The document discusses various types of computer output devices. It describes printers such as dot matrix, inkjet, and laser printers. It also mentions plotters, computer output microfilm, monitors, voice response systems, and projectors. It provides details on the functioning and use of different printers and how they produce hard and soft copy output.

1. Unit-2-Chap3

2.  Printers
 Plotters
 Computer output micro film
 Monitor
 Voice response system
 Projector
 Headphone and headset

3.  Output is data that have been processed into
useful information.
 It can be displayed or viewed on a monitor ,
printed with a help of printer, or hear with the
help of speakers or headsets.
 There are two categories of output
◦ Hard copy
◦ Soft copy

4.  The physical form of output is known as hard
copy.
 It refers to the recorded information copied
from a computer onto a paper or some other
durable surface such as microfilm
 It is permanent form of output
 Highly portable
 Paper is one of the widely used output media
 Eg: printouts, whether text or graphics from
printers

5.  The electronic version of output, which
usually resides in computer memory and/or
on disk is soft copy.
 Not permanent form of output
 It is usually displayed on the screen.
 It is not tangible, cannot be touched.
 Includes audio and videos that is generated
by the computer.
 Includes textual or graphical form of
information

6.  A printer prints information and data from
the computer onto paper.
 Printer prints 80 or 132 columns of
characters in each line and prints each single
sheets or continuous roll of paper, depending
upon the printer itself.
 The quality of printer depends on how clear
the print is produced, I,e resolution
 Resolution is used to describe the sharpness
and clarity of image.
 Higher the resolution, better the image.

7.  For printers the resolution is measured in dpi
 The more dpi, the better quality print will be.
 Printers are divided into two basics
categories: impact printers and non-impact
printers.
 Impact printers work by physically striking a
head or needle against an ink-ribbon to make
a mark on paper.
 Includes drum printers, daisy wheel printers,
dot-matrix printers.

8.  Non-impact printers are opposite to impact
printers.
 Eg: laser printers and ink-jet printers.
 They use techniques other than physically
striking the page to transfer ink to page.
 Different printers
◦ Dot matrix
◦ Daisy wheel
◦ Drum printer
◦ Ink-jet
◦ Laser
◦ HYDRA

9.  Also known as wire matrix printer
 Uses oldest printing technique.
 Prints one character at a time
 It prints a characters and images as patterns
of dots.
 The speed of dot matrix measures in cpi
 Varies from 200 to 500 cps
 The print quality is determined by the
number of pins, varies from 9 to 24.
 More pins per inch, more the resolution is.

10.  The best dot matrix printer (24 pins) can
produce near letter-quality-type image.
 Are inexpensive and low operating costs.
 They print bi-directional, they print
characters in both directions.
 Drawback is
◦ prints the data only in black and white color.
◦ Image printing is limited.
 Used in cash registers, used in situations
where copies are required and quality is not
important.

13.  The paper is pressed against the rubber-
coated cylinder and is pulled forward as
printing progresses.
 The printer consists of an electro-
magnetically driven print head, which is made
up many pins.
 The character is formed by moving the
electro-magnetically driven head across the
paper, which strikes the printer ribbon
situated between the paper and printpin
head.

14.  As the head stamps onto the paper through
the inked ribbon, a character is produced that
is made up of these dots

15.  The drawback of dot matrix printer is that
pattern of dots make up each character is
visible on the print produced by it, making it
to look unprofessional.
 The print head of this printer resembles a
daisy flower with printing arms that appear
like the petals of the flower.
 Commonly called as letter quality printers.
 Produces high quality resolution output.
 Have speed upto 90cps

16.  Also called as smart printers, because their
bi-directional printing and built-in
microprocessor control features.
 This gives only alphanumeric output.
 They cannot print graphics
 Cannot change font unless the wheel is
changed physically.
 Slower because it takes time to rotate the
wheel for required letter on the wheel.
 Slower but expensive than dot matrix printers

19.  The dot matrix and daisy wheel printers are
character and serial printers i.e. one character
at time.
 Drum printer is line printer, can print one line
of data in single operation.
 It is used because of its speed as it uses a
special tractor-fed paper with pre-punched
holes along each side.
 Speed varies from 300 to 2000 lines per min
with 96-160 characters on 15 inch line.

20.  It is faster than character printers but very
noisy, have limited font-capability , produce
lower quality printouts.
 Used for heavy printing applications.
 Drum printers with high speed are expensive
 The strike of the hammer should be precise.
 A single miss of strike can create a wavy and
slightly blurred printing.

