Input devices:

An input device is any hardware device that sends data to a computer, allowing you to interact with
and control it. Examples of input devices include the following:

1. Keyboard:

A simple device comprising keys and each key denotes either an alphabet, number or
number commands which can be given to a computer for various actions to be performed.
It has a modified version of typewriter keys. The keyboard is an essential input device and
computer and laptops both use keyboards to give commands to the computer. Most
keyboards have a very similar layout. The individual keys for letters, numbers and special
characters are collectively called the character keys. The layout of these keys is derived from
the original layout of keys on a typewriter. The most widely used layout in the English
language is called QWERTY, named after the sequence of the first six letters from the top
left.

2. Mouse:

It is also known as a pointing device. Using mouse we can directly click on the various icons
present on the system and open up various files and programs. A mouse comprises 3
buttons on the top and one trackball at the bottom which helps in selecting and moving the
mouse around, respectively. In case of laptops, the touchpad is given as a replacement of
the mouse which helps in the movement of the mouse pointer. As you move a computer
mouse, the data sent to the computer is the X-Y axis movements used to display the mouse
cursor on the screen. You can see a live example of this on our x-axis definition.

3. Joy Stick:

It is a device which comprises a stick which is attached at an angle to the base so that it can
be moved and controlled. The lower spherical ball moves in a socket.The Joystick can be
moved in all four directions. The function of joystick is similar to that of a mouse. It is mainly
used in Computer Aided Designing (CAD) and playing computer games. It is also used to
control the movement in video games. Apart from a computer system, a joystick is also used
in the cockpit of an aeroplane, wheelchairs, cranes, trucks, etc. to operate them well.

4. Touch Screen:

Touch screen is an input device. Touch screen technology is the direct manipulation type
gesture based technology. Direct manipulation is the ability to manipulate digital world
inside a screen without the use of command-line-commands. A device which works on
touch screen technology is coined as Touch screen. A touch screen is an electronic visual
display capable of ‘detecting’ and effectively ‘locating’ a touch over its display area. It is
sensitive to the touch of a human finger, hand, pointed finger nail and passive objects like
 stylus. Users can simply move things on the screen, scroll them, make them bigger and
many more.

Working: It works by the first touch of finger or other pointing devices, then followed by the
movement of the finger. The touch screen gives the data of the movement of the pointing
device. It gives the data of either it is single touch or multiple touch in a single time and the
device works accordingly. If the touch is moving then the touch screen gives the data of the
movement in the x or y axis. According to the input given by the touch screen the device
works as programmed for the data received.

Output devices:

An output device can receive data from another device and generate output with that data, but it
cannot send data to another device. Examples of output devices include the following:

1. Monitor:

The device which displays all the icons, text, images, etc. over a screen is called the Monitor.
When we ask the computer to perform an action, the result of that action is displayed on
the monitor. It forms images from tiny dots, called pixels that are arranged in a rectangular
form. The sharpness of the image depends upon the no. of the pixels. Various types of
monitors have also been developed over the years. There are two kinds of viewing screen
used for monitors.

 Cathode-Ray Tube (CRT): CRT stands for Cathode Ray Tube. CRT is a technology
used in traditional computer monitors and televisions. The image on CRT display is
created by firing electrons from the back of the tube of phosphorus located towards
the front of the screen.
 Liquid Cristal Display (LCD): A liquid crystal display (LCD) monitor is a computer
monitor or display that uses LCD technology to show clear images, and is found
mostly in laptop computers and flat panel monitors. They are much more cheaper
than CRT.
 Light Emmiting Diode (LED): LED monitor is a screen display technology that uses a
panel of LEDs as the light source. Currently, a large number of electronic devices,
both small and large, use LED display as a screen and as an interaction medium
between the user and the system.

2. Printer:

A device which makes a copy of the pictorial or textual content, usually over a paper is
called a printer. For example, an author types the entire book on his/her computer and later
gets a print out of it, which is in the form of paper and is later published. Multiple types of
 printers are also available in the market, which can serve different purposes. There are two
types of printers:

 Impact Printers: The printers that print the characters by striking against the ribbon
and onto the paper are called impact printers. It has very low consumable costs.
Impact printers are very noisy and useful for bulk printing due to low cost. There has
to be physical contact with the paper to produce an image.
 Non-Impact Printers: The printers that print the characters without striking against
the ribbon and onto the paper, are called Non-impact Printers. These printers print a
complete page at a time, also called as Page Printers. They are faster than impact
printers. It produces hight quality output. Non impact printer also supports many
fonts and different character sizes.

3. Speakers:

A device through which we can listen to a sound as an outcome of what we command a

computer to do is called a speaker. Speakers are attached with a computer system and also
are a hardware device which can be attached separately. With the advancement in
technology, speakers are now available which are wireless and can be connected using
BlueTooth or other applications. Sound moves in pressure waves. When air particles are
compressed and rarified fast enough, we hear it as sound.
When a speaker moves back and forth it pushes on air particles which changes the air
pressure and creates sound waves.
Working: Speakers work by converting electrical energy into mechanical energy (motion).
The mechanical energy compresses air and converts the motion into sound energy or sound
pressure level (SPL). When an electric current is sent through a coil of wire, it induces a
magnetic field. In speakers, a current is sent through the voice coil which produces an
electric field that interacts with the magnetic field of the permanent magnet attached to the
speaker. Like charges repel each other and different charges attract. As an audio signal is
sent through the voice coil and the musical waveform moves up and down, the voice coil is
attracted and repelled by the permanent magnet. This makes the cone that the voice coil is
attached to move back and forth. The back and forth motion creates pressure waves in the
air that we perceive as sound.

4. Projector:

A projector is an output device that projects an image onto a large surface, such as a white
screen or wall. It may be used an alternative to a monitor or television when showing video
or images to a large group of people. Projectors come in many shapes and sizes though they
are commonly about a foot long and wide and a few inches tall. They can be mounted on
ceilings or may be freestanding and portable. Ceiling-mounted projectors are typically
larger, especially ones that project a long distance (such as 30 feet or more).
These projectors are commonly found in classrooms, conference rooms, auditoriums, and
places of worship. Portable projectors can used wherever there is a bright surface (such as a
white or light colored wall). Most projectors have multiple input sources, such as HDMI
ports for newer equipment and VGA ports for older devices. Some projectors support Wi-Fi
and Bluetooth as well.
Working: There is a lamp inside the projector, which is a source of luminous flux. Passing
through the optical system, the flow in accordance with the principles of light projection is
divided into three colors: red, blue and green. The tinted colored images pass through a
dichroic crystal, which leads to the birth of a million colors. Next, it enters the modulator:
liquid crystal or micromirror matrix, which creates a pixel structure. The control unit,
receiving signals from the image source, adjusts the direction of the modulating matrix. The
lens, in accordance with the principle of focusing, collects streams of different colors and
forms an image on the screen.