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As the aim of this lecture is to introduce you the study of
Human Computer
Interaction, so that after studying this you will be able to:
. Describe the
advantages and disadvantages of different input output devices
keeping in view different aspects of HCI
In previous lectures our topics of discussion were covering the
human aspects. From
now we will pay some attention towards computers. We will study
some computer
aspects. You may have studied many of them before in any other
course, but that are
also part of our discussion, as at one side of our subject is
human and at the other side
computer lies.
Today will look at some input and output devices of computer.
Let us fist look at
input devices.
13.1 Input devices
Input is concerned with recording and entering data into
computer system and issuing
instruction to the computer. In order to interact with computer
systems effectively,
users must be able to communicate their interaction in such a
way that the machine
can interpret them. Therefore, input devices can be defined as:
a device that, together
with appropriate software, transforms information from the user
into data that a
computer application can process.
One of the key aims in selecting an input device and deciding
how it will be used to
control events in the system is to help users to carry out their
work safely, effectively,
efficiently and, if possible, to also make it enjoyable. The
choice of input device
should contribute as positively as possible to the usability of
the system. In general,
the most appropriate input device will be the one that:
. Matches the
physiology and psychological characteristics of users, their
training and their expertise. For example, older adults may be
hampered by
conditions such as arthritis and may be unable to type;
inexperienced users
may be unfamiliar with keyboard layout.
. Is appropriate for
the tasks that are to be performed. For example, a drawing
task from a list requires an input device that allows continuous
movement;
selecting an option from a list requires an input device that
permits discrete
movement.
. Is suitable for the
intended work and environment. For example, speech input
is useful where there is no surface on which to put a keyboard
but is unsuitable
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in noisy condition; automatic scanning is suitable if there is a
large amount of
data to be generated.
Frequently the demands of the input device are conflicting, and
no single optimal
device can be identified: trade-offs usually have to be made
between desirable and
undesirable features in any given situation. Furthermore, many
systems will use two
or more input devices together, such as a keyboard and a mouse,
so the devices must
be complementary and well coordinated. This means that not only
must an input
device be easy to use and the form of input be straightforward,
there must also be
adequate and appropriate system feedback to guide, reassure,
inform and if necessary,
correct user’s errors. This feedback can take various forms. It
can be a visual display
screen: a piece of text appears, an icon expands into a window,
a cursor moves across
the screen or a complete change of screen presentation occurs.
It can be auditory: an
alarm warning, a spoken comment or some other audible clue such
as the sound of
keys clicking when hit. It can be tactile: using a joystick. In
many cases feedback
from input can be a combination of visual, auditory and tactile
responses. For
example, when selecting an icon on a screen, the tactile
feedback from the mouse
button or function keys will tell users that they instructed the
system to activate the
icon. Simultaneously, visual feedback will show the icon
changing shape on the
screen. This is coordinated with the sound of the button
clicking or the feel of the key
resisting further pressure. Let us now discuss various types of
devices in terms of their
common characteristics and the factors that need to be
considered when selecting an
input device. We will discuss text entry devices first.
13.2 Text entry devices
There are many text entry devices as given below:
Keyboard
Keyboard
The most common method of entering information into the computer
is through a
keyboard. Since you have probably used them a lot without
perhaps thinking about
the related design issue, thinking about keyboards is a
convenient starting point for
considering input design issue. Broadly defined, a keyboard is a
group of on—off
push button, which are used either in combination or separately.
Such a device is a
discrete entry device. These devices involve sensing essentially
one of two or more
discrete positions (for example, keys on keyboards,
touch-sensitive switches and
buttons), which are either on or off, whereas others (for
example, pens with digitizing
tablets, moving joysticks, roller balls and sliders) involve
sensing in a continuous
range. Devices in this second category are therefore, known as
continuous entry
devices.
When considering the design of keyboards, both individual keys
and grouping
arrangements need to be considered. The physical design of keys
is obviously
important. For example, of keys are too small this may cause
difficulty in locating and
hitting chosen keys accurately. Some calculators seeking extreme
miniaturization and
some modern telephones suffer from this. Some keyboards use
electro mechanical
switches, while others use sealed, flat membrane keyboards. When
pressing a key on
a membrane keyboard, unless appropriate feedback is given on
screen, or using sound
it may be difficult to tell which key , if any , has been
presses. On the other hand,
membrane keyboards can typically withstand grease, dirt and
liquids that would soon
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clog up typical electromechanical switches. This can be an
important consideration in
environments such as production floors, farm and public places.
Alterations in the arrangement of the keys can affect a user’s
speed and accuracy.
