computer fundamentals by neha g. kurale

1. Computer Fundamentals
 Hardware & software
 Operating System
 Viruses and Their Types
 Networking Concept

2. COMPUTER FUNDAMENTALS
Input/output Devices
video

3. CONTENTS
• Introduction
• Input Devices
– Keyboard,mouse,joystick,scanners,digital
camera, bar code reader, touch
Sreeen,Speech input device (microphone)
• Output Devices
– Monitor , Speaker, Printers ( different
types)

4. 1.Introduction

5. What’s available for input…
 touch - fingers, feet, breath
 sound - voice, other sounds
 gesture
 gaze
 brainwaves…

6. and output…
 textual information
 visual images - photos, diagrams, icons
 moving images
 sounds - music, voice
 Etc..

7. 2.Input Devices
Used by a person to communicate to a computer.
Person to
computer
Input Devices video

8. Output Devices
Displays information from the computer to a person.
Output Devices video

9. Input Devices
Keyboard.
Mouse
Microphone
Digital Camera
Scanner
Video

10. The Keyboard
THE MOST COMMONLY USED INPUT DEVICE IS
THE KEYBOARD ON WHICH DATA IS ENTERED BY
MANUALLY KEYING IN OR TYPING CERTAIN KEYS.
A KEYBOARD TYPICALLY HAS 101 OR 105 KEYS.

11. Keyboard
 The keyboard allows the computer user to enter words, numbers,
punctuation, symbols, and special function commands into the
computer’s memory.

12. The Mouse
IS A POINTING DEVICE WHICH IS USED TO
CONTROL THE MOVEMENT OF A MOUSE POINTER
ON THE SCREEN TO MAKE SELECTIONS FROM THE
SCREEN. A MOUSE HAS ONE TO FIVE BUTTONS.
THE BOTTOM OF THE MOUSE IS FLAT AND
CONTAINS A MECHANISM THAT DETECTS
MOVEMENT OF THE MOUSE.

13. Pointing devices - direct
 Touch screens

14. Touch screens
 Often used for applications with occasional use, for example
 Bank ATMs, Information Kiosks, etc.
 No extra hardware - used for input and for output
 Can be precise to 1 pixel
 Good for menu choice - not so good for other functions
 Intuitive to use

15. Touch screens
 BUT
 Tiring if at wrong angle (needs to be 30-45% from
horizontal)
 Get greasy, jammy
 Finger can obscure screen
 Alternative - use stylus to touch screen, or lightpen

16. Indirect Pointing Devices
 Need more cognitive processing than direct methods,
but can be more efficient
 mouse
 tracker ball
 track point
 touchpad…

17. Indirect pointing
devices - other
 Tracker ball, trackpad, trackpoint
 Less space on desktop
 Good in moving environments,
e.g. car, train

18. Indirect pointing devices -
other
 Joystick
 The main use of a joystick is to play
computer games by controlling the way that
something moves on the screen.

19. Microphones - Speech Recognition
•Use a microphone to talk to your
computer
•Add a sound card to your computer
•Sound card digitizes audio
input into 0/1s
•A speech recognition program can
process the input and convert it into
machine-recognized commands or
input

20. Audio Input: Speech Recognition
 Speech recognition is a
type of input in which the
computer recognizes words
spoken into a microphone.
 Special software and a
microphone are required.
 Latest technology uses
continuous speech
recognition where the user
does not have to pause
between words.

21. Microphones - Speech Recognition

22. Digital camera
A digital camera can store many more
pictures than an ordinary camera. Pictures
taken using a digital camera are stored inside
its memory and can be transferred to a
computer by connecting the camera to it. A
digital camera takes pictures by converting the
light passing through the lens at the front into a
digital image.

23. Scanner
A scanner can be used to input pictures and
text into a computer. There are two main types
of scanner; Hand-held and Flat-bed.

24. Light pen
•A light pen is a small ‘pen-shaped’ wand,
which contains light sensors.
•It is used to choose objects or commands on
the screen either by pressing it against the
surface of the screen or by pressing a small
switch on its side.
•A signal is sent to the computer, which then
works out the light pen’s exact location on the
screen.
•The advantage of a light pen is that it doesn’t
need a special screen or screen coating.

