Explain various input devices of computer ?
https://www.computersprofessor.com/2016/04/Computers-input-devices.html
Input
Devices
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An input device is used to feed data
and instructions into the computer,
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Keyboard
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The keyboard is the main input
device for computers. Computer keyboards loo very similar to the keyboards of
Typing keys : These include the letters of the alphabet. The QWERTY patterns has been a standard right from the time computer keyboards were introduced.
Numeric keys : These include a set of 17 keys, arranged in the same configuration found on calculators to speed up data entry of numbers.
Function keys : These are used by applications and operating systems to input specific commands.
Control keys : These are used handle control of the cursor and the screen.
Advantage
The keyboard is easy to use and cheap.
Disadvantages
· The keyboard cannot be used to draw figures.
· The process of moving the cursor to another position is very slow.
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Pointing
Devices
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A pointing input device enables the
users to easily control the movement of the pointer to select items on a
display screen, to select commands from commands menu, to draw graphs, etc.,
Mouse
It is the key input device used in a
graphical user interface (GUI).
It can be used to handle the pointer easily on the screen to perform various
functions such as opening a program of file. The mouse has two buttons and a
scroll wheel. It can be held in the hand and easily moved.
Point
Placing the mouse pointer over the
word or the object on the screen.
Click
Pressing either the left or the
right button of the mouse is known as clicking. Clicking a mouse button
initiates some action.
Drag
Dragging means pointing to a desired
location while pressing the left button.
Scroll
The scroll wheel, which is placed in
between the left and right buttons of the mouse, is used to vertically scroll
through long documents.
Mechanical
mouse
This type of mouse has a rubber or
metal ball at its bottom and an electronic circuit containing sensors. When
the mouse is moved over a flat surface, the sensors detect the direction of
movement of the ball. The electronic circuit translates the movement into
signals and feeds it as input to the computer.
Optical
mouse
The optical mouse is more advanced
than the mechanical mouse. It contains a ball inside. The movement of the
mouse is detected using laser technology, by using optical sensors.
Cordless
mouse
A cordless or wireless mouse is not
connected to the computer. The movement of the mouse is detected using radio
waves or infrared light waves.
Advantages
· The
mouse is easy to use and can be used to quickly place the cursor anywhere on
the screen.
· It
also helps to quickly and easily drawn figures.
· It
is cheap.
· Its
point-and-click capabilities make it unnecessary to remember and type in
commands.
Disadvantages
· The
mouse needs extra desk space to be placed and moved easily.
· The
ball in the mechanical mouse must be cleaned to removed dust from it.
Trackball
A trackball is a pointing device
that is used to control the position of the cursor on the screen. It is
usually used in notebook computers, where it is placed on the keyboard. The
user rolls the ball to position the cursor at an appropriate position on the
screen and then clicks one of the buttons (identical to mouse buttons) near
the trackball, either to select objects or to position the cursor for text
entry.
Advantages
·
The
trackball provides better resolutions.
·
It
occupies less space.
·
It
is easier to use as compared to a mouse.
Disadvantage
The trackball chamber is often
covered with dust, so it must be cleaned regularly.
Touchpad
A touchpad is a small, flat,
rectangular stationary pointing device with a sensitive surface of 1.5–2
square inches. The user has to slide his or her fingertips across the surface
of the pad to point to a specific object on the screen. There are also
buttons around the edge of the pad that work like mouse buttons. Touchpads
are widely used in laptops, and are in built on the laptops keyboards.
Advantages
·
Touchpads
occupy less space.
·
They
are easier to use as compare to a mouse.
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Handheld
Devices
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Joystick
A joystick is a cursor control
device widely used in computers games and computer aided design (CAD) /
computer aided manufacturing (CAM) applications. A joystick has one or more
push buttons, called switches, whose position can also be read by the
computer.
The
lever of a joystick moves in all directions to control the movement of the
pointer on the computer screen.
Stylus
A stylus is a pen-shaped input
device used to enter information or write on the touchscreen of a handheld
device. It is a small stick that can also be used to draw lines on a surface
as input into a device, choose an option from a menu, move the cursor to
another location on the screen, take notes, and create short messages.
Touchscreen
A touchscreen is a display screen
that can identify the occurrence and position of a touch inside the display
region. The user can touch the screen either by using a finger or a stylus.
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Optical
Devices
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Optical devices, also known as
data-scanning devices, use light as a source of input for detecting or
recognizing different objects such as characters, marks, codes, and images.
The optical device converts these objects into digital data and sends it to
the computer for further processing.
