Week 5 Lecture ICT

1. Lecture 5
Operating Systems

3. The Role of An OS
• User/ programmer convenience:
simple, consistent way for
applications to interact with
the hardware.
• Greater resource utilization:
manages the hardware and
software resources of the
computer system, often invisibly.

4. Benefit for application developers
• Don’t have to manage hardware complexity:
Application developers can design software for
an OS and it will run on all machines that
support that OS.
The OS hides and manages the hardware
complexity and provide an Application
Programmer Interface (API).

5. Kernel
Command
Interpreter
(Shell)
File
Manager
Device
Manager
GUI
Loader
OS Components

6. Kernel
• The heart of the OS
• Responsible for all the essential operations like
managing resources, task scheduling, etc.
• Also contains low-level HW interfaces.
• Size important, as it is memory-resident

7. Core Tasks of an OS
1. Processor management
2. Memory management
3. Device management
4. Storage management
5. Application Interface
6. User Interface

8. Processor Management
• Various programs compete for the attention of
the microprocessor.
• The OS plays the role of the honest referee,
making sure that each application gets the
necessary attention required for its proper
execution.
• It tries to optimally manages the limited
processing capacity of the microprocessor to
the greatest good of all the users & apps

9. Memory Management
• Straight forward for a single-user, single
tasking
• The OS ensures that:
– each application has enough private memory
– applications do not run into other application’s
private memory.
• The OS is responsible for efficient utilization
of hierarchical system memory (e.g. RAM,
cache, etc.).

10. Storage Management
• A file system is a collection of directories,
subdirectories, and files organized in a logical
order
• The OS is responsible for maintaining the file
system through indexing of filenames and their
disk location.
• The OS can find any file in a logical and timely
fashion

11. Device Management
• Applications talk to devices through the OS and
OS talks to and manages devices through
device drivers
Example: When we print to a laser printer, we
do not need to know its details. All we do is to
tell the printer device driver about what needs
to be printed and it takes care of the details

12. Application Interface
• Application developers do not need to know
much about the hardware
• The OS provides all applications with a straight-
forward and consistent interface to hardware
Example: An application uses the OS to store
data on the disk drive without knowing exact
physical characteristics of the disk.

13. User Interface
• Users communicate with the computer using a
consistent user interface provided by the OS
• This UI can be a command-line interface in which a
user types in the commands. Example:
copy a:/file1.html c:/file1.html
• Or, it can be a graphical UI, where Windows, Icons,
Menus, and a Pointing device (such as a mouse) is
used to receive and display information. Example:
With the help of the mouse, drag file1.html
from drive a to drive c

14. Types of Operating Systems
Classification according to type of computers
and applications they support
1. Real-Time Operating System (RTOS)
2. Single-User, Single Task
3. Single-User, Multi-Tasking
4. Multi-User

15. RTOS
• Used to run computers embedded in
machinery, robots, scientific instruments and
industrial systems
• An important part of an RTOS is managing the
resources of the computer so that a particular
operation executes in precisely the same
amount of time every time it occurs
• Examples: QNX, Real-time Linux

16. Single-User, Single Task
• OS designed to manage the computer so that
one user can effectively do one thing at a time
Example: MS-DOS is an example single-
tasking single-user OS with a command line
interface.

17. Single-User, Multi-Tasking
• Most popular OS
• Used by most of PCs and Laptops
• Lets a single user interact with several
programs, simultaneously
Examples: Windows, Mac OS, Linux

18. Multi-User
• A multi-user OS allows many users to take
advantage of the computer's resources,
simultaneously
Examples: Linux, Unix, Windows Terminal Server

19. Survey of common
Operating Systems
for 1. PCs
2. Embedded Systems

20. Personal Computer (PC)
Operating Systems
1. Microsoft OS
2. Unix or Unix-like OS
3. Other OS

21. Microsoft
Operating Systems1

22. Disk Operating System (DOS)

29. UNIX or UNIX-like
Operating Systems2

34. Other
Operating Systems3

38. Embedded
Operating Systems
• Microsoft CE
• Android
• Other Embedded OS

41. Pocket PC OS Palm OS
Symbian OS

42. OS Survey
Summary

45. http://tinyurl.com/5hb8pp