Unit-2

Computer Programming Fundamentals

Input Devices
 Input devices are used to take raw data as input
from the user.
 Input device enables the user to send data,
information, or control signals to a computer. The
Central Processing Unit (CPU) of a computer receives
the input and processes it to produce the output.

Some of the popular input devices are:

1) Keyboard
The keyboard is a basic input device that is used to enter
data into a computer or any other electronic device by
pressing keys. It has different sets of keys for letters,
numbers, characters, and functions. Keyboards are
connected to a computer through USB or a Bluetooth
device for wireless communication.
2) Mouse
The mouse is a hand-held input device which is used to
move cursor or pointer across the screen. It is designed
to be used on a flat surface and generally has left and
right button and a scroll wheel between them. Laptop
computers come with a touchpad that works as a mouse.
It lets you control the movement of cursor or pointer by
moving your finger over the touchpad.
i) Trackball Mouse:

It is stationary input device that has ball mechanism to

move cursor on screen. The ball is half inserted in device
and can be easily rolled with finger to move pointer on
screen. So it is an ideal device if you have limited desk
space as you don't need to move it like a mouse.
ii) Cordless or Wireless Mouse:

This type of mouse lacks cable and uses wireless

technology such as infrared, Bluetooth or Wi-Fi to control
movement of cursor. It is used to improve the experience
of using a mouse. It uses batteries for its power supply.
3) Scanner
The scanner uses pictures and pages of text as input. It
scans picture or document. The scanned document then
converted into a digital format or file and is displayed on
screen as an output. It uses optical character recognition
techniques to convert images into digital.
i) Flatbed Scanner:

It has a glass pane and a moving optical CIS or CCD array.

The light illuminates the pane, and then image is placed
on glass pane. The light moves across the glass pane and
scans the document and thus produces its digital copy.
ii) Handheld Scanner:

It is a small manual scanning device which is held by hand

and is rolled over a flat image that is to be scanned. The
drawback in using this device is that hand should be
steady while scanning otherwise it may distort image.
Example barcode scanner, used in shopping centers.

4) Joystick
It is made up of a stick with a spherical base. The base is
fitted in a socket that allows free movement of stick. The
movement of stick controls cursor on screen. In joystick,
cursor keeps moving in direction of joystick whereas, in
mouse, the cursor moves only when mouse moves.

5) Light Pen

A light pen is a computer input device that looks like a

pen. The tip of light pen contains a light-sensitive
detector that enables the user to point or select objects
on display screen. Its light sensitive tip detects the object
location and sends corresponding signals to the CPU. It is
not compatible with LCD screens, so it is not in use today.

6) Microphone
It is a computer input device that is used to input the
sound. It receives sound vibrations and converts them
into audio signals or sends to a recording medium. The
audio signals are converted into digital data and stored in
computer. The microphone also enables the user to
telecommunicate with others. It is also used to add
sound to presentations.
i) Dynamic:

It is the most commonly used microphone with a simple

design. It has a magnet which is wrapped by a metal coil
and a thin sheet on front end of magnet. The sheet
transfers vibrations from sound waves to coil and from
coil to electric wires which transmit sound like an
electrical signal.
ii) Condenser:

It is designed for audio recording and has a very sensitive

and flat frequency response. It has a front plate called
diaphragm and a back plate parallel to the front plate.
When sound hits the diaphragm, it vibrates diaphragm
and alters the distance between the two plates. The
changes in distance are transmitted as electric signals.
7) Magnetic Ink Character Recognition (MICR)

MICR computer input device is designed to read text

printed with magnetic ink. MICR is a character
recognition technology that makes use of special
magnetized ink which is sensitive to magnetic fields. It is
widely used in banks to process cheques and other
organizations where security is a major concern.
A document printed in magnetic ink is required to pass
through a machine which magnetizes the ink, and the
magnetic information is then translated into characters.

