CS-611
COMPUTER FUNDAMENTAL
& PC SOFTWARE
An ISO 9001:2000 Certified Organization
BCA-1 IGNOU
BLOCK 1
Computer Fundamentals:Hardware
& Software
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Introduction
Definition:
An electronic, digital device that stores and processes
information.
Final Result
(example -Display of image)
Digitized Data
(1010101010)
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History
 The tool known as ABACUS was the age-old tool used by
man to count and calculate was designed and developed by
Chinese some 5000 years ago.
 Blaise Pascal designed a working mechanical calculator in
1642.
 Gottfried Von Leibnitz a German, modified Pascal’s
calculating machine which could multiply numbers directly.
 In 1833 Charles Babbage an English scientist, designed
Analytical Engine using tooth wheels so that it could perform
all mathematical operations in a predetermined sequence
using a set of operational instructions.
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History
 Lady Ada Lovelace is considered as the first lady Computer
Programmer as she has developed the concept of writing
systematic operational instructions for the analytical engine.
 In 1850 George Boole an English mathematician proposed
logic theory of using the binary (two) number system. This
number system had
(0 and 1).
 Bool proposed a logic popularly known as Boolean algebra.
Computer processors are designed on this system of logic.
 A statistician Dr. Herman Hollerith, developed a punched
card that would contain data coded in form of punched holes.
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Applications of Computers
Computers have a very big impact on our day-to-day life.
They can be used for a number of applications like:
– Business
– Education
– Research
– Office
– Accounting
– Military
– Space
– Entertainment
– Medical
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Applications of Computers
Following are the broad application
areas
where
computers
are
used
extensively
•Entertainment: It can be used to make cartoon
movies, animation and special effects in movies,
games etc.
•Day to day life: Collages, Hospitals, Railway and
Airline Booking Systems, Shops, Bank, ATM
centers etc. to carry out day to day work.
For
example:
Train
ticket
bookings
can be done with help of computer.
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Applications of Computers
•
Communication: Nowadays Internet is
becoming integral part of life to gather
information about different topics or to
send and receive emails etc.
•
Scientist: use it for research purposes,
space programs, nuclear programs etc.
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Advantages
•
Speed: Computers carry out the jobs in microseconds or less time. The
human beings cannot think of doing the jobs in such speeds. Few lakh
calculations can be done in a second
•
Accuracy: While doing a job human being may commit mistakes where
as if the data given to the computer is correct then the computer does
the job without any mistakes.
•
Efficiency: Unlike the human beings efficiency is very high in
computers as it is a machine it does not get tired or bored of doing a job.
•
Storage: Computer has memory in which the data can be stored for
future use. For example the details of the students, customers, suppliers
etc. can be stored in the computers to be used whenever it is required.
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Limitations
•
Computers cannot think by themselves and they require human
direction to perform specific tasks.
•
If the data given is wrong then it gives the wrong result.
•
Instructions given also should be correct that is instead of
addition if you ask it to multiply it will multiply.
•
It will not work without electricity.
•
Investment and maintenance in this equipment is also required.
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Generations of Computers
 First Generation (1940-1956): Vacuum Tubes
The computers of this generation were made of vacuum tubes for
circuitry and magnetic drums for memory
 Second Generation (1956-1963): Transistors
The computers of this generation made up of transistors replacing
vacuum tubes
 Third Generation (1965-1971): Integrated Circuits
The computers of these generations were made up of IC (Integrated
Circuits)
 Fourth Generation (1971): Microprocessors
The computers of this generation saw the advent of Large Scale
Integration (LSI) and Very Large Scale Integration (VLSI)
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Classification of Computers
Personal Computers:
A microcomputer is the smallest general
purpose processing system.
Minicomputers:
A minicomputer is medium sized computer
that is more powerful than a microcomputer.
Mainframes computers:
Computers with large storage capacities and very high
speed of processing.
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Classification of Computers
 Super computers:
These have extremely large storage area
and computing speeds, which are many
times faster than earlier discussed
machines.
 Laptop/Note Book Computers:
These are small in size and weigh few
Kgs & you can carry any place.
