Types of
Input Devices
Keyboard
Keyboard is
designed to resemble a regular typewriter with a few additional keys. Data is
entered into computer by simply pressing keys. All computer keyboards have a
typing area that includes the
letters of
the alphabet, numbers, punctuation marks, function keys and other basic keys
that provide additional functionality. The number of keys on a typical keyboard
varies from 82 keys to 108 keys.
Advantages
of using keyboards for data input include
Entering data and instructions with keyboards
is generally faster than
with
pointing devices.
It is not
necessary to buy additional equipment because most computer
systems are
normally supplied with keyboards.
Disadvantages
of using keyboards for data input include
It takes a lot of time to practice in order to
type quickly and accurately.
Typing speeds are still very slow when
compared with computer
speeds.
Mouse
• A
mouse is the most widely used pointing device with a GUI
environment on personal computers.
•
A pointing device is used to communicate with
the computer by pointing to locations on the monitor on the screen.
• Mouse
has two buttons, left one to select the pointed option and right one to display
the properties of the pointed option.
• A
mechanical mouse has a rubber ball on its underside to detect movement
of the mouse.
• It
is the most common and least expensive pointing device.
• An optical mouse uses devices
that emit and sense light to detect the mouse's movement.
• These
are accurate and do not need a mouse
pad.
• A
cordless mouse (either mechanical or optical) transmits data
• using
wireless technology such as radio waves or infrared light waves.
Advantages
of using a mouse include
• A mouse is user-friendly for computer
beginners.
• A mouse is easy and convenient to use with a
graphical user interface.
• Using a mouse to select items or move to a
particular position on the
• screen
is faster than using a keyboard.
Disadvantages
of using a mouse include
• It
is not easy and convenient to input text with a mouse.
• A
mouse is not accurate enough for drawings that require high precision.
• A mouse usually requires a flat surface to
operate.
• A mouse needs more desk space to operate when
compared with a trackball.
Trackball
• A trackball
is a stationary pointing device with a ball mechanism
on its top.
•
This pointing device comes in various shapes and
forms but with the same functions.
•
The three shapes,which are commonly used are a
ball,button and square.
•
Like the mouse
a track ball is also used to control cursor movements and the actions on
a computer screen.
•
The cursor is activated when the buttons on the
device are pressed.
•
Track ball is used by many computer enthusiasts
and graphic designers .
•
Trackballs are not supplied normally so an
additional cost is always charged.
• Advantages
of a trackball include
• A trackball is good for limited desk space
because the user does not
have to move the entire device.
• Disadvantages
of trackball include
• A trackball is usually not as accurate as a
mouse.
• The ball mechanism of trackballs also requires
more frequent cleaning
than a mouse.
Touchpad
• Is
a small pressure- and motion-sensitive area on a portable computer that you can
use
to move the mouse pointer.
• When
we move our finger across the pad, the mouse pointer on the screen moves in the
same
direction.
• A
touch pad is an alternative to a mouse.
Advantages
of a touch pad include
• Easy and Fast one finger control.
• Ideal for portable devices
Disadvantages of using a touchpad
include
• Expensive & found in specific devices e.g.
laptops
Joystick
• A
joystick is a pointing device with a vertical lever mounted on a base.
• The
lever usually includes buttons called triggers, which activate certain events
when pressed.
• The
device that moves in all directions and controls the movement of the cursor.
• Joysticks
are mainly used for computer games and ultrasound scanners in hospitals.
• Joysticks
are mainly used in CAD/CAM systems and flight simulators.
• A
joystick also consists of buttons that can be programmed to indicate certain
actions once a particular position on the screen has been selected using a
stick.
• It
offers three types of control: digital,glide,and direct.
• Digital control allows movement in a
limited number of directions such as top,down,left, and right.
• Glide and direct control allows movements in all directions(360)
degrees.
Advantages of using a joystick
include
• A joystick allows fast interactions required
in most games.
Disadvantages of using a joystick
include
• It is difficult to use a joystick to select
objects accurately on the screen.
Touch
Screen
·
A touch screen is an input/output
touch-sensitive display.
·
Touch screens
are often used for information kiosks located in
department stores, hotels, airports, and museums.