10) Touchpad

It is usually found in laptops as a substitute for mouse. It

allows you to move or control the cursor on screen using
your finger. Just like a mouse, it also has two buttons for
right and left click. Using the touchpad, you can perform
all the tasks that you do with a mouse.
Output Devices
 The output device displays result of processing of
raw data that is entered in the computer through an
input device.
 There are number of output devices that display
output in different ways such as text, images, hard
copies, and audio or video.

1) Monitor
The monitor is display unit or screen of the computer. It
is the main output device that displays the processed
data or information as text, images, audio or video.
i) CRT Monitor

CRT monitors are based on the cathode ray tubes.

Cathode rays tube produces a beam of electrons through
electron guns that strike on the inner phosphorescent
surface of the screen to produce images on screen. The
monitor contains millions of phosphorus dots of red,
green and blue color. These dots start to glow when
struck by electron beams.
ii) LCD Monitor

The LCD monitor is a flat panel screen that is compact

and light-weight as compare to CRT monitors. It is based
on liquid crystal display technology which is used in
screens of laptops, tablets, smart phones. An LCD screen
comprises two layers of polarized glass with a liquid
crystal solution between them. When light passes
through first layer, electric current aligns liquids crystals.
The aligned liquid crystals allow a varying level of light to
pass through second layer to create images on screen.
iii) LED monitor

The LED monitor is an improved version of LCD monitor.

It also has a flat panel display and uses liquid crystal
display technology like LCD monitors. The difference
between them lies in the source of light to backlight the
display. The LED monitor has many LED panels, and each
panel has several LEDs to backlight the display, whereas
LCD monitors use cold cathode fluorescent light to
backlight the display. Modern electronic devices such as
mobile phones, LED TVs, laptop and computer screens,
use LED display as it not only produces greater light
intensity but also consumes less power.

2) Projector

A projector is an output device that enables the user to

project the output onto a large surface such as a big
screen or wall. It can be connected to a computer to
project their output onto a screen. It uses light and
lenses to produce magnified texts, images, and videos.
So, it is an ideal output device to give presentations or to
teach a large number of people.

3) Printer
A printer produces hard copies of processed data. It
enables the user, to print images, text or any other
information onto paper. Printers enable the generation
of hard copies for record-keeping, presentations and
other purposes, from household to professional settings.
Based on the printing mechanism, the printers are of two
types: Impact Printers and Non-impact Printers.
 o Impact Printers: They are of two types:
A. Character Printers
i. Dot Matrix printers
ii. Daisy Wheel printers
B. Line printers
i. Drum printers
ii. Chain printers
o Non-impact printers: They are of two types:
A. Laser printers
B. Inkjet printers

Impact Printer
The impact printer uses a hammer or print head to print
character or images onto paper. The hammer or print
head strikes or presses an ink ribbon against the paper to
print characters and images.
A) Character Printers
Character printer prints a single character at a time or
with a single stroke of the print head or hammer. It does
not print one line at a time. Today, these printers are not
in much use due to their low speed and because only the
text can be printed. Character printers are of two types-
i) Dot Matrix Printer
Dot Matrix Printer is an impact printer. The characters
and images printed by it are patterns of dots. These
patterns are produced by striking ink soaked ribbon
against paper with a print head. The print head contains
pins that produce a pattern of dots on the paper to form
the individual characters. Speed of Dot Matrix printers is
around 200-500 characters per second.
ii) Daisy Wheel Printer

It consists of a wheel or disk that has spokes or

extensions and looks like a daisy, so it is named Daisy
Wheel printer. At the end of extensions, molded metal
characters are mounted. To print a character the printer
rotates the wheel, and when the desired character is on
the print location the hammer hits disk and the extension
hits the ink ribbon against paper to create impression. It
cannot be used to print graphics and is often noisy and
speed is very low around 25-50 characters per second.

