This document provides an overview of how computers represent and output data. It discusses that computers use the binary number system to represent data as strings of 1s and 0s at the hardware level. It also explains different output devices like monitors that display visual output and speakers that produce audio output. Printers are also covered as a way for computers to provide physical printed output. The document discusses different types of monitors, printers, and other output technologies in detail.

1. Information and Communication
Technology Fundamentals
Instructor: Fakhera Nazir

2. How computers represent data and
why?

3. 5A-3
How Computers Represent Data
• Number systems
• A manner of counting
• Several different number systems exist
• Decimal number system
• Used by humans to count
• Contains ten distinct digits
• Origin: Probably because human beings normally have
10 fingers
• Digits combine to make larger numbers

4. 5A-4
How Computers Represent Data
• Clocks have 24 hours
• Each hour  60 minutes
• Each minute  60 seconds
• When we time something, we count in seconds,
minutes and hours

5. 5A-5
How Computers Represent Data
• Computers use electronic switches called
transistors
• A switch can either be ON or OFF
• Only two numeric values can be represented by
one switch, 0 and 1
= 1 = 0

6. • Binary number system
• Used by computers to count
• Two distinct digits, 0 and 1
• 0 and 1 combine to make numbers
How Computers Represent Data

7. 5A-7
How Computers Represent Data
• Bits and bytes
• Binary numbers are made of bits
• Bit (Binary Digit) represents a switch
• A byte is 8 bits
• Byte represents one character

8. • Any number from the decimal number system can
also be written using binary number system
• Decimal to Binary conversion is required
• Each digit in the decimal number system has a
place value
• Ones (100), Tens(101), Hundreds(102), Thousands(103)
How Computers Represent Data

9. • The place value is expressed in powers of 10
• 10 to the power of digit position
• 10 is called the base of the Decimal number system
• In binary number system the base is 2
• Place value is 2 to the power of digit position
How Computers Represent Data
Image Courtesy: www.emu8086.com

10. Conversion from decimal to binary
• Technique # 1
• Map digits 0-9 to some binary values
• 0-9 are 10 digits
• 3 bits can have 8 combinations
• 4 bits can have 16 combination
• We would have to use 4 bits since 10 > 8
• 010  00002 , 110  00012 ,…, 910  10012
• This scheme is called Binary Coded Decimal (BCD)

11. Conversion from decimal to binary
• BCD
• So 910  0910  0000 10012
• 1010  0001 00002
• What about binary numbers between 00001001 and
00010000 ?
• 00001010, 00001011, 00001100, 00001101, 00001110,
00001111
• Not Used!
• BCD is used only when you have to represent each
digit of a number individually
• Digital Cricket Score Board

12. Conversion from decimal to binary
• Technique # 2
• Lets count from 0 in both decimal and binary simultaneously
and make sure every binary number is used
• 010  02
• 110  12
• 210  102
• 310  112
• 410  1002
• 510  1012
• 610  1102
• 710  1112
• 810  10002
• 910  10012
• 1010  10102
• 1110  10112
• 1210  11002
• 1310  11012
• 1410  11102
• 1510  11112
• 1610  100002
• 1710  100012
• 1810  100102
• 1910  100112
• 2010  101002
• 2110  101012
• 2210  101102
• 2310  101112
And so on..

13. Conversion from decimal to binary
• Technique # 2
• Did You notice some pattern?
• All odd numbers in decimal end with 1 in binary
• All even numbers is decimal end with 0 in binary
• The bits pattern repeats itself after the addition of every 1 on
the Left Hand Side
• Same things happens in decimal
• E.g. digits 0-99 repeat after addition of digits 1-9 on the L.H.S

14. Conversion from decimal to binary
• Technique # 2
• How would you represent 24510 in binary using
technique number 2 ??
• Some conversion procedure or formula is required
so that we can convert any number from decimal to
binary without having to count from 0 till that
number

