Graphical User Interfaces are typically
designed for a specific set of input and
output devices. GUI usually built using
toolkits that provide generic intetractive
elements such as window, menus, icons,
buttons and tabs. GUI use these graphical
elements to offer a consistent visual
language to represent information stored in
computer for make it easier to people.
The devices used for input and output determine the
nature and capacity of information transferred between
human and computer.
The terms “input” and “output” are used both as verbs to
describe the process of entering or displaying the data, and
as nouns referring to the data itself entered into or
displayed by the computer.
Characteristics of the I/O devices influence user interface
design to a large degree
The choice of an inappropriate or inadequate design will
diminish the performance of the task
Combinations of I/O devices can increase the usability of a
Input devices are used to convert our information
or data into a form which can be understood by
the computer. A good input device should provide
timely, accurate and useful data to the main
memory of the computer.
A keyboard contains keys that allow a user to enter data
and instructions to the computer.
All computer keyboards have typing area that includes
the letters of the alphabet, numbers, punctuation marks,
and other basic keys.
Many desktop computer keyboards also have a numeric
keypad located on the right side of the keyboard.
A standard computer keyboard is called a QWERTY
keyboard because of the layout of its typing area which is
similar to that of a typewriter.
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•Not dependent on a GUI OS.
•Using short cuts can be faster than
using the mouse.
•Most computers come with a
keyboard supplied .
•People are used to using keyboards
to enter data, they need very little
•A skilled typist can enter data very
•Specialist keyboards are available
e.g. ergonomic, gaming keyboards
•When using a keyboard too
much, it can cause carpal
•It is difficult to ex. draw things
in graphics programs with a
•It is easy to make mistakes
when typing in data
•Disabled people often find
keyboards difficult to use
A mouse is the most widely used pointing device with a GUI
environment on personal computers.
A mechanical mouse has a Rubber ball on its underside to
detect movement of the mouse.
An optical mouse uses devices that emit and sense light to
detect the mouse’s movement.
A cordless mouse(either optical or mechanical)transmits data
using wireless technology such as radio waves or infrared light
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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
It is not easy and convenient
to input text with a mouse.
Issuing commands by using a
mouse is slower than by using
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.
Touch pad is a small pressure and motion-sensitive
area on a portable computer that you can use to move the
mouse pointer. When you move you finger across the pad,
the mouse pointer on the screen moves in the same
direction. A touch pad is an alternative to a mouse.
Easy and fast one finger control.
Ideal for portable devices.
Expensive & found in specific devices (e.g.: Laptop)
Used mainly for CAD(Computer Aided Designing) and
It is a stick having a spherical ball at its both lower and
The lower spherical ball moves in a socket. The joystick
can be moved in all four directions.
The user moves the joystick left/right, forward/back and
data about these movements are sent to the computer.
Small joysticks can also be found on some mobile
•Controlling objects in computer games.
•Scanners in hospitals.
A touch screen is an alternative to a
separate pointing device. With a touch
screen the user selects items on the
screen by touching the surface. This
makes touch screen systems very
intuitive and simple to use.
Often used for information terminals
in public places e.g. libraries or
museums where mice or keyboards
may be stolen or damaged.
A pointing device often used by
designers and artists to allow natural
hand movements to be input to
A stylus is held like a pen and moved
over the surface of the tablet. Data about
the stylus movements are sent to the
Since it is so like using a pen, it is very
easy to create ‘hand-drawn’ sketches.
Magnetic Strip Reader
• Is a short length of magnetic tape stuck on the
surface of a tag, card or document.
• On plastic tags or cards the strip is sealed in.
• Tags with stripes identify the item they are attached
• On credit card
• On bank cards
• A phone Card
• Cash issue Terminals
Is set of parallel printed lines of differing thickness,
which represent a number.
• The number represented by the bars is also printed
above or below the bar code.