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Organization of a Computer
Main
Memory
Input Unit
Output Unit
Control
Unit
ALU
Secondary
Memory
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Input Unit
Any device designed to assist in the entry of data into a
computer.
 Mouse
 Light Pen
 Touch Screen
 Joy Stick
 Keyboard
 Scanners
 Optical Character Readers (OCR)
 Magnetic Ink Character Reader (MICR)
 Mark Sense Reader
 Bar Code Reader
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Output Unit
Any peripheral device that converts the stored binary coded
data into convenient external forms as text, pictures &
Sound
1. Visual Display Unit
2. Printer
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3. Speakers
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Central Processing Unit
 Arithmetic-Logic Unit (ALU): The ALU is an
electronic circuit used to carry out the arithmetic
operations. (Addition, Subtraction, Multiplication and
Division)
 Control Unit: The control unit coordinates the
activities of all the other units in the system.
 Memory Unit: is used to store data temporarily.
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The storage capacity of the memory is generally
measured in megabytes.

8 Bits = 1 Byte

1024 Bytes = 1 Kilobyte (KB)

1024 Kilobytes = 1 Megabyte (MB)

1024 Megabytes = 1 Gigabyte (GB)
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Memory
Memory is the main part of computer where
we store our data either for temporarily or
permanently
There are Two Types of Memory
1.Primary Memory
2.Secondary Memory
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Primary Memory
We can also called internal memory. This memory
consists of semiconductor memory chips and is used
to store the data and programs.
Two Types of Primary Memory
1. RAM (Random Access Memory) or Volatile Memory
2. ROM (Read Only Memory) or Non-Volatile Memory
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Secondary Memory
This is the permanent memory. But user can delete
the data whenever they want.
Examples:
Floppy disks Fixed (hard) disks, Pen Drive
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Optical disks.
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Secondary Memory
This memory is external memory. This memory can
store a large amount of data for permanently.
Types of Secondary Memory
1. Floppy Disk:- A floppy disk is made of flexible
plastic material coated with iron oxide. This is used
to store data and instructions. We can move the
data from one place to another. The Floppy disks
are available in two sizes 5.25 inches and 3.5
inches and their capacity range from 360 KB to
1.44 MB per disk.
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2.
Magnetic Disk:- A magnetic disk is
circular platter of plastic which is coated with
magnetized material. One of the key
component of a magnetic disk is a
conducting coil named as Head which
performs the job of reading and writing on
magnetic surface. The head remains fix
while the disk rotates for reading and writing
operation.
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3. Winchester Disk:-
This is sealed rigid magnetic oxide
medium disk, which holds 10 MB to 10
GB of data. These disks are not
removable from the drive.
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4.Magnetic Tape:Magnetic tapes are mounted on reels
or cassette of tape to store amount of
data. These are cheaper and removable
from the drive. Information retrieval from
tapes is sequential and not random. It
takes long time for searching. They are
low cost, low speed, portable.
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5.Optical Memories
This memory is used to store a very-2 large
amount of data. Data is written in optical disk
through laser beam.
Three Optical Devices
1. CD-ROM
2. WORM
3. Erasable Optical Disk.
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High Speed Memory
Cache Memory: These are small fast
memories placed between the
processor and the main memory.
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Two important Computer
terminologies
 Hardware:
This comprises the Electronic,
Electrical and mechanical
components of the machine.
 Software:
Program means the set of
meaningful instructions written in
a particular order so as to carry
out some task.
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Computer Language
 The term computer language
includes a wide variety of languages
used to communicate with computers.
 Computer language is a system of
communication.
 The computer languages must have
instructions to manipulate
input/output, text etc.
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Classification of Computer Language
These languages are broadly
classified as :
 Machine level language
 Assembly level language
 High level language
 Fourth generation languages
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Classification of Computer Language
Machine level language –
A program written using binary numbers i.e. 0’s and 1’s specified
for the processor’s operation and absolute binary address
Assembly level language Language uses mnemonics or abbreviations to represent a
particular operation.
High level language In this, instructions are written in simple English.
(Examples: BASIC, COBOL, FORTRAN, PASCAL, C, C++ and
Java etc
Fourth generation languages These are the application development tools, which improve the
efficiency and productivity. Examples: DBMS, RDBMS
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Kinds of software
Two kinds of software are:
•
System Software:
software control and direct the operation of the computer.
