Home » Operating System — Dispatcher

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 — Dispatcher


The dispatcher is the module that gives control of the CPU to the process selected by the short-time scheduler(selects from among the processes that are ready to execute).

Dispatcher is a special program which comes into play after scheduler. When scheduler completed its job of selecting a process, then after it is the dispatcher which takes that process to the desired state/queue. The dispatcher is the module that gives control of the CPU to the process selected by the short-term scheduler.

Functions of Dispatcher:

  • Switching context
  • Switching to user mode
  • Jumping to the proper location in the user

Difference Between Scheduler and Dispatcher

The main difference between scheduler and dispatcher is that the scheduler selects a process out of several processes to be executed while the dispatcher allocates the CPU for the selected process by the scheduler.


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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.