25. Bar codes
•A bar code is a set of lines of different thicknesses
that represent a number
•Bar Code Readers are used to input data from bar
codes. Most products in shops have bar codes on
them
•Bar code readers work by shining a beam of light
on the lines that make up the bar code and
detecting the amount of light that is reflected back

26. 2. Output Types
 Text output
 Graphics output
 Video output
 Audio output

27. Output Devices: Engaging our Senses
 Output devices are peripheral devices that enable us to
view or hear the computer’s processed data.
 Visual output – Text, graphics, and video
 Audio output – Sounds, music, and synthesized speech

28. Output Devices
 Monitors
 Printers
 Speakers
 Data Projectors

29. Monitors
 A monitor is a peripheral device which displays
computer output on a screen.
 Screen output is referred to as soft copy.
 Types of monitors:
 Cathode-ray tube (CRT)
 Liquid Crystal Display (LCD or flat-panel)
CRT LCD

30. Monitors
 CRT
 cathode ray tube
 electron gun shoots a stream of electrons at a specially phosphor-
coated screen
 on impact, the phosphor flares up for a fraction of a second
 electron gun sweeps across the screen many times a second
 LCD
 liquid crystal display
 one of several types of “flat-panel” displays
 forms output by solidifying crystals and “backlighting” the image with
a light source
 TV sets are CRTs and many desktop monitors use this technology
 LCD is primarily used for laptops and other portable devices

31. Video Display Terminology
 Pixel
 picture element (smallest unit of an image, basically a
single dot on the screen)
 Resolution
 number of pixels in the image
 Common resolution size is 1024x768
 Refresh rate
 how often a CRT’s electron gun rescans
 LCD displays do not use an electron gun, so do not
perform refreshing
The CRT electron gun
“shoots” 3 electrons at
the screen representing
the amount of red, green
and blue for the pixel

32. Printers
 Ink Jet Printer
 least expensive, color, slower with a higher per page cost
than laser printers
 Laser Printer
 More expensive, faster, lower per page cost than ink jet,

33. Printers
 A printer is a peripheral device
that produces a physical copy or
hard copy of the computer’s
output.

34. Types of Printers
 Inkjet printer, also called a
bubble-jet, makes characters
by inserting dots of ink onto
paper
 Letter-quality printouts
 Cost of printer is inexpensive
but ink is costly
 Laser printer works like a
copier
 Quality determined by dots
per inch (dpi) produced
 Color printers available
 Expensive initial costs but
cheaper to operate per
page
Inkjet Laser

35. Plotter
 A plotter is a printer that uses a pen that moves over a large
revolving sheet of paper.
 It is used in engineering, drafting, map making, and seismology.

36. Audio Output: Sound Cards and
Speakers
 Audio output is the ability of the computer to output sound.
 Two components are needed:
 Sound card – Plays contents of digitized recordings
 Speakers – Attach to sound card

37. Questions
1.Enlist and Explain Input Devices.
2.Enlist and Explain Output Devices.

38. Computer software and OS

39. Contents
 We will learn
1. What is Operating System?
2. What OS does?
3. Structure of OS
4. Evolution of OS
 Batch Processing, Multiprogramming, Time sharing
systems
5. Operating System Functions
6. Main Funtions of OS
7. Types of OS
 Single User, Multi User systems

40. Operating Systems
Operating Systems video

41. What is OS?
 Operating System is a software, which makes a computer to
actually work.
 It is the software the enables all the programs we use.
 The OS organizes and controls the hardware.
 OS acts as an interface between the application programs and
the machine hardware.
 Examples: Windows, Linux, Unix and Mac OS, etc.,

42. What OS does?
An operating system performs basic tasks such
as,
controlling and allocating memory,
prioritizing system requests,
controlling input and output devices,
facilitating networking and
managing file systems.

43. Structure of Operating
System: Application Programs
System Programs
Software (Operating System)
HARDWARE
(Contd…)

44. Structure of Operating System
(Contd…):
 The structure of OS consists of 4 layers:
1. Hardware
Hardware consists of CPU, Main memory,
I/O Devices, etc,
2. Software (Operating System)
Software includes process management
routines, memory management routines,
I/O control routines, file management
routines.
(Contd…)

45. Structure of Operating System
(Contd…):
3. System programs
This layer consists of compilers, Assemblers,
linker etc.
4. Application programs
This is dependent on users need. Ex. Railway
reservation system, Bank database
management etc.,

46. Evolution of OS:
 The evolution of operating systems went through
seven major phases.
 Six of them significantly changed the ways in which
users accessed computers through the open shop,
batch processing, multiprogramming, timesharing,
personal computing, and distributed systems.
 In the seventh phase the foundations of concurrent
programming were developed and demonstrated in
model operating systems.
(Contd…)

47. Evolution of OS (contd..):
Major
Phases
Technical
Innovations
Operating
Systems
Open Shop The idea of OS IBM 701 open shop
(1954)
Batch
Processing
Tape batching,
First-in, first-out
scheduling.
BKS system (1961)
Multi-
programming
Processor multiplexing,
Indivisible operations,
Demand paging,
Input/output spooling,
Priority scheduling,
Remote job entry
Atlas supervisor
(1961),
Exec II system (1966)
(Contd…)