Examples - Operating System, Compiler, and Interpreter
etc.
•
Application Software:
software used for specific applications such as letter
typing, accounting, billing and inventory etc.
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Introduction to Operating Systems
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Operating System
Operating system is an interface between user
and machine. It is an essential component of
computer system. The primary objective of an
OS is to make computer system convenient to
use and utilize computer hardware in an efficient
manner.
An operating system is a large collection of
software which manages resources of the
computer system such as memory, processor,
file system and input/output devices.
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Operating System
 This is the system software, which
acts as an interface between the
user and computer.
 All the computers require operating
system without which one cannot
work with the computer.
 Operating system control, coordinates, synchronizes all the
operations of the computer.
 Examples: Microsoft Disk Operating
System (MS-DOS), MicrosoftWindows 98, Microsoft-Windows XP,
Microsoft-Windows 2003 Server,
UNIX, LINUX etc.
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Microsoft Disk
Operating System
(MS-DOS),
MicrosoftWindows XP
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Functions Operating Systems
The main functions of Operating System are
1. Act as an interface between the user and the computer
2. To monitor the use of the resources of computers
(Resources can be hardware or Software)
3. To control and coordinate Input and Output devices
4. It manage the program and data files i.e. to store, to
retrieve, to delete files
5. Help the application programs execute commands
given by the user
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Examples of OS
Examples of operating systems are
•
Microsoft Windows 98, Microsoft Windows XP, Microsoft
Windows 2000, Microsoft Windows 2003, UNIX, Linux, Novell
Netware, Solaris etc.
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Evolution of Operating System
1.Serial Processing
2.Batch Processing
3.Multiprogramming
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Types of Operating System
Different types of Operating Systems
1. Batch Processing System
2. Multiprogramming Operating System
1. Multitasking OS
2. Multi-User OS
3. Time Sharing System
4. Real Time System
3. Network Operating System
4. Distributed Operating System
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Multiprogramming Operating System:The interleaved execution of two or more
different and independent programs by the same
computer.Multiprogramming is carried by placing
the two or more user programs in main memory
and executed them concurrently. The CPU
switches from one program to another.
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Multi-Processing:A system that makes the use of more
than one CPU is called multiprocessing
system. A multi-processing which describe
interdependent computers with two or more
independent CPU s have the ability to
simultaneously execute programs. In this
system, instructions from different and
independent programs can be processed at
the same instant of time by different CPU.
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BLOCK 2
Computer Fundamentals:
Communication, Networking,
Security
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BASIC TERMS
• Data are entities that convey meaning.
Information is obtained by processing data
using desired functions.
• Signals are electric or electromagnetic
encoding of data,and signaling is
propagation of signal along communication
medium.
• Transmission is communication of data
achieved by the propagation and
processing of signals
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DATA COMMUNICATION CODES
(Data encoding)
• Computer manages, store and exchange
data using electronic pulses or digital
signals 0 or 1
0
OFF
(absence)
1
ON
(presence)
• Every char (letter, number, symbols) is
composed of a group of bits called codes.
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Data Codes
ASCII*
Controlling authority ANSI
Number of bits
7
Number of Character 128
EBCDIC**
IBM
8
256
*American Standard code for information interchange
**Extended Binary coded decimal interchange code
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Communication Speed or Rate:• The speed at which two computers
exchange or transmit data is called
communication rate on transmission
speed.
• The unit of measurement of speed is
measured using bps (bits per second)
or baud.
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Private Vs Switched Channels
• Private leased lines are permanently
connected circuits between two or
more points.These lines are available
for private use by the leasing party.
• Switched lines or dial up lines are
available to any subscriber. For e.g.
Telephone connection at our home or
office
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Analog and Digital Transmission
• An analog signal is one that is continuous
with respect to time, and may take on any
value within a given range of values.
– Human voice, video and music when
converted to electrical signal using suitable
devices produce analog signals.
• A digital signal may take on only a discrete
set of values within a given range. Most
computers and computer-related
equipment are digital.