·
Touch screens are also used for ATM machines to
allow easy
access of bank accounts.
Advantages of a touch screen
include
·
No extra peripherals are needed except the
monitor.
·
A touch screen allows easy access to commands,
which are usually
identified by words or
symbols on the screen.
Disadvantages of a touch screen
include
·
Touch screens are not suitable for inputting a
large amount of data because they require a lot of arm movements.
·
Only items already on the screen can be
selected.
Light Pen
- A light pen is a pointing device that can detect the presence of light.
- Light pens are used by health care professionals (such as doctors and dentists) and design work.
- It facilitates drawing images and selects objects on the display screen by directly pointing to the objects.
- Using light pens users can interact more easily with applications such as drag and drop and highlighting.
- Pushing the light pen tip against the screen activities a switch,which allows the user to make the menu selections,draw,and perform other input functions.
Advantages of light pens include
- Using a light pen is more direct and precise than using a mouse.
- Light pen is also convenient for applications with limited desktop space.
Disadvantage of light pens includes
- Light pens normally require a specially designed monitor to work with.
Graphics Tablet
·
A
graphics tablet is a flat, rectangular, electronic plastic board, on
which a
stylus writes or draws.
·
It
is mainly used for computer-aided design and drafting by architects, mapmakers,
artists, and designers.
·
Each
location on the graphics tablet corresponds to a specific location on the
screen.
·
A
graphics tablet can be used to digitize drawing with great accuracy.
Advantages of graphics tablet
include
·
A
stylus can be pointed to different positions on the tablet quickly.
Disadvantages of graphics tablet
include
·
A
stylus and a graphics tablet normally have to work together, and
cannot work separately.
Digital
Camera
Digital
camera stores images digitally rather than recording them on a film. Once a
picture has been taken, it can be transferred to a computer system and then
manipulated with an image editing software and printed.
The big
advantage of digital cameras is that making photos is both inexpensive and fast
because there is no film processing.
Scanners
A scanner is
an input device that converts a document into an electronic format that can be
stored on the disk. The electronic image can be edited, manipulated, combined,
and printed by using the image editing software. The scanners are also called optical
scanners as they use a light beam to scan the input data.
They can
store images in both gray-scale and color mode.
―
Hand-held Scanner
―
Flat-bed Scanner
A flatbed scanner works like a copy machine except that it
creates a file of the document rather than a paper copy.
•
It
consists of a box containing a glass plate on its top and a lid that covers the
glass plate.This glass plate is used for placing the document to be scanned.
•
For
scanning,an A4 size document takes about 20 seconds.
•
The
flat scanners are larger in size and more expensive than the hand-held
scanners.
A handheld scanner can be manually
passed over the image to be
scanned. A portable device you can use to
copy an image from
paper to your computer. Hand-held scanners
are ideal for capturing
small images, such as signatures and logos. A
hand-held scanner is
smaller, less expensive, and more portable
than a flatbed scanner.
Scanners are mainly used for image
processing, which consists of
capturing, storing, analysing, displaying,
printing, and manipulating
images. Many scanners also include optical
character recognition (OCR)
software, which can convert an image of text
into a text file that can be edited.
Advantages of a scanner include
·
A
scanner with appropriate OCR software can work as an OCR
system.
Disadvantages of a scanner include
·
A
scanner is best for two-dimensional objects only, difficult to scan 3-D
objects
·
Scanned images usually take up a lot of
storage space.
Optical
Character Reader (OCR)
The scanned
document is stored as a bitmap in the computer’s memory. If the scanned
document contains text and you want to edit it, OCR software is required. The
OCR software translates the bitmap image of text to the ASCII codes that the
computer can interpret as letters, numbers, and special characters.
Because of
OCR data entry becomes easier,error free
and less time consuming.
It is very
expensive and if the document is not typed properly,it will become difficult
for the OCR to recognize the characters.
Optical
Mark Recognition (OMR)
OMR is the process of detecting the presence of
intended marked responses. A mark registers significantly less light than the
surrounding paper. Optical mark reading is done by a special device known as optical
mark reader.
OMR readers are often used for marking multiple choice answer sheets,
capturing data from questionnaires, enrolment forms, and lottery tickets.
