csc cheatsheet

1. Chapter One
Introduction to Computer
What is a Computer?
A computer is an electronic device that accepts data
from the user, processes it, produces results, displays
them to the users, and stores the results for future
usage.
Characteristics (features) of Computer
1. SPEED: The data processing speed of the
electronic computer is very fast because the signals
can pass at the speed of electricity which is near to
that of speed of light. (MIPS) Millions of Instructions
Per Second
2. ACCURACY: The accuracy of the computer is
consistently high, and every calculation is
performed with the same accuracy.
3. AUTOMATION: A computer is an automatic
machine, capable of functioning automatically once
the appropriate set of instruction (program) and
data are provided to the computer.
4. DELIGENCE: The computer can perform
repetitive tasks without being bored and never get
tired.
5. RELIABILITY: The computer system is
particularly master a lot of work without any
mistakes and tiredness.
6. VERSATILITY: Versatility refers to the capability
of a computer to perform different kinds of works
with same accuracy and efficiency.
STORAGE CAPACITY (MEMORY): A computer
has built-in memory called primary memory where it
stores data. Secondary storage are removable devices
such as CDs, pen drives, etc., which are also used to
store data.
Applications of computer
Computers play a role in every field of life. They are
used in homes, business, educational institutions,
research organizations, medical field, government
offices, entertainment, etc.
1. Home
Computers are used at homes for several purposes like
online bill payment, watching movies or shows at
home, home tutoring, social media access, playing
games, internet access, etc. They provide
communication through electronic mail. They help to
avail work from home facility for corporate employees.
Computers help the student community to avail online
educational support.
2. Medical Field
Computers are used in hospitals to maintain a
database of patients’ history, diagnosis, X-rays, live
monitoring of patients, etc. Surgeons nowadays use
robotic surgical devices to perform delicate operations,
and conduct surgeries remotely. Virtual reality
technologies are also used for training purposes. It also
helps to monitor the fetus inside the mother’s womb.
3. Entertainment
Computers help to watch movies online, play games
online; act as a virtual entertainer in playing games,
listening to music, etc. MIDI instruments greatly help
people in the entertainment industry in recording
music with artificial instruments.
Videos can be fed from computers to full screen
televisions. Photo editors are available with fabulous
features.
4. Industry
Computers are used to perform several tasks in
industries like managing inventory, designing purpose,
creating virtual sample products, interior designing,
video conferencing, etc. Online marketing has seen a
great revolution in its ability to sell various products to
inaccessible corners like interior or rural areas. Stock
markets have seen phenomenal participation from
different levels of people through the use of
computers.
5. Education
Computers are used in education sector through online
classes, online examinations, referring e-books, online
tutoring, etc. They help in increased use of audio-visual
aids in the education field.
6. Government
In government sectors, computers are used in data
processing, maintaining a database of citizens and

2. supporting a paperless environment. The country’s
defense organizations have greatly benefitted from
computers in their use for missile development,
satellites, rocket launches, etc.
7. Banking
In the banking sector, computers are used to store
details of customers and conduct transactions, such as
withdrawal and deposit of money through ATMs.
Banks have reduced manual errors and expenses to a
great extent through extensive use of computers.
8. Business
Nowadays, computers are totally integrated into
business. The main objective of business is transaction
processing, which involves transactions with suppliers,
employees or customers. Computers can make these
transactions easy and accurate. People can analyze
investments, sales, expenses, markets and other
aspects of business using computers.
9. Training
Many organizations use computer-based training to
train their employees, to save money and improve
performance. Video conferencing through computers
allows saving of time and travelling costs by being able
to connect people in various locations.
10. Arts
Computers are extensively used in dance,
photography, arts and culture. The fluid movement of
dance can be shown live via animation. Photos can be
digitized using computers.
11. Science and Engineering
Computers with high performance are used to
stimulate dynamic process in
Science and Engineering. Supercomputers have
numerous applications in area of Research and
Development (R&D). Topographic images can be
created through computers. Scientists use computers
to plot and analyze data to have a better
understanding of earthquakes.
Capabilities and limitations of
computer
CAPABILITIES
• Can process data faster than any other machine
designed to perform a similar task.
• Can tirelessly perform the similar operations million
of times in exactly the same way without getting
bored.
• Can make decisions based on alternative courses of
action.
• Can store facts, instructions, and information.
• Can verify the accuracy of its own work by means of
a parity check.
• Capable of executing the instructions on its own,
without human intervention.
• Provides new time dimension.
Limitations:
• Cannot generate information on its own.
• Cannot correct wrong instructions.
• Cannot come out with an original decision.
Advantages and Disadvantages
of Computer
Advantages of Computer:
1. Multitasking – Multitasking is one among the main
advantage of computer. Person can do multiple
task, multiple operation at a same time, calculate
numerical problems within few seconds. Computer
can perform millions or trillions of work in one
second.
2. Speed – Now computer isn’t just a calculating
device. Now a day’s computer has vital role in
human life. One of the most advantages of
computer is its incredible speed, which helps
human to finish their task in few seconds.
3. Cost/ Stores huge – Amount of knowledge it’s a
coffee cost solution. Person can save huge data
within a coffee budget. Centralized database of
storing information is that the major advantage
which will reduce cost.
4. Accuracy – One among the basis advantage of
computer is which will perform not only
calculations but also with accuracy.
5. Data Security – Protecting digital data is
understood as data security.
6. Task completer – Completes tasks that might be
impossible for humans to complete.
7. Communication – Computer helps the user in
better understanding and communication with
the other devices.
8. Productivity – The level of productivity gets
automatically doubled as the computer can
done the work at very fast.
9. Reduces work load – Information are often
accessed by more than one person with the
necessity for work to be duplicated.
10.Reliability – Computers can perform same sort
of work repeatedly without throwing up errors

3. thanks to tiredness or boredom, which are
quite common among humans.
11.Storage – The pc has an in-built memory where
it can store an outsized amount of knowledge .
You can also store data in auxiliary storage
devices.
Disadvantages of computer:
1. Virus and hacking attacks – Virus may be a worm
and hacking is just an unauthorized access over
computer for a few illicit purpose. Virus can go to
other system from email attachment, viewing an
infected website advertisement, through
removable device like USB etc.
2. Online Cyber Crimes – Online cyber-crime means
computer and network may have utilized in order
to commit crime. Cyberstalking and fraud are the
points which comes under online cyber-crimes.
3. Reduction employed opportunity – Mainly past
generation wasn’t used of the pc or they need the
knowledge of computer they faced an enormous
problem when computer came in field.
4. High cost – Computers are expensive. Even the
foremost affordable computers are still very
expensive for the typical person in South Africa.
Since computers empower people.
5. Distractions/disruptions – If you’ve got ever spent
hours browsing the web or watching videos on
YouTube, then you recognize how distracting
computers can be! Because of their high
entertainment value.
6. Increases waste and impacts the environment –
With the speed that computers and other
electronics get replaced, all of the old devices that
get thrown away have a big impact on the
environment.
7. Health Problems: – Prolonged use of computers can
lead to various health Hazards. Too much sitting
near the screen results in eye strain and drying up
of the eyes. Also, prolonged sitting leads to neck
and back problems.
HISTORY OF COMPUTERS
The first counting device was used by the primitive
people. They used sticks, stones and bones as
counting tools. As human mind and technology
improved with time more computing devices were
developed. Some of the popular computing
devices starting with the first to recent ones are
described below;
Abacus
The history of computer begins with the birth of
abacus which is believed to be the first computer.
It is said that Chinese invented Abacus around
4,000 years ago.
It was a wooden rack which has metal rods with
beads mounted on them. The beads were moved
by the abacus operator according to some rules to
perform arithmetic calculations. Abacus is still
used in some countries like China, Russia and
Japan. An image of this tool is shown below;
Napier's Bones
It was a manually-operated calculating device which
was invented by John Napier (1550-1617) of
Merchiston. In this calculating tool, he used 9 different
ivory strips or bones marked with numbers to multiply
and divide. So, the tool became known as "Napier's
Bones. It was also the first machine to use the decimal
point.
Pascaline
Pascaline is also known as Arithmetic Machine or
Adding Machine. It was invented between 1642 and
1644 by a French mathematician-philosopher Biaise
Pascal. It is believed that it was the first mechanical
and automatic calculator.
Pascal invented this machine to help his father, a tax
accountant. It could only perform addition and
subtraction. It was a wooden box with a series of gears
and wheels. When a wheel is rotated one revolution, it
rotates the neighboring wheel. A series of windows is
given on the top of the wheels to read the totals.
Stepped Reckoner or Leibnitz wheel
It was developed by a German mathematician-
philosopher Gottfried Wilhelm Leibnitz in 1673. He
improved Pascal's invention to develop this machine. It
was a digital mechanical calculator which was called
the stepped reckoner as instead of gears it was made
of fluted drums.
Difference Engine
In the early 1820s, it was designed by Charles Babbage
who is known as "Father of Modern Computer". It was
a mechanical computer which could perform simple
calculations. It was a steam driven calculating machine
designed to solve tables of numbers like logarithm
tables.
Analytical Engine
This calculating machine was also developed by
Charles Babbage in 1830. It was a mechanical
computer that used punch-cards as input. It was
capable of solving any mathematical problem and
storing information as a permanent memory.

4. Tabulating Machine
It was invented in 1890, by Herman Hollerith, an
American statistician. It was a mechanical tabulator
based on punch cards. It could tabulate statistics and
record or sort data or information. This machine was
used in the 1890 U.S. Census. Hollerith also started the
Holleriths Tabulating Machine Company which later
became International Business Machine (IBM) in 1924.
Differential Analyzer
It was the first electronic computer introduced in the
United States in 1930. It was an analog device invented
by Vannevar Bush. This machine has vacuum tubes to
switch electrical signals to perform calculations. It
could do 25 calculations in few minutes.
Mark I
The next major changes in the history of computer
began in 1937 when Howard Aiken planned to develop
a machine that could perform calculations involving
large numbers. In 1944, Mark I computer was built as a
partnership between IBM and Harvard. It was the first
programmable digital computer.
GENERTION OF
COMPUTERS
First Generation Computers: Vacuum Tubes (1940-
1956)
The technology behind the primary generation
computers was a fragile glass device, which was called
vacuum tubes. These computers were very heavy and
really large in size. These weren’t very reliable and
programming on them was a really tedious task as they
used high-level programming language and used no
OS. First-generation computers were used for
calculation, storage, and control purpose. They were
too bulky and large that they needed a full room and
consume rot of electricity.
Main first generations computers
are:
ENIAC: Electronic Numerical Integrator and
Computer, built by J. Presper Eckert and John V.
Mauchly was a general-purpose computer. It had been
very heavy, large, and contained 18,000 vacuum tubes.
EDVAC: Electronic Discrete Variable Automatic
Computer was designed by von Neumann. It could
store data also as instruction and thus the speed was
enhanced.
UNIVAC: Universal Automatic Computer was
developed in 1952 by Eckert and Mauchly.
Main characteristics of first generations computers
are:
Main electronic component Vacuum tube.
Programming language Machine language.
Main memory Magnetic tapes and magnetic drums.
Input/output devices Paper tape and punched cards.
Speed and size Very slow and very large in size (often
taking up entire room).
Examples of the first generation IBM 650, IBM 701,
ENIAC, UNIVAC1, etc.
Second Generation Computers: Transistors (1956-
1963)
Second-generation computers used the technology of
transistors rather than bulky vacuum tubes. Another
feature was the core storage. A transistor may be a
device composed of semiconductor material that
amplifies a sign or opens or closes a circuit.
Transistors were invented in Bell Labs. The use of
transistors made it possible to perform powerfully and
with due speed. It reduced the dimensions and price
and thankfully the warmth too, which was generated
by vacuum tubes. Central Processing Unit (CPU),
memory, programming language and input, and output
units also came into the force within the second
generation.
Programming language was shifted from high level to
programming language and made programming
comparatively a simple task for programmers.
Languages used for programming during this era were
FORTRAN (1956), ALGOL (1958), and COBOL (1959).
Main characteristics of second
generation computers are:- Main
electronic component Transistor.
Programming language Machine language and
assembly language.
Memory Magnetic core and magnetic tape/disk.
Input/output devices Magnetic tape and punched
cards.
Power and size Smaller in size, low power
consumption, and generated less heat (in comparison
with the first generations computers).
Examples of second generations PDP-8, IBM1400
series, IBM 7090 and 7094, UNIVAC 1107, CDC 3600
etc.
Third Generation Computers: Integrated Circuits.
(1964-1971)
During the third generation, technology envisaged a
shift from huge transistors to integrated circuits, also
referred to as IC. Here a variety of transistors were
placed on silicon chips, called semiconductors. The
most feature of this era’s computer was the speed
and reliability. IC was made from silicon and also
called silicon chips.
A single IC, has many transistors, registers, and
capacitors built on one thin slice of silicon. The value
size was reduced and memory space and dealing

5. efficiency were increased during this generation.
Programming was now wiped out Higher level
languages like BASIC (Beginners All-purpose Symbolic
Instruction Code). Minicomputers find their shape
during this era.
Main characteristics of third generation computers
are:
Main electronic component Integrated circuits (ICs)
Programming language High-level language
Memory Large magnetic core, magnetic tape/disk
Input / output devices Magnetic tape, monitor,
keyboard, printer, etc.
Examples of third generation IBM 360, IBM 370, PDP-
11, NCR 395, B6500, UNIVAC 1108, etc.
Fourth Generation Computers: Micro-processors
(1971-Present)
In 1971 First microprocessors were used, the large
scale of integration LSI circuits built on one chip called
microprocessors. The most advantage of this
technology is that one microprocessor can contain all
the circuits required to perform arithmetic, logic, and
control functions on one chip.
The computers using microchips were called
microcomputers. This generation provided the even
smaller size of computers, with larger capacities. That’s
not enough, then Very Large Scale Integrated (VLSI)
circuits replaced LSI circuits. The Intel 4004chip,
developed in 1971, located all the components of the
pc from the central processing unit and memory to
input/ output controls on one chip and allowed the
dimensions to reduce drastically.
Technologies like multiprocessing, multiprogramming,
time-sharing, operating speed, and virtual memory
made it a more user-friendly and customary device.
The concept of private computers and computer
networks came into being within the fourth
generation.
Main characteristics of fourth generation computers
are:
Main electronic component Very large-scale
integration (VLSI) and the microprocessor (VLSI has
thousands of transistors on a single microchip).
Memory semiconductor memory (such as RAM, ROM,
etc.)
Input/output devices pointing devices, optical
scanning, keyboard, monitor, printer, etc.
Examples of fourth generation IBM PC, STAR 1000,
APPLE II, Apple Macintosh, Alter 8800, etc.
Fifth Generation Computers
The technology behind the fifth generation of
computers is AI. It allows computers to behave like
humans. It is often seen in programs like voice
recognition, area of medicines, and entertainment.
Within the field of games playing also it’s shown
remarkable performance where computers are
capable of beating human competitors.
The speed is highest, size is that the smallest and area
of use has remarkably increased within the fifth
generation computers. Though not a hundred percent
AI has been achieved to date but keeping in sight the
present developments, it is often said that this dream
also will become a reality very soon.
In order to summarize the features of varied
generations of computers, it is often said that a big
improvement has been seen as far because the speed
and accuracy of functioning care, but if we mention
the dimensions, it’s being small over the years. The
value is additionally diminishing and reliability is in fact
increasing.
Main characteristics of fifth generation computers
are:
Main electronic component Based on artificial
intelligence, uses the Ultra Large-Scale Integration
(ULSI) technology and parallel processing method (ULSI
has millions of transistors on a single microchip and
Parallel processing method use two or more
microprocessors to run tasks simultaneously).
Language Understand natural language (human
language).
Size Portable and small in size.
Input / output device Trackpad (or touchpad),
touchscreen, pen, speech input (recognize
voice/speech), light scanner, printer, keyboard,
monitor, mouse, etc.
Example of fifth generation Desktops, laptops,
tablets, smartphones, etc.