Barcode
Reader
A barcode reader is a handheld input
device that is used to capture and read information stored in a bar code. It
consists of a scanner, a decoder, and a cable used to connect the reader to a
computer. The function of the barcode reader is to capture and translate the
bar code into numerical and / or alphabets. It is connected to a computer for
further processing of the captured information.
Advantage
·
Barcodes
readers are cheap.
·
They
are portable.
·
They
are handy and easy to use.
Disadvantages
· Barcode
readers must be handled with care. If they develop a scratch, the user may
not be able to read the code.
· They
can interpret information using a limited series of thin and wide bars. To
interpret other unique identifiers, the bar display area must be widened.
Image
Scanner
A scanner is a device that captures
images, printed text, and handwriting, from different sources such as
photographic prints, posters, and magazines and converts them into digital
image for editing and display on computers.
Advantages
· Any
printed or handwritten document can be scanned and stored in a computer for
further processing.
· The
scanned and stored document will never deteriorate in quality with time. The
document can be displayed and printed whenever required.
· There
is no fear of loss of documents. The user can scene important documents and
store them permanently in the computer.
Disadvantage
· Scanners
use usually costlier than other input devices.
· The
documents that are scanned and stored as images have a higher size as
compared to other equivalent text files.
· Text
documents are scanned and stored as images. Therefore, they occupy more space
and are also uneditable because computers cannot interpret individual characters
and numbers in the image.
Optical
Character Recognition
Optical character recognition (OCR)
is the process of converting printed materials into text or word processing
files that can be easily edited and stored. The steps involved in OCR include
:
· Scanning
the text character by character.
· Analyzing the scanned image to translate the character images into character codes.
Advantages
· Printed
documents can be converted into text files.
· Advanced
OCR can recognize handwritten text and convert it into computer-readable text
files.
Disadvantages
·
OCR
cannot recognize all types of fonts.
·
Documents
that are poorly or have strike over cannot be recognized.
· Very
old documents when passed through OCR may not convert into an exact copy of the text file.
Optical
Mark Recognition
Optical mark recognition (OMR) is
the process of electronically extracting data from marked fields, such as
check boxes and fill-in fields, on printed forms. The OMR sheet is scanned by
the reader to detect the presence of a mark by measuring the reflected light
levels.
Advantage
Optical mark readers work at very
high speeds. They can read up to 9,000 forms per hour.
Disadvantages
·
It
is difficult to gather large amounts of information using an OMR.
·
Some
data may be missing in the scanned document.
·
It
is a sensitive device that rejects the OMR sheet if it folded, torn, or
crushed.
Magnetic
Ink Character Reader
Magnetic ink character reader (MICR)
is used to verify the legitimacy of paper documents, especially bank checks.
It consists of magnetic ink printed characters that can be recognized by
high-speed magnetic recognition devices.
MICR is widely used to enhance security, speed up the sorting of
documents, and minimize the exposure to cheque fraud.
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Audio–visual
Input Devices.
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Today, all computers are
multimedia-enabled, that is, computers not only allow one to read or write
text. But also enable the user to record songs, view animated moves, etc.
Audio
Input Devices
Audio devices are used to either
capture or create sound. They enable computers to accept music, speech, or
sound effects for recording and / or editing. Microphones and CD players are
examples of two widely used audio input devices. The sound card is a hardware
unit that converts analogue signals generated through the microphone into
digital data, so that it can be stored in the computer. When the user wants
to hear the pre-recorder audio input, the sound card converts the digital
data into equivalent analogue signals and sends them to the speakers.
A
computer with a microphone and speakers can be used to make telephone calls
and do videoconferencing (using a web camera or ‘webcam’) over the internet.
Video
Input Devices
video input devices are used to
capture video from the outside world into the computer. Here, the term video
means moving picture along with sound (as in television). As we have sound
cards to convert analogue audio signals into digital data and vice versa, we
also have video cards to convert analogue video signals to digital data to
store it in the computer (and vice versa). Digit camera and web camera are
popular examples of video input devices.
Advantages
·
Audio
devices can be used by people who have visual problems.
· Audio
input devices are best used in situation where users want to avoid input
through keyboard or mouse.
·
Video
input devices are very useful for applications such as videoconferencing.
·
They
can be used to record memorable moments in one’s life.
·
They
can also be used for security purposes.
Disadvantages
· Audio
input devices are not effective in noisy places.
· With
audio input devices, it is difficult to clearly distinguish between two
similar sounding words.
· Videos
and images captured using video input devices have very big file sizes, and
they must be compressed before being stored on the computer.
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