Home » Operating System — Process Scheduling and Scheduling Queues

Operating System

Chapter 1: Introduction to Operating System 

— Definition of Operating System.

— Evolution of operating systems – simple batch systems, multi-programmed batch systems, time sharing systems.

— Functions of an operating system

— Characteristics of Operating System

— Single user and multi-user operating systems

Open-source and closed-source operating systems.

Important Questions with their Answers of “Introduction to operating system”

— MCQs and Fill in Blanks

— Short term Questions

— Long Term Questions


Chapter 2: Process Overview

Definition of process, process states, process life cycle,

Process Control Block (PCB),

Process Scheduling – Scheduling queues,

Schedulers (short term, medium term and long term).

Dispatcher.

Context Switch.

Important Questions with their Answers of “Process Overview”

— MCQs and Fill in blanks

Short term Questions

Long Term Questions


Chapter 3: CPU Scheduling

  • CPU Scheduler,
  • Preemptive and non-preemptive scheduling.
  • Scheduling criteria – CPU utilization, Throughput, Turnaround time, Waiting time, Response time.
  • Scheduling Algorithms: First-Come-First-Serve, Shortest-Job-First, Priority Scheduling, Round-Robin.

Important Questions with their Answers of “CPU Scheduling”

  • MCQs and Fill in blanks
  • Short term Questions
  • Long Term Questions

Operating System — Process Scheduling and Scheduling Queues


Process Scheduling

The act of determining which process is in the ready state, and should be moved to the running state is known as Process Scheduling.

Process scheduling is the activity of the process manager that handles the removal of the running process from the CPU and the selection of another process on the basis of a particular strategy.

The prime aim of the process scheduling system is to keep the CPU busy all the time and to deliver minimum response time for all programs. For achieving this, the scheduler must apply appropriate rules for swapping processes IN and OUT of CPU.

Types of Process Scheduling: There are two types of scheduling:-

  1. Pre-emptive Scheduling:- In Pre-emptive Scheduling, all the processes are executed by using some amount of time of CPU. The time of CPU is divided into the number of minutes and time of CPU divided into the process by using some rules. If the time is divided into equal interval than it is called Quantum Time.
  2. Non Pre-emptive Scheduling:- In Non Pre-emptive Scheduling, no time scheduling is used and also, CPU will be automatically free after executing the whole process, means that when the execution of the process will completed, then the CPU will be Free. When two or more process are given then this will first Complete the process and after completing the first process, this will automatically start the second process.

Process Scheduling Queue

The OS maintains all PCBs in Process Scheduling Queues. The OS maintains a separate queue for each of the process states and PCBs of all processes in the same execution state are placed in the same queue. When the state of a process is changed, its PCB is unlinked from its current queue and moved to its new state queue.

The Operating System maintains the following important process scheduling queues −

  • Job queue − This queue keeps all the processes in the system.
  • Ready queue − This queue keeps a set of all processes residing in main memory, is ready and is waiting to execute. A new process is always put in this queue.
  • Device queues − The processes which are blocked due to unavailability of an I/O device constitute this queue.


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‘Operating System’ Practical

  1. To install and configure MS Windows 7/8/10 on a computer
  2. To get familiar with general Windows commands – ECHO, CLS, DIR, TREE, MD, CD, TYPE, RD, DEL, MOVE, COPY , REN, ATTRIB, COLOR, DATE, TIME, ERASE, FIND, FC, MORE, CMD, PATH, SYSTEMINFO, SHUTDOWN, TASKLIST, TASKKILL, VER, VOL, CHKDSK
  3. To use wildcard characters for copying, moving, renaming, and deleting files and directories in a given hierarchical directory structure under Windows’s command prompt.
  4. To get familiar with windows control panel components.
  5. To use Windows backup and restore features.
  6. To get familiar with commonly used Windows PowerShell cmdlets like Get-ChildItem, GetContent, Get-Command, Get-Help, Clear-Host, Copy-Item, Move-Item, Remove-Item, Rename-Item, Get-Location, Set-Location, Write-Output, Get-Process, Stop-Process.
  7. To write scripts in Windows PowerShell to automate tasks.