Transcript Slide 1

Information and Communication
Technology Fundamentals
Credits Hours: 2+1
Instructor: Ayesha Bint Saleem
Presentation Credits
• “Introduction to Computer” by Peter
Norton
• “Using Information Technology” by Williams
and Sawyer
How computers represent data and
why?
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
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
5A-5
How Computers Represent Data
• Computers use electronic switches called
transistors
• A switch can either be ON or OFF
=1
=0
• Only two numeric values can be
represented by one switch, 0 and 1
5A-6
How Computers Represent Data
• 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
• Bits and bytes
• Binary numbers are made of bits
• Bit (Binary Digit) represents a switch
• A byte is 8 bits
• Byte represents one character
5A-8
How Computers Represent Data
• 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
• 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
Image Courtesy: www.emu8086.com
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)
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
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
• 1610  100002
010  02
• 810  10002
And so on..
• 1710  100012
110  12
• 910  10012
• 1810  100102
210  102
• 1010  10102
• 1910  100112
310  112
• 1110  10112
• 2010  101002
410  1002 • 1210  11002
• 2110  101012
510  1012 • 1310  11012
• 2210  101102
610  1102 • 1410  11102
• 2310  101112
710  1112 • 1510  11112
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
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
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 +
= 1x16 +
1x8+
0x4+
= 16 + 8 + 0 + 0 + 1 = 2510
0x 21 +
0x2 +
1x 20
1x1
Conversion from decimal to binary
• Technique # 2
• Conversion from decimal to binary on board
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
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
5A-19
Output Devices
Sources for Output
• Seeing it
• Video card + Display Screen/Projector
• Hearing it
• Sound card + speaker
• Having it
• Printers
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
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
4A-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
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
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
CRT Monitors
• CRT drawbacks
• Very large
• Very heavy
• Use a lot of electricity
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
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
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
Flat Panel Monitors
• Drawbacks to LCD
• More expensive than CRT
• Must sit directly in front of screen
• Can be more fragile than CRT
More on Monitors
Pixel (picture element)
the smallest unit on the
screen that can be
turned on and off or
made different shades
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More on Monitors
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
Image Courtesy: http://en.wikipedia.org/wiki/Dot_pitch
Copyright © 2003. Exclusive rights by The
More on Monitors
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?
Copyright © 2003.
More on Monitors
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.
Copyright © 2003.
More on Monitors
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
Copyright © 2003.
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 phosphor to produce light
• Plasma monitor
• Gas is excited to produce light
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
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
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
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
Hearing It
• Sound System
• Sound Card
• Speakers/ Headphones
• Integral part of the computer experience
• Capable of recording and playback
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
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
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
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
4B-46
Dot Matrix Print Head
Resolution depends on number of pins on a
print-head. More pins  greater resolution
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
4B-48
Dots Per Inch
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
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
4B-51
Commonly Used Printers
• All-in-one peripherals
• Scanner, copier, printer and fax
• Popular in home offices
• Prices are very reasonable
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)
4B-53
High-Quality Printers
• Special purpose printers
• Used by a print shop
• Output is professional grade
• Prints to a variety of surfaces
4B-54
High-Quality Printers
• Photo printers
• Produces film quality pictures
• Prints very slow
• Prints a variety of sizes
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
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
4B-57
High-Quality Printers
• Plotters
• Large high quality blueprints
• Older models draw with pens
• Operational costs are low
• Output is very slow
4B-58
Ergonomics and Input Devices
• Ergonomics
• Study of human and tool interaction
• Concerned with physical interaction
• Attempts to improve safety and comfort
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
3A-60
Carpal Tunnel Syndrome
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
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
3A-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
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