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Parallel and Serial Transmission
• Parallel Data Transmission:- Multiple
parallel lines connecting the transmitting
and receiving units. Each wire carries a bit
of information. Usually, one character id
transferred in one go.
• Serial Data Transmission:- Each bit is
sent sequentially one after another. It
requires one pair of wire conductors
receiving and transmitting units.
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Communication
Protocol/Standard
• Protocols are technical customs or guide
lines that govern the exchange of signal
transmission and reception between
equipments.
• Some of the functions that communication
protocol regulates are:
•
•
•
•
Control of information transfer
Structure and formats of data
Error recoveries Re-transmission control
Interface managemen
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DATA COMMUNICATION MODES
• Synchronous and Asynchronous
Transmission
• Simplex, Half Duplex and Full duplex
Communication
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Synchronous and
Asynchronous Transmission
• Synchronous Transmission:- characters are
transmitted as groups with control character in the
beginning and at the end of the bit train. The
transmission and receiving intervals between each
bit are precisely timed.
• Asynchronous Transmission:- Each Char is
transmitted separately, one char at a time. Each
char begin with a start bit (coding begin) and end
with a stop bit (coding end). Then next character is
sent, with start and stop bits.
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Simplex, Half Duplex and Full
Duplex Communication
• The direction in which information can flow over
a transmission path is determined by the
properties of both the transmitting and the
receiving devices. There are three basic options:
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Communication Hardware
• Sender and Receiver Hardware
• Communication Devices
• Communication Channel
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Sender and Receiver Hardware
•
•
Sender and Receiver Hardware are used for
handling Communication messages, data
transfer etc.
Nodes and Workstations
Data Communication is done using various
communication devices and software interconnected for information exchange. The
devices used to communicate in a data
communication network are called
workstations. These workstations includes
Computer, terminal, printer etc.
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Sender and Receiver Hardware
•
Multiplexer
Multiplexing is a form of data transfer in
which communication channels are used
for several transmissions. Ex. Telephone
lines.
In other words multiplexing is a type of
network mechanism, which allows a
number of simple, low cost terminals to
share each communication line,
introduces almost no delay and requires
no special computer software.
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Communication Devices
Modem or Modulation Demodulation
• Computer generates digital data which is
unsuitable for long distances . Data must be
converted to analog data is called modulation.
• The converted data in the form of analog signals
can travel without any noise over long
distances. This data when reaches its
destination is converted back to digital data with
the help of demodulation.
• Codec performs the opposite function of a
modem
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Communication Channels
• The most basic hardware required for
communication is the media through which
data is transferred .
• Two wires open line
• Twisted Pair Cable
• Coaxial Cable
• Fiber Optical Cables
• Wireless
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Two wires open line
• This is the simplest of all the transmission
media. It consists of a simple pair of
metallic wires made of copper or
sometimes aluminium of between 0.4 and
1 mm diameter, and each wire is insulated
from the other.
• Distance: upto about 50 meters
• Data transfer rate: upto 19200 bits per
second.
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Twisted Pair Cable
•
•
•
A twisted pair cable consists of pairs and
copper wires. They are twisted together to
enable canceling out noise and external
disturbance to the signal that they carry.
Distance: upto1km
Data Transfer rate: upto 1-2 megabytes per
second
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Coaxial Cable
• Distance: upto 1km
• Data transfer rate: upto 100 megabytes
per second
• A coaxial cable is of two types - a 75-ohm
cable, which is used by the cable TV
operators and the 50-ohm cable which is
used in high-speed broadband networks
and are low loss cables.
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Fibre Optic Cables
• This contains a very thin (as thin as the human
hair) cable made of optical fibre. The cable
transmits much more data and much faster than
others. This cable carries signals in light pulses.
Telephone companies and large government
organization which need and can afford it, are
using it.
• Distance: long and medium transmission links
• Data transfer rate: upto 1000 megabytes per
second
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Wireless
• There will be no wires here and data will
transmitted into radio waves, microwaves
and through satellite channels.
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Introduction to Networking
A networking means connecting two or more
computers together for sharing of information
and resources.
A computer network is a collection of
hardware and software that enables a group
of computers to communicate. It provides
shared resources includes data files,
applications and hardware (printer) and other
related resources.