48. Evolution of OS (contd..):
Timesharing Simultaneous user
interaction,
On-line file systems
Multics file system
(1965),
Unix (1974)
Concurrent
Programming
Hierarchical systems,
Extensible kernels,
Parallel programming
concepts, Secure parallel
languages
RC 4000 system (1969),
13 Venus system
(1972),
14 Boss 2 system
(1975).
Personal
Computing
Graphic user interfaces OS 6 (1972)
Pilot system (1980)
Distributed
Systems
Remote servers WFS file server (1979)
Unix United RPC (1982)
24 Amoeba system
(1990)

49. Batch Processing:
 In Batch processing same type of jobs batch (BATCH- a
set of jobs with similar needs) together and execute at a
time.
 The OS was simple, its major task was to transfer control
from one job to the next.
 The job was submitted to the computer operator in form
of punch cards. At some later time the output appeared.
 The OS was always resident in memory. (Ref. Fig. next
slide)
 Common Input devices were card readers and tape
drives.

50. Batch Processing
(Contd…):
 Common output devices were line printers, tape drives,
and card punches.
 Users did not interact directly with the computer
systems, but he prepared a job (comprising of the
program, the data, & some control information).
OS
User
program
area

51. Multiprogramming:
 Multiprogramming is a technique to execute number of
programs simultaneously by a single processor.
 In Multiprogramming, number of processes reside in
main memory at a time.
 The OS picks and begins to executes one of the jobs in
the main memory.
 If any I/O wait happened in a process, then CPU switches
from that job to another job.
 Hence CPU in not idle at any time.

52. Multiprogramming (Contd…):
OS
Job 1
Job 2
Job 3
Job 4
Job 5
• Figure dipicts the layout of
multiprogramming system.
• The main memory consists of 5
jobs at a time, the CPU executes
one by one.
Advantages:
•Efficient memory utilization
•Throughput increases
•CPU is never idle, so
performance increases.

53. Time Sharing Systems:
 Time sharing, or multitasking, is a logical extension of
multiprogramming.
 Multiple jobs are executed by switching the CPU
between them.
 In this, the CPU time is shared by different processes, so
it is called as “Time sharing Systems”.
 Time slice is defined by the OS, for sharing CPU time
between processes.
 Examples: Multics, Unix, etc.,

54. Operating Systems
functions:
 The main functions of operating systems are:
1. Program creation
2. Program execution
3. Input/Output operations
4. Error detection
5. Resource allocation
6. Accounting
7. protection

55. Types of OS:
Operating System can also be classified as,-
 Single User Systems
 Multi User Systems

56. Single User Systems:
 Provides a platform for only one user at a time.
 They are popularly associated with Desk Top operating
system which run on standalone systems where no
user accounts are required.
 Example: DOS

57. Multi-User Systems:
 Provides regulated access for a number of users
by maintaining a database of known users.
 Refers to computer systems that support two or
more simultaneous users.
 Another term for multi-user is time sharing.
 Ex: All mainframes and are multi-user systems.
 Example: Unix

58. A diagram showing how the user interacts with application
software on a typical desktop computer. The application
software layer interfaces with the operating system, which
in turn communicates with the hardware. The arrows
indicate information flow.

59. Software & Hardware?
 Computer Instructions or data, anything that can be
stored electronically is Software.
 Hardware is one that is tangible. The storage devices
(Hard disk, CD’s etc.,), mouse, keyboard CPU and
display devices (Monitor) are Hardware.
For example: There is a problem in the Software
implies – Problem with program or data

60. Types of Software
• System Software
• Application Software
• Open source Software and
• Proprietary Software

61. Video
Computer Software

62. • Software is a set of instructions, data or
programs used to operate computers and
execute specific tasks.
• Opposite of hardware, which describes the
physical aspects of a computer,
• software is a generic term used to refer to
applications,
• scripts and programs that run on a device.
• Software can be thought of as the variable
part of a computer, and hardware the
invariable part.
Software

63. Software is often divided into categories. Application
software refers to user-downloaded programs that fulfill a
want or need.
Examples of applications include office suites, database
programs, web browsers, word processors, software
development tools, image editors and communication
platforms.
Contd…

64. Application Software
Spreadsheets: The spreadsheet packages
are designed to use numbers and formulas to do
calculations with ease. Examples of spreadsheets
include:
Budgets
Payrolls
Grade Calculations
Address Lists
The most commonly used spreadsheet programs
are Microsoft Excel and Lotus 123.

65. Application Software
(contd…):
Graphic Presentations: The presentation
programs can be easier using overhead
projectors. Other uses include:
 Slide Shows
 Repeating Computer Presentations on
a computer monitor
 Using Sound and animation in slide
shows
The most recognized graphic presentation programs are
Microsoft PowerPoint and Harvard Graphics.