B) Line Printers:
Line printer prints one line at a time. It is a high-speed
impact printer as it can print 500 to 3000 lines per
minute. Drum printer and chain printer are examples of
line printers.
i) Drum Printer:

Drum printer is a line printer that is made of a rotating

drum to print characters. The drum has circular bands of
characters on its surface. It has a separate hammer for
each band of characters. When you print,drum rotates
and when desired character comes under the hammer,
hammer strikes ink ribbon against the paper to print
characters. The drum rotates at a very high speed and
characters are printed by activating the appropriate
hammers. Furthermore, it can print only a predefined
style as it has a specific set of characters. These printers
are very noisy due to the use of hammering techniques.

ii) Chain Printer:

Chain printer is a line printer that uses a rotating chain to
print characters. The characters are embossed on the
surface of the chain. The chain rotates horizontally
around a set of hammers, for each print location one
hammer is provided, i.e., the total number of hammers is
equal to the total number of print positions.
The chain rotates at a very high speed and when the
desired character comes at print location, corresponding
hammer strikes the page against ribbon and character on
the chain. They can type 500 to 3000 lines per minute.
They are also noisy due to the hammering action.

Non-Impact Printer:
Non-impact printers don't print characters or images by
striking a print head or hammer on ink ribbon placed
against paper. They print characters and images without
direct physical contact between the paper and the
printing machinery. These printers can print a complete
page at a time, so they are also known as page printers.
i) Laser Printer:

A laser printer is a non-impact printer that uses a laser

beam to print characters. The laser beam hits the drum,
which is a photoreceptor and draws the image on the
drum by altering electrical charges on drum. The drum
then rolls in toner and charged image on drum picks the
toner. The toner is then printed on the paper using heat
and pressure. The laser printers use powdered toner for
printing instead of liquid ink and produce quality print
objects with a resolution of 600 dots per inch (dpi).

ii) Inkjet Printer:

The inkjet printer is a non-impact printer that prints

images and characters by spraying fine,ionized drops of
ink. The print head has tiny nozzles to spray ink. The
printer head moves back and forth and sprays ionized
drops of ink on paper, which is fed through the printer.
These drops pass through an electric field that guides ink
onto paper to print correct images and characters.

4) Speakers
Speakers are important output devices that transform
electrical impulses into audible sounds. The audio system
improves multimedia experience by providing high-
quality audio output, whether listening to the song,
viewing films, playing video games.
Types of speakers
o Stereo Speakers: Stereo speakers comprise left and

right speakers. They are the most fundamental

speaker, found in desktop computers, laptop
computers. Stereo speakers offer a simple yet
efficient method of reproducing sound.

o Soundbars: Soundbars are slim and elongated

speakers that provide an all-in-one audio solution for
TVshome entertainment systems. Soundbars offer
improved audio quality compared to TV speakers.

o Portable Speakers: Portable speakers are small,

lightweight, wireless devices designed for audio
enjoyment. Bluetooth audio systems are available in
various styles and sizes with long battery life and
waterproof.
5) Headphones/Earphones
Headphones and earphones are personal audio devices
worn over the ears or inserted into the ear canal. They
deliver Music to the user directly, giving a private and
immersive listening experience. Earphones are tiny and
fit within the ear, whereas headphones have two
speakers that cover both ears. They offer ease, mobility,
and ability to concentrate on audio information.
o Over-Ear Headphones: Over-ear headphones
feature large ear cups that fully envelop the ears.
One of their notable advantages is their comfort, as
the ear cups completely cover the ears.

o In-Ear Earphones: In-ear earphones, known as

earbuds or earphones, are inserted right away into
ear canal. They are compact, light, transportable. In
order to ensure a secure and comfortable fit, in-ear
earbuds are available in different sizes.
 o True Wireless Earbuds: True wireless earbuds are in-
ear headphones with no wires connecting them.
Each earbud is self-contained and connects to the
smartphone through Bluetooth.

