Input and output devices

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Table of Contents
Input devices.............................................................................................................................. 2
Key boards......................................................................................................................................3
Mouse............................................................................................................................................4
Mechanical Mouse .................................................................................................................................................................4
Laser Mouse ............................................................................................................................................................................4
Optical Mouse.........................................................................................................................................................................5
Blue Track Mouse:..................................................................................................................................................................5
Joysticks.........................................................................................................................................5
Pointing-stick..................................................................................................................................6
Track ball .......................................................................................................................................6
Touch pad ......................................................................................................................................7
Game controller..............................................................................................................................8
Touch screen ..................................................................................................................................8
Output devices........................................................................................................................... 9
Monitor........................................................................................................................................10
CRT (cathode ray tube) monitors: .....................................................................................................................................10
LCD (Liquid Crystal Display) monitors:..............................................................................................................................11
LED (Light-Emitting Diodes) monitors: .............................................................................................................................12
Speakers.......................................................................................................................................13
Head phones.................................................................................................................................13
Data projector..............................................................................................................................14
Printer..........................................................................................................................................15
Impact printers:.........................................................................................................................16
Non-impact printer:...................................................................................................................18
Plotters ........................................................................................................................................20

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Input and Output devices
Input devices
In computing, an input device is a peripheral (piece of computer hardware equipment) used to
provide data and control signals to an information processing system such as a computer or other
information appliance. Examples of input devices include keyboards, mouse, touch -pad, track
ball, pointing stick, game controllers and joysticks.

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Key boards
A keyboard is a typewriter-style device, which uses an arrangement of buttons or keys, to act as
mechanical levers or electronic switches. Keyboards are the main input device for computers. A
keyboard typically has characters engraved or printed on the keys and each press of a key
typically corresponds to a single written symbol. However, to produce some symbols requires
pressing and holding several keys simultaneously or in sequence. While most keyboard keys
produce letters, numbers or signs (characters), other keys or simultaneous key presses can
produce actions or execute computer commands.
Keyboard is the most commonly used device for direct (human) input of alphanumeric data into
computers.
In normal usage, the keyboard is used as a text entry interface to type text and numbers into a
word processor, text editor or other programs. In a modern computer, the interpretation of key
presses is generally left to the software. A computer keyboard distinguishes each physical key
from every other and reports all key presses to the controlling software. Keyboards are also used
for computer gaming, either with regular keyboards or by using keyboards with special gaming
features, which can expedite frequently used keystroke combinations. A keyboard is also used to
give commands to the operating system of a computer, such as Windows' Control-Alt-Delete
combination, which brings up a task window or shuts down the machine. A command-line
interface is a type of user interface operated entirely through a keyboard, or another device doing
the job of one.

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Mouse
A mouse is a pointing device that detects two-dimensional motion relative to a surface. This
motion is typically translated into the motion of a pointer on a display, which allows for fine
control of a graphical user interface.
Physically, a mouse consists of an object held in one's hand, with one or more buttons. Mice
often also feature other elements, such as touch surfaces and "wheels", which enable additional
control and dimensional input.
Various types of mouse are available in market and the selection solely depends on your
requirement. Let’s take a quick look at the available options:
Mechanical Mouse: Also called as the ball mouse, a mechanical mouse has rubber or metal ball
on its underside. When the ball rolls, mechanical sensors inside the mouse detect the direction
and move the pointer on the screen of the PC. This type of mouse requires a flat surface or a
mouse pad to work efficiently. One of the drawbacks of the device is that it is more prone to
attracting dust.
Optical-mechanical Mouse: An optical-mechanical mouse is same as the mechanical mouse
except that the sensors used in it are optical and not mechanical. The device is a combination of
optical and mechanical technologies, wherein, the ball is present but the mouse movement is
detected optically leading to more accuracy.
Laser Mouse: A laser mouse is the new generation mouse with two necessary components –
light emitter and light detector. A laser mouse uses laser as the light emitter and has a precise
scanning of mouse movement. You will find a laser mouse ranging anywhere between 1000-
5700 dots-per-inch (DPI).

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OpticalMouse: An optical mouse also has light emitter and light detector but it uses LED as the
light emitter. It generally has lower DPI than laser mouse and users might find difficulty in using
the device on black or shiny surfaces.
Blue Track Mouse: The next generation mouse from Microsoft, it is based on the Blue Track
Technology that enables the mouse to track efficiently on any surface, be it a granite countertop
or a carpet. The blue beam in mouse is a combination of image sensor and pixel geometry & is
four times larger than the average laser beam used in laser mouse. It generates high-contrast
pictures of the surface for an exceptional tracking accuracy.
Joysticks
A joystick is an input device consisting of a stick that pivots on a base and reports its angle or
direction to the device it is controlling. A joystick, also known as the control column, is the
principal control device in the cockpit of many civilian and military aircraft, either as a center
stick or side-stick. Joysticks are often used to control video games, and usually have one or more
push-buttons whose state can also be read by the computer. A popular variation of the joystick
used on modern video game consoles is the analog stick.