66. Application Software
(contd…):
Database Management System (DBMS):
 A DBMS is a software tool that allows multiple users to
store, access, and process data into useful information.
 Database programs are designed for these types of
applications:
 Membership lists
 Student lists
 Grade reports
 Instructor schedules
All of these have to be maintained so you can find what
you need quickly and accurately.
 Example:Microsoft Access, dBASE, Oracle.

67. System Software:
System Software includes the Operating System and all the
utilities that enable the computer to function.
System software is a term referring to any computer software
which manages and controls the hardware so that application
software can perform a task.
Example:
Operating Systems, Compiler, Loader, Linker, Interpreter.

68. System Software:
Operating System:
 Operating System is a software, which makes a computer to
actually work.
 It is the software the enables all the programs we use.
 The OS organizes and controls the hardware.
 OS acts as an interface between the application programs and
the machine hardware.
 Examples: Windows, Linux, Unix and Mac OS, etc.,

69. System Software (contd):
Source
Languages
Target Languages
‘C’ language ‘C’ language
‘Pascal’ language Machine language
FORTRAN language
C++ language
ADA language
Compiler: A compiler is a program that reads a
program in one language – the source language and
translates into an equivalent program in another
language – the target language.

70. System Software (contd):
Loader: A loader is the part of an operating
system that is responsible for loading programs
into memory, preparing them for execution and
then executing them.
The loader is usually a part of the operating
system's kernel and usually is loaded at system
boot time and stays in memory until the system is
rebooted, shut down, or powered off.
In Unix, the loader is the handler for the system
call execve().

71. System Software (contd):
Linker: A linker or link editor is a program that
takes one or more objects generated by
compilers and assembles them into a single
executable program.
Linkers can take objects from a collection called a
library. The objects are program modules
containing machine code and information for the
linker.
The linker takes care of arranging the objects in a
program's address space.

72. System Software (contd):
Interpreter: An interpreter is a computer program that
translates and executes instructions written in a computer
programming language line-by-line, unit by unit etc.,
An interpreter needs to be able to analyze, or parse, instructions
written in the source language.
Example: Lisp systems, etc.,

73. Open Source Software:
 Open source software (OSS) is computer
software whose source code is available
under a license that permits users to use,
change, and improve the software, and to
redistribute it in modified or unmodified
form.
 It is often developed in a public,
collaborative manner.
Well-known OSS products are Linux,
Netscape, Apache, etc.,

74. Proprietary Software:
 Proprietary software (also called non-free software)
is software with restrictions on using, copying and
modifying as enforced by the proprietor. Restrictions
on use, modification and copying is achieved by
either legal or technical means and sometimes both.
 Proponents of proprietary software are Microsoft.
 Ex: CAD, Nortan Antivirus etc.,

75. Hardware
It refers to the physical elements of a computer. This is also sometime called the
machinery or the equipment of the computer.
Examples of hardware in a computer are the keyboard, the monitor, the mouse
and the central processing unit.
However, most of a computer's hardware cannot be seen; in other words, it is not
an external element of the computer, but rather an internal one, surrounded by the
computer's casing (tower).
A computer's hardware is comprised of many different parts, but perhaps the most
important of these is the motherboard. The motherboard is made up of even
more parts that power and control the computer.

76. In contrast to software, hardware is a physical
entity. Hardware and software are interconnected,
without software, the hardware of a computer would
have no function. However, without the creation of
hardware to perform tasks directed by software via
the central processing unit, software would be
useless.

77. Contd..

78. video
 Hardware Software

79. Questions
 What is OS?
 Explain Evolution of O.s
 What is mean by multi Programming
 Explain Timesharing OS
 Explain Functions of OS
 What are the types of OS

80. video
 RAM ROM
 Storage devices
 Storage Devices
 Computer Memory, Processing, and Storage

82. Memory

83. 1. Introduction
• Memory Devices
(RAM,ROM,PROM,EPROM)
• Storage Devices (Auxiliary Storage
Devices-Magnetic Tape, Hard Disk, Floppy
Disk .Optical Disks: CD-R Drive,CD-RW
disks,DVD,Blue ray Discs)

85. Characteristics of Storage Devices
 Speed
 Volatility
 Access method
 Portability
 Cost and capacity

86. Basic Units Of Measurement
• Bit
Binary digit
Smallest unit of measurement
Two possible values 0 1
on off
OR
•Byte
•8 bits

87. Small Units Of Measurement (Processor
And Memory Speed)
Millisecond (ms) – a thousandth of a second
(1/1,000 = 10-3)
Microsecond (μs) - a millionth of a second
(1/1,000,000 = 10-6)
Nanosecond (ns) – a billionth of a second
(1/1,000,000,000 = 10-9)

88. Large Units Of Measurement
(Memory, Storage)
• Note: powers of two are used because
computer memory and storage are based on
the basic unit (bit).
• Kilobyte (KB) – a thousand bytes (1,024 = 210)
• Megabyte (MB) - a million (1,048,576 = 220)