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A networking is basically a communication system
of computers. Just as the telephone system
allows two people to talk to one another,
networks allow computers to communicate.
The entire computer network can be classified into
two Broad categories:1.LAN (Local Area Network)
2.WAN (Wide Area Network)
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1. LAN :- A private network with in a range of
10 kilometers which is controlled by a single
organization. It permits exchange of data
and information among them with in a
localized area. Typically it covers a building,
a cluster of buildings.
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LAN Topologies
A network Topology refers to the physical
layout of the network in which all the devices
are connected. The point of connection to
the network by the station are called nodes.
There are several types of topologies
1. Star Topology
2. Bus Topology
3. Ring Topology
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1. Start Topology:In this topology a number of stations are
connected directly to a central station.
The central controller manages and
controls all communications between
stations on the network.
Node
Node
Node
Node
Node
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2. Bus Topology:All the stations are connected to a single
communication line. This single
communication line is referred to as a bus..
On a Bus Network, all stations share the
same medium.
Node
Node
Node
Node
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3.
Ring Topology:-
In this topology each station attached to
an adjacent station using point-to-point link.
Called a ring.
A
E
B
D
C
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LAN Access Method
Many techniques have been proposed, but
two of these are commonly used
(i) Carrier-Sense Multiple Access with
Collision Detection (CSMA/CD)
(ii) Token passing
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Communication Architecture for
Networking
Instead of using entire data communication as a
single module, the task is broken into various
subtasks. Each subtask operates separately by
different layers of the communication architecture.
System that follow the OSI (Open System
Interconnecting) are said to be open to one
another at different layers and thus called open
systems.
The easiest way design network is to break
processes down into layers.
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1. Physical Layer:- This layer defines the
mechanical, electrical, functional and procedural
standards for the physical transmission of data.
2. Data Link Layer:- It provides the functions and
protocols to transfer data between network
resource and to detect errors.
3. Network Layer:- This layer establishes
connections between networks. It includes
operational procedures for inter network
communication.
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4. Transport Layer:- This layer is responsible for
transparent and reliable transfer of data.
5. Session Layer:- This layer provides the
mechanism for organizing and structuring interaction
between applications.
6. Application Layer:- This layer supports the
applications of users and enables them to connect to
the network.
7. Presentation Layer:- This layer presents data to
the application layer.
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LAN Hardware & Software
The Basic Hardware components of LAN
1. Transmission Channel.
2. Network Interface Unit (NIU)
3. Server
4. Workstation
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Network Interface Unit
This unit connects each device in
the LAN network to shared
transmission device. It contains the
rules or logic to access the LAN. NIU
is also used to implement LAN
protocols and for device attachments.
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Server
A server is an important component of a network. The
server runs the NOS and offers network services to
users at their individual workstations. These services
includes file storage, security, user management etc.
1. File Server:- is used to share storage space for files.
2. Printer Server:- Printer connected to the server can
be accessed directly by all the users of the network.
3. Modem Server:- is also used to share telephone
lines and modem by all connected workstations in a
network.
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Workstation:- When a computer is connected
to a network. It becomes node on the network is
called a workstation.
LAN Software:- Software of LAN OS facilitates
the sharing of expensive resources such as printer,
storage space etc. among all LAN users provides
security for data.
Various types of LAN OS
Ex. Novel Netware, Windows NT
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Communication Switching
Techniques
• In a WAN, two computing devices are not
connected directly.
• A network of switching nodes provides a
transfer path between the two devices.
• The process of transferring data blocks
from one node to another is called data
switching.
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• Circuit Switching
In circuit switching there is a dedicated
communication path between the sending and
receiving devices, like telephone network where a
dedicated path is set between the caller and the
called party for the duration of a telephone call is an
example of Circuit Switching.
• Message Switching
In message Switching, the message is then passed
through the network from one node to another till it
reaches the intended destination. Example E-Mail,
Telegrams
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• Packet Switching
It combines the advantages of message and
circuit switching. Same like Message Switching
in which data is transmitted in blocks stored by
the first switching node in the network and is
forward to the next until it reaches its
destination. Max length of packets is between
128 bytes to 4096 bytes.