22.  Commonly used at homes
 Places extremely small droplets of ink onto
the paper to create an image.
 Non-impact printer
 Uses serials of nozzles to spray the ink onto
the paper.
 Originally manufactured for monochrome
printing i.e. black and white only.
 Now it comes for cyan, magenta, yellow,
black
 Combination is called CMYK

23.  Ink-jet printers are costlier than dot-matrix
printers, quality is much better.
 Printers can print any shape of character,
which user specify.
 Can print different sized prints, graphics such
as graphs, charts.
 Resolution is 600dpi or more
 They print high quality text and graphics
printouts
 Affordable, medium pace of printing (6 pages
per min)

27.  Provides highest quality text and images for
personal computers today.
 Very fast printer that operates on the same
principle as photocopy machine.
 Also known as page printers because they
process ,store and print in terms of pages.
 Produce sharp, crisp images of both text and
graphics
 Resolution of 300 to 2400 dpi
 They are quite, fast (4- 32 text only pages per
min) for microcomputers 200 pages for
mainframes

28.  Can print different font, sizes and styles.
 Expensive than other printer and difficult to
maintain.
 Costs depends on the combination of paper ,
toner replacement and drum replacement.
 Useful when there is high volume printing
because of their speed.

30.  The core component is photoconductive
drum.
 A rotating beam causes the beam of laser to
sweep across the photoconductive drum
 Initially the beam of laser charges the
photoconductive drum positively.
 When charged drum is exposed to an optical
image through a beam of light to discharge,
invisible image is formed.
 At the point when laser strikes the surface of
drum, it creates a dot of positive charge.

31.  These points are represented as black dots
which will be printed on paper.
 After this, printer coats the drum with a black
powder called toner.
 This toner is negatively charged hence it
clings to those areas of drum which is
positively charged.
 When the powder is fixed onto the drum, it is
rotated onto a paper through a pressure
roller

32.  This pressure roller transfers the toner to
paper.
 Finally the paper passes through a fuser and
a pair of heated rollers.
 As the paper passes through these rollers,
the loose powder gets melted and gets fused
with fibers of the paper
 Then the paper is brought out of the printer

34.  Hybrid document reproduction apparatus
printer, known as all-in-one printer.
 Consolidates multiple machines into one.
 Includes devices like printer, scanner,
photocopier and fax machine.
 Some come with memory card slots , have
inbuilt wireless capabilities
 Used by small organization because of its
small size, less space requirement and cost
effectiveness

35.  They save power to great extent, as only one
outlet of power is required to run various
machine
 Easy to install and easy to use because of GUI
that helps user to understand its functions
easily

38.  Is a pen-based output device that is attached
to computer for making vector graphics, i.e.
images created by series of many straight
lines
 Used to draw high definition charts, graphs,
blueprints, maps , circuit diagrams and other
line based diagrams.
 Similar to printer but draws lines using a pen.
 Multicolor plotter uses pens with different
inked pens.

39.  Color plots can be made by using four pens
and no need of human intervention to change
them.
 Plotter draws a crisper lines and graphics
 The lines drawn by these are continuous and
very accurate.
 It is considered as slow output device
because it requires excessive mechanical
movement to plot.
 It is unable to produce solid fills and shading.

40.  They are expensive than printers and produce
more number of printouts than standard printers.
 Used mainly for Computer Aided Design CAD,
Computer Aided manufacturing CAM applications
such as printing out plans for houses or car
parts.
 Used in AUTOCAD programs to draw graphics
output.
 There are two types of plotters: drum plotter
(where paper moves) and flatbed plotter (where
paper is stationary)

41.  The paper on which the design is to be
printed is placed over the drum.
 These plotters contain one or more pens that
are mounted over the carriage which is
horizontally placed over the drum.
 The drum can rotate in both direction i.e.
clockwise or anticlockwise direction under the
control of plotting instructions sent by the
computer.
 The curves are created by drawing very short
straight lines.

43.  Consists stationary, horizontal plotting
surface on which paper is fixed.
 The pen is mounted on the carriage, which
can move leftwards, rightwards, horizontally
or vertically to draw lines.
 Paper does not move
 Can work on any size of paper from A4 to
very big sized sheets .
 They are used to design aircrafts, buildings,
ships.
 Disadvantage is it is slow device and takes
hours together to complete complex drawing.

