The document provides an overview of computer hardware input and output devices. It describes common input devices like the keyboard, mouse, and scanners that allow data to be entered into the computer. It also discusses output devices like monitors, printers, and speakers that allow the computer to display or present information to users. A diagram shows the basic components of a computer system including the central processing unit, memory, hard drive, and connections to input and output devices.

1. Computer Hardware- Brief
overview of input devices and
output devices- Key board,
Mouse, trackball, OCR, VDU,
Printers, Plotters & Scanners, etc.

2. A simplified view of a computer
system
Monitor
Central
Processing
Unit
Keyboard
Hard Disk
Main
Memory
Floppy Disk

3. Input Devices
 An input device captures data and sends it to a computer system.
 Input devices convert physical movement, such as key pressing, or environmental data,
such as temperature, sound or light into electrical signals.
 There are two types of input device: manual and
automatic.

4. Output Devices
 An output device is used to display or use information that comes out of a computer
system.
 Output devices convert electrical signals from a computer system into…
 Sound (speakers or headphones)
 Images & Text (screen or printer)
 Movement (actuator, electric motor)

5. Keyboard
Device Uses Advantages Disadvantages
The most common
input device People are familiar Incorrect use or over-
with keyboards, so use can cause RSI
You press keys to input they don’t need to be
data into the computer trained Many people cannot
type and look at the
The most common Skilled typists can work screen at the same time,
type of keyboard is the very quickly so typing can be time
Keyboard QWERTY keyboard consuming
typewriter keys A lot of different
keyboards are available,
•Cursor movement e.g. ergonomic
keys
They are very reliable
•Numeric keys and cheap
•Function keys
•Del, insert, esc etc

6. Key Board continued
• The American Standard Code for Information
Interchange (ASCII, pronunciation: ASS-kee is
a character-encoding scheme originally based on
the English alphabet.
• Extended Binary Coded Decimal Interchange
Code (EBCDIC) is an 8-bit character
encoding used mainly on IBM
mainframe and IBM midrange
computer operating systems.
• HEX code

7. Light pen
•It is pointing device used to select a displayed menu
option on the CRT
•It is photo sensitive pen like device, photocell-
sensing element detects the
light coming from the screen and corresponding
signals are send to the processer.

8. Mouse
• Device that controls the movement of the
cursor or pointer on a display screen.
• Invented by Dauglas Engal Bart in 1963 and
pioneered by Xerox in the 1970
• Point -and - click programs

9. Three basic type of mouse
• Mechanical – has a rubber or metal ball on its
underside that can roll in all directions
• Opt mechanical- same as mechanical, but uses
optical sensors to direct motion of the ball
• Optical – uses laser to detect the mouse
movement
They responds more quickly and precisely
than mechanically and opt mechanical mouse.

10. Joy stick
• It is pointing device
• It is just like lever that moves in all directions
and controls the movement of a pointer or
some other display symbol.
• Computer games
• CAD and CAM systems

11. Trackballs
• Pointing devise
• Mouse lying on its back
• To move the pointer, rotate the ball with
thumb, finger or with palm of hand
Popular for portable computer

12. Scanners
• Scanning device translates images of text,
drawings, photo in to digital form.
• important type of scanners are
• Optical scanners
• Magnetic – ink character reader

13. Optical Character Reader (OCR)
• Detects alpha numeric character printed or type written
on paper
• The text which is scanned is illuminated by a low
frequency source.
• The light absorbed from dark areas and reflected from
the lighted areas, provide binary data corresponding to
dark and lighted areas.

14. Optical Mark Reader (OMR)
• Special mark such as squires or bubbles are
prepared on examination answer sheets with
pencil or ink
• OMR detects these mark and sends corresponding
signals to the processor.
• If mark is present the amount of reflected light is
reduced.
• Analysis of objective type questions

15. Optical Barcode Readers
• Read UPC (universal product code ) bars and send
electrical pulses to be processed by the computer.
• bars detected as 10 digits
• First 5 digits identify the manufacturer or supplier
• Second 5 digits identify the products
• The code also contains check digit to that the
information is correct.

16. Magnetic ink character readers (MICR)
• Widely used in banks to process large number of
cheques.
• Special ink contains iron oxide is used to write
characters
• When cheque is entered into MICR it passes
through a magnetic field
• The read head reads the character with magnetic
ink

17. CCD Camera
• To provide vision to computers sensors like
video camera, opticron cameras
• (Charged Coupled Device)
• Provide signals proportional to the intensity of
light falling on the object
• CCD image sensors are widely used in
professional, medical, and scientific
applications where high-quality image data is
required.

18. Sensors
• Sensor collects specific kind of data directly
from environments and transmit to computer.
• Used for detecting kind of things such as
speed, movement, weight, pressure,
temperature, humidity, wind, fog, gas, smoke,
light shape, images etc..