• There are two approaches to packet switching
* Datagram
* Virtual circuit
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WAN Devices/Hardware
• Bridges
– Bridges are used to connect two LANs that use
identical LAN protocols over a wide area.
– Bridges operate at the data link layer (layer 2) of the
OSI model.
• Routers
– Routers can be used to connect networks that may not
be similar.
– Routers operates at the network layer (layer 3).of the
OSI model.
• Gateways
– Gateways are used to connect two dissimilar LANs.
– gateway operates on, the application layer (layer 7) of
the OSI model.
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Types of Wide Area Networks
• Public Networks
– Public Networks are those networks which are
installed and run by the telecommunication
authorities and are made available to any
organisation or individual who subscribe it.
– Public Switched Telephone Networks (PSTN)
– Public Switched Data Networks (PSDN),
– Value Added Services (VANs/VADs) and
– the Integrated Services Digital Networks
(ISDN).
• Private Networks
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Few Applications
E-Mail:E-Mail system is basically used for
sending messages electronically to
individuals or group of individuals in an
inter or intra office environment. We can
attach a file of any application software.
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EDI
EDI (Electronic Data Interchange):- It means
replacing paper documents with electronic
documents and replacing traditional methods of
transmission such as Mail, Phone, in-person
delivery with electronic transmission.
It can be used to electrically transmit documents
such as purchase orders, invoice, shipping
notice, receiving advices, transmit financial
information and payments in electronic from.
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Internet
Internet is the world’s largest Network. It is a
global network. It is the best flower gifted by
information technology.
Services:1. E-Mail
2. Usenet- Views and News:
Usenet is the BBS (Bulletin Board Service)
of internet. The messages in this BBS are
organized into thousand of News groups
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3. Telnet (Remote Login)
Telnet allows an Internet user to access a
remote computer (host). After properly
connectivity and logging into the remote host, the
user can enter data, run programs or do any other
operations.
4. FTP (File Transfer Protocol):-
It permits an internet user to move a file from
one computer to another. The files may have data,
graphics, text etc.
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5. Navigators (Information Servers)
There are several powerful tools
used on internet for searching
information. Means to develop easy
method of discovering, locating,
retrieving information from Gopher,
WWW. WAIS (Wide Area Information
Server)
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Security:- Security means protection of
data against accidental or intentional,
destruction, discloser or modification.
Computer data security refers to the
technological safeguards and
managerial procedure which can be
applied to computer Hardware, Software
and data.
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Privacy:Privacy applied to an individual. It is
the right of an individual to decide what
information he/she wishes to share with
others.
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Breaches of Security
1. Theft of PC
2. Damage due to breakage:- Floppies are
easily breakable when we shifted from one
place to another. Damage can also occur due
to natural causes such as storm or flood due
to electrical or other fires.
3. Environmental Damage:- Environmental
conditions like temperature and humidity
ranges, voltage limits, dust etc effects to PC
and get damaged.
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4. Inadvertent Corruption/loss:1. Usage of inferior media:- If sub standard
media used, it would be cheaper, it may develop faults
and data held.it may become unusable.
2. Erasure of files:- Files may be get erased
from media due to incorrect actions by operator,
wrong programming techniques, defective software.
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5. Unauthorized Access
6. Modification Erasures:-The person
accessing the data files may be authorized
to read the data, modify or delete the data.
7. Environmental Losses
8. Malicious damage/leakage
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9. Computer Viruses:This is the latest threat to computer users.
The problems created by viruses include:1. Destruction of File Allocation Table (FAT)
2. Erasing of specific programs or data on disc.
3. Destroy parts of programs/data held on disc by
created bad sectors.
4. Overwriting of entire disc directories.
5. Hang the system at periodic intervals.
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Security Measures
One of the best and first steps in ensuring data
security is to create an awareness and
develop a culture within the organization in
which information can be lost/altered.
The other steps that can be taken are:1. IT Planning:- The organization must decide
on a policy for introduction of IT. This must be
done at highest level.
2. Selection of technology
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3. Physical protection of machine.