6) Plotter
A plotter is a specialized output device used to generate
high-quality, accurate, and detailed graphics. It's popular
in fields like engineering, architecture, and graphic
design. Plotters utilize a pen or marker to draw
continuous lines on diverse media such as paper, or film.
Plotters are capable of creating accurate drawings, maps,
blueprints, and technical diagrams. They are valued for
their ability to handle large-format prints and deliver
precise output, making them essential tools in industries
that require precise graphical representation.

Computer Hardware
Hardware refers to the physical components of a
computer or a machine that we can see and touch. It is a
physical component that is used in different ways to
build a computer or any other machine. The Memory
Devices, Processor, Central Processing Unit, Mouse, and
the keyboard all are examples of hardware in computer
system. The screen on which you are viewing this page
example of hardware. A computer system would not be
existing without hardware and not able to run software.

Computer Software
Software is a collection of procedures, instructions,
documentation that tells a computer exactly what to do
or allows users to interact with a computer. Most of the
computers may be useless without software. For
example, if a software program, MS-Word is not installed
into your computer, you cannot make any document that
can be completed through MS-Word. Also, you cannot
surf the Internet or visit any website if your system has
no Internet browser software. The browser could not run
on computer without an operating system. The Google
Chrome, MS Word, Excel are examples of software.

Different types of Computer Software

1. System Software
System software is the software that maintains and
controls the basic functions of a computer system. It
serves as a bridge between the user and the hardware,
ensuring the computer runs smoothly. Operating
systems, device drivers, and utility programs are a few
examples of system software.
o Operating systems: An OS, or operating system, is

the essential software that controls the resources of

computer hardware and applications.
o Device Drivers: Device drivers are software elements

that help the operating system, and other linked

hardware devices communicate with one another.
o Utility programs: They are software applications

created to perform particular tasks to enhance

system performance or offer extra features.

2. Application Software

Application software refers to programs and software

applications executing certain tasks or giving end users
features. These programs are made to satisfy users'
requirements in various areas, including communication,
creativity, entertainment, and productivity.
o Productivity Software: project management tools,
word processors, spreadsheets, and presentation
software programs are all examples of productivity
software. Users can create, edit, control files,
presentations related activities with those tools.
o Creative Software: 3-D modeling programs,
photograph- and video-editing programs, image
design tools, and music-production software are all
examples of creative software.
o Entertainment Software: Video games, multimedia
players, and streaming programs are examples of
entertainment software. These allow users to
participate in entertaining, recreational activities.
o Communication Software: Email clients, instant
messaging programs, video conferencing tools, and
web browsers are all examples of communication
software, allow users to connect, work together.
Hardware Software

Hardware is a physical component of computers Software is a program that enables users to

that executes the instruction. interact with the computer, its hardware.

It is manufactured in factories. It is developed by software programmers or

software development companies.

Storage Devices, Input Devices, Output Devices, Operating Systems, Application Software, and
and Internal components are the primary Programming Software are the main categories
categories of hardware. of software.

Hardware can be seen and touch as it is a physical, The software can be seen but cannot be touched
electronic device. as it is virtual, not physical.

Computer viruses cannot affect hardware. Computer viruses can affect software.

Hardware can be replaced with a new one if it is The software is reinstalled if it gets damaged.
damaged.

Through the network, hardware cannot be The software can be transferred easily.
transferred electrically. Only, it can be physically
transferred.

Examples of hardware are Keyboard, Printer, Examples of software are Google Chrome,
Monitor, Mouse, Hard disk and more. MySQL, MS Word, Excel, PowerPoint, Notepad,
Photoshop and more.

Operating System
 An Operating System can be defined as an interface
between user and hardware.
 The operating system is a connecting medium
between the user and the hardware.
 It helps the users to access the hardware in an
efficient manner.
  It also makes sure that all the computer resources
will be used in an efficient and smooth way without
any problems.
 For example, when seniors pass their instructions to
the juniors, and in the same way, the users gives the
instructions to the operating system.
 It is responsible for the execution of all the
processes, Resource Allocation, CPU management,
File Management and many other tasks.