20. Output devices
• Output devices translate information processed
by the computer in to a form that human can
under stand
• Hard copy – printed out put
• Soft copy – display screen, audio or voice form
Display screens
Printers , plotters, multifunction devices
Vedio output devices
Audio output devices
Virtual - reality devices – stereoscopic or haptic

21. Display screen or monitor
Monochrome
Displays two colour, one for the background
and one for foreground
The colour can be black and white
Green and black
Amber and black

22. Gray scale
• Display different shades of gray
• Gray scaling – is the process of converting a
continuous tone image to an image that a
computer can manipulate
• 16-256 shades

23. Colour monitors
• Colouur monitors can display 16 to 1 million
different colours.
• RGB monitors – red, green and blue
• Full page monitors – 16 or more
• VGA -14
• Portrait or landscape
• Viewable area

24. • Pixel, or pel, (picture element) is a physical
point in a raster image, or the smallest
addressable element in a display device; so it
is the smallest controllable element of a
picture represented on the screen.
• Each pixel is a sample of an original image;
more samples typically provide more accurate
representations of the original
• 1 cm37.795276 pixel
• 1 pixel0.02645833 cm

25. • VGA - Video Graphics Array - display hardware
first introduced with the IBM PS/2 line of
computers in 1987
• SVGA - Super Video Graphics Array or Ultra
Video Graphics Array,
• XGA -extended graphics array, 640 by 480 or
1024 by 768pixels
• DPI is not really used to describe the
resolution number of dots per inch in a digital
print and the printing resolution of a hard
copy print dot gain

26. • Refresh rate how many times per seconds the
screen refreshed to avoid flickering, (72 Hz)
• Band width :- The range of signal frequencies the
monitor can handle.
• Dot Pitch:-the amount of space between each
pixel, the smaller the dot pitch, the sharper the
image

27. Video display unit
• Also called as monitors or CRT
• VDT (video display terminal )
• Images are represented on the screen by
individual dots or pixels
• A stream of bits defining the image is sent
from the computer to the CRT gun
• Where bits converted to electrons

28. • 1. Three Electron guns (for red,
green, and blue phosphor dots)
2. Electron beams
3. Focusing coils
4. Deflection coils
5. Anode connection
6. Mask for separating beams for
red, green, and blue part of
displayed image
7. Phosphor layer with red,
green, and blue zones
8. Close-up of the phosphor-
coated inner side of the screen

29. Flat Panel Displays
• They are much thinner, less in weight and
consumes less power.
• LCD- Liquid crystal display
• LED- light emitting diode
 Display conventional (using discrete LEDs) and
surface-mounted device (SMD) panels , red,
green, and blue diodes mounted in a single
package
• Electroluminescent Displays (ELDs) are a type of
Flat panel display created by sandwiching a layer
of electroluminescent material such as GaAs
between two layers of conductors `

30. Plasma Display Panel (PDP)
• is a type of flat panel display common to large TV
displays 30 inches (76 cm) or larger.
• They are called "plasma" displays because the
technology utilizes small cells containing
electrically charged ionized gases, or what are in
essence chambers more commonly known as
fluorescent lamps.
• Advantages
• Picture quality
– Capable of producing deeper blacks allowing for
superior contrast ratio
– Wider viewing angles than those of LCD; images do
not suffer from degradation at high angles like LCDs

31. Clarity of Picture on Screen
1. Resolution :- sharpness and clarity of image
640by 480 pixel screen is capable of
displaying 640 distinct dots on each of 480
lines or 300,000 pixels
2. Dot pitch
Amount of space between pixels, closer the dots
crisper the image.
3. Refresh rate
number of times per second the pixel are
recharged so that their glow remains bright.

32. 1. Monochrome versus colour screens
• Monochrome displays only two colour
• Colour 16 and 16.7 million colours depending
on their type.
2. Text versus Graphics (character mapped
bitmapped display)
character mapped display only text – letters
numbers and special characters.
Bitmapped consisting of rows and columns of
dots of a graphic image in computer memory
(eg: monochrome 1 bit is sufficient)

33. Video display adaptors
• VGA – video graphic adapter
• SVGA - super video graphic adapter
• XGA – extended graphic adapter (640x480 or
1024x768)
DPI dots per inch simply by the number of rows
and coloumns

34. Paper output devices
• Printers, plotters and MFD printed text or
images on paper
• Printers may be portable or desktop
• Impact-daisywheel and dot matrix
• non impact- laser, inkjet, thermal
• Plotters :-pen , electrostatic and thermal
• MFD: combines printing, scanning, copying
and faxing

35. Printers
• Printers used with computer may be classified
on the basis of how the printed
1. Character printers:- Print one character at a
time
2. Line printers:- print one line of the text at a
time
3. Page printers: print one page of the text one
time.

