Transcript In put Devices and Media

In put Devices and
Media
In order for a computer
to do anything it must
be told what to do.
The Keyboard
The Keyboard
• The keyboard is the
most common input
device available.
Nearly every
computer comes
with one. It has a
series of keys similar
to a typewriter.
The Keyboard
• Each key has a letter,
number, symbol or
word on it.
• The user presses the key
(or combination of
keys) desired, causing a
special code to be
added to the keyboard
buffer.
The Keyboard
• This code (known as an
ASCII code) remains in
the buffer until the CPU
is ready for it.
• It is then decoded and
the computer takes the
appropriate action —
displaying a character,
moving the cursor, and
so on.
The Keyboard
• Keyboards are best
suited for data entry
or typing text
documents, even
though they can be
used for several
other things.
What Really is a Mouse
• A mouse is a handheld device that is
moved on the
surface of the desk
or on a mouse-pad.
• It has a ball
underneath and
usually two or more
buttons (and maybe
a wheel) on the top.
How it works
• When the mouse is
moved, this causes the
ball to be moved. As
the ball moves, the
mouse pointer moves
on the screen.
• When the pointer is over
an item that the user
wishes to select, he/she
can click one of the mouse
buttons.
Mouse most commonly used
for
• selecting a menu
• command or
‘pressing’ a button
on the screen
• highlighting icons
and text
• a pointing device.
Disadvantages of the mouse
• It is limited to objects
on the screen
• When the ball gets
dirty the mouse
pointer moves
erratically.
The Joystick
WHAT IS IT ?
• A joystick is a device with a
stick perpendicular to its base,
as well as buttons on the stick
and/or the base.
• designed to resemble those
used in fighter jets in order for it
to feel more realistic
HOW DOES IT WORK
• It is primarily used in
playing computer
games or in virtual
reality
• The user moves the
stick, causing an object
on the screen to be
moved.
• . When
the user presses
one of the buttons it
usually triggers some
appropriate action in the
game or simulation, such
as firing missiles.
Advantages
• It gives the user the
feeling of a more
realistic action.
• It moves objects in
any direction.
Disadvantages
• It is limited to certain
applications.
• A program must be
specially written in order for
a joystick to be used.
• it does not suit most
applications anyway
The Optical Mark Reader
HOW DOES IT WORK?
• An optical Mark Reader
(OMR) is a device that
senses the presence of
pencil and pen marks that
are made on special forms.
WHAT DO THEY LOOK LIKE?
• Such forms usually have
several options with circles
next to them. A person is
asked to fill out the form by
shading the circles for the
correct options.
WHAT IS IT USED FOR?
• This is an especially fast
method of data entry for
situations where a person is
asked to choose various
options such as
questionnaires, multiplechoice exams or
registration forms.
Advantages
• Reduced cost of
inputting large volumes
of data
• Fast method of inputting
data
• Less labour needed to
input the data.
Disadvantages
• If options are not shaded
properly the machine may
misread selections.
• Forms that are creased jam
the machine, causing down
time.
• Badly damaged forms have
to be rewritten or keyed in
manually.
The Optical Character
Reader
The Optical Character
Reader
•A device that senses
the presence of text
by recognising the
characters.
HOW DOES IT WORK?
• When the document is
scanned, a photo-electric
device reads the characters,
which are then converted to
electrical signals.
• The signals represent patterns
that give an indication of the
characters involved.
• it is a fast method of data
entry for documents that
were already typed/written.
• the accuracy of the input is
dependent on the quality of
the formation of characters.
What is it used for?
• Capturing data from
airline tickets
• Reading postal codes
• Capturing data from
telephone and
electricity bills
Advantages
• Reduced cost of inputting
large volumes of data
• Quick method of inputting
data
• Less labour needed to
input the data.
Disadvantages
•The OCR may
misread
characters that
are not formed
properly.
Touch sensitive devices
• A touch screen is another way to input
data.
• It is a specially mounted screen that is
sensitive to touch, so you do not need
to use a keyboard or mouse.
• Banks, malls and restaurants use
touch screens to provide information
to the public.
Touch sensitive devices
• A touch pad is a flat rectangular
surface which also senses movement
of a finger on its surface.
• These devices are usually found on
notebook computers.
• A light pen is similar to a mouse, but
you can move it over the screen and
point at items on the screen to input
data.
Scanner
• A scanner allows you to transfer
pictures, graphics and text to your
computer.
• It scans the image from the top to
the bottom, one line at a time and
transfers it to the computer.
• You can then take that copy and use
it in a paint program, send it out as a
fax or print it.
Microphone
• Data can be entered into a
computer through a microphone.
• The computer responds to this data
by carrying out instructions, such as
printing a document or turning the
spoken words into text in a word
processor.
• These are called voice-activated or
voice-input recognition systems.
Digitiser
• Digitisers convert drawings and
photographs into data for architects
and makers of maps.
• You can use a digital camera to store
pictures, not on film but in an
electronic format.
• Pictures from the camera are then
transferred to a computer using a
cable and a computer program.
Digitiser
• Moving pictures can also be captured by a
computer using a video digitiser.
• This method is often used by the television
industry to edit TV programmes.
• With digital video cameras now available in
shops, video editing through computers will
become commonplace.
Direct data entry (DDE) devices