Transcript Operating Systems

Operating
Systems
By the end of this session,
you will know:
What an Operating System is.
The functions it performs.
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.
Operating Systems
User
Applications Software
Operating System
Computer Hardware
The OS acts like a
bridge between the
applications
software and the
computer
hardware.
Users need
applications
software to carry
out tasks, the
software needs the
operating system
in order to
communicate with
the hardware.
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.
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.
Operating Systems
Functions:
• 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!
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.
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.
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.
Operating Systems
Question!
• Transferring data to a printer?
Which 3 of
the following
is an OS
responsible
for?
• 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?
SELF ASSESSMENT
1. One of the roles of an operating system is to
allocate -
2. 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 ____________
Rubrics
Q.Nos
Answers
Marks
1.
Resources
(1)
Correct
(0)
wrong
2.
Windows
Correct
wrong
3.
Unix
Correct
wrong
4.
Windows
Correct
wrong
5.
Operating System
Correct
wrong
RECAP
Tasks of the operating
system
Next Class
Will be studying about :
– Multiprogramming
– Multitasking
– Multiuser
Operating System
Learning Onjectives:
1) Recap of Previous Class:
- Definition of OS, Tasks, Examples.
2) What are Multiprogramming, Multitasking,
Multiuser?
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
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!
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.
Operating Systems
Multitasking:
CPU
Backing Store
Program A
(Not used)
Program C
(Being used)
Program B
(Just used)
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.
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).
Operating Systems
Multiuser:
Terminal
2
Terminal
1
Central Computer
OS
Terminal
4
Terminal
3
Processing power will
be given in a ‘round
robin’ way!
PEER ASSESSMENT
1. ____________ is allowed as the OS swaps each program in
and out of memory in turn when needed.
2. The program not being used is temporarily stored on the
__________until needed again.
3. An operating system that can be used by many people at
once.
4. An operating system that is designed for
use by one person at a time 5. There are 2 Types of Multiprogramming OS ____________
& ________________
Rubrics
Q.Nos
Answers
1.
Multitasking
Marks
(1)
Correct
2.
Backing storage
Correct
wrong
3.
Multiuser
Correct
wrong
4.
Singleuser
Correct
wrong
5.
Multitasking
Multiuser
Both Correct – 1
If one correct - ½
Both
wrong
(0)
wrong