Various studies have shown that typing involves a great deal of
analyses of trained
typists suggest that typing is not a sequential act, with each
key being sought out and
pressed as the letters occur in the works to be typed. Rather,
the typist looks ahead,
processes text in chunks, and then types it in chunks. For
alphabetic text these chunks
are about two to three world long for numerical material they
are three to four
characters long. The effect is to increase the typing speed
significantly.
QWERTY keyboard
Most people are quite familiar with the layout of the standard
alphanumeric keyboard,
often called the qwerty keyboard, the name being derived from
the first letters in the
upper most row from left to center. This design first became a
commercial success
when used for typewriters in the USA in 1874, after many
different prototypes had
been tested. The arrangement of keys was chosen in order to
reduce the incidence of
keys jamming in the manual typewriters of the time rather than
because of any
optimal arrangement for typing. For example, the letters ‘s’,
,t, and ‘h’ are far apart
even though they are far apart even though they are frequently
used together.
Alphabetic keyboard
One of the most obvious layouts to be produced is the alphabetic
keyboard, in which
the letters are arranged alphabetically across the keyboard. It
might be expected that
such a layout would make it quicker for untrained typists to
use, but this is not the
case. Studies have shown that this keyboard is not faster for
properly trained typists,
as we may expect, since there is no inherent advantage to this
layout. And even for
novice or occasional users, the alphabetic layout appears to
make very little difference
to the speed of typing. These keyboards are used in some pocket
electronic personal
organizers, perhaps because the layout looks simpler to use than
the QWERTY one.
Also, it dissuades people from attempting to use their
touch-typing skills on a very
small keyboard and hence avoids criticisms of difficulty of use.
Dvorak Keyboard
With the advent of electric and electronic keyboards and the
elimination of levered
hammers such considerations are no longer necessary. Attempts at
designing
alternative keyboards that are more efficient and quicker to use
have produced, among
others, the Dvorak and Alphabetic boards. The Dvorak board,
first patented in 1932,
was designed using the following principles:
. Layout is arranged
on the basis of frequency of usage of letters and the
frequency of letter pattern and sequences in the English
language.
. All vowels and the
most frequently used consonants are on the second or
home row, so that something like 70% of common words are typed
on this
row alone.
. Faster operation is
made possible by tapping with fingers on alternate hands
(particularly the index fingers) rather than by repetitive
tapping with one
finger and having the majority of keying assigned to one hand,
as in the
QWERTY keyboard, which favors left-handers. Since the
probability of
vowels and consonants altering is very high, all vowels are
typed with the left
hand and frequent home row consonants with the right.
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The improvements made by such as ergonomic design are a
significant reduction in
finger travel and consequent fatigue and a probable increase in
accuracy. Dvorak also
claimed that this arrangement reduces the between –row movement
by 90% and
allows 35% of all words normally used to be typed on the home
row. Despite its
significant benefits, the dvorak layout, show in figure has
never been commercially
successful. The possible gain in input speed has to be weighed
against the cost of
replacing existing keyboards and retraining millions of people
who have learned the
QWERTY keyboard.
Chord keyboards
In chord keyboards several keys must be pressed at once in order
to enter a single
character. This is a bit like playing a flute, where several
keys must be pressed to
produced with a small number of keys, few
keys are required, so chord keyboards can be
very small, and many can be operated with
just one hand. Training is required learn the
finger combination required to use a chord
keyboard. They can be very useful where
space is very limited, or where one hand is
involved in some other task. Training is
required to learn the finger combinations
required to use a chord keyboard. They can
be very useful where space is very limited,
or where one hand is involved in some other
task. Chord keyboards are also used for mail
sorting and a form of keyboard is used for
recording transcripts of proceeding in law courts.
Special keyboards
Some keyboards are even made of touch-sensitive buttons, which
require a light touch
and practically no travel; they often appear as a sheet of
plastic with the buttons
printed on them. Such keyboards are often found on shop till,
though the keys are not
QWERTY, but specific to the task. Being fully sealed, they have
the advantage of
being easily cleaned and resistant to dirty environment, but
have little feel, and are not
popular with trained touch-typists. Feedback is important even
at this level of humancomputer
interaction! With the recent increase of repetitive strain
injury (RSI) to
a o e
“ q j k x b m w v z
u i d h t n s
1 2 3 4 5 6 7 8 9 0
? , . p y f g c r l
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users’ finger, and the increased responsibilities of employers
in these circumstances, it
may be that such designs will enjoy resurgence in the near
future. The tendons that
control the movement of the fingers becoming inflamed owing to
overuse cause RSI
in fingers and making repeated unnatural movement.