Functions of Operating System

1.Memory Management
It is the management of the main or primary memory.
Whatever program is executed, it has to be present in
the main memory. When the program is completed, the
memory is released and can be used by other programs.
Therefore, there can be more than one program present
at a time. Hence, it is required to manage the memory.
The operating system:
∙ Allocates and deallocates the memory.
∙ Keeps a record of which part of primary memory is used
by whom and how much.
∙ Distributes the memory while multiprocessing.
∙ In multiprogramming, operating system selects which
processes acquire memory when and how much memory
they get.

2.Device Management
Operating system manages the communication between
computer system and the peripheral devices connected
to I/O port of the system. It also makes sure when a
program is executed or terminated, it will stop
communication between device and computer.
An operating system regulates device connection using
drivers. This management is done by the OS. The OS:
∙ Allocates and deallocates devices to different processes.
∙ Keeps records of the devices.
∙ Decides which process can use which device for how
much time.

3.File Management
It specifies which process receives the file and for how
long. It also keeps track of information, location, uses,
status, and so on. These groupings of resources are
referred to as file systems. The files on a system are
stored in different directories. The OS:
∙ Keeps records of the status and locations of files.
∙ Allocates and deallocates resources.
∙ Decides who gets the resources.

4.Process Management
The process is a program under execution. When more
than one process runs on the system the OS decides how
and when a process will use the CPU. Hence, the name is
also CPU Scheduling. The OS does
∙ Allocates and deallocates processor to the processes.
∙ Keeps record of CPU status.
Certain algorithms used for CPU scheduling are :
∙ First Come First Serve (FCFS)- In this which comes first
is served first by the CPU until it is completed.
∙ Shortest Job First (SJF)- process which has shortest
execution time will be served first by CPU.
∙ Round-Robin Scheduling- there is a specific time quanta
assigned for each process. If process is not executed in
time quanta, it is sent to waiting queue for its next turn.
∙ Priority-based scheduling- Processes are given priority
based on different criteria and scheduled according to
highest priority.
5.Resource Allocation
Operating system manages all resources of computer
system. It ensures use of all resources by managing
which resource is used by which process and for how
much time.

6.Handling the I/O Operations

Input/output devices like mouse, keyboards, printers are
external I/O devices and have different natures of each
device. The operating system appropriately manages
input and output operation of these devices.

7.Scheduling of resources and jobs

Operating system prepares list of tasks to be performed
by device of computer system.
 OS decides which device to use for which task. This
action becomes complicated when multiple tasks are
to be performed in a computer system.
 The scheduling programs of operating system
determine order in which tasks are completed.
 It performs these tasks based on priority of
performing tasks given by user.

8.Security
Computer security is important aspect of operating
system. Reliability of operating system is determined by
how much better security it provides. Modern operating
systems use a firewall for security. A firewall is a security
system that monitors every activity happening in the
computer and blocks that activity in case of any threat.

9.Monitoring activities
Operating system takes care of activities of computer
system during various processes. This aborts the program
if there are errors. OS sends messages to user for any
error in input/output device. It also provides security to
system when used in systems operated by multiple
users. So that illegal users cannot get data from system.

10. Storage Management

The OS uses storage management for:
∙ Improving the performance of the data storage
resources.
∙ It optimizes the use of various storage devices.
∙ Assists businesses in storing more data on existing
hardware, speeding up data retrieval process, preventing
data loss, and lowering IT costs
 Difference between Single User and Multi-User OS

Terms Single User Operating System Multi-User Operating System

Definition A Single-User Operating System is a A Multi-User Operating System is a system

system in which only one user can that allows more than one user to access a
access the computer system at a time. computer system at one time.