6. Types of Computer
We can categorize computer in two ways: on the
basis of data handling capabilities and size.
On the basis of data handling capabilities, the
computer is of three types:
1. Analogue Computer
2. Digital Computer
3. Hybrid Computer
1) Analogue Computer
Analogue computers are designed to process analogue
data. Analogue data is continuous data that changes
continuously and cannot have discrete values. We can
say that analogue computers are used where we don't
need exact values always such as speed, temperature,
pressure and current.
2) Digital Computer
Digital computer is designed to perform calculations
and logical operations at high speed. It accepts the raw
data as input in the form of digits or binary numbers (0
and 1) and processes it with programs stored in its
memory to produce the output. All modern computers
like laptops, desktops including smartphones that we
use at home or office are digital computers.
3) Hybrid Computer
Hybrid computer has features of both analogue and
digital computer. It is fast like an analogue computer
and has memory and accuracy like digital computers.
It can process both continuous and discrete data. It
accepts analogue signals and convert them into digital
form before processing. So, it is widely used in
specialized applications where both analogue and
digital data is processed. For example, a processor is
used in petrol pumps that converts the
measurements of fuel flow into quantity and price.
Similarly, they are used in airplanes, hospitals, and
scientific applications.
On the basis of size, the computer can be of five
types:
1) Supercomputer
Supercomputers are the biggest and fastest
computers. They are designed to process huge amount
of data. A supercomputer can process trillions of
instructions in a second. It has thousands of
interconnected processors.
Supercomputers are particularly used in scientific and
engineering applications such as weather forecasting,
scientific simulations and nuclear energy research.
2) Mainframe computer
Mainframe computers are designed to support
hundreds or thousands of users simultaneously. They
can support multiple programs at the same time. It
means they can execute different processes
simultaneously. These features of mainframe
computers make them ideal for big organizations like
banking and telecom sectors, which need to manage
and process high volume of data.
Mainframe computers are designed to support
hundreds or thousands of users simultaneously. They
can support multiple programs at the same time. It
means they can execute different processes
simultaneously. These features of mainframe
computers make them ideal for big organizations like
banking and telecom sectors, which need to manage
and process a high volume of data that requires
integer operations such as indexing, comparisons, etc.
3) Minicomputer
It is a midsize multiprocessing computer. It consists of
two or more processors and can support 4 to 200 users
at one time. Mainframe computers are used in
institutes and departments for tasks such as billing,
accounting and inventory management. A
minicomputer lies between the mainframe and
microcomputer as it is smaller than mainframe but
larger than a microcomputer.
4) Workstation
Workstation is a single user computer that is designed
for technical or scientific applications. It has a faster
microprocessor, a large amount of RAM and high
speed graphic adapters. It generally performs a specific
job with great expertise; accordingly, they are of
different types such as graphics workstation, music
workstation and engineering design workstation.
5) Microcomputer
Microcomputer is also known as a personal computer.
It is a general-purpose computer that is designed for
individual use. It has a microprocessor as a central
processing unit, memory, storage area, input unit and
output unit. Laptops and desktop computers are
examples of microcomputers. They are suitable for
personal work that may be making an assignment,
watching a movie, or at office for office work.
Computer hardware and
software
Computer Hardware Basics
Hardware – any physical device or equipment used in
or with a computer system (anything you can see and
touch).
External hardware
External hardware devices (peripherals) – any
hardware device that is located outside the computer.
Input device – a piece of hardware device which is
used to enter information to a computer for
processing.

7. Examples: keyboard, mouse, trackpad (or touchpad),
touchscreen, joystick, microphone, light pen, webcam,
speech input, etc.
Output device – a piece of hardware device that
receives information from a computer.
Examples: monitor, printer, scanner, speaker, display
screen (tablet, smartphone …), projector, head phone,
etc.
Internal hardware
Internal hardware devices (or internal hardware
components) – any piece of hardware device that is
located inside the computer.
Examples: CPU, hard disk drive, ROM, RAM, etc.
Computer Software Basics
Computer software
Software – a set of instructions or programs that tells
a computer what to do or how to perform a specific
task (computer software runs on hardware).
Main types of software – systems software and
application software.
Application software
Application software – a computer program that
provides users with tools to accomplish a specific task.
Examples of application software: word processing,
spreadsheets, presentation, database management,
Internet browsers, email programs, media players,
accounting, pronunciation, translation, desktop
publishing, enterprise, etc.
System Software
System software – it is designed to run a computer’s
hardware and application software, and make the
computer system available for use. It serves as the
interface between hardware, application software, and
the user.
Main functions of system software – allocating
system resources, managing storage space, storing and
retrieval of files, providing security, etc.
Main types of systems software – operating system,
device driver, utility software, programming software,
etc.
Utility software – a type of system software that helps
set up, analyze, configure, strengthen, maintain a
computer and performs a very specific task (e.g.
antivirus software, backup software, memory tester,
screen saver, etc.).
What is Mobile Computing?
Mobile Computing System mean Wireless
communication and its applications are generic
technology that refers to numerous devices that
are supportable to access transmitted data like
voice, video, and text anytime and anywhere over
the wireless network infrastructure and in which
to include mobile communication, mobile
hardware, and mobile software and this react as
human-computer interaction. Cause of these has
improved the quality of our lives.
Features of Mobile Computing
• Easy to handle and carry these small devices.
• Data can be transferred easily between users.
• Collect simulated data to current zone or your
time.
• Arbitrary network, easily connect to other
environment and transmit data.
• Having fast processor speed.
• Good battery life.
• Huge memory capacity.
• Bar code scanner
• Windows Operating System
• Camera
• Global positioning system.
• Durability
Advantage of Mobile
Computing
• Seamless and reliable communication
• Increased Productivity- Mobile devices can
be used in the field by a variety of businesses,
saving time and money for both clients and
employees.
• Entertainment- Mobile devices may be used
for entertainment, personal use, and even
presentations to clients and colleagues.
• Portability- one of the key benefits of mobile
computing is that you are not limited to a
single location in order to complete tasks or
access email when on the go.
• Cloud Computing- This program allows you
to save data on an online server and access
them from any computer with an internet
connection. You can also access these files on
several mobile devices.
Disadvantages of Mobile
Computing
• The obstacle to battery consumption.
• The transmission bandwidth is inefficient.
• Over the whole network, there are link losses.
• Fluctuation in the stability of the network.
• Small screen sizes.
• The issue of interoperability.
HARDWARE COMPONENTS

8. What is computer Architecture?
Computer Architecture is a functional description
of requirements and design implementation for
the various parts of a computer. It deals with the
functional behavior of computer systems. It comes
before the computer organization while designing
a computer.
What is computer organization?
Computer Organization comes after the decision
of Computer Architecture first. Computer
Organization is how operational attributes are
linked together and contribute to realizing the
architectural specification. Computer Organization
deals with a structural relationship.
Major Blocks of Digital
Computer
A digital computer consists of the following
Blocks/ Components
ALU: The Arithmetic-Logic unit that performs the
computer's computational and logical functions.
RAM: Memory; more specifically, the
computer's main, or fast, memory, also known as
Random Access Memory (RAM).
Control Unit: This is a component that directs
other components of the computer to perform
certain actions, such as directing the fetching of
data or instructions from memory to be processed
by the ALU; and
Man-machine interfaces: i.e. input and output
devices, such as keyboard for input and display
monitor for output.
HARDWARE COMPONENT
A Computer system has in general two major parts.
They are hardware and software.
Block Diagram of Digital computer
A digital computer is considered to be a calculating
device that can perform arithmetic operations at
enormous speed. It is defined as a device that operates
upon information/data. To be able to process data the
computer is made of various functional units to perform
its specified task.
Input Unit:
Keyboard is the one of the most commonly used input
devices. Other commonly used input devices are the
Mouse, Scanner, Microphone etc. All the input devices
perform the following functions.
• Accept the data and instructions from the
outside world.
• Convert it to a form that the computer can
understand.
• Supply the converted data to the computer
system for further processing.
Central Processing Unit:
The Control Unit (CU) and Arithmetic Logic Unit
(ALU) of the computer are together known
as the Central Processing Unit (CPU). The CPU is like
brain performs the following functions:
• It performs all calculations.
• It takes all decisions.
• It controls all units of the computer.
Memory Unit(Storage Unit):
The memory unit is responsible for storing data and
instruction. It preserves the intermediate and fina
results before these are sent to the output devices. It also
saves the data for the later use. The various storage
devices of a computer system are divided into two
categories.
1. Primary Storage:
• Stores and provides very fast.
• Used to hold the program being currently
executed in the computer.
• The primary memory is temporary in nature
• The data is lost, when the computer is
switched off.
• In order to store the data permanently, the
data has to be transferred to the secondary
memory.
• Therefore, most computers have limited
primary storage capacity.
2. Secondary Storage:
• Secondary storage is used like an archive.
• It stores several programs, documents, data
bases etc.
• The programs that you run on the compute
are first transferred to the primary memory
before it is actually run.
• The secondary memory is slower and
cheaper than the primary memory.
• Some of the commonly used secondary
memory devices are Hard disk,CD, etc.,
Control Unit:

9. • It controls all other units in the computer.
• The control unit instructs the input unit, where
to store the data after receiving it from the user.
• It controls the flow of data and instructions
from the storage unit to ALU.
• It also controls the flow of results from the ALU
to the storage unit.
The control unit is generally referred as the central
nervous system of the computer that control
and synchronizes its working.
Arithmetic Logical Unit:
• All calculations are performed in the Arithmetic
Logic Unit (ALU) of the computer.
• It also does comparison and takes decision.
• The ALU can perform basic operations such as
addition, subtraction, multiplication, division,
etc and does logic operations viz, >, <, =, ‘etc.
• Whenever calculations are required, the control
unit transfers the data from storage unit to ALU
once the computations are done, the results are
transferred to the storage unit by the control unit
and then it is send to the output unit for
displaying results.
Output Unit:
• The output unit of a computer provides the
information and results of a computation to
outside world. Printers, Visual Display Unit
(VDU) are the commonly used output devices.
• Other commonly used output devices are
Speaker, Headphone, Projector etc.
Computer - Input Devices
Following are some of the important input devices
which are used in a computer −
• Keyboard
• Mouse
• Joy Stick
• Light pen
• Track Ball
• Scanner
• Graphic Tablet
• Microphone
• Magnetic Ink Card Reader (MICR)
• Optical Character Reader (OCR)
• Bar Code Reader
• Optical Mark Reader (OMR)
Keyboard
Keyboard is the most common and very popular input
device which helps to input data to the computer. The
layout of the keyboard is like that of traditional
typewriter, although there are some additional keys
provided for performing additional functions.
The keys on the keyboard are as follows –
• Typing Keys: letter keys (A-Z) and digit keys
(09)
• Numeric Keypad: It is used to enter the
numeric data or cursor movement. Generally, it
consists of a set of 17 keys.
• Function Keys: The twelve function keys are
present on the keyboard which are arranged in
a row at the top of the keyboard. (f1-f12)
• Control keys: It includes four directional arrow
keys. Control keys also include Home, End,
Insert, Delete, Page Up, Page Down, Control
(Ctrl), Alternate (Alt), Escape (Esc).
• Special Purpose Keys: Keyboard also contains
some special purpose keys such as Enter, Shift,
Caps Lock, Num Lock, Space bar, Tab, and
Print Screen.
Mouse
• Mouse is the most popular pointing device.
• It is a very famous cursor-control device having
a small palm size box with a round ball at its
base, which senses the movement of the mouse
and sends corresponding signals to the CPU
when the mouse buttons are pressed.
• Generally, it has two buttons called the left and
the right button and a wheel is present between
the buttons.
• A mouse can be used to control the position o
the cursor on the screen, but it cannot be used to
enter text into the computer.
Joystick
• Joystick is also a pointing device, which is used
to move the cursor position on a monitor screen
It is a stick having a spherical ball at its both
lower and upper ends.
• The lower spherical ball moves in a socket. The
joystick can be moved in all four directions.
Light Pen
• Light pen is a pointing device similar to a pen.
• It is used to select a displayed menu item o
draw pictures on the monitor screen.
• It consists of a photocell and an optical system
placed in a small tube.
Track Ball
• Track ball is an input device that is mostly used
in notebook or laptop computer, instead of a
mouse.
• This is a ball which is half inserted and by
moving fingers on the ball, the pointer can be
moved.
Scanner
• Scanner is an input device, which works more
like a photocopy machine.

10. • It is used when some information is available
on paper and it is to be transferred to the hard
disk of the computer for further manipulation.
Digitizer
• Digitizer is an input device which converts
analog information into digital form.
• Digitizer can convert a signal from the
television or camera into a series of numbers
that could be stored in a computer.
Microphone
• Microphone is an input device to input sound
that is then stored in a digital form.
• The microphone is used for various applications
such as adding sound to a multimedia
presentation or for mixing music.
Magnetic Ink Card Reader (MICR)
• MICR input device is generally used in banks as
there are large number of cheques to be
processed every day.
• The bank's code number and cheque number are
printed on the cheques with a special type of ink
that contains particles of magnetic material that
are machine readable.
Optical Character Reader (OCR)
• OCR is an input device used to read a printed
text.
• OCR scans the text optically, character by
character, converts them into a machine
readable code, and stores the text on the system
memory.
Bar Code Readers
• Bar Code Reader is a device used for reading bar
coded data (data in the form of light and dark
lines).
• Bar coded data is generally used in labelling
goods, numbering the books, etc.
• It may be a handheld scanner or may be
embedded in a stationary scanner.
Optical Mark Reader (OMR)
• OMR is a special type of optical scanner used to
recognize the type of mark made by pen or
pencil.
• It is used where one out of a few alternatives is
to be selected and marked.
Types of Output Devices
1. Visual Output Devices: For examples are video
card, projector, monitor and so on.
2. Data Output Devices: For example – GPS and
more
3. Print Output Devices: For example are plotter,
printer, braille reader, and more.
4. Sound Output Devices: For examples are sound
card, headphones, speakers, etc.
Examples of Output Devices
1. Monitor
2. Printer
3. Headphones
4. Computer Speakers
5. Projector
6. GPS
7. Sound card
8. Video card
9. Braille reader
10. Speech Synthesizer
11. Plotter
12. Touchscreen
Monitor
The monitor contains the various components like as
circuitry, screen, and button for getting to adjust
settings of screen, power supply, and casing that helps
to keep all those components.
The main function of monitor is to make
communication in between users and computer.
Types of Monitor Are:
1. TFT Monitors: TFT stands for “Thin Film
Transistor”, and these transistors are used for
making high quality flat panel liquid-crystal
displays (LCDs). It allows to display has transistor
for every pixel on the screen.
2. LED Monitors: LED stands for “Light Emitting
Diodes”, and LED monitor is a flat screen flat-
panel computer monitor. It can run at the lower
temperature as well as consuming less power.
3. DLP Monitors: DLP stands for “Digital Light
Processing”, and it is built with chip that is
construct with tiny microscopic mirrors and a
spinning color wheel to create an image. It is able
to deliver great response time as well as 3D
capabilities.
4. CRT Monitors: CRT stands for “Cathode Ray
Tube”, and it is based on the cathode ray tubes.
They are similar to vacuum tubes which produce
images into form of video signals.
5. LCD Monitors: LCD stands for “Liquid Crystal
Display”, and it is worked as the technology of
liquid crystal display that is getting light weight
than CRT monitor.

11. 6. Touch Screen Monitor: These monitors allow to
user for getting to interact with computer with the
help of their fingers otherwise stylus and they are
better alternative to keyboard and mouse for
navigating a GUI.
7. Plasma Screen Monitors: Plasma monitor also
like as a flat panel display, and it totally based on
the plasma display technology.
8. OLED Monitors: OLED stands for “Organic
Light Emitting Diode”, and they are flat displays
which are made with pixels from OLEDs rather
than liquid crystal filled units.
Printer
The primary function of the printer is to create a copy,
when it is moved from the computer to the printer, and
then printer can receive electronic data transferred by
computer and produce the hard copy.
Printers are divided into two categories, like as
Impact Printers
• Character Printer
• Line Printer
Non Impact Printers
• Laser Printers
• Inkjet Printers
1. Impact Printer
These printers allow to print all characters with
striking on the ribbon, and pressed on the paper.
They produce much more noise.
There are two types, such as
Character Printer: These printers are able to
print only text and one character at a time.
Examples are – chain, band, dot matrix, and
daisy wheel printers.
Line Printer: Line printers are capable to print
line by line. For examples – drum printer and
chain printer
Non Impact Printers
These printers are capable to print without getting any
striking on the ribbon.
There are two types of non impact printers, like as –
• Laser Printers
• Inkjet Printers
Laser Printers: These printers use the laser beam to
produce the dots to form the character for printing. The
laser beam is getting to hits the drum, that is a
photoreceptor and draw the image on the drum by
altering electrical charges.
These printers can get smearing problems compare to
inkjet printer, because they don’t allow ink.
Inkjet Printers: These types of printer help to produce
the hard copy by spraying the ink onto the paper.
Today’s, these printers are mostly used in domestic
and commercial.
Headphone
The main function of headphone is to convert the
electronic signals into audio without getting any
hindrance other.
Types of Headphones
• Over-Ear Headphones
• In-Ear Headphones
• Ear buds
• Bluetooth Headphones
• Noise-Cancelling Headphones
• Closed-Back Headphones
• Open-Back Headphones
• On-Ear Headphones
Speakers
The primary function of speaker is to transform the
signals from the sound card of computer into audio
Computer speakers produce the sound with using o
internal amplifiers which allow to vibrate at various
frequencies according to data from the computer.
Projector
The main aim is to project the computer images o
videos on the big screen or wall.
Types of Projectors
DLP Projector: DLP stands for “Digital Light
Processing”, and it is getting more popularity
because it is lightweight, as well as produces the
crisp output.
LCD Projector: LCD stands for “Digital Ligh
Processing”, and it is able to produce the ultra quality
video output, so it is mostly used in the theaters.
CRT Projector: CRT stands for “Cathode Ray Tube”
and it uses a small, high-brightness cathode ray tube as
the image generating element.
GPS
GPS is a radio-based navigation system that helps to
compose of sender and receiver edges. Sender transmits
the signals to satellite that allows to ping to the sende
accurate location of sender system in the form o
latitude and longitude coordinates.
Plotter
Plotter is also hardware output device that is similar to
printer but it allows to print wide format materials such
as banners, brochures, pamphlets, etc. Mostly, plotters
are used in the engineering and basically draw a certain
image on a number of straight lines.
Sound Card

12. The sound card helps to control output of sound signals
with using of speakers and headphones. Sound card is a
dual purpose output device that helps to convert input
audio data into analog audio that can be played with
using of speakers, as well as it can also convert analog
audio from microphone into digital data.
Types of Sound Card
• USB Sound Cards
• PCMCIA / PC Cardbus
• On-Board Sound Cards
CPU
1. Control Unit (CU)
• The control unit controls the way input and
output devices, the Arithmetic, and Logic
Unit, and the computer’s memory respond
to the instruction sent to the CPU.
• It fetches the input, converts it in a
decoded form, and then sends it for
processing to the computer’s processor,
where the desired operation is performed.
• There are two types of Control units – the
Hardwire CU and the Micro programmable CU.
Functions of Control Unit:
1. It controls the sequence in which instructions move
in and out of the processor and also the way the
instructions are performed.
2. It is responsible for fetching the input, converting it
into signals, and storing it for further processing.
3. It controls the functioning of other components of
the CPU like ALU and Registers.
2. Arithmetic Logic Unit (ALU)
• The Arithmetic and Logical Unit is responsible
for arithmetical and logical calculations as well
as taking decisions in the system.
• It is also known as the mathematical brain of the
computer.
• The ALU makes use of registers for the
calculations.
• It takes input from input registers, performs
operations on the data, and stores the output in
an output register.
Functions of ALU:
1. It is mainly used to make decisions like
performing arithmetic and logical operations.
2. It acts as a bridge between the computer’s
primary memory and the secondary memory.
3. All information that is exchanged between the
primary and secondary memory passes through
the ALU.
3. Registers
Registers are a part of a computer’s memory that is used
to store the instructions temporarily to provide the
processor with the instructions at times of need. These
registers are also known as Processor registers as they
play an important role in the processing of data. These
registers store data in the form of memory address and
after the processing of the instruction present at that
memory address is completed, it stores the memory
address of the next instruction. There are various kinds
of registers that perform different functions.
Functions of Registers:
1. Input registers are used to carry the input.
2. Output registers are used to carry the output.
3. Temporary registers store data temporarily.
4. Address registers store the address of the
memory.
5. The program counter stores the address of the
instructions.
6. Data registers hold the memory operand.
7. Instruction registers hold the instruction codes.
4. Cache
Cache is a type of Random Access Memory which
stores small amounts of data and instructions
temporarily which can be reused as and when
required. It reduces the amount of time needed to
fetch the instructions as instead of fetching it from
the RAM, it can be directly accessed from Cache
in a small amount of time.
Functions of Cache:
1. They reduce the amount of time needed to fetch
and execute instructions.
2. They store data temporarily for later use.
5. Buses
A bus is a link between the different components of the
computer system and the processor. They are used to
send signals and data from the processor to differen
devices and vice versa. There are three types of buses –
Address bus which is used to send memory address
from process to other components. The data bus, which
is used to send actual data from the processor to the
components, and the Control bus, used to send contro
signals from the processor to other devices.
Functions of Bus:
1. It is used to share data between differen
devices.
2. It supplies power to different components of the
system.
6. Clock
As the name suggests, the clock controls the timing and
speed of the functions of different components of the

13. CPU. It sends out electrical signals which regulate the
timing and speed of the functions.
Functions of Clock:
1. It maintains the synchronization of the
components of the computer system.
2. It keeps track of the current date and time.
Memory unit
Memory unit is a component of a computer system. It
is used to store data, instructions and information. It is
actually a work area of computer, where the CPU
stores the data and instruction. It is also known as a
main/primary/internal memory.
There are two types of memory: -
1. Read only memory (ROM):- ROM is a part of
the memory unit. This is read only memory. It can
not be used to written. ROM is used in situations
where the data must be held permanently.
2. Random access memory (RAM):- RAM is also
part of memory unit. It is used for temporary
storage of program data. Its data is lost when
power is turned off. It is primary memory. RAM
is volatile memory. They are of following
different type
1. Static memory
2. Dynamic memory
3. Cache memory: Cache memory is a chip-based
computer component that makes retrieving data
from the computer's memory more efficient. It
acts as a temporary storage area that the
computer's processor can retrieve data from
easily.
4. PROM: A programmable read-only memory
(PROM) is a form of digital memory where the
contents can be changed once after manufacture of
the device. The data is then permanent and cannot
be changed.
5. EPROM: EPROM in full erasable programmable
read-only memory, form of computer memory that
does not lose its content when the power supply is
cut off and that can be erased and reused. EPROMs
are generally employed for programs designed for
repeated use but that can be upgraded with a later
version of a program.
Main Types of Secondary Memory (Auxiliary)
Secondary Memory is the external memory, which is
located outside of the computer and this memory is not
accessible directly by the CPU. Secondary storage is
needed to keep programs in data long-term. It has non-
volatile nature i.e. it is used to store data or information
and programs on a permanent basis.
For example: Magnetic Disc, Magnetic Tape, Flash
Memory, Optical storage, etc.
Magnetic Tape
Magnetic tape storage offers a low-cost, high-density
storage medium. The storage medium, access
electronics, and mechanical components make up a
tape unit. A tape player works in a sequential manner
i.e. the data on a tape can only be accessed in order.
To get to data on a tape, and I/O program will have to
tell the tape unit to rewind the tape and then scan it
sequentially from the beginning until it found a match.
The addressed data can then be accessed.
Magnetic Disk
Magnetic storage devices have been around since the
1950s, though they’ve evolved greatly over time. A
magnetic disk is a circular disk that is coated with
magnetic material where data can store on both
surfaces of the disc.
It uses the magnetization process to write, rewrite and
access data. The data is stored in tracks and sectors
within magnetic disks.
Hard Disk
The hard disk is one type of Magnetic disk, Where we
store several gigabytes of data. A single hard disk
usually consists of several platters. Each platte
requires two read-write heads, one for each side. Every
track has a unique location and is divided into severa
sections called sectors.
Platters of hard disks rotate thousands of times in one
second. The rotation is measured in RPM (Rotation Pe
Minute). And normally the speed of the hard disk is
from 5200 RPM to 10000 RPM or even more.
Floppy Disks
Floppy disks are a magnetic storage medium fo
computer systems. It is also called flexible disks o
diskettes that can store several million characters o
information. It is composed of a thin, flexible magnetic
disk sealed in a square by plastic.
It is used to distribute software, transfer files and create
backup copies of data.
The main purpose of using floppy disks are,
• Share files between different computers.
• Load new program or software on the
computer.
• Store back up of data and small programs to
future adaption.
Compact disk
A compact disk is a portable storage device. It is a
molded plastic disk that contains digital data and i
scanned by a laser beam to reproduce captured sound
and other material.
The storage capacity usually ranges from 650 to
750MB. Compact disks are of the following types:

14. CD-ROM
CD-ROM Stands for “Compact Disc Read-Only
Memory“. A CD-ROM is a CD that can be read by a
computer with an optical drive.
Here the data on the disc is “read-only“. This means the
data burned/stored on a CD cannot be changed.
CD-RW
CD-RW stands for (Compact Disc-Re-Writable) is
similar to CD-ROM except that you can erase the
previous content and write on it multiple times.
CD-RWs, as opposed to CDs, it is available for
specialized readers that have sensitive laser optics.
DVD
The DVD stands for “Digital Versatile Disk” It is a so-
called Digital Video Disc. DVDs have much more
storage capacity. They used a laser beam for a shorter
wavelength. The bottom layer DVD ROM is
polycarbonate plastic. In this, tracks are placed closer
together.
The storage capacity of DVD ROM is 4.7 to 8.5 GB
running on both sides. DVD can store any kind of digital
data, software, and other computer files, as well as video
programs that are watched using DVD players.
OPERATING SYSTEM SOFTWARE
Operating System Definition:
• It is a software that works as an interface
between a user and
the computer hardware.
• The primary objective of an operating
system is to make computer system
convenient to use and to utilize computer
hardware in an efficient manner.
• The operating system performs the basic
tasks such as receiving input from the
keyboard, processing instructions and
sending output to the screen.
Onion shell model of an operating system
An OS consists of different component such as
hardware, kernel, shells and utilities and application
programs.
Hardware:
• Physical part of computer system.
• Examples RAM, ROM, Cache Memory,
Registers, Hard Disk, CD-ROM, Floppy Disk, etc
Kernel:
• Access Computer resource: A Kernel can access
various computer resources like the CPU, I/O
devices and other resources. It acts as a bridge
between the user and the resources of the
system.
• Resource Management: It is the duty of a
Kernel to share the resources between various
process in such a way that there is uniform
access to the resources by every process.
• Memory Management: Every process needs
some memory space. So, memory must be
allocated and deallocated for its execution. All
these memory management is done by a
Kernel.
• Device Management: The peripheral devices
connected in the system are used by the
processes. So, the allocation of these devices is
managed by the Kernel.
Libraries:
• Libraries are the set of tools required.
• The OS libraries includes functions for file
management, for getting the current date and
time, and other facilities related to the
operating system.
Shell:
• The shell is the outermost layer of the operating
system.
• Shells incorporate a programming language to
control processes and files, as well as to start
and control other programs.
• The shell manages the interaction between you
and the operating system by prompting you for
input, interpreting that input for the operating
system, and then handling any resulting output
from the operating system.
• Shells provide a way for you to communicate
with the operating system.
Applications:
• Applications are the programs or software
which run in the top most layer.
Booting:
• Booting is the process of restarting a computer
or its operating system software.
• It starts with switching on the computer and
ends when the Operating System is loaded into
main memory and the computer is ready to
take commands from the user.

15. Booting is of two types:
1. Cold booting: When the computer is started after
having been switched off.
2. Warm booting: When the operating system alone is
restarted after a system crash or freeze.
Different terms related to booting are:
1. Boot Loader:
• The program that starts the chain reaction that
ends with the entire operating system being
loaded is the boot loader or bootstrap loader.
• The boot loader's only job is to load other
software for the operating system to start.
2. Boot Devices:
• The boot device is the device from which
the operating system is loaded.
• These include the local hard disk drive,
optical drive, floppy drive, a network
interface card, and a USB device.
3. Boot Sequence:
• There is a standard boot sequence that all
personal computers use.
• First, the CPU runs an instruction in
memory for the BIOS.
• That instruction contains a jump instruction
that transfers to the BIOS start-up program.
• This program runs a power-on self-test
(POST) to check that devices the computer
will rely on are functioning properly.
• Then, the BIOS goes through the configured
boot sequence until it finds a bootable
device. Once BIOS has found a bootable
device, BIOS loads the boot sector and
transfers execution to the boot sector.
• If the boot device is a hard drive, it will be a
master boot record (MBR).
Importance of operating system
1. OS provides a platform for Application Programs.
2. OS manages Input-Output unit.
3. OS provides consistent user interface.
4. Multitasking
Functions of operating system
The functions of an operating system are as follows−
• Provide a user interface
• Resource Management − An OS manages a
computer's resources like memory, processes
involved, etc. very efficiently.
• Handles I/O operations
• Security − Operating system protects the data and
resources of computer
• Helps in coordination between software and users.
Uses of operating system in our daily use
1. OS is used in mobile devices and smart phones in
the form of a mobile operating system.
2. OS is used in ATM machines and banks.
3. OS is used in desktop and laptop computers as an
interface to install other software.
4. OS is used in servers that provides resources in a
network.
Types of Operating System
Following are the major types of operating system −
1. Disk Operating System (DOS)
2. Windows Operating System
3. Unix Operating System
Let us now discuss each operating system in detail.
Disk Operating System
MS-DOS is one of the oldest and widely used operating
system. DOS is a set of computer programs, the major
functions of which are file management, allocation of
system resources, providing essential features to
control hardware devices.
DOS commands can be typed in either upper case or
lower case.
Features of DOS
Following are the significant features of DOS −
• It is a single user system.
• It controls program.
• It is machine independence.
• It manages (computer) files.
• It manages input and output system.
• It manages (computer) memory.
• It provides command processing facilities.
• It operates with Assembler.
Types of DOS Commands
Following are the major types of DOS Command −
Internal Commands − Commands such as DEL, COPY,
TYPE, etc. are the internal commands that remain
stored in computer memory.
External Commands − Commands like FORMAT,
DISKCOPY, etc. are the external commands and remain
stored on the disk.
Windows Operating System
The operating system window is the extension of the
disk operating system.
It is the most popular and simplest operating system; it
can be used by any person who can read and
understand basic English, as it does not require any
special training.
However, the Windows Operating System requires
DOS to run the various application programs initially.
Because of this reason, DOS should be installed into
the memory and then window can be executed.
Elements of Windows OS
Following are the significant element of Windows
Operating System (WOS) −
• Graphical User Interface