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Pointing-stick
A pointing stick is an isometric joystick used as a pointing device, as with a touchpad or
trackball, and typically mounted in a computer keyboard. Movements of the pointing stick are
echoed on the screen by movements of the pointer (or cursor) and other visual changes.
The pointing stick operates by sensing applied force, by using a pair of resistive strain gauges. A
pointing stick can be used by pushing with the fingers in the general direction the user wants
the cursor to move. The velocity of the pointer depends on the applied force so increasing
pressure causes faster movement. The relation between pressure and cursor or pointer speed
can be adjusted, similar to the way the mouse speed is adjusted in a traditional desktop
computer.
Track ball
A trackball is a pointing device consisting of a ball held by a socket containing sensors to detect
a rotation of the ball about two axes—like an upside-down mouse with an exposed protruding
ball. The user rolls the ball with the thumb, fingers, or the palm of the hand to move a pointer.
Compared with a mouse, a trackball has no limits on effective travel; at times, a mouse can
reach an edge of its working area while the operator still wishes to move the screen pointer
farther. With a trackball, the operator just continues rolling, whereas a mouse would have to be
lifted and re-positioned. Some trackballs have notably low friction, as well as being made of
dense material such as glass, so they can be spun to make them coast. The trackball's buttons
may be situated to that of a mouse or to a unique style that suits the user.

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Touch pad
A touchpad is a pointing device featuring a tactile sensor, a specialized surface that can translate
the motion and position of a user's fingers to a relative position on the operating system that is
outputted to the screen. Touchpads are a common feature of laptop computers, and are also
used as a substitute for a mouse where desk space is scarce. Because they vary in size, they can
also be found on personal digital assistants (PDAs) and some portable media players. Wireless
touchpads such as Apple's Magic Trackpad are also available as detached accessories.

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Game controller
A game controller is a device used with games or entertainment systems to provide input to a
video game, typically to control an object or character in the game. A controller is usually
connected to a game console or computer by means of a wire or cord, although, since the mid-
2000s, wireless controllers have become widespread. Input devices that have been classified as
game controllers include keyboards, mice, gamepads, joysticks, etc. Special purpose devices,
such as steering wheels for driving games and light guns for shooting games, are also game
controllers.
Touch screen
A touchscreen is an input device normally layered on the top of an electronic visual display of an
information processing system. A user can give input or control the information processing
system through simple or multi-touch gestures by touching the screen with a special stylus/pen
and-or one or more fingers. Some touchscreens use ordinary or specially coated gloves to work
while others use a special stylus/pen only. The user can use the touchscreen to react to what is
displayed and to control how it is displayed (for example by zoom the text size).

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Output devices
An output device is any piece of computer hardware equipment used to communicate the results
of data processing carried out by an information processing system (such as a computer) which
converts the electronically generated information into human-readable form. Examples of output
devices include monitors, printers, plotters, speakers, head phones and data projectors.

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Monitor
Monitor is a standard output devices. This shows the output information. Monitor is also one of
the important parts of computer, because without monitor, system can't work. So, that this is the
standard output device.
At present, computer monitors are available in a variety of shapes, designs, and colors. However,
based on the technology used to make computer monitors, they can be broadly categorized into
three types.
1. CRT (Cathode Ray Tube)
2. LCD (Liquid Crystal Display)
3. LED (Light-Emitting Diodes)
CRT (cathode ray tube) monitors:
These monitors employ the CRT technology used most commonly in the manufacturing of
television screens. In this, a stream of intense high energy electrons is used to form images on a
fluorescent screen. A cathode ray tube is a basically a vacuum tube containing an electron gun at
one end and a fluorescent screen at another end. From this electron gun, a process called
thermionic emission generates a strong beam of electrons. These electrons travel through a
narrow path within the tube with high speed using various electro-magnetic devices and finally
strike the phosphor points present on the fluorescent screen, thus creating an image. There are
several advantages of using CRT monitors:
•CRT monitors are affordable and cost effective.
•Unlike conventional CRT monitors, modern technological advancements have resulted in the
development of flat screen CRT monitors that reduce the glare and are good for the eyes.
However, the only concern with buying CRT monitors is that they are heavy and can occupy a
great deal of work space. Also, these devices get heated up very easily.