45.  It is an extremely high-speed , low cost
process, which records computer-generated
information directly from the computer tape
or cartridge to miniaturized microflim media.
 The microflim product is in roll format, which
form at a highly significant speed from that
of the paper printer.
 Traditional microflim is 16 mm wide, with a
film image i.e. 1/24 of the size of the original
document , often called as 24x

46.  There are two ways to create a microfilm
◦ Photographic process
◦ Non-photographic process
 Photographic process
◦ Oldest method of creating microfilms.
◦ Is a form of miniature photography, which uses a
microfilm camera for producing microfilms.
◦ When the original documents are fed through a
microfilm camera, it captures the document into
reduced size photo.
◦ Once a photographs are taken, the rolls of films are
removed from the camera for further processing
and development.
◦ The processed images can be rolled on film rolls or
cut into sections and loaded to flat microfiche
holders.

47.  Non-photographic process
◦ User can entirely avoid the film developing process.
◦ This process uses a monitor and the computer
output is read onto the magnetic tape.
◦ After this , data is printed on microfilm machine
directly to a computer recorder.
◦ It is possible to couple a microfilm machine directly
to a computer
◦ Recorder can directly receive information from the
computer.
◦ Recorder projects the computer information onto
the screen, a high speed camera photographs the
displayed information.

49.  Also known as visual display unit, is the most
frequently used output device for producing
soft copy output.
 Is a TV-like display attached to computer on
which the output can be displayed and
viewed.
 A monochrome screen uses only one color to
display text on contrasting background.
 Monitors are available in various size like
14,15,17,19 and 21 inches.

50.  The size of the display is described based on
two parameters
◦ Aspect ratio
◦ Screen size
 Aspect ratio is the ratio of the width of the
display screen to the height.
 Computer display have an aspect ratio of 4:3
 Screen size is normally measured diagonally ,
the distance from one corner to the opposite
corner.

51.  The image produced by monitors are not
solid but created by the configurations of
dots.
 These dots are known as picture elements or
pixels.
 More no. of pixels the sharper the picture.
The screen clarity depends on three basic
qualities:
◦ Resolution
◦ Dot pitch
◦ Refresh rate

52.  Refers to the no. of pixels in horizontal and
vertical directions on the screen
 In medium resolution graphics, pixels are
large
 In high resolution graphics, pixels are small.
 The average display is 800 X 600 or 1024 x
768 pixels.
 The more dots or pixels available to create
the image , sharper it will be

53.  It is the measurement of the diagonal
distance between two like-colored pixels on
the display screen.
 Measured in millimeters , common values are
.51mm, .31 mm, .28mm, .27mm, .26mm, .25
mm
 The smaller the dot pitch, sharper the image
when displayed on the screen.

54.  Refresh rate is the no. of times per second the
pixels are recharged so that their glow remains
bright.
 Screen pixels are made up phosphor.
 An electron beam strikes the phosphor and
causes it to emit light, resulting the display of
image.
 The refresh rate is measured in Hz , varies from
60-75Hz.
 The higher the refresh rate, more solid the
images looks on the screen.
 The pixels don’t flicker.

56.  Most of the monitors use CRT, which are glass
vacuum tubes into which electron gun emits a flow
of electrons guided by an electrical field towards a
screen covered in small phosphorescent elements.
 A beam of electrons emitted by an electron gun,
passes through focusing and deflection systems
that direct the beam towards specified positions on
the phosphor-coated screen.
 The phosphor then emits a small spot of the light
at each position contacted by the beam.
 When the electron beam strikes the phosphor , it
continues to glow briefly, this condition is known
as persistence.

57.  The primary components of an electron gun
are the heated metal cathode and control
grid.
 Heat is supplied to the grid by directing a
current through a coil of wire called the
filament.
 This causes the electron to be “boiled off” the
hot cathode surface.
 The negatively charged electrons are then
accelerated towards phosphor coating by a
highly positive voltage.

58.  Before reaching the phosphor coated screen,
the electrons have to be passed through the
monitor’s focusing elements.
 Focusing can be accomplished either by
electric or magnetic fields.
 The deflection plates create a magnetic fields,
which control the direction of the electron
beam, guiding them to strike the proper
position on the screen.

59.  When the electron in the beams collide with the
phosphor coating , their kinetic energy is
absorbed by the phosphor.
 Some of this energy is converted into heat while
rest of the energy causes the phosphor to move
up to the higher energy levels.
 When these electrons begin to return to the
ground state, they emit the light at certain
frequencies that is colors.
 As a result the Image which is seen on the screen
is the combination of the electron light emission.

60.  The electron gun is made up of a cathode, a
negatively charged metallic electrode, and
one or more anodes
 The cathode emits the electrons attracted by
anode.
 The anode acts as a accelerator and
concentrator for the electrons, forming a flow
of electrons aimed at the screen

61.  LCD screen have long been used on notebook
computers but are also becoming popular as
desktop monitor
 LCD screen is collection of multiple layers.
 A fluorescent light source, known as
backlight makes up the rearmost layer.
 Light passes through the first of the two
polarising filters.
 The polarised light then passes through the
layers that contain thousand of liquid crystal
blobs aligned in tiny containers called cells.

