and Architecture of Debian Operating Systems Features and Packages of Debian Operating Systems Installation of Operating System on a New PC Organizational Structure and Development in Debian Operating Systems User Interface in Operating System Types Of Memory in OS Operating System in Nokia Multilevel Paging in OS Memory Mapping Techniques in OS Memory Layout of a Process in Operating System Hardware Protection in Operating System Functions of File Management in Operating System Core of Linux Operating System Cache Replacement Policy in Operating System Cache Line and Cache Size in Operating System What is Memory Mapping? Difference Between Network Operating System And Distributed Operating System What is the difference between a Hard link and a Soft Link? Principles of Preemptive Scheduling Process Scheduling Algorithms What is NOS? What is the Interrupt I/O Process? What is Time Sharing OS What is process termination? What is Time-Sharing Operating System What is Batch File File system manipulation What is Message-passing Technique in OS Logical Clock in Distributed System

Round-Robin Scheduling Algorithm in OS

Round-Robin is a Preemptive Scheduling Algorithm and is the most commonly used algorithm in CPU Scheduling.In this, each Process is assigned with a fix time interval to execute, which is called quantum. In the round-robin, the Process gets preempted if it is executed in the given time period, and the rest of the Processes executes accordingly. Round robin is a starvation free CPU scheduling algorithm as all the Processes get fair sharing of CPU. Round-Robin is a Preemptive version of the first-come-first-serve scheduling. Time-sharing is the objective of this algorithm. In the round-robin algorithm, each Process is cyclically executed.

Advantages of the Round-Robin Scheduling Algorithm

The advantages of the round-robin scheduling algorithm are:

  1. Round-Robin is independent of starvation or convoy effect.
  2. In Round-Robin, every process gets a fair allocation of CPU.
  3. If the number of processes present in the running queue is known, then it becomes easy to estimate the worst-case response time of the process.
  4. Handles all the processes without priority.
  5. Round-Robin is easy to implement.

Disadvantages of Round-Robin Scheduling Algorithm

The disadvantages of the round-robin scheduling algorithm are:

  1. Average Waiting Time is Higher.
  2. It depends on the length of the time slice.
  3. If the time quantum is more than the response time is also more.
  4. If the time quantum is less than the context switching overhead is more.

Example of Round-Robin Scheduling Algorithm

In the following explained example, we have 4 processes with process ID P1, P2, P3, and P4. The arrival time and burst time of the proceses are given in the following table. (The Quantum time is 6).

       Process ID      Arriving Time      Burst Time  Completion Time     Turnaround Time       Waiting Time
            P1                0              8           25            25             17
            P2                1              5             11            10              5
            P3                2             10            29            27             17
            P4                3              11            34            31             20
Round-Robin Scheduling Algorithm

Steps for Gantt Chart

Step 1. In the above Gantt chart, firstly the Process P1 starts its execution, which has burst time = 8. But each process is executing only for 6 seconds because quantum time is 6. The process P2, P3, and P4 are in the waiting queue.

Step 2. At time=6, the process P1 is added to the end of the queue, and the process P2 starts its execution.

Step 3. At time=11, the process P2, which has the burst time=5, completes its execution in the given time of quantum.

Step 4. After P2, the process P3 starts its execution, which has burst time=10, but again it is also executed for 6 seconds due to the limit of quantum time. At time=17, the process P3 is added to the end of the queue.

Step 5. After P3, the next process P4 starts its execution, the burst time of P4 is 11, but it also executes for only 6 seconds.

Step 6. After P4, the process P1 again starts its execution because P1 Process left its execution due to less quantum time. So, process P1 again starts its execution to complete its execution.

Step 7. At time=29, P3 completes its execution, and P4 starts its execution again. The burst time of P4 is 11, and it is also executed for 6 intervals. At time=34, the process P4 completes its execution.

The waiting time and Turnaround time are calculated with the help of the following formula.

       Waiting Time = Turnaround time – Burst Time

       Turnaround Time = Completion time – Arrival time 

Process Turnaround Time

P1= 25-0 =0

P2= 11-1=10

P3= 29-2 = 27

P4= 34-3=31

Average Turnaround Time= 0+10+27+31/4

                                              = 68/4


Process Waiting Time

P1= 25-8=17




Average Waiting Time=17+5+17+20/4