36. • Impact printers: electro- mechanical that
causes hammers and pins to strike against a
ribbon and paper to print the text.
• Non impact: thermal, chemical, electrostatic,
laser beam or inkjet technology.
• Character printer: print one characters at a
time. The printing speed lies in between 60-
600 characters per second

37. • Dot Matrix impact type character printer
it is a type of computer printing which uses a
print head that runs back and forth, or in an
up and down motion, on the page and prints
by impact, striking an ink-soaked cloth ribbon
against the paper, much like the print
mechanism on a typewriter.

38. 1. Faster than letter quality printer
2. Printing speed is in b/w 8-600cps
3. Slower the speed better the quality
4. Most of the dot matrix printers are
bidirectional
5. It can print any type of fonts, bold , italics etc

39. • Daisywheel printer (letter quality impact
character printer)
It uses interchangeable pre-formed type
elements, each with typically 96 glyphs
Its speed is 20-75cps
Costlier than dot matrix printer
Font is fixed type
It cannot print graphics

40. Daisy wheel Daisy flower

41. Non impact type printers
• Thermal printing (or direct thermal printing)
is a digital printing process which produces a
printed image by selectively heating coated
thermochromic paper, or thermal paper as it
is commonly known, when the paper passes
over the thermal print head.

42. • The coating turns black in the areas where it is
heated, producing an image. Two-color direct
thermal printers can print both black and an
additional color (often red) by applying heat at
two different temperatures.
• Printed head consists of 5x7 or 7x9 matrix of
tiny heating elements.
• It gives highest quality printing

44. • Inkjet character printer
• A high-pressure pump directs liquid ink from a
reservoir through a gun body and a microscopic
nozzle, creating a continuous stream of ink
droplets via the Plateau-Rayleigh instability.
• The charged droplets pass through an
electrostatic field and are directed (deflected) by
electrostatic deflection plates to print on the
receptor material (substrate), or allowed to
continue on un deflected to a collection gutter for
re-use.

45. • The more highly charged droplets are
deflected to a greater degree. Only a small
fraction of the droplets is used to print, the
majority being recycled.
• Speed of inkjet printer lies in the range of 40-
300cps
• Average lifespan of an print head is about 10
billion characters.

47. Line printers
• Prints one line if the text at one time
• Printing speed lies in the range of 300- 3000 lines
per minute.
• Used for large volume jobs
1. Drum printer
2. Chain printer
3. Band printer
4. Bar printer
5. Comb printer
6. Wheel printer

48. Drum printer
• In a typical drum printer design, a fixed font
character set is engraved onto the periphery
of a number of print wheels, the number
matching the number of columns (letters in a
line) the printer could print.
• The wheels, joined to form a large drum
(cylinder), spin at high speed and paper and
an inked ribbon is stepped (moved) past the
print position.
•

49. • As the desired character for each column
passes the print position, a hammer strikes
the paper from the rear and presses the paper
against the ribbon and the drum, causing the
desired character to be recorded on the
continuous paper

51. Chain printer
Chain printer uses a rapidly rotating chain,
which is called print chain.
magnetically driven hammers are located in
each print position.
The noise level of the printer is high

52. Band printers
• Are a variation of chain printers, where a thin
steel band is used instead of a chain, with the
characters embossed on the band.
• Again, a selection of different bands were
generally available with a different mix of
characters so a character set best matched to
the characters commonly printed could be
chosen

53. • Bar printers
were similar to chain printers but were
slower and less expensive. Rather than a chain
moving continuously in one direction, the
characters were on fingers mounted on a bar
that moved left-to-right and then right-to-left
in front of the paper.

54. • Wheel printers
• Each of the 120 print positions had its own type
wheel which rotated under electromechanical
control.
• Once all were in position, print hammers struck
the wheels against a ribbon and the paper.

55. Laser Printer
• The laser printer was invented at Xerox in
1969 by researcher Gary Starkweather, who
had an improved printer working by 1971 and
incorporated into a fully functional networked
printer system by about a year later.

56. Working
• A laser beam projects an image of the page to be
printed onto an electrically charged rotating drum
coated with selenium or, more common in modern
printers, organic photoconductors.
• Photoconductivity allows charge to leak away from
the areas exposed to light.
• Powdered ink (toner) particles are
then electrostatically picked up by the drum's charged
areas, which have not been exposed to light.
• The drum then prints the image onto paper by direct
contact and heat, which fuses the ink to the paper.

57. `

60. Plotters
• The plotter is an output device where
a computer printer for printing vector
graphics.
• In the past, plotters were used in applications
such as computer-aided design, though they
have generally been replaced with wide-
format conventional printers

62. Cutting plotters
• Use knives to cut into a piece of material (such
as paper, mylar or vinyl) that is lying on the flat
surface area of the plotter.
• It is achieved because the cutting plotter is
connected to a computer, which is equipped with
specialized cutting design or drawing
computer software programs.
• Those computer software programs are
responsible for sending the necessary cutting
dimensions or designs in order to command the
cutting knife to produce the correct project
cutting needs

64. 1. Actuator
2. Speaker and head phone
3. Buzzer

65. Input & Output Devices
Drag the input and output devices to the correct side...