There are very verities of specially shaped keyboards to relieve
the strain of typing or
to allow people to type with some injury or disability. These
may slope the keys
towards the hands to improve the ergonomics position, be
designed for single-handed
use, or for no hands at all. Some use bespoke key layouts to
reduce strain of finger
movements. The keyboard illustrated is produced by PCD Maltron
Ltd. for lefthanded
use.
Phone pad and T9 entry
With mobile phones being used for SMS text messaging and WAP,
the phone keypad
has become an important form of text input. Unfortunately a
phone only has digits 0-
9, not a full alphanumeric keyboard.
To overcome this for text input the numeric keys are usually
pressed several times.
Figure shows a typical mapping of digits to letters. For
example, the 3 keys have ‘def’
on it. If you press the key once you get a ‘d’, if you press 3
twice you get an ‘e’, and if
you press it three times you get an ‘f’. The main
number-to-letter mapping is standard,
but punctuation and accented letters differ between phones. Also
there needs to be a
way for the phone to distinguish, say, the ‘dd’ from ‘e’. on
some phones you need to
pause far short period between successive letters using the same
key, for others you
press an additional key (e.g. ‘#’).
Most phones have at least two modes for the numeric buttons: one
where the keys
mean the digits (for example when entering a phone number) and
one where they
mean letters (for example when typing an SMS message). Some have
additional
modes to make entering accented characters easier. Also a
special mode or setting is
needed for capital letters although many phones use rules to
reduce this, for example
automatically capitalizing the initial letter in a message and
letters following full
stops, question marks and exclamation marks.
This is all very laborious but you can see experienced mobile
users make use of
highly developed shorthand to reduce the number of keystrokes.
If you watch a
teenager or other experienced txt-er, you will see they often
develop great typing
speed holding the phone in one hand and using only their thumb.
As these skills
spread through society it may be that future devices use this as
a means of small
format text input. For those who never develop this physical
dexterity some phones
have tiny plug-in keyboards, or come with foldout keyboards.
Another technical solution to the problem is the T9 algorithm.
This uses a large
dictionary to disambiguate words by simply typing the relevant
letters once. For
example, ‘3926753’ becomes ‘example’ as there is only one word
with letters that
match (alternative like ‘ewbosld’ that also match are not real
words). Where there are
ambiguities such as ‘26’, which could be an ‘am’ or an ‘an’, the
phone gives a series
of option to choose from.
Handwriting recognition
Handwriting is a common and familiar activity, and is therefore
attractive as a method
of text entry. If we were able to write as we would when we use
paper, but with the
computer taking this form of input and converting it to text, we
can see that it is an
intuitive and simple way of interacting with the computer.
However, there are a
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number of disadvantages with hand writing recognition. Current
technology is still
fairly inaccurate and so makes a significant number of mistakes
in recognizing letters,
though it has improved rapidly. Moreover, individual differences
in handwriting are
enormous, and make te recognition process even more difficult.
The most significant
information in handwriting is not in the letter shape itself but
in the stroke
information– the way in which the letter is drawn. This means
that devices which
support handwriting recognition must capture the stoke
information, not just the final
character shape. Because of this, online recognitions far easier
than reading
handwritten text on paper. Further complications arise because
letters within words
are shaped and often drawn very differently depending on the
actual vide enough
information. More serious in many ways is the limitation on
speed; it is difficult to
write at more than 25 words a minute, which is no more than half
the speed of a
decent typist.
The different nature of handwriting means that we may find it
more useful in
situation where a keyboard-based approach would have its own
problems. Such
situation will invariably result in completely new systems being
designed around the
handwriting recognizer as the predominant mode of textural
input, and these may bear
very little resemblance to the typical system. Pen-based systems
that use handwriting
recognition are actively marked in the mobile computing market,
especially for
smaller pocket organizers. Such machines are typically used for
taking notes and
jotting down and sketching ideas, as well as acting as a diary,
address book and
organizer. Using handwriting recognition has many advantages
over using a
keyboard. A pen-based system can be small and yet still accurate
and easy to use,
whereas small keys become very tiring, or even impossible, to
use accurately. Also
the pen-based approach does not have to be altered when we move
from jotting down
text to sketching diagrams; pen-based input is highly
appropriate for this also.
Some organizer designs have dispensed with a keyboard
completely. With such
systems one must consider all sorts of other ways to interact
with the system that are
not character based. For example, we may decide to use gesture
recognition, rather
than commands, to tell the system what to do, for example,
drawing a line through a
word in order to delete it. The important point is that a
different input device that was
initially considered simply as an alternative to the keyboard
opens up a whole host of
alternative designs and different possibilities for interaction.
