1. Operating Systems What an Operating System is.
By the end of this session, you will know:
What an Operating System is.
The functions it performs.

2. Operating Systems What is it?
An OS is a set of programs that controls how the hardware of a computer works… It is the means of communication between the user and the computer, deals with the loading and running of application programs and manages the transfer of data and files to and from the peripheral devices.

3. Applications Software
Operating Systems
The OS acts like a bridge between the applications software and the computer hardware.
User
Applications Software
Users need applications software to carry out tasks, the software needs the operating system in order to communicate with the hardware.
Operating System
Computer Hardware

4. Operating Systems Functions:
Accepts data from input devices and transfers it to the computer’s memory.
Makes sure any output is sent to the correct output device.
Manages the transfer of data between the computer’s memory and backing storage devices.

5. Operating Systems Functions:
Allocates memory space to programs and data.
Loads applications software into memory and controls the running of them.
Deals with any errors that occur when a program is being run and informs the user.

6. Operating Systems Functions: …So, the OS is quite important!
Provides a human computer interface for the user
Provides special facilities for multiprogramming.
Manages system security by restricting access to prevent unauthorised access to the system.
…So, the OS is quite important!

7. Examples of operating systems
There are a number of operating systems that you could use on your computer.
The one that you are most likely to be familiar with is one of the Microsoft Windows operating systems.
Almost all personal computers are loaded with Windows before you purchase them and most schools use a network version.

8. If you use an Apple Mac computer then you will be familiar with Apple's unique operating system, Mac OS. Many people find this far easier and more intuitive than Microsoft's Windows versions.

9. Linux is an alternative operating system for most computers
Linux is an alternative operating system for most computers. It has the advantage of being free of charge. This is because it is 'open source' software.

10. Which 3 of the following is an OS responsible for?
Operating Systems
Question!
Which 3 of the following is an OS responsible for?
Transferring data to a printer?
Allocating storage space on a disk?
Positioning text in a word processing document?
Finding a database record?
Accepting keyboard input?
Adding colour to a drawing on screen?

11. SELF ASSESSMENT
One of the roles of an operating system is to allocate -
A well known brand of operating system –
3. Which operating system would a Mainframe computer use? Windows,Mac-OS,Unix,Office
4. Which operating system would a desktop PC most often use? Windows,Unix,Office,Linux
5. Software and hardware cannot communicate without an ____________

12. Rubrics Q.Nos Answers Marks (1) (0) 1. Resources Correct wrong 2.
(1) (0) 1.
Resources
Correct
wrong 2.
Windows 3.
Unix 4. 5.
Operating System

13. RECAP

14. Tasks of the operating system

15. Next Class Will be studying about : Multiprogramming Multitasking
Multiuser

16. Operating System Learning Onjectives: 1) Recap of Previous Class:
Definition of OS, Tasks, Examples.
2) What are Multiprogramming, Multitasking, Multiuser?

17. A multiprogramming OS holds more than one program in memory.
Operating Systems
Multiprogramming:
A multiprogramming OS holds more than one program in memory.
There are 2 Types of Multiprogramming OS you need to know : Multitasking and Multiuser

18. Operating Systems Multitasking:
A Multitasking OS allows two or more programs to run at the same time.
…It’s like having MS Word, iTunes and Solitaire open on your computer at the same time!

19. Operating Systems Multitasking:
Multitasking is allowed as the OS swaps each program in and out of memory in turn when needed.
The program not being used is temporarily stored on the backing storage until needed again.

20. Operating Systems Multitasking: CPU Backing Store Program A (Not used)
Program C (Being used)
Program B
(Just used)

21. Operating Systems Multiuser:
A Multiuser OS allows many different users at different terminals (in a network) to share the processing time on a central computer.

22. Operating Systems Multiuser:
This is allowed as the OS switches quickly between the terminals and giving each one a small amount of processing time on the central computer (called a time slice).

23. Processing power will be given in a ‘round robin’ way!
Operating Systems
Multiuser:
Terminal 2
Terminal 1
Central Computer OS
Terminal 3
Terminal 4
Processing power will be given in a ‘round robin’ way!

24. PEER ASSESSMENT
____________ is allowed as the OS swaps each program in and out of memory in turn when needed.
The program not being used is temporarily stored on the __________until needed again.
An operating system that can be used by many people at once.
An operating system that is designed for
use by one person at a time -
5. There are 2 Types of Multiprogramming OS ____________ & ________________

25. Rubrics Q.Nos Answers Marks (1) (0) 1. Multitasking Correct wrong 2.
(1) (0) 1.
Multitasking
Correct
wrong 2.
Backing storage 3.
Multiuser 4.
Singleuser 5.
Both Correct – 1
If one correct - ½
Both wrong