4. Identification of points of exposure of weak links.
There are four Principles for ensuring Security and
recovery in case of breaches of Security:1. Prevent
2. Detect
3. Minimize Damage
4. Recovery
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Various Security Measures
1. Physical Security
1. Physically bolt down the PC
2. Floppies, Keyboards should be lock
3. Keep a record of all floppies in use.
4. Use lockable rooms for PC specially those
handling sensitive data.
5. Locate the PC in such a way that it is
conveniently accessible to the user but
hidden from casual passerby.
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2. Software Security
1 Use original software for operating system or
software package.
2. Use Licensed software
3. Use correct procedure for shutting down the PC
4. Introduce password to access your applications.
Password should not be visible on the screen
5. Keep backups of all your files.
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3. Network Security
1. Keep the servers away and limit physical access
to them for direct use of server.
2. Run servers in the background mode.For direct
use, a separate password would be necessary.
3.Be aware that the network cables can be tapped,
so that conceal them to prevent easy access, if
possible, use fibre optical wire.
4. Use codes and ciphers in data communication.
5. Prohibit the use of passwords embedded in
communication access script
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4. Password Security
1. Identification:- User code indicates an
object with a unique identify assigned to it.
2, Authentication:- This could be be achieved
by asking some standard questions and getting
answers to them. If answers match . The person is
authentication.
3. Authorization:- Only a given user, terminal
or other resource can access data to which
permission has been granted to read, write or alter.A
matrix can be created ti indicate which users have
access to which file record. Otherwise he is denied.
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CRYPTOGRAPHY
CRYPTOGRAPHY is the process of transforming plain text or
original information into an unintelligible form (cipher) text.
A data key control the transformation process.Authorized receiver
is assumed to have that key.
(Encryption Process)
HELLO
Algorithm
XRVJF
Plain Text
Decryption process
XRVJF Cipher
Text
Algorithm
HELLO
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Plain Text
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Cipher Systems
These includes two classes are called
1. Transposition
2. Substitution
1. Transposition Cipher:- A transposition involves
rearrangement or change in the sequence of the
letters of the plain text, message.
2 Substitution Cipher involves a replacement of the
plain text letter by other letters without any change in
their sequence.
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Code System:-
A code system is a specialized form of
substitution in which entire words, long phrases or
even sentences of the plain text are replaced by
arbitrarily selected equivalents. These may be other
words, groups of letters, groups of figures or some
combination of these.
A code system makes use of a codebook in
which the words, phrases and sentences of the
vocabulary are listed in an organised manner and
accompanied by their equivalent code groups.
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DES (Data Encryption Standard)
IBM developed the DES algorithm. DES
specifies a method for Encryption 64 bit blocks
of plain text into corresponding 64 bit blocks of
cipher text employing a user-specified 56-bit
key.
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VIRUS
Vital Information Resources Under Stress
Computer Virus are computer program which are
a collection of coded information. The basic
difference between a normal program and a
Virus is that, virus are self replicating they
have the capability of executing themselves
without being asked for.
Viruses
Corrupt the most sensitive area of the disk the
File Allocation Table (FAT)
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The Process of Infection
The infection may begin as soon as a computer
boots from a contaminated disk or executes an
infected program. Whatever viruses are present
gets activated which immediately begin to spread
throughout the system.
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Classification of Viruses
1. Boot Infectors: Infect the boot system
2. System Infectors:Infect the Hard disks
3. Executable Program Infectors:Infects the
.EXE, .COM files.
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Some Viruses
1. Score Virus:- activates two, four and seven days after
the disk has become infected.
2. Brain Virus:- Pakistani Virus
3. Lehigh Virus:-with the booting of a PC from an
infected disk then virus spread all the disk.
4. Friday the 13th: attacks not only the command.com
but also attack other exe files.
5. Sunnyvale Slug: This Virus displaying a message
‘Greetings form Sunnyvale.
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6. Raindrops:- This virus infects .com files. The first three
bytes of the file are replaced by jumps instructions at the end
of the file.
7. Happy Birthday 30th:
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Prevention
1. Use the CHKDSK
2. Don ‘t use pirated software on your system.
3. Write protect tags should be used on the original
software disk.
4. Proper backup of all data and program files should
be kept.
5. Copying of data files should be carefully
6. Restrict the use of outside floppies, Pen drives.
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Cure
Virus can be cured by anti-virus program.
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