Bootloader The bootloader loads all the resources The bootloader distributes the resources of
of the CPU in the profile of a single the CPU based on the priority of the users.
superuser.

Super User A superuser gets all the powers of Superuser does not exist for a multi-user
maintaining the system and making operating system as each entity has control
changes to ensure the system runs over their working.
smoothly.

Complexity Single-User Operating System is simple The Multi-User Operating systems are
and easy to design. complicated as they have to apply complex
techniques to share the resources among
various users.

Performance Only one task at one time gets Schedules different tasks for performance at
performed. any rate.

Example MS-DOS, Windows 95, Windows NT, Mainframes, IBM AS400, Linux & Unix
Windows 2000, Personal Computers, Distributed OS, etc.
etc.

Multiprogramming Operating System

 Each process needs two types of system time: CPU
time and IO time.
 In multiprogramming, when a process does its I/O,
CPU can start execution of other processes.
  Therefore, multiprogramming improves efficiency of
the system.

Advantages of Multiprogramming OS
o Overall performance is increased as the CPU always

had one program to execute.

o Response time can also be reduced.

Disadvantages of Multiprogramming OS
o Multiprogramming systems provide an environment

in which various systems resources are used

efficiently, but they do not provide any user
interaction with the computer system.

Multiprocessing Operating System

 In Multiprocessing, Parallel computing is achieved.
 There are more than one processors present in
system which can execute more than one process at
the same time.
 This will increase the throughput of the system.
Advantages of Multiprocessing operating system:
o Increased reliability: Due to multiprocessing,
processing tasks can be distributed among several
processors. This increases reliability as if one
processor fails, task can be given to another
processor for completion.
o Increased throughout: As several processors
increase, more work can be done in less time.
o For Example: UNIX Operating system is one of the

most widely used multiprocessing systems.

Disadvantages of Multiprocessing operating System
o Multiprocessing operating system is more complex

and sophisticated as it takes care of multiple CPUs

simultaneously.
Multitasking Operating System

 The multitasking operating system is a logical

extension of multiprogramming system that
enables multiple programs to run simultaneously.
 It allows a user to perform more than one computer
task at the same time.
Advantages of Multitasking operating system
o This operating system is more suited to supporting

multiple users simultaneously.

o The multitasking operating systems have well-
defined memory management.
Disadvantages of Multitasking operating system
o The multiple processors are busy at the same time to

complete any task in a multitasking environment, so

the CPU generates more heat.
Real Time Operating System
 In Real-Time Systems, each job carries a certain
deadline within which job is supposed to be
completed otherwise, huge loss will be there even if
the result is produced, it will be completely useless.
 Real-Time system used in military applications, if you
want to drop a missile, then missile is supposed to
be dropped with a certain precision.

Advantages of Real-time operating system:

o Easy to layout, develop and execute real-time

applications under the real-time operating system.

o In a Real-time operating system, the maximum

utilization of devices and systems.

Disadvantages of Real-time operating system:
o Real-time operating systems are very costly.

o Real-time operating systems are very complex and

can consume critical CPU cycles.

Time-Sharing Operating System
 In Time Sharing operating system, computer
resources are allocated in a time-dependent fashion
to several programs simultaneously.
 Thus it helps to provide a large number of user's
direct access to the main computer.
 It is a logical extension of multiprogramming.
 In this, CPU is switched among multiple programs
given by different users on a scheduled basis.
 A time-sharing operating system allows many users
to be served simultaneously, so CPU scheduling
schemes , Input/output management are required.

Advantages of Time Sharing Operating System

o The time-sharing operating system provides
effective utilization and sharing of resources.
o This system reduces CPU idle and response time.
Disadvantages of Time Sharing Operating System
o Data transmission rates are very high in comparison

to other methods.
o Security and integrity of user programs loaded in

memory and data need to be maintained as many

users access the system at the same time.
o Time-sharing operating systems are very difficult and

expensive to build.