15. Conversion from decimal to binary
• Technique # 2
• First Consider Conversion to binary to decimal
• Binary number system has a base ‘2’
• For conversion calculate place value of each digit position
and multiply by the corresponding digit value (0 or 1)
(1 1 0 0 1)2
24 23 22 21 20
=1x 24 + 1x 23 + 0x 22 + 0x 21 + 1x 20
= 1x16 + 1 x 8 + 0 x 4 + 0 x 2 + 1 x 1
= 16 + 8 + 0 + 0 + 1 = 2510

16. Conversion from decimal to binary
• Technique # 2
• Conversion from decimal to binary on board

17. Other Number Systems
• Hexa-Decimal Number System
• 16 possible values
• 0,1,2,…9,A,B,..F
• Base 16
• Octal Number System
• 8 possible values
• 0,1,2,..7
• Base 8

18. 5A-18
How Computers Represent Data
• Text codes
• Converts letters into binary
• Standard codes necessary for data transfer
• ASCII – 7 bits + parity bit
• American English symbols
• Extended ASCII – 8 bits no parity
• Graphics and other symbols
• Unicode – 32 bits
• All languages on the planet

19. Output Devices

20. Sources for Output
• Seeing it
• Video card + Display Screen/Projector
• Hearing it
• Sound card + speaker
• Having it
• Printers

21. The Seeing part
• Monitor
• Most common output device
• Can display text, images, video/animation
• Video card
• Intermediary device between CPU and monitor
• Affects the quality of images displayed

22. 4A-22
Monitors
• Most common output device
• Cathode Ray Tubes
• Flat Panel Display
• Categorized by color output
• Monochrome
• One color with black background
• Used for Text-only displays
• Grayscale
• Varying degrees of gray
• Used in low end portable systems to keep cost down
• Color
• Display 4 to 16 million colors

23. CRT Monitors
• Cathode Ray Tube (CRT)
• Most common type of monitor
• Phosphor is arranged in dots called pixels
• Phosphor are compounds which exhibit sustained glowing after
exposure to energized particles such as electrons
• Electrons fired from the back using electron gun
• Electrons excite phosphor to glow
• Electron Gun aims at every pixel
• Line by line
• Starting from top left corner to right edge
• Then next line from left to right

24. CRT Monitors
• Cathode Ray Tube (CRT)
• Circuitry of the CRT adjusts the intensity of each beam
• Monochrome: pixel ON or OFF
• Grayscale: Intensity determines how brightly pixel glows
• Shadow mask is fitted with the screen
• Holes in mask ensures proper pixel is lit
• The electron gun systematically redraws every pixel on the
screen, several times a minute
• Each pixel has a unique address used by computer to locate
the pixel and control its appearance

25. CRT Monitors
• CRT color
• Phosphor dots arranged in triads
• Red, green, and blue dots
• Three colors blend to make colors
• Three Electron beams at each pixel
• Beams themselves are colorless
• Dots are colored
• Varying the intensity of each of the three beams creates new
colors

26. CRT Monitors
• CRT drawbacks
• Very large
• Very heavy
• Use a lot of electricity

27. Flat Panel Monitors
• Liquid Crystal Display (LCD)
• Used in laptops, Desktop versions exist
• Solve the problems of CRT
• Made up of two glass plates separated by a special kind of
liquid crystal
• Molecules of crystals line up in a way that alters their optical
properties
• images are created on the screen by transmitting or blocking out light
• Active Matrix Display vs. Passive Matrix Display

28. Flat Panel Monitors
• Passive matrix LCD
• Pixels arranged in a grid
• Pixels are activated indirectly
• Row and column are activated by video card
• Color displayed by pixel is determined by electricity from
transistors
• At the row end
• At the top of the column
• Limited viewing angle
• Animation can be blurry
• Pixels not refreshed very quickly
• Dual-Scan LCD
• Pixels scanned twice as often

29. Flat Panel Monitors
• Active matrix LCD
• Each pixel is activated directly by dedicated transistor
• Individual control over each picture
• Animation is crisp and clean
• Pixels refreshed much more rapidly
• Wider Viewing angle
• Thin Film Transistor Technology (TFT) – an enhancement
• Transistors arranged in a thin film
• Pixels have 4 transistors
• One each for red, green, blue
• One for opaqueness