89. Large Units Of Measurement
(Memory, Storage)
• Gigabyte (GB) – a billion (1,073,741,824 = 230)
–~ A complete set of encyclopedias requires
about 700 MB of storage
–~ 30 minutes of video (1/4 of the information
stored on a typical DVD)

90. Large Units Of Measurement
(Memory, Storage)
• Terabyte (TB) – a trillion (1,099,511,627,776 =
240)
–~ 20 million four-drawer filing cabinets full of
text
–~ 200 DVD’s of information

91. CONTENTS
• Introduction
• RAM,ROM,PROM,EPROM
• Auxiliary Storage Devices-Magnetic
Tape, Hard Disk, Floppy Disk
• Optical Disks: CD-R Drive,CD-RW
disks,DVD,Blue ray Discs.

92. • Memory Devices
– Memory: Is one or more sets of chips
that store data/program instructions,
either temporarily or permanently .
– It is critical processing component in
any computer
– PCs use several different types
2. RAM,ROM,PROM,EPROM

93. RAM,ROM,PROM,EPROM
• Memory Devices
– Two most important are
• RAM(Random Access Memory)
• ROM(Read-only Memory)
– They work in different ways and perform
distinct functions
– CPU Registers
– Cache Memory

94. RAM
• RAM is packaged as a chip.
• Basic storage unit is a cell (one bit per cell).
• Multiple RAM chips form a memory.
• Random Access Memory
Volatile
Used for temporary storage
Typical ranges 256 MB - 4 GB
• Random Access means direct access to any
part of memory

95. Nonvolatile Memories(ROM)
 DRAM and SRAM are volatile memories
Lose information if powered off.
 Nonvolatile memories retain value even if powered off.
Generic name is read-only memory
(ROM).
Misleading because some ROMs can be
read and modified.

96. Nonvolatile Memories(ROM)
 Types of ROMs
 Programmable ROM (PROM)
 Eraseable programmable ROM (EPROM)
 Electrically eraseable PROM (EEPROM)
 Flash memory (used in portable digital devices)
 Firmware (Program instruction used frequently)
 Program stored in a ROM
Boot time code, BIOS (basic input/output
system)
graphics cards, disk controllers.

97. Memory

98. 3. Storage Vs. Memory
Memory (e.g., RAM)
•Keep the information for a shorter period
of time (usually volatile)
•Faster
•More expensive

99. 3. Storage Vs. Memory
Storage (e.g., Hard disk)
• The information is retained
longer (non-volatile)
• Slower
• Cheaper

100. CONTENTS
• Introduction
• RAM,ROM,PROM,EPROM
• Auxiliary Storage Devices-Magnetic
Tape, Hard Disk, Floppy Disk
• Optical Disks: CD-R Drive,CD-RW
disks,DVD,Blue ray Discs.

101. Categories Of Storage
• Magnetic
– Floppy disks
– Zip disks
– Hard drives
• Optical
– CD-ROM
– DVD
• Solid state storage devices
– USB Key (a very common form of solid state
storage)

102. Magnetic Storage
 Exploits duality of magnetism and electricity
 Converts electrical signals into magnetic charges
 Captures magnetic charge on a storage medium
 Later regenerates electrical current from stored magnetic charge
 Polarity of magnetic charge represents bit values zero and one

103. 1. Magnetic Drives

104. Magnetic Disk
 Flat, circular platter with metallic coating that is rotated beneath
read/write heads
 Random access device; read/write head can be moved to any location
on the platter
 Hard disks and floppy disks
 Cost performance leader for general-purpose
on-line secondary storage

105. 1. Magnetic Drives: Storage Capacities
Floppy disks
~ 1 MB
Hard drives
~80 – 500 GB (TB is possible but very rare)

106. Floppy Disks
A FLOPPY DISK IS A PORTABLE, INEXPENSIVE
STORAGE MEDIUM THAT CONSISTS OF A THIN,
CIRCULAR, FLEXIBLE PLASTIC DISK WITH A
MAGNETIC COATING ENCLOSED IN A SQUARE-
SHAPED PLASTIC SHELL.

107. Structure Of Floppy Disks
 Initially Floppy disks were 8-inches wide, they then shrank to 5.25
inches, and today the most widely used folly disks are 3.5 inches
wide and can typically store 1.44 megabytes of data.
 A folly disk is a magnetic disk, which means that it used magnetic
patterns to store data.
 Data in floppy disks can be read from and written to.
 Formatting is the process of preparing a disk for reading and
writing.
 A track is a narrow recording band that forms a full circle on the
surface of the disk.

108. Hard Disks
 Another form of auxiliary storage is a hard disk. A hard disk consists
of one or more rigid metal plates coated with a metal oxide
material that allows data to be magnetically recorded on the
surface of the platters.
 The hard disk platters spin at a high rate of speed, typically 5400 to
7200 revolutions per minute (RPM).
 Storage capacities of hard disks for personal computers range from
10 GB to 120 GB (one billion bytes are called a gigabyte).