• When bar code are used on shop goods, the number
coded identifies the product and have following
1. Country of region
3. An item number for the product.
• Used in Barcodes
• Library System
• Warehouse stock
Optical Character Recognition(OCR)
Optical Character Recognition (OCR) is a software technology that
can convert images of text into an actual text file that can then be edited,
e.g. using word-processing software). The result is just as if the text had
been typed in by hand.
OCR is typically used after a page of a book has been scanned. The
scanned image of the page is then analyzed by the OCR software which
looks for recognizable letter shapes and generates a matching text file.
Advanced OCR software can recognize normal handwriting as well as
printed text - this is usually called handwriting recognition.
Magnetic ink character reader (MICR)
Characters are printed using an ink containing iron oxide.
As the document passes into the reader the ink is magnetized, so
that the character shapes can then be recognized electrically.
It is used by banks industry for check processing.
Each check contains MICR characters at the lower left edge.
These characters represent check number ,bank number and
Optical Mark Recognition (OMR) is a technology that
allows the data from a multiple-choice type form to be
read quickly and accurately into a computer.
Special OMR forms are used which have spaces that
can be colored in (usually using a pencil). These marks
can then be detected by an OMR scanner.
Common uses of OMR are multiple-choice exam
answer sheets and lottery number forms.
Using a microphone human speech is coded into
a sequence of electrical signals.
The computer searches a set of stored patterns
for the sound which has been input
It is now popular for inputting data into word
processing or database packages.
Useful for handicapped people with limited movement
No typing or data preparation is necessary.
Few words can be recognized and the error rate is high.
Not suitable in noisy places.
• Is used for input device for a speech
• The voice pattern of user is then converted
into instructions to the operating system or
application software or text.
• Uses as voice mail messages.
• Read data or information from the source.
• Source could be written document, a price
tag, a graphics image , or photograph.
• To scan text or images which manipulated in
some way before being printed .
Types of Scanner:
A normal PC has no senses, but we can give it some: We can
connect sensors to it...
A sensor is a device that converts a real-world property (e.g.
temperature) into data that a computer can process.
A sensor measures a specific property data and sends a signal to the
What it Detects
Light / dark
Pressure (e.g. someone standing on it)
Dampness / dryness
How full / empty a container is
How close / far something is
Switch or button
If something is touching / pressing it
• Is used to store, picture in digital form.
• Store images using different ways like floppy disk,
memory stick, mini CD ,PC Card and micro device.
• Can be connected to a computer easily through USB
• Image resolution for digital camera measured by
• Higher resolution photo takes up more memory .
Web camera ( Web Cams)
• Is simply a digital camera that is
used to capture still images and
• These images can then be
transmitted to a computer where
they are stored in graphics format
• Pictures can be used on the
• Camera placed on top the screen
such a system allow video
• Output device provide results in a suitable
form after data processing.
• Output devices are used to get data out of a
• They should be able to do this as accurately
and quickly as possible, and with the
minimum of human intervention.
• A monitor is a peripheral device which displays
computer output on a screen.
• Most common output deice.
• It is known as display screen.
• The output display by monitor is called soft copy so it
is ideal for showing the results from an enquire
where no printed is needed.
TYPES OF MONITOR:
Cathode-ray tube (CRT)
Liquid Crystal Display (LCD or flat-panel)
• This is same type that is
use in Television
• Use picture tube
• Less expensive than a
• Take up more desk space
and use more energy
than LCD monitors
• LCD screens are most often seen on portable or laptop
• The molecules this substances line up in such a way that the
light behind the screens and creates an image.
•Used for notebook computers, PDAs, cellular phones, and
•More expensive than a CRT monitor
•Take up less desk space and use less energy than CRT monitors
•Types of LCD monitors:
– Passive-matrix LCD
– Active-matrix LCD
– Gas plasma display
– Field emission display
A printer is a peripheral device
that produces a physical copy or
hard copy of the computer’s
It prints character ,symbols and
graphics on paper.
Print resolution is commonly
measured in dots per inch (dpi)
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