Speech recognition
Speech recognition is a promising are of text entry, but it has
been promising for a
number of years and is still only used in very limited
situations. However, speech
input suggests a number of advantages over other input methods:
. Since speech is a
natural form of communication, training new users is much
easier than with other input devices.
. Since speech input
does not require the use of hands or other limbs, it enables
operators to carry out other actions and to move around more
freely.
. Speech input offers
disabled people such as the blind and those with severs
motor impairment the opportunities to use new technology.
However, speech input suffers from a number of problems:
. Speech input has
been applied only in very specialized and highly constrained
tasks.
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. Speech recognizers
have severe limitations whereas a human would have a
little problem distinguishing between similar sounding words or
phrases;
speech recognition systems are likely to make mistakes.
. Speech recognizers
are also subject to interference from background noise,
although the use of a telephone-style handset or a headset may
overcome this.
. Even if the speech
can be recognized, the natural form of language used by
people is very difficult for a computer to interpret.
The development of speech input systems can be regarded as a
continuum, with
device that have a limited vocabulary and recognize only single
words at one end of
the spectrum and systems that attempt to understand natural
speech at the other,
Isolated word recognition systems typically require pauses
between words to be
longer than in natural speech and they also tend to be quite
careful about how she
speaks. Continuous speech recognition systems are capable, up to
a point, of problems
and system complexity. Although these systems still operate by
recognizing a
restricted number of words, the advantage is that they allow
much faster data entry
and are more natural to use.
One way of reducing the possible confusion between words is to
reduce the number of
people who use the system. This can overcome some of the problem
caused by
variations in accent and intonation. Speaker-dependent systems
require each user to
train a system to recognize her voice by repeating all the words
in the desired
vocabulary one or more times. However, individual variability in
voice can be a
problem, particularly when a user has a cold. It is not uncommon
for such systems to
confuse words like three and repeat. Speaker-independent
systems, as the name
suggests, do not have this training requirement; they attempt to
accommodate a large
range of speaking characteristics and vocabulary. However, the
problem of individual
variability means that these types of system are less reliable,
or have a smaller
vocabulary than speaker-dependent systems.
The perfect system would be one that would understand natural
speech to such extent
that it could not only distinguish differences in speech
presentation but also have the
intelligence to resolve any conflicts in meaning by interpreting
speech in relation to
the context of the conversation, as a human being does. This is
a deep unsolved
problem in Artificial Intelligence, and progress is likely to be
slow.
13.3 Positioning, Pointing
And Drawing
Pointing devices are input devices that can be used to specify a
point or path in a one-,
two- or three- dimensional space and, like keyboards, their
characteristics have to be
consider in relation to design needs. Pointing devices are as
follow:
. Mouse
. Touch pad
. Track ball
. Joystick
. Touch screen
. Eye gaze
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Mouse
The mouse has become a major component
of the majority of desktop computer systems
sold today, and is the little box with the tail
connecting it to the machine in our basic
computer system picture. It is a small, palmsized
box housing a weighted ball- as the
box is moved on the tabletop, the ball is
rolled by the table and so rotates inside the
housing. This rotation is detected by small rollers that are in
contact with the ball, and
these adjust the values of potentiometers.
The mouse operates in a planar fashion, moving around the
desktop, and is an indirect
input device, since a transformation is required to map from the
horizontal nature of
desktop to the vertical alignment of the screen. Left-right
motion is directly mapped,
whilst up-down on the screen is achieved by moving the mouse
away-towards the
user.
Foot mouse
Although most mice are hand operated, not all are- there have
been experiments with
a device called the footmouse. As the name implies, it is
foot-operated device,
although more akin to an isometric joysticks than a mouse. The
cursor is moved by
foot pressure on one side or the other of pad. This allows one
to dedicate hands to the
keyboard. A rare device, the footmouse has not found common
acceptance.
Touch pad
Touchpads are touch-sensitive tablets
usually around 2-3 inches square. They
were first used extensively in Apple
Powerbook portable computers but are
now used in many other notebook
computers and can be obtained
separately to replace the mouse on the
desktop. They are operated by stroking a finger over their
surface, rather like using a
simulated trackball. The feel is very different from other input
devices, but as with all
devices users quickly get used to the action and become
proficient.
Because they are small it may require several strokes to move
the cursor across the
screen. This can be improved by using acceleration settings in
the software linking the
trackpad movement to the screen movement. Rather than having a
fixed ratio of pad
distance to screen distance, this varies with the speed of
movement. If the finger
moves slowly over the pad then the pad movements map to small
distances on the
screen. If the finger is moving quickly the same distance on the
touchpad moves the
cursor a long distance.
Trackball and thumbwheel
Trackball is really just an upside-down mouse. A weