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Lesson Note

Subject: Computer Studies

Topic: Operation System
Lesson Objectives: by the end of this lesson, the learners should be able to:
Define the term Operating System;
Give examples of operating systems;
state the functions of an operating system.

Lesson Summary/Discussions
Definition: The term Operating System can be defined as a Software that acts as an intermediary between the computer hardware, other computer software and the computer user. It can also be seen as the core system software that controls the activities of the computer system. New computer system must be loaded with any operating system before installing other software.
Operating System is loaded into the computer memory when it is switched on.

Types of Operating System

The basic types of Operating Systems are:

  • Single program
  • Multi-tasking.
  • Multi-user

1. Single Program Operating System: These are operating system that allows only one programme to run at a time. The computer user can only open one programme at a time. If the user decided to work on another programme in the same computer,
he must close the first programme before opening another one. This makes working with such operating system burdensome especially when you want to copy some data from the spreadsheet to another application package.

Examples of single programme operation system are:

  • Microsoft Disk Operating System (DOS),
  • IBMPC-1DOS c.t.c.

2. Multi-tasking: Multi-tasking operation system allows more that one program
to run at the same time. The programmes are run in turns with the processor.
The present programme that is running is minimized so that another programme can be viewed. Examples of multi-tasking operating system are:
Windows Operating System Vista
Sun Solaris

Versions of Windows Operating System are:
Windows 95
Windows 98
Windows ME
Windows XP professional edition
Windows XP Home Edition
Windows NT

3. Multi-User Operating System: This is a set of programme (Software) that gives access to more than one computer user to share information with only one main computer (referred to as a network server) at the same time. Multi-User network is used in cyber cafés, banks, schools’ computer laboratory and industries.

Server, in terms of computer, is a computer or a programme which provides services to other programs or user, either in the same computer or over a computer network.

Clients are computers in a network that requests and or consumes the services provided hy another computer called a server.


  1. It schedules and loads programs in order to provide continuous sequence
  2. of job response to events.
  3. It allocates system resources.
  4. It protects the software, hardware and other data from wrong usage.
  5. It provides detailed records of processing or operational activities.
  6. It helps in files and disk management.
  7. It serves as system security. Sometimes it does this by restricting some program to the administrator with a password.
  8. It communicates with the computer user through the terminals.
  9. It monitors and controls the activities of a computer such as input, processing, output and storage devices.

See previous lessons in computer Studies
Lesson Evaluation

  1. Define Operating Syslem.
  2. What is the full meaning of DOS?
  3. Explain the types of operating system with examples.
  4. State any four functions of operating system.
  5. Mention five versions of windows operating system.

Questions answered correctly? Bravo!

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