Advantages of OMR readers
include
·
OMR
has a better recognition rate than OCR because fewer mistakes
are made by machines to read marks than by reading hand written characters.
·
Large
volumes of data can be collected quickly and easily without the
need for specially trained
staff.
·
The
cost of inputting data and the chance of data input errors could be
reduced because it is not
necessary to type the details for data entry.
Disadvantages of OMR readers
include
·
The
OMR reader needs to be reprogrammed for each new document design.
OMR readers are relatively slow.
·
The
person putting marks on the documents must follow the
instructions precisely.
·
Any
folding or dirt on a form may prevent the form from being read
correctly.
Handwriting
Recognition
·
Handwriting
recognition is a technique which allows
a
computer system to recognize characters and
other
symbols written by hand in natural handwriting.
·
The
technology is used for identification
and
also on devices such as PDA and tablet PCs. After one writes on a
screen
with a stylus, the computer turns that person’s handwriting into digital
text.
Advantages of handwriting
recognition include:
· Handwriting
recognition works regardless of which language text is
written
in i.e. it is language Independent.
· It requires a minimal or no training to use.
· It has very minimal system requirements and
provides immediate input.
Disadvantages of handwriting
recognition include:
•
Cannot
recognize mathematical symbols
•
Only
understand linear structures
•
It
is very tiring for the arms.
• Handwriting needs to
be clear for it to be recognised.
Magnetic
Ink Character Reader (MICR)
• A
magnetic ink character recognition (MICR) reader can read text printed
with magnetized ink. It reads the characters by examining their shapes in a
matrix form. Magnetic ink character
• recognition
is used most exclusively by the banking industry for processing checks. The
characters represent the
• check
number, the bank number, and the account number of customers
Advantages
of MICR readers include
• MICR is difficult to forge.
• Documents can still be read when folded or
written on.
Disadvantages
of MICR readers include
• MICR readers and encoders are very expensive.
• The system can only accept a few different
character sets.
Bar Code
Reader
Ø A bar code reader uses laser beams to read bar codes.
Ø A bar code reader
reads a bar code by using light patterns
that pass through the bar code lines.
Ø Bar code readers are
widely used in a POS e.g. supermarkets, department stores, libraries, etc.
Ø The light in the wave
form data is converted from analog to digital,in order to be processed by a
decoder and then transmitted to the computer software.
Ø The pen in the bar
code unit reads the information stored in the bar code and converted into a
series of characters by which the operating system gets the information stored
in the bar code.
Advantages of using bar codes
and bar code readers include
Ø The process of data
entry is fast and accurate.
Ø Bar codes can be
printed by normal printing methods.
Ø No need to write down
or key in the name of the item or its actual price.
Disadvantages of using bar codes
and bar code readers include
Ø A bar code reader may
misread a bar code if there is any dirt or mark
on
the code.
Ø
Only numbers can be coded.OMR is the
process of detecting the presence of intended marked responses. A mark
registers significantly less light than the surrounding paper. Optical mark
reading is done by a special device known as optical mark reader.
voice recognition
·
The field of computer science that deals with designing computer
systems that can recognize spoken words and translate into text.
·
Voice
recognition implies
only that the computer can take dictation, not that it understands what
is being said.
·
A number of voice
recognition systems are available on the market. The most
powerful can recognize thousands of words. However, they generally require an
extended training session during which the computer system becomes
accustomed to a particular voice and accent. where an individual
speaker reads sections of text into the SR system. These systems analyze the
person's specific voice and use it to fine-tune the recognition of that
person's speech, resulting in more accurate transcription. Such systems are said to be speaker
dependent.
·
Many systems also
require that the speaker speak slowly and distinctly and separate each word
with a short pause.
·
These systems are
called discrete speech systems.
·
There have been made
great strides on continuous speech systems -- voice recognition
systems that allow you to speak naturally. There are now several
continuous-speech systems available for personal computers.
·
The
term voice recognition or speaker
identification refers to
finding the identity of "who" is speaking, rather than what they are
saying. Recognizing
the speaker can simplify the task of translating speech in systems that have
been trained on a specific person's voice or it can be used to authenticate or
verify the identity of a speaker as part of a security process.