109. sectors
each track is
divided into pie-
shaped wedges
cluster
two or more
sectors
combined
tracks
data is recorded in
concentric circular
bands

110. Optical Mass Storage Devices
 Store bit values as variations in light reflection
 Higher areal density & longer data life than magnetic storage
 Standardized and relatively inexpensive
 Uses: read-only storage with low performance requirements, applications
with high capacity requirements & where portability in a standardized
format is needed

111. 2. Optical Drives
CD's (Compact Disk)
~ 700 MB storage
CD-ROM (read only)
CD-R: (record) to a CD
CD-RW: can write and erase CD to reuse it (re-writable)
• DVD(Digital Video Disk)

112. Compact Discs (CD)
 A compact disk (CD), also called an optical disc, is a flat round,
portable storage medium that is usually 4.75 inch in diameter.
 A CD-ROM (read only memory), is a compact disc that used the same
laser technology as audio CDs for recording music. In addition it can
contain other types of data such as text, graphics, and video.
 The capacity of a CD-ROM is 650 MB of data.

113. DVD-ROM
– Over 4 GB storage (varies with
format)
– DVD- ROM (read only)
– Many recordable formats (e.g.,
DVD-R, DVD-RW; ..)
– Are more highly compact than
a CD.
– Special laser is needed to read
them
DVD (Digital Video Disk)

114. Blu-ray Technology
 Name
Derived from the blue-violet laser used to
read and write data.
 Developed by the Blu-ray Disc Association
with more than 180 members.
Dell
Sony
LG

115. Blu-ray Technology Cont.
 Data capacity
 Because Blu-ray uses a blue
laser(405 nanometers) instead of
a red laser(650 nanometers) this
allows the data tracks on the disc
to be very compact.
 This allows for more than twice as
small pits as on a DVD.

116. Blu-ray Technology Cont.
 BD-ROM (read-only) - for pre-recorded content
 BD-R (recordable) - for PC data storage
 BD-RW (rewritable) - for PC data storage
 BD-RE (rewritable) - for HDTV recording
Formats

117. Questions
• Enlist and explain memory devices.
• Write short note on
RAM,ROM,PROM,EPROM
• Enlist and explain Storage Devices
• Write short note on Optical Disk
• Explain basic units of measurment

118. COMPUTER FUNDAMENTALS
Computer Threats

119. Video
 Computer Threats
 Computer Threats

120. CONTENTS
• Introduction( Viruses, Bombs,
Worms)
• Types of Viruses
• Characteristics of Viruses
• Categories of Viruses
• Computer Security-
–Antivirus Software
–Password, Firewalls

121. In the beginning, man created
the virus, and it was bad.
The first computer virus
Several stories
Pakistani Brain Virus (1986): This is the first
widely spread IBM Compatible virus. This is
commonly mistaken for the first virus.
Apple Virus 1 (1981): Boot sector infecting virus.
Possibly created for pirated games.
Animal (1975) (Univac): “Guess an animal” game.
Copied to other users’ home directories when
run.

122. 1.Introduction
A virus is a program that attaches itself to some
form of host such as legitimate, executable
program.
•Virus lives within the program, which is said
to be ‘infected’.
•Execution of the host program implies
execution of the virus.
•May or may not damage the infected
program.
A virus is able to replicate
•Creates (possibly modified) copies of itself.

123. Viruses
 Needs to have some form of
distribution
such as via disks or a computer network.
 Examples: W95.CIH (Chernobyl), Sampo
and Hare

124. Classifying Viruses: categories
• Boot Sector
• TSR (Terminate and stay resident)
• Multipartite
• Macro
• Companion
• Polymorphic

125. Boot Sector
 Infects the boot sector on a disk
replaces the original boot sector with itself
• stores the original boot sector somewhere else or replaces it totally
Virus takes control when the system is booted
from the diskette
may infect other diskettes that are inserted, unless they are write
protected
may also infects hard disks

126. Master Boot Record/Boot Sector
Viruses
BOOT SECTOR VIRUS (APPLE VIRUSES 1,2,3,
“ELK CLONER”), PAKISTANI BRAIN (X86)

127. TSR
 A terminate and stay resident (TSR) virus
is a virus that stays active in memory
after the application (or bootstrapping,
or disk mounting) has terminated.
• TSR viruses can be boot sector infectors
or executable infectors.
• The Brain virus is a TSR virus.

128. Multipartite
 A multipartite virus is a virus that can infect either boot sectors or
executables.
• Such a virus typically has two parts, one for each type.
• When it infects an executable, it acts as an executable infector.
• When it infects a boot sector, it works as a boot sector infector.

129. Macro
 A macro virus is a virus composed of a sequence of instructions that
is interpreted rather than executed directly.
• Macro viruses can infect either executables (Duff’s shell virus) or data
files (Highland’s Lotus 1-2-3 spreadsheet virus).
• Duff’s shell virus can execute on any system that can interpret the
instructions

130. Macro
 Piece of self-replicating code written in an
application's macro language
􀁺 a macro virus requires an auto-execute macro
􀁺 one which is executed in response to some event
e.g opening or closing a file or starting an application
 once the macro virus is running, it can copy itself to other documents
delete files, etc.

131. Polymorphic
 A virus may be encrypted to try to disguise itself and
hide what it does
 For an encrypted virus to actually run, it has to decrypt its code and data
- The portion that does this is referred to as a
decryptor
 Encryption techniques can use random keys to
make the virus code hard to spot
-However the decryptor itself will have a signature

132. Polymorphic
A polymorphic virus is a randomly
encrypted virus that is also
programmed to randomly vary its
decryption routine

133. Viruses Types:
Worms
Trojan Horse
Bombs

134. Computer Worm
 A self-replicating computer program, similar to a
computer virus
 Unlike a virus, it is self-contained and does not need
to be part of another program to propagate itself
 Often designed to exploit computers’ file transmission
capabilities

135. Worm
 A program or algorithm that replicates itself over a
computer network or through e-mail and sometimes
performs malicious actions such as using up the
computer and network resources and possibly
destroying data.
 Examples: Klez, Nimda, Code Red

136. Computer Worm
In addition to replication, a worm may
be designed to:
delete files on a host system
send documents via email
carry other executables as a payload

137. Trojan
 A malicious program disguised as legitimate software
Cannot replicate itself, in contrast to some other types of “malware” like
worms and viruses
but they can be contained within a worm.
 Depending on their purpose, a Trojan can be destructive or a resource hog
and is almost always considered a root compromise.
 Ex: Back Orifice, NetBus, SubSeven

138. Can legitimate networking tools be
considered Trojans?
Yes! Many applications are installed by
hackers and worms that would be
considered legitimate tools. If they were not
installed by you and are being used for
malicious purposes, they are considered
Trojans … even though your antivirus
software will not detect them as such.

139. Logic Bomb
 “Slag code”
 Programming code, inserted
surreptitiously, designed to execute
(or “explode”) under particular
circumstances

140. Logic Bomb
Does not replicate
Essentially a delayed-action
computer virus or Trojan
horse

141. How do viruses work? (Characteristics)
Possible attacks include:
 Replicating itself
 Interrupting system/network use
 Modifying configuration settings
 Flashing BIOS
 Format hard drive/destroy data
 Using computer/network resources
 Distribution of confidential info
 Denial of Service attacks
Once a virus gains access to a computer, its
effects can vary.

142. Typical methods of infection
Removable media or drives
Downloading Internet files
E-mail attachments
Unpatched software and services
Poor Administrator passwords
Poor shared passwords

143. Virus prevention
 Patching the operating system
 Patching services
 Patching client software
 Passwords
 Antivirus software
 Firewalls
Computer Security

144. Passwords
As discussed earlier when talking about
Trojans, strong passwords are a vital part of
keeping your systems free of infection.
Antivirus software does not catch the majority
of the Trojans . These Trojans are typically
legitimate networking tools that were never
intended to be used as a Trojan.

145. Passwords
 Having strong passwords will deter most worms and scanners that
attempt to crack passwords as a means of entry.
 The Administrator account and those users who have Administrator
privileges are at the greatest risk, but all users on the network
should follow the same password policy.

146. Virus Detection (Antivirus software)
The primary method of detection of
antivirus software is to check
programs and files on a system for
virus signatures. However, good
antivirus software uses many methods
to search the system for viruses.

147. Antivirus Software
AV software considerations
•Features
•Cost (per workstation/server)
•Frequency of updates
•Ease of update installation
•Server administration
•Certification

148. Antivirus software options
 Aladdin Knowledge
 Alwil Software
 AVG Antivirus
 Central Command
 Command Software
 Computer Associates
 Data Fellows Corp.
 Dr. Solomon’s Software
 ESET Software
 Finjan Software
 Frisk Software
 Kaspersky Lab
 McAfee
 Network Associates
 Norman Data Defense
 Panda Software
 Proland Software
 Sophos
 Symantec Corporation
 Trend Micro, Inc.

149. Cleaning viruses
 Cleaning viruses depends entirely on your local antivirus solution. The virus
must be identified before it can be removed, so it makes sense to try your
antivirus scanner first.
 If your software identifies, but can’t remove the virus, check the
manufacturer’s website for manual removal instructions.

