AS Level ICT

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AS Level ICT

Selection and use of input devices and
input media: Simple devices

Selecting suitable input methods


An ideal solution to the inputting of data would
make it:


Automatic


Fast


Cheap


Accurate


There are very few input devices that match these
criteria, and most solutions involve some level of
compromise when the choice of input device is
made

Selecting suitable input methods


There are two types of input method


These are:


The manual method
: this method requires a
person enter the data (e.g. data entry using a
keyboard)


The automatic method
: this method requires
the work to be sorted into ‘batches’ which the
system then ‘reads’ automatically (e.g. optical
mark sheets)

Selecting suitable input methods


Whichever method is chosen, both involve the use
of input devices

Input devices


Input devices are used to get data into a system


They should be able to do this as accurately and
quickly as possible, and with the minimum of
human intervention

Input devices


The most common types of input devices are:


Keyboards


Point and Click devices (including mouse,
tracker balls, touch sensitive pads, joysticks,
light pens, touch screens, and graphic tablets)


Readers (including magnetic strip readers,
barcode readers, optical character
readers/recognition, magnetic ink character
readers/recognition, and optical mark
readers/recognition)

Input devices


Punched cards and tape (including punched
cards and Kimball tags)


Sound capture devices (including voice
recognition and microphones)


Terminals (including EPOS and EFTPOS
terminals)


Digital imaging devices (including video
digitisers, scanners, digital cameras, and web
cams)


Tonal devices (including touch tone telephones)

Keyboards


The most common type of keyboard is the
QWERTY keyboard (so called because the top line
of letters are q, w, e, r, t, and y)

Keyboards


Qwerty keyboard

Keyboards


Concept keyboard


Another type of keyboard is the concept keyboard


The can be specially designed so that people with
restricted vision can use them to interface with a
computer


Concept keyboards can also be programmed to
perform common functions with one keystroke (e.g.
a computerised till in a fast food restaurant)

Keyboards


Concept keyboard

Each button can be
programmed to do
whatever you want


An overlay sheet
with pictures or
symbols is placed on
the grid so that the
user can tell what
pressing on different
areas will do

Keyboards


Concept keyboard

Concept keyboards
are used when fast
input is needed and
are ideally suited to
selecting from a
limited range of
choices

Keyboards
-

Advantages


Keyboards


and QWERTY keyboards in particular


do have some advantages as a device for
inputting data:


They are cheap


they are usually supplied with
the computer


They are in universal use


most people know
how to use one

Keyboards
-

Disadvantages


Keyboards also have several disadvantages:


They are slow to use


even the best typists can
only manage a maximum of 100 words per
minute


They cost a lot to operate


the workers who are
entering the data have to be paid


Entered data tends to be inaccurate


this is
often due to transcription and transposition
errors being made

Keyboards
-

Disadvantages


They are associated with particular health
problems (RSI


Repetitive Strain Injury)

‘Point and Click’ devices


‘Point and Click’ devices include mouse, tracker
balls, touch sensitive pads, joysticks, light pens,
touch screens, and graphic tablets

Mouse


The mouse translates movement on the desktop
into digital information


This is information is converted into movement of
the cursor on the screen


A mouse will also have one, two, or three buttons
which can be clicked to help the user to select what
functions they wish to use

Tracker ball


The tracker ball is essentially an upside down
mouse


Instead of moving the mouse on the table top, the
ball is rotated


This achieves the same result as using a mouse
but takes up far less room

Touch sensitive pad


These are most commonly found on laptop
computers


A stylus or the user’s finger is pressed gently onto
the pad, and as it is moved the cursor moves on
the screen

Joystick


These are most commonly used to interact with
computer games, although they are also used in
other circumstances (e.g. on hospital scanners)


Like the tracker ball, the movement of the joystick
moves the cursor on the screen

Light pen


Light pens are usually used with specialist design
software


The light pen works by being touched against the
screen


As the pen is moved on the screen, the cursor
moves

Touch screen


The touch screen is a special type of screen which
is sensitive to touch


Selections can be made by touching the screen


These are particularly useful in banks, building
societies, and shops, where customers who are not
used to using a keyboard can interact with a
computer system

Graphics tablet/Digitiser


A graphics tablet allows the user to create designs
directly onto the screen


A special stylus


sometimes called a digitiser


is
connected to the computer via the graphics tablet,
and as the user ‘draws’ on the tablet with the stylus
the drawing appears on screen

‘Point and Click’ devices
-

Advantages


Most are very simple and require little or no training
to use


The most common


the mouse and the touch
sensitive pad


come as standard with either a
desktop or laptop computer respectively


‘Point and Click’ devices
-

Disadvantages


The main disadvantage of ‘Point and Click’ devices
is that they generally require good eye
-
hand
coordination, and in some cases


for example, the
graphics

tablet/
digitiser

and light pen


a degree of
artistic talent, in order to be used effectively

Sound capture devices


The most common use of sound capture devices
involves the use of voice recognition software and
microphones

Sound capture devices


Voice recognition software ‘remembers’ the way a
user speaks, and converts their speech into text
that appears on screen


Although voice recognition software has become
increasingly sophisticated, many such programs
have difficulty converting more than 90% of
common words accurately

Sound capture devices
-

Advantages


They should be very easy to use and require little
or no training


They are faster than typing


They can achieve 99% accuracy


They can be cheap


most desktop and laptop
computers come with a microphone installed as
standard; all that is needed is the purchase of the
voice recognition software

Sound capture devices
-

Disadvantages


The software needs to be ‘trained’ to recognise
each users voice


this can take a considerable
amount of time


Because men and women usually have different
voice pitch (i.e. varying frequency of vibration), and
because the software is programmed to register a
limited range of voice pitch, the software tends to
be more accurate when transcribing text spoken by
men rather than by women

Sound capture devices
-

Disadvantages


Background noise can cause errors (e.g. a
telephone ringing or someone other than the user
speaking as the device is being used)


They do not work with database software

Digital imaging devices


These include video digitisers, scanners, digital
cameras (still and motion), and web cams

Video Digitisers


The video digitiser is a combination of hardware
and dedicated software that converts an analogue
signal into a digital signal


This is the basis of most set top boxes that give
access to digital television on standard television
sets


It can also be used to ‘capture’ still images from
video

Scanners


Scanners are used to scan text or images so that
they can be stored on and manipulated by
computer


The scanner converts the text or image into a
digital signal which it sends to the computer


The user can then decide whether they want to
store or manipulate what they have scanned

Digital cameras


Digital cameras convert the analogue image seen
through the camera’s lense into a digital signal that
can be stored


Each picture is split up into millions of tiny squares
(or pixels), each of which is a different colour


Each pixel is stored as a ‘bit’ of digital information

Webcams


Web cameras (webcams for short) are small digital
cameras which are attached to computers so that
still and motion digital images can be ‘captured’
and used


They are often used in conjunction with the Internet
so that people can videoconference

Digital imaging devices
-

Advantages


They are easy to use and usually require little
training to use


They are relatively inexpensive, and are become
increasing cheaper and more available (e.g. many
mobile phones have digital cameras capable of
capturing still images and short movies)

Digital imaging devices
-

Disadvantages


They require specialist software to manipulate any
text that has been captured (i.e. any text scanned
in requires character recognition software to
convert the text into a document format that can be
altered or reformatted)


They require specialist software to manipulate any
images that have been captured (e.g. the removal
of ‘red eye’; the cropping and/or resizing of an
image)

AS Level ICT

Selection and use of input devices and
input media: Simple devices