Multithreading Operating System

 A process is a program being executed.
 A process can be further divided into independent
units known as threads.
 A thread is like a small light-weight process within a
process or collection of threads is called a process.
 Multithreading allows application to divide its task
into individual threads. In multi-threads, same
process or task can be done by number of threads.
Advantages of Multithreading
 Increased performance and resource utilization.
 With the use of multithreading, multitasking can be
achieved.

Disadvantages of Multithreading
 It also introduces complexity and potential issues
related to synchronization and concurrency.
Computer Virus
 Computer viruses are unwanted software programs
or pieces of code that interfere with the functioning
of the computer.
 They spread through contaminated files, data, and
insecure networks.
 Once it enters your system, it can replicate to
produce copies of itself to spread from one program
to another program and from one infected computer
to another computer.
 So, we can say that it is a self-replicating computer
program that interferes with the functioning of the
computer by infecting files, data, programs, etc.
Types of Computer Virus
1.Overwrite Virus
It is the simplest computer virus that overwrites the code
of host computer system's file with its own malicious
code. The content of infected file is replaced partially or
completely without changing the size of file. Thus, it
destroys original program code by overwriting it with its
defective code. The infected files must be deleted or
replaced as this virus cannot be removed or disinfected.
2.Append Virus
This virus appends its malicious code to the end of host
program's file. After that, it alters file's header in a way
that file's header is redirected to start of the malicious
code of the append virus. Thus, this code is executed
each time the program runs. However, it does not
destroy the host program rather it modifies it in a way
that it holds the virus code and enables code to run itself.

3.Macro Virus
Macro virus alters or infects the macros of a document or
data file. It is embedded as a macro in a document and
adds its codes to the macros of the document. The virus
spreads when infected documents are opened in other
computers. It also spreads through software programs,
which execute macros such as Ms Word, Ms Excel.

4.Boot Virus
Boot virus alters the boot sector program stored in the
hard disk or any other storage device such as floppy
disks. It replaces the boot sector program with its own
malicious version. It infects the computer only when it is
used to boot up the computer. If it enters after the boot-
up process, it will not infect the computer. Usually, it
enters into your system through corrupt media files,
infected storage devices and insecure computer
networks. The spread of this virus is very rare these days
due to the decline in the use of floppy disk and use of
boot-sector safeguards in present-day operating systems.

5.Resident Virus
The resident virus stays permanently in the primary
memory (RAM) of computer. When you start the
computer, it becomes active and corrupts the files and
programs running on the computer.

6.Multipartite Virus
Multipartite virus spreads and infects in multiple ways. It
infects both the boot sector and the executable files
stored on the hard drive simultaneously. When you turn
on a computer, the boot sector virus is triggered as it
latches on to the hard drive, which has the data for
starting up the computer. Once it is triggered, the
program files also get infected.

7.File Infector Virus

It is one of the commonly found computer viruses. It
mainly infects the executable files; the files with .com or
.exe extensions. The virus becomes active when the
infected file is executed. The active virus overwrites the
file partially or completely. Thus it may destroy the
original file partially or completely.
8.Computer Worm
Computer worm is similar to a virus but is technically
different from virus. It can replicate and spread like a
virus but unlike viruses, it does not need a host program
to spread. Being able to self-replicate it can produce
multiple copies of itself. It spreads through networks
such as an email sent to an infected email id can infect
your system with a computer worm.

9.Trojan Horse
Trojan horse is a malware like a virus or a worm. It can't
replicate like virus and worm. Trojan horse hides itself in
a program. Once you install any such program, the trojan
horse enters into your computer. It can provide
unauthorized access to your computer, send your files to
other computers, and may delete files or make other
unwanted changes in your computer.