16. • Icons (pictures, documents, application,
program icons, etc.)
• Taskbar
• Start button
• Windows explorer
• Mouse button
• Hardware compatibility
• Software compatibility
• Help, etc.
Versions of Windows Operating System
Following are the different versions of Windows
Operating System −
Version Year
Window 1.01 1985
Windows XP Professional x64 2005
Windows NT 3.1 1993
Windows Vista 2007
Windows 95 1995
Windows 7 2009
Windows 98 1998
Windows 8 2012
Windows 2000 2000
Windows 10 2015
Windows ME 2000
Windows Server 2016 2016
Windows XP 2001
Unix Operating System
The Unix Operating System is the earliest operating
system developed in 1970s. Let us consider the
following points relating to the Unix Operating System
−
• It is an operating system that has multitasking
features.
• It has multiuser computer operating systems.
• It runs practically on every sort of hardware and
provides stimulus to the open source
movement.
• It has comparative complex functionality and
hence an untrained user cannot use it; only the
one who has taken training can use this system.
Another drawback of this system is, it does not give
notice or warn about the consequences of a user’s
action (whether user’s action is right or wrong).
1.

17. What is computer security?
 Computer security is the protection that is set up for computer systems and keeps critical information from unauthorized access, theft, or misuse. There are various
practices in place that are widely in use, mainly for the protection of computer systems and networks and preventing potential malicious activities.
2. Differentiate between computer virus and worm.
 The table given below shows a comparative analysis between the points of difference between a virus and worm
Difference Between Virus and Worm
Computer Virus Computer Worm
A computer virus is a program, wherein a code
copies itself and replicates itself to other
programs/files on a device and may result in
corrupting or damaging the device
A computer worm is an independent
malicious program, which when enters
a system can start causing harm/damage
to the device
An initiation is required by the host, i.e., a virus
spreads only when an infected program is
executed in a device
A worm only needs to enter the device,
then it can automatically affect the
other files and programs. No execution
is needed
• •
• •
• •
•
Few different types of computer viruses include:
Boot sector virus
Direct Action virus
Polymorphic virus
Macro virus
Spacefiller virus
Overwrite virus
File Infector virus
• •
• •
•
Few of the different types of computer
worms are as follows:
Internet worms
Instant messaging worms
Email worms
File sharing worms
Internet relay chat (IRC) worms
A virus may spread when a file is open and then
the same malicious code is copied and spread
around whenever other files are opened in the
host computer
A worm only requires a medium to
enter the device. This may be through
the internet, email, online messaging
applications, etc.
Time taken by a virus to spread in the system is
lesser in comparison to a worm
A worm can quickly spread through a
device
A virus corrupts the files or deletes them
automatically
On the other hand, a worm also affects
the bandwidth and network connections
of the device
Examples of computer virus include Creeper,
Blaster, Slammer, etc.
Examples of computer worm include
Morris worm, storm worm, etc.

18. 3. What are the precaution that should
be applied to protect your computer
from viruses?
 The precaution that should be applied
to protect my computer from viruses are :
• Always have a backup of core
files and programs • Never download
programs from untrusted sites.
• Be cautious when opening email attachments.
• Disable image previews in your email client.
• Use an anti-malware solution.
• Use a firewall.
• Regularly update your OS.
• Monitor all devices proactively.
• Utilize Administrator rights.
• Pay attention to virus warnings and
notifications.
• Inform your IT department.
• Take care in removing the virus.
4. What are computer virus and its
Removal Program? Explain with
Example.
 A computer virus is a malicious piece of
computer code designed to spread from device
to device. A subset of malware, these self-
copying threats are usually designed to damage
a device or steal data.
Antiviruses have made great progress in being
able to identify and prevent the spread of
computer viruses. When a device does become
infected, though, installing an antivirus
solution is still your best bet for removing it.
Once installed, most software will conduct a
“scan” for the malicious program. Once
located, the antivirus will present options for
its removal. If this is not something that can be
done automatically, some security vendors
offer a technician’s assistance in removing the
virus free of charge.
5. How computer are protected from virus
 Computer virus protection
When you arm yourself with information and
resources, you’re wiser about computer security
threats and less vulnerable to threat tactics. Take
these steps to safeguard your PC with the best
computer virus protection:
• Use antivirus protection and a firewall
• Get antispyware software
• Always keep your antivirus protection and
antispyware software up-to-date
• Update your operating system regularly
• Increase your browser security settings
• Avoid questionable Websites
• Only download software from sites you trust.
• Carefully evaluate free software and file-sharing
applications before downloading them.
• Don't open messages from unknown senders
• Immediately delete messages you suspect to be
spam
6. Define multimedia and multimedia
systems.
 Multimedia is a form of communication that
uses a combination of different content forms
such as text, audio, images, animations, or
video into a single interactive presentation, in
contrast to traditional mass media, such as
printed material or audio recordings, which
features little
 no interaction between

19. Q.1.) What is e-mail? Differentiate
between MAN and WAN.
A method of exchanging messages instantly
from one system to another with the help of
the internet is called an Email.
The difference between MAN and WAN is
tabulated bellow
SN MAN SN WAN
1 MAN stands for
Metropolitan Area
Network. It is a
medium-sized
network that can
cover a broad area
such as cities and
towns.
1 WAN stands for
Wide
Area
Network. It
connects
countries and
spans a broad
geographic
area. As an
example,
consider the
Internet.
2 The speed of data
transmission in a
MAN is higher
than that of a
WAN.
2 The speed is
less as
compared to
MAN.
3 Fault Tolerance of
MAN is higher
than WAN.
3 Fault Tolerance
of WAN is lower
than MAN.
4 Designing and
maintaining a
MAN is complex
and costly.
4 Designing and
maintaining a
WAN is more
complex and
costly than
MAN.
5 Network
Propagation Delay
is average in
MAN.
5 Network
Propagation
Delay is high in
WAN.
Q.2.) Explain bus, ring and star
topology with example.
Topology is viewed in two ways
1. Logical Topology/ Signal Topology
- Deals with the way data passes from one
device to the next in the network e. g Ethernet
and Token Ring 2. Physical Toplogy
- Refers to the physical layout or arrangement
of cmponents on the network e.g Star, Bus,
Ring, Mesh, Tree/Hierachical Topologies
1. Bus Topolgy
Alternatively referred to as a line topology, a
bus topology is a network setup in which each
computer and network device are connected
to a single cable or backbone. The following
sections contain both the advantages and
disadvantages of using a bus topology with
your devices.
Advantages of bus topology
• It works well when you have a small
network.
• Easiest network topology for
connecting computers or peripherals in
a linear fashion.
• Requires less cable length than a star
topology.
Disadvantages of bus topology
• Difficult to identify the problems if the
whole network goes down.
• It can be hard to troubleshoot
individual device issues.
• Not great for large networks.
• Terminators are required for both ends
of the main cable.
• Additional devices slow the network
down.
• If a main cable is damaged, the network
fails or splits
2. Ring Topology
A ring network is a network topology in which
each node connects to exactly two other
nodes, forming a single continuous pathway
for signals through each node - a ring. Data
travels from node to node, with each node
along the way handling every packet.
Advantages of ring Topology
• Very orderly network where every
device has access to the token and the
opportunity to transmit
• Performs better than a bus topology
under heavy network load