62.  These cells are aligned in row across the
screen, one or more cells make up a pixel.
 Electric leads around the edge of the LCD
create an electric field that twists the crystal
molecule which lines the light up with the
second polarising filter and allow it to pass
through.

64.  SIZE: LCD is light weight and compact, which
saves desktop space when compared to CRT.
 RESOLUTION: LCD is designed to work in a
single resolution while CRT is designed for
many resolutions.
 PIXEL DENSITY: LCD ‘s pixel density is not
tight as dot pitch of CRT
 BRIGHTNESS: the illuminated phosphor of
CRT is not nearly as bright as what can
produced with its florescent backlight.

65.  POWER CONSUMPTION: LCD consumes less
power when compared to CRT and has low
emission risk.
 FLICKERS: with CRT monitors the goal is to
get a faster refresh rate of at least 85Hz, but
LCD monitors are designed to run much
slower refresh rate.
 PIXEL RESPONSE TIME: the time taken by a
pixel to change its state is called pixel
response time.

66.  VIEWING ANGLE: CRT can be viewed almost at
any angle, but LCD is best viewed ‘head on’.
Even when viewing a LCD head on, narrow
viewing angles can appear to have
inconsistent color and brightness
 VIEWING AREA: the viewing area of CRT is
usually less than its advertised area, LCD
monitors are measured exactly.
 COST: prices for LCD screens is quite high
but they are coming down. They are still
much more costlier than CRT.

67.  The voice response system has an audio-
response device that produces audio outputs.
 These are pre-recorded in computer system.
 Each sound has a unique code.
 Whenever an enquiry is sought from the
system, the computer responds in digital
form which is sent to voice devices that
unscramble the digital information and
produces sound messages to the requesting
computer

68.  There are two basic approaches to get a
computer to talk to the user.
 The first is synthesis by analysis, in which the
devices analyzes the input of an actual
human voice speaking words, stores, process
the spoken sounds and reproduces them
when needed.
 The second approach is synthesis by rule, in
which the device applies a complex set of
linguistic rules to create artificial speech.

69.  The standard computer system can provide audio
output with the addition of two components:
◦ Speech synthesizer that does the speaking
◦ Screen reading software that tells the synthesizer what
to say.
 The synthesizer can be a computer card inserted
into the computer or the software that works
with the computer’s sound card.
 Screen reader is a software program that allows
the user to control the synthesizer so that he can
text, which is displayed on the computer
monitor, with the combinations of keystrokes.

70.  Some screen review software use the
standard computer keyboard keys, some
numeric keypad and some special external
keypads.
 A visual impaired user can use a screen
reader to read anything on the screen.
 The screen reading software can even notify a
user about various computer messages that
‘pop up’ on the monitor from time to time.
 Used in places like airlines, bus terminals ,
banks.

71.  Also called screen.
 They have allowed the world to share greater
information pertaining to culture, technology,
medicine and community.
 Used to project information from a computer
on to a large screen, so that it can be
simultaneously viewed by a large group of
people.
 Commonly used for classrooms training or
conference or multimedia presentation with
large audience

72.  LCD Projectors
◦ LCD- Liquid Crystal Display
◦ Used by most of the technology
◦ Most of the LCD’s contains three separate LCD
glass panels, one for each red, green and blue
components of the image signal being fed into the
projector.
◦ As light passes through the LCD panels, individual
pixels can be opened to allow light to pass or
closed to block the light.
◦ This activity modulates the light and produces the
image that is projected onto the screen.

74.  DLP projectors
◦ DLP- Digital Light Processing
◦ It uses single DMD (digital micro-mirror device)
chip that has thousands of tiny mirrors, each
representing a single pixel.
◦ These mirrors tilt back and forth, directing the light
either into the lens path to turn pixel ON, or away
from the lens path to turn it OFF and create the
image.
◦ It handles images extremely well.

76.  Headphone is an audio device equipped with
a pair of speakers attached to a head strap
worn by the users.
 Comes with CD, DVD players, mp3 players,
ipod etc.
 Comprise high quality speakers, light weight
and very comfortable to wear.
 They can easily connect to a computer via a
mini stereo plug.
 Allows only to hear

78.  Headset is used when we want to user to
speak.
 It is combination of one or two speaker and
the microphone with both the speaker and
the microphone attached to head strap.
 The speakers allows the person to hear the
conversation and the microphone allows the
user to communicate with person on the
other end.