10.Cavity virus
It is also known as a space filler virus. As name suggests,
this virus tends to install itself by occupying the empty
sections of a file. It is not easy to detect this virus as it
fills empty spaces without changing the size of the file.
11.CMOS Virus
It infects the CMOS, which stands for complementary
metal-oxide semiconductor and is a memory chip that
contains the system configuration. This virus can erase or
reset the system configuration.

12.Encrypted Virus
It encrypts its payload to make its detection more
difficult. It comprises two parts: an encrypted virus body
and a decryptor, which decrypts the virus when it is
executed. After decryption, the virus can execute itself in
order to replicate and become a resident.

13.Executable Virus
It is a non-resident computer virus, which resides in an
executable file. Whenever the infected file is executed, it
infects the other files.

14.Polymorphic Virus
It creates its thousands of copies itself; in each copy, it
changes sequence and byte values to evade detection by
antivirus software. Even best antiviruses may not be able
to detect this virus. Polymorphic viruses affect data types
functions, generally spread through spam infected sites.
15.Rabbit Virus
It is capable of creating new processes, and each new
process further creates new processes. This process
continues until this virus utilizes all available resources in
system and system falls short of resources. It may cause
target system to slow down and crash. For eg, it is like an
Infinite loop that repeatedly creates processes that
consume lots of CPU cycles ,operating system resources.

16.Stealth Virus
It is a hidden computer virus, which specifically attacks
operating system processes. It usually hides itself in
partitions, files or boot sectors and is capable of going
unnoticed during antivirus or anti-malware scans, i.e., it
can avoid detection intentionally.
Characteristics of computer viruses
 They can be spread through various means, such as
email attachments, infected software downloads,
and USB drives.
 They can hide themselves on a computer, making
them difficult to detect and remove.
 They can cause harm to a computer's operating
system, files, and programs.
 Some viruses are designed to steal personal
information, such as login credentials or credit card
numbers.
 Some viruses can be used to remotely control an
infected computer, part of a botnet.
 Some viruses are designed to spread to as many
computers as possible in order to cause widespread
damage.
 They are transferred from one element to another.
Antivirus software
 Antivirus software is a sort of application that
defends computers from malware such as viruses,
computer worms, trojans, spyware, botnets,
rootkits, keyloggers, and other threats.
 Antivirus software scans your computer for viruses,
finds them, and removes them.
 Anti-virus software comes in range of versions and
formats.
 Antivirus software is designed to protect computers
and, once viruses are detected, to destroy them.
 Most of the antivirus software allows for both
automated and manual screening.
List of Top 10 Antivirus Software
1. Norton
Each of Norton's antivirus packages provides great
protection against malware and system load is
significantly reduced. They contain firewall extensive
browser protection features to keep you secure online.

2. Bitdefender
It also provides the best value with features such as
secure browser with a virtual keyboard, a Wi-Fi network
scanner, defense system against encrypting ransomware.

3. Kaspersky
Kaspersky show great malware detection capability and
have a quality to moderate effect on the system.

4. McAfee
McAfee Antivirus Plus is only antivirus solution that
identifies rising number of devices in a single household.

5. Webroot
Webroot Secure AntiVirus is a fascinating Windows and
Mac application that employs unique approach to
malware detection.
6. ESET
ESET is a secure antivirus that excels at guarding your
gadgets against malware, phishing scams, ransomware
and online threats.It also provides excellent capabilities
that can assist you in recovering your device if it is lost.

7. Sophos
Sophos is simple antivirus with strong malware detection
rates, a user-friendly dashboard, and a few useful
features, such as remote management.

8. Avast
Avast offers a variety of features and tools to improve
your cybersecurity. Avast's plan includes standard
features and functionalities.

9. Panda
Panda Dome is a multi-featured antivirus with a high-
quality cybersecurity defenses. It has password organizer
which includes password analyzer that examines all of
your passwords and informs you how strong they are and
how long it will take someone to crack them.

10. BullGuard BullGuard is excellent anti-malware,

provides number of handy bonus features and a booster
that boosts System speed for gamers.