30. Flat Panel Monitors
• Drawbacks to LCD
• More expensive than CRT
• Must sit directly in front of screen
• Can be more fragile than CRT

31. Copyright © 2003. Exclusive rights by The
Pixel (picture element)
the smallest unit on the
screen that can be turned
on and off or made
different shades
More on Monitors

32. Copyright © 2003. Exclusive rights by The
Factors affecting screen
clarity:
• Dot pitch (dp)
• the amount of space between
the centers of adjacent pixels
• the closer the dots, the crisper
the image
• Ranges between .15 mm and
.40 mm
• Should be less than .22
More on Monitors
Image Courtesy: http://en.wikipedia.org/wiki/Dot_pitch

33. Copyright © 2003.
Factors affecting screen clarity:
• Resolution
• the image sharpness of a display screen;
• the more pixels there are per square inch, the finer the
level of detail.
• Dot Pitch directly translates into resolution. How?
• Larger resolution numbers make smaller images.
Why?
More on Monitors

34. Copyright © 2003.
Factors affecting screen clarity:
• Color depth
• the amount of information, expressed in bits, that is
stored in a dot
• The more bits in a dot or pixel, the more shades of
gray and colors can be represented.
More on Monitors

35. Copyright © 2003.
Factors affecting screen clarity:
Refresh rate
•Phosphor dots fade quickly after electron gun charges
them with electrons
•Need to be refreshed using electron beam
• the number of times per second that the pixels are
recharged so that their glow remains bright is called
refresh rate
• The higher the refresh rate, the more solid the image
looks ( flickers less)
•RR of 100Hz means pixels are refreshed 100 times
every second
More on Monitors

36. Other Types of Monitors
• Paper-white displays
• High contrast between fore and background
• Used by Document designers
• Electro-luminescent displays (ELD)
• Similar to LCD
• Uses phosphorescent screen to produce light
• Grid of wires are used
• Plasma monitor
• Neon Gas is excited to produce light
• Controlling amount of light at each electrodes on
glass grid

37. Video Cards
• Video card - Device between the CPU and monitor
• Removes burden of drawing from CPU
• Controlling electron gun etc
• At a resolution of 1024x768 and 24 bits/pixel, CPU
must send 2,359,296 bytes to the monitor for each
screen
• Screen changes constantly as user works

38. Video Cards
• Greater requirement for high-end video cards
• Video cards now have their own processor and RAM
• RAM is dual-ported
• Send screen-full data to monitor
• Receive screen-full of data from CPU
• Upto 512MB
• Chip rate determines refresh rate
• Also called video controller/ video adapter

39. Data Projectors
• Replaced overhead and slide projectors
• Project image onto wall or screen
• LCD projectors
• Most common type of projector
• Small LCD screen
• Very bright light
• Require a darkened room

40. Data Projectors
• Digital Light Projectors (DLP)
• A series of mirrors control the display
• May be used in a lighted room
• A projector is rated in lumens
• Measure of how bright the projector is
• Higher lumens ratings result in a brighter projector

41. Hearing It
• Sound System
• Sound Card
• Speakers/ Headphones
• Integral part of the computer experience
• Capable of recording and playback

42. Sound Systems
• Sound card
• Device between the CPU and speakers
• Converts digital sounds to analog
• Can be connected to several devices
• Modern cards support Dolby Surround Sound
• Speakers
• Convert electrical signals from sound card into
sound waves

43. Sound Systems
• Headphones and headsets
• Replacement for speakers and microphones
• Offer privacy
• Does not annoy other people
• Outside noise is not a factor
• Headsets have speakers and a microphone

44. 4B-44
Having it
• Printers!
• Impact printers
• Generate output by striking the paper
• Uses an inked ribbon
• Non-impact printers
• Use methods other than force
• Tend to be quiet and fast

