The document discusses operating systems and computer networks. It defines an operating system as software that manages computer hardware and resources and provides common services. It describes the core tasks of an OS including processor management, memory management, device management, storage management, application interface, and user interface. It also discusses types of operating systems such as real-time, single-user single-task, single-user multi-tasking, and multi-user. The document then covers computer networks, defining them as connected computers that share resources. It describes network components, topologies including client-server, point-to-point, bus, ring and star, and types of networks based on distance such as LAN, MAN and WAN.
1. Lecture 09 & 10
Operating Systems
Network, Communication,
OSI
2. Operating System
An operating system (OS) is software that
manages computer hardware and
software resources and provides common
services for computer programs
3. Core Tasks of an OS
Processor management
Memory management
Device management
Storage management
Application Interface
User Interface
4.
5. Processor Management
The CPU executes each process a bit at a time. The
CPU's clock times the execution of a process, and
when a time limit is reached, then the clock signals the
CPU that it is time to switch to another process.
The CPU executes just one process, and the
processes that are ready and waiting for their turn at
execution are kept in a queue (a waiting line, like at
the post office) in primary storage.
6. Memory Management
Straight forward for a single-user, single tasking
Each app must have enough private memory in
which to execute
App can neither run into the private memory
space of another app, nor be run into by another
app
Different types of memory (e.g. main, cache) in
the system must be used properly, so that each
app can run most effectively
7. Storage Management
The OS manages storage through one of its
sub-modules, the File Manager
A file system is a collection of directories,
subdirectories, and files organized in a logical
order.
File manager maintains an index of the
filenames & where they are located on the disk.
File manager make it easy to find the required
file in a logical and timely fashion.
8. 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
9. Application Interface
App developers do not need to know much about
the hardware, while they are developing their app
The OS provides all apps with a straight-forward
and consistent interface to the HW
Example: An app uses the OS to store data on the
disk drive. For that, the app does not need to know
about the exact physical characteristics of that drive;
it just tells the OS to do that through the app
interface, and the OS takes cares of all the details of
the task
10. 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
11. Types of OS
Real-Time Operating System (RTOS)
Single-User, Single Task
Single-User, Multi-Tasking
Multi-User
12. Real Time Operating Systems
Used to run computers embedded in machinery, robots, scientific
instruments and industrial systems
Typically, it has little user interaction capability, and no end-user
utilities, since the system will be a "sealed box" when delivered for
use
Examples: Wind River, QNX, Real-time Linux, Real-time Windows
NT
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
In a complex machine, having a part move more quickly just
because system resources are available may be just as
catastrophic as having it not move at all because the system
was busy
13. Single-User, Single Task
OS are designed to manage the computer so that
one user can effectively do one thing at a time
The Palm OS used in many palmtop computers
(PDA’s) is an example of a single-user, single-task OS
Single-User, Multi-Tasking
Most popular OS
Used by most all PC’s and Laptops
Examples: Windows, Mac OS, Linux
Lets a single user interact with several programs,
simultaneously
14. Multi-User
A multi-user OS allows many users to take
advantage of the computer's resources,
simultaneously
The OS must make sure that the requirements of
the various users are balanced, and that the
programs they are using each have sufficient and
separate resources so that a problem with one user
doesn't affect any of the other users
Examples: Linux, Unix, VMS and mainframe OS,
such as MVS
16. Uses of Computing
Communication
Internet
E-Mail
Instant Messaging
FTP
Newsgroups Chat Rooms
Web Folders Fax Machine or Computer Fax/Modem
Video Conferencing
Internet telephony (enables you to talk to other people over the
Internet Sometimes called Voice over IP )
Internet printing (allows you to print to network printer from
anywhere in the world )
20. Hub
The network traffic controller
Device that provides central point for
cables in network
Components of Conventional
Computer Networks
21. Cables
Are either electrical or optical
Not required at all for wireless networks
Wire, cable, and other tangible materials used to send
communications signals
22. Routers
Connects computers and transmits data to correct
destination on network
Routers forward data on Internet using fastest
available path
33. Point to Point
Simple network that connects fewer than 10
computers
Each computer, or peer, has equal capabilities
34. Bus
All computers and devices connect
to central cable, or bus
No server is required
One computer sends data to
another by broadcasting the address
of the receiver and the data over the
bus
All the computers in the network
look at the address simultaneously,
and the intended recipient accepts
the data
35. Ring
Cable forms closed ring, or
loop, with all computers and
devices arranged along ring
Data travels from device to
device around entire ring, in one
direction
No server is required
36. Star
All devices connect to a central
device, called hub
All data transferred from one
computer to another passes
through hub
This topology allows multiple
messages to be sent
simultaneously