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LCD (Liquid CrystalDisplay)monitors:
Liquid crystal display, also known as liquid crystal diode, is one of the most advanced
technologies available at present. It is a flat-panel display. Typically, an LCD monitor consists of
a layer of color or monochrome pixels arranged schematically between a couple of transparent
electrodes and two polarizing5/16/2015 filters. Optical effect is achieved by polarizing the light
in varied amounts and making it pass through the liquid crystal layer.
Some major advantages of using an LCD monitor include:
 These monitors are compact, lightweight, and do not consume much desk space.
 Secondly, these monitors do not consume much electricity and can even be operated by
using batteries.
 Also, the images transmitted by these monitors do not get geometrically distorted and
have little flicker.
However, LCD monitors do have certain disadvantages. Most importantly, these monitors are
very expensive. Secondly, image quality is not constant when viewed from different angles.
Also, an LCD monitor’s resolution is always constant. Any alterations can result in a reduced
performance.

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LED (Light-Emitting Diodes) monitors:
LED monitors are the latest types of monitors in the market today. Like LCD, it is again a flat
panel display making use of light-emitting diodes for back-lightning instead of Cold Cathode
Fluorescent (CCFL) back-lightning used in LCDs. Primarily, the display is of LCD only but the
back-lightning is done by LEDs.
LED monitors are said to use much lesser power than CRT and LCD. Thus, they are also
considered environmental friendly. Other core advantages of LED monitors are:
 They produce images with higher contrast
 They have less negative environmental impact when disposed
 Because of the technology, the monitor panels can be made very thin
 Do not produce much heat while running

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Speakers
Computer speakers, or multimedia speakers, are speakers external to a computer that disable the
lower fidelity built-in speaker. They often have a low-power internal amplifier. Computer
speakers range widely in quality and in price. The computer speakers typically packaged with
computer systems are small, plastic, and have mediocre sound quality. Some computer speakers
have equalization features such as bass and treble controls.
Head phones
Headphones are a pair of small loudspeakers that are designed to be held in place close to a user's
ears. They are electroacoustic transducers which convert an electrical signal to a corresponding
sound in the user's ear. Headphones are designed to allow a single user to listen to an audio
source privately, in contrast to a loudspeaker which emits sound into the open air, allowing
anyone nearby to listen. They are also known as ear speakers, earphones. In the context of
telecommunication, a headset is a combination of headphone and microphone.

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Data projector
A data projector is an image projector that receives a video signal and projects the corresponding
image on a projection screen using a lens system. All data projectors use a very bright light to
project the image, and most modern ones can correct any curves, blurriness, and other
inconsistencies through manual settings. Video projectors are widely used for many applications
such as, conference room presentations, classroom training, home theatre and concerts.
Projectors are widely used in many schools and other educational settings, sometimes connected
to an interactive whiteboard to interactively teach pupils.

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Printer
“A printer is an external output device that takes data from a computer and generates output in
the form of graphics / text on a paper”.
A printer is an electromechanical device which converts the text and graphical documents from
electronic form to the physical form. Generally they are the external peripheral devices which are
connected with the computers or laptops through a cable or wirelessly to receive input data and
print them on the papers. A wide range of printers are available with a variety of features ranging
from printing black and white text documents to high quality colored graphic images.

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There are two types of printers.
1. Impact printers
2. Non-impact printers
Impact printers:
An impact printer is a type of printer that operates by striking a metal or plastic head against an
ink ribbon. The ink ribbon is pressed against the paper, marking the page with the appropriate
character, dot, line, or symbol. The three most common forms of impact printers are dot-matrix,
daisy-wheel, and line printers.
Dot-MatrixPrinters:
The technology behind dot-matrix printing is quite simple. The paper is pressed against a drum
(a rubber-coated cylinder) and is intermittently pulled forward as printing progresses. The
electromagnetically-driven print head moves across the paper and strikes the printer ribbon
situated between the paper and print head pin. The impact of the print head against the printer
ribbon imprints ink dots on the paper which form human-readable characters.
Dot-matrix printers vary in print resolution and overall quality with either 9 or 24-pin print
heads. The more pins per inch, the higher the print resolution. Most dot-matrix printers have a
maximum resolution of around 240 dpi (dots per inch). While this resolution is not as high as
those possible in laser or inkjet printers, there is one distinct advantage to dot-matrix (or any
form of impact) printing. Because the print head must strike the surface of the paper with enough
force to transfer ink from a ribbon onto the page, it is ideal for environments that must produce
carbon copies through the use of special multi-part documents. These documents have carbon (or
other pressure-sensitive material) on the underside and create a mark on the sheet underneath
when pressure is applied. Retailers and small businesses often use carbon copies as receipts or
bills of sale.