45. 4B-45
Commonly Used Printers
• Dot matrix printers
• Impact printer
• Used to print to multi-sheet pages
• Print head strikes inked ribbon
• Speed measured in characters per second
• 50-500 cps
• Line printers
• Print entire line using large print head
• 3000 lines/minute
• Band printers
• Uses revolving band embossed with alphanumeric characters
• 2000 lines/minute

46. 4B-46
Dot Matrix Print Head
Resolution depends on number of pins on a print-
head. More pins  greater resolution

47. 4B-47
Commonly Used Printers
• Ink-jet printers
• Non-impact printer
• Inexpensive home printer
• Color output common using CMYK
• Cyan, magenta, yellow, black
• Sprays ink onto paper
• Speed measured in pages per minute
• Quality expressed as dots per inch

48. 4B-48
Dots Per Inch

49. 4B-49
Commonly Used Printers
• Laser printer
• Non-impact printer
• Produces high quality documents
• Color or black and white
• Print process
• Laser draws text on drum
• Toner, tiny ink particles, sticks to drum
• Toner melted to page using pressure and heat
• Color Printing
• Same process four times
• Different toner color each time
• CMYK

50. 4B-50
Commonly Used Printers
• Speed measured in pages per minute
• 4 to 16 pages of text / minute
• Slower of graphics
• Quality expressed as dots per inch
• Commonly 300-600 dpi both horizontally and vertically
• Upto 1200 dpi for professional quality printing

51. 4B-51
Commonly Used Printers
• All-in-one peripherals
• Scanner, copier, printer and fax
• Popular in home offices
• Prices are very reasonable

52. 4B-52
Comparing Printers
• Determine what you need
• Determine what you can spend
• Initial cost
• Cost of operating (ink toner + maintenance)
• Image quality (dpi)
• Speed (ppm)

53. 4B-53
High-Quality Printers
• Special purpose printers
• Used by a print shop
• Output is professional grade
• Prints to a variety of surfaces

54. 4B-54
High-Quality Printers
• Photo printers
• Produces film quality pictures
• Prints very slow
• Prints a variety of sizes

55. 4B-55
High-Quality Printers
• Thermal wax printers
• Produces bold color output
• Color generated by melting wax
• Colors do not bleed
• Operation costs are low
• Output is slow
• Used for presentation graphics and handouts

56. 4B-56
High-Quality Printers
• Dye sublimation printers
• Produces realistic output
• Very high quality
• Color is produced by evaporating ink
• Operation costs are high
• Output is very slow

57. 4B-57
High-Quality Printers
• Plotters
• Large high quality blueprints
• Older models draw with pens
• Operational costs are low
• Output is very slow

58. 3A-58
Ergonomics and Input Devices
• Ergonomics
• Study of human and tool interaction
• Concerned with physical interaction
• Attempts to improve safety and comfort

59. 3A-59
Ergonomics and Input Devices
• Repetitive Strain Injury (RSI)
• Caused by continuous misuse of the body
• Many professions suffer from RSI
• Carpal Tunnel Syndrome
• Carpal tunnel is a passage in the wrist
• Holds nerves and tendons
• Prolonged keyboarding swells tendons

60. 3A-60
Carpal Tunnel Syndrome

61. 3A-61
Ergonomics and Input Devices
• Office hardware suggestions
• Office chairs should have
• Adjustable armrests and height
• Armrests
• Lower back support
• Desks should have
• Have a keyboard tray
• Keep hands at keyboard height
• Place the monitor at eye level

62. 3A-62
Ergonomics and Input Devices
• Techniques to avoid RSI
• Sit up straight
• Have a padded wrist support
• Keep your arms straight
• Keyboard properly
• Take frequent breaks

63. Ergonomics and Monitors
• Eyestrain
• Fatigue of the eyes
• Steps to avoid
• Choose a good monitor
• Place the monitor 2 – 3 feet away
• Center of screen below eye level
• Avoid reflected light

64. Ergonomics and Monitors
• Electronic magnetic fields (EMF)
• Generated by all electronic devices
• EMF may be detrimental to health
• Although no conclusive study exists
• Steps to avoid
• Keep the computer at arms length
• Take frequent breaks
• Use an LCD monitor