150. Perform Basic Computer Safety
Maintenance
Use an Internet “firewall”
Update your computer
Use up-to-date antivirus software

151. Use an Internet Firewall
 A firewall is software or hardware that creates a protective barrier
between your computer and potentially damaging content on the
Internet or network.
 The firewall helps to guard your computer against malicious users, and
also against malicious software such as computer viruses and worms.

152. Use an Internet Firewall
 Commercial hardware and
software firewalls may also
be used

153. “Update” Your Computer
 Download service packs and updates
 Especially important for Windows XP users: “SP2”

154. Use Up-to-date Antivirus Software
 McAfee and Symantec are
prominent vendors
 Make certain to keep “virus
definitions” up-to-date

155. Questions
 Define: Virus , Computer Worm , computer security.
 Explain Characteristics of virus.
 Explain types of virus.
 How does Virus Works?
 List Antivirus Software.

156. INTRODUCTION TO
COMPUTER NETWORKS

157. What is a Computer Network?
A system containing any combination of computers, computer terminals,
printers, audio or visual display devices, or telephones interconnected by
telecommunication equipment or cables: used to transmit or receive
information.
The Network Diagram

158. Types of Network
There are many types of computer networking which are used world
wide these days. There are some types of network that are using
Worldwide:
 LAN - Local Area Network
 WAN - Wide Area Network
 WLAN - Wireless Local Area Network
 PAN - Personal Area Network
 SAN - Storage Area Network
 GAN - Global Area Network
 MAN - Metropolitan Area Network
 CAN - Controller Area Network
 DAN - Desk Area Network
 VPN - Virtual Private Network

160. Distinguish Between LAN,WAN,MAN

161. Network Classification By Their Component Role

163. Peer To Peer Network
 In peer to peer network each computer is responsible for making its own
resources available to other computers on the network.
 Each computer is responsible for setting up and maintaining its own
security for these resources.
 Also each computer is responsible for accessing the required network
resources from peer to peer relationships.
 Peer to peer network is useful for a small network containing less than 10
computers on a single LAN .
 In peer to peer network each computer can function as both client and
server.
 Peer to peer networks do not have a central control system. There are no
servers in peer networks.
 Peer networks are amplified into home group.

164. Advantages & Disadvantages of Peer To Peer Network
Advantages:
 Use less expensive
computer hardware
 Easy to administer
 No NOS required
 More built in
redundancy
 Easy setup & low cost
Disadvantages:
 Not very secure
 No central point of storage or
file archiving
 Additional load on computer
because of resource sharing
 Hard to maintain version control

165. Client/Server Network
 In client-server network relationships, certain computers act as
server and other act as clients. A server is simply a computer, that
available the network resources and provides service to other
computers when they request it. A client is the computer running a
program that requests the service from a server.
 Local area network(LAN) is based on client server network
relationship.
 A client-server network is one on which all available network
resources such as files, directories, applications and shared devices,
are centrally managed and hosted and then are accessed by client.
 Client serve network are defined by the presence of servers on a
network that provide security and administration of the network.

166. Advantages and Disadvantages of Client/Server Network
Advantages:
• Very secure
• Better performance
• Centralized backup
• very reliable
Disadvantages:
• Requires professional
administration
• More hardware intensive
• More software intensive
• Expensive dedicated software

167. Types of Servers

168.  File server: These servers provide the services for storing, retrieving
and moving the data. A user can read, write, exchange and manage
the files with the help of file servers.
 Printer server: The printer server is used for controlling and
managing printing on the network. It also offers the fax service to
the network users.
 Application server: The expensive software and additional
computing power can be shared by the computers in a network with
he help of application servers.
 Message server: It is used to co-ordinate the interaction between
users, documents and applications. The data can be used in the for
of audio, video, binary, text or graphics.
 Database server: It is a type of application server

169. Applications of Computer Network :
 Sharing of resources such as printers
 Sharing of expensive software's and database
 Communication from one computer to another computer
 Exchange of data and information among users via network
 Sharing of information over geographically wide areas.

170. Components of Computer Network
Two or more computers
Cables as links between the computers
A network interfacing card(NIC) on each computer
Switches
Software called operating system(OS)

171. Network Benefits
The network provided to the users can be divided into two categories:
 Sharing
 Connectivity
Sharing Resources
Types of resources are:
 Hardware: A network allows users to share many hardware devices
such as printers , modems, fax machines, CD ROM, players, etc.
 Software: sharing software resources reduces the cost of software
installation, saves space on hard disk.

172. Other Benefits of Computer Network
 Increased speed
 Reduced cost
 Improved security
 Centralized software managements
 Electronic mail
 Flexible access
Disadvantages of Computer Networks
High cost of installation
Requires time for administration
Failure of server
Cable faults

186. Questions
• What is mean by computer network?
• Enlist Types of Network?
• Give the difference between LAN,MAN,WAN
• Explain peer to peer network with advantages and disadvantages