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Daisy-Wheel Printers:
If you have ever worked with a manual typewriter before, then you understand the technological
concept behind daisy-wheel printers. These printers have print heads composed of metallic or
plastic wheels cut into petals. Each petal has the form of a letter (in capital and lower-case),
number, or punctuation mark on it. When the petal is struck against the printer ribbon, the
resulting shape forces ink onto the paper. Daisy-wheel printers are loud and slow. They cannot
print graphics, and cannot change fonts unless the print wheel is physically replaced. With the
advent of laser printers, daisy-wheel printers are generally not used in modern computing
environments.
Line Printers:
Another type of impact printer somewhat similar to the daisy-wheel is the line printer. However,
instead of a print wheel, line printers have a mechanism that allows multiple characters to be
simultaneously printed on the same line. The mechanism may use a large spinning print drum or
a looped print chain. As the drum or chain is rotated over the paper's surface, electromechanical
hammers behind the paper push the paper (along with a ribbon) onto the surface of the drum or
chain, marking the paper with the shape of the character on the drum or chain.

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Non-impact printer:
A non-impact printer prints characters and graphics on a piece of paper without striking the
paper. Some of these printers use spray ink while others use heat and pressure to create images.
These printers are faster than impact printer.
Non-impact printers do not use a striking device to produce characters on the paper; and because
these printers do not hammer against the paper they are much quieter. Two types of nonimpact
printers often used with microcomputers are laser printers and ink-jet printers.
Laser printer:
Laser stands for light amplification by stimulated emission of radiation. The laser printer is a
non-impact printer. Its working is similar to photocopying machine. It uses laser beams to burn
special powder on page to create a permanent image. The power is contained in toner.
Laser printer prints complete page at a time. It is also known as page printer. The printing speed
of laser printers is 5 to 300 pages per minute (ppm). The speed depends on the contents being
printed. The plain text is printed faster than graphics.
Laser printer prints text and graphics in a high quality resolution, a typical laser printer provides
the resolution of 1200dpi or more. Laser printer prints at higher speed than inkjet and dot matrix
printers. It does not make much noise. Laser printer is mostly used in business field.

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Ink-jet printer:
An ink-jet printer is a type of non-impact printer. It prints characters and graphics by spraying
tiny drops of liquid ink on paper. These printers can produce quality text and graphics in both
black-and-white and color including photos. A typical inkjet printer provides resolution of 300
dots per inch. The latest inkjet printers provide higher resolution.
The price of inkjet printers is less than laser printers. However, they are slower than laser
printers. Most inkjet printers can print from 10 to 35 pages per minute. However, they print
graphics and colors at slower rate. The print quality of inkjet printers is higher than dot matrix
printer. They are also comparatively inexpensive. Most inkjet printers usually have two print
cartridges. One cartridge contains black ink and the other contains color.

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Difference between impact and non-impact printers
Impact printer / Dot-matrix Printer Non-impact Printer / Laser Printer
1. It prints characters or images by striking print
hammer or wheel against an inked ribbon.
1. It prints characters and images
without striking the papers.
2. Its speedis slower. 2. Its speedis faster.
3. Its printing quality is lower. 3. Its printing quality is higher.
4. It normally uses continuous paper sheet. 4. Its normally uses individual
paper sheet.
5. It generates noise during printing. 5. It does not generate noise
during printing.
6. It uses inked ribbon for printing. 6. It uses toner or cartridge for
painting.
7. It is less expensive. 7. It is more expensive.
8. Dot matrix is an impact printer. 8. Laser printer is a non-impact
printer
Plotters
A plotter is an output device that is used to produce high quality graphics in a variety of colors.
Plotters are used to create maps, architectural drawings, graphs and charts.
Types of Plotters
Different types of plotters are as follows:
1. Flatbed plotter
2. Drum Plotter

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Flatbed plotter:
Flatbed plotter is used to plot of draw images. It contains pens for drawing images. The paper is
places on table-like surface. Software instructs the pens to move down on the paper. The pen
then moves on the paper for creating images. Most flatbed plotters have one or move pens of
different colors and widths.
Drum plotter:
Drum plotter uses a rotating drum or cylinder. The drawing pens are mounted on the drum. The
pens move to the left and right as the drum rotates. This movement creates the desired image.
The advantage of drum plotter is that the length of the plot is almost unlimited. The roll paper
can be used to draw very lengthy images. The width of the image depends on the width of the
drum.