20. • Does not require a central node to
manage the connectivity between the
computers
• Due to the point to point line
configuration of devices with a device
on either side (each device is connected
to its immediate neighbor), it is quite
easy to install and reconfigure since
adding or removing a device requires
moving just two connections.
• Point to point line configuration makes
it easy to identify and isolate faults.
• Reconfiguration for line faults of
bidirectional rings can be very fast, as
switching happens at a high level, and
thus the traffic does not require
individual rerouting.
Disadvantages of Ring Topology
• One malfunctioning workstation can
create problems for the entire network.
This can be solved by using a dual ring
or a switch that closes off the break.
• Moving, adding and changing the
devices can affect the network
• Communication delay is directly
proportional to number of nodes in the
network
• Bandwidth is shared on all links
between devices
• More difficult to configure than a Star:
node adjunction = Ring shutdown and
reconfiguration
3. Star Toplogy
Star networks are one of the most common
computer network topologies. In its simplest
form, a star network consists of one central
node, typically a switch or hub, which acts as a
conduct to transmit messages. In star
topology, every node (computer workstation
or any other peripheral) is connected to a
central node. The switch is the server and the
peripherals are the clients.
Advantages
• If one node or its connection breaks it
doesn’t affect the other computers and
their connections.
• Devices can be added or removed
without disturbing the network
Disadvantages
• An expensive network layout to install
because of the amount of cables
needed
• The central hub is a single point of
failure for the network.
Q.3.) Write Short note on optical
Fiber.
Fiber optics, or optical fiber, refers to the
technology that transmits information as light
pulses along a glass or plastic fiber.
A fiber optic cable can contain a varying
number of these glass fibers -- from a few up
to a couple hundred. Another glass layer,
called cladding, surrounds the glass fiber core.
The buffer tube layer protects the cladding,
and a jacket layer acts as the final protective
layer for the individual strand.
Fiber optic cables are commonly used because
of their advantages over copper cables. Some
of those benefits include higher bandwidth
and transmit speeds.
Fiber optics is used for long-distance and high-
performance data networking. It is also
commonly used in telecommunication
services, such as internet, television and
telephones. For example, Verizon and Google
use fiber optics in their Verizon FIOS and
Google Fiber services, respectively, providing
Gigabit internet speeds to users.
Q.4.) Explain Client Server Concept in
Networking.
Client-server networking refers to a network
setup that utilizes client hardware devices and
servers. The client-server network model can
be used over a LAN (local area network) or the
Internet. Common examples of client-server
networks include DNS (Domain Name

21. Systems), web browsers and web servers, and
FTP (file transfer protocol) clients.
Most people experience client-server
networking daily using computers,
smartphones, and tablets connected to the
Internet. Their devices are the clients that
request access to a webpage's content, which
is then delivered to them by a website's
servers.
Q.5.) Explain the advantage and disadvantages of
computer network.
Computer networking refers to interconnected
computing devices that can exchange data and
share resources with each other. These
network devices use a system of rules, called
communication protocols, to transmit
information over physical or wireless
technologies.
Advantages of computer network
• It makes file sharing easier : It allows easier
accessibility for people to sharing their files,
which greatly help them with saving more
time and effort, since they could do file
sharing more efficiently.
• It is an inexpensive system : Installing
network software on the devices would not
cost too much, as you are assured that it
lasts and can effectively share information
to your peers. Also, there is no need to
change the software regularly, as mostly it
is not required to do so.
• It is highly flexible : This technology is
known to be very flexible, as it gives users
the opportunity to explore everything
about essential things, such as software
without affecting their functionality.
• Great storage capacity : Organizations have
an abundance of data that needs to be
stored. For that purpose, they are required
to store them in a central server. A central
server is a remote server that is accessible
to each and every employee. So, if in case
one loses the data, others have it.
Disadvantage of computer network
• Lack of robustness : Computer networks
rely on the main server called the central
server. If the central server malfunctions or
there is an issue in the central server, then
the entire network would stop functioning.
So, this is a major disadvantage due to
dependency on a single server.
• Lack of productivity : Since a network has a
lot of advantages and applications, it is
certain that it results in simultaneous use of
many services that cause distraction. Thus,
due to employees focusing on a myriad of
tasks, productivity issues are quite
common. • Spread of computer virus : As
computers in a network are
interconnected, there is a high probability
that if one of the computers is affected by
the virus, others too can get affected. This
spread can actually damage the entire
system. Also, if the central server gets
corrupted, then it's quite dangerous as the
network depends on the central server.
Q.6.) What are network topology and
protocols?
Network topology refers to how various nodes,
devices, and connections on your network are
physically or logically arranged in relation to
each other. There are two approaches to
network topology: physical and logical. Physical
network topology, as the name suggests, refers
to the physical connections and
interconnections between nodes and the
network— the wires, cables, and so forth.
A network protocol is an established set of
rules that determine how data is transmitted
between different devices in the same
network. Essentially, it allows connected
devices to communicate with each other,
regardless of any differences in their internal
processes, structure or design.
Q.7.) Define Hub, Switch and Modem.
Modem:
A modem is short for a modulator-
demodulator. Its function is to facilitate the
transmission of data, by converting an

22. analogue signal to code and decoding digital
information. This means that it converts the
telephone connection information into digital
information for the computer to understand,
and converts computer digits into analog
waves so that it can be transmitted over
telephone lines. It could be seen as the center
for information collection from WAN, as it
directly connects to the outside world.
Switch: A network switch’s primary function is
to connect network segments on a single
network. Therefore is quite different from a
router and modem; it is used to expand the
capability of the router, by providing additional
posts. It connects many devices together on
the same network; sending data to a device
that needs or requests it. A switch is able to
improve the performance of a network by
increasing network capacity.
A switch connects two or more nodes in the
same or different network. Unlike the router
which labels through IP address, switches use
MAC addresses to direct the data to its correct
destination.
Network Hub:
A hub is a device that allows several network
devices to connect together to exchange data
on a single network however, they have no
management component. Network hubs are
also known as repeaters. They are less
‘intelligent’ than switches. Unlike switches,
which forward data to the intended devices,
hubs merely send the data packets to all its
ports. So as the name repeaters suggests, it
only repeats the data from an incoming port to
all the other devices; this leads to frequent
collisions between packets.
Q.8.) Write short notes on: Internet, Search Engine
and www.
-INTERNET
The internet is a globally connected network
system facilitating worldwide communication
and access to data resources through a vast
collection of private, public, business,
academic and government networks. It is
governed by agencies like the Internet
Assigned Numbers Authority (or IANA) that
establish universal protocols.
The terms internet and World Wide Web are
often used interchangeably, but they are not
exactly the same thing; the internet refers to
the global communication system, including
hardware and infrastructure, while the web is
one of the services communicated over the
internet.
-SEARCH ENGINES
A search engine is a software system designed
to carry out web searches. They search the
World Wide Web in a systematic way for
particular information specified in a textual
web search query. The search results are
generally presented in a line of results, often
referred to as search engine results pages
(SERPs). The information may be a mix of links
to web pages, images, videos, infographics,
articles, research papers, and other types of
files. Some search engines also mine data
available in databases or open directories.
-WORLD WIDE WEB (WWW)
The World Wide Web (WWW), commonly
known as the Web, is an information system
enabling documents and other web resources
to be accessed over the Internet.
Documents and downloadable media are
made available to the network through web
servers and can be accessed by programs such
as web browsers. Servers and resources on the
World Wide Web are identified and located
through character strings called uniform
resource locators (URLs). The original and still
very common document type is a web page
formatted in Hypertext Markup Language
(HTML). This markup language supports plain
text, images, embedded video and audio
contents, and scripts (short programs) that
implement complex user interaction.

24.  users.
 A multimedia computer system is one that can
create, integrate, store, retrieve delete two or
more types of media materials in digital form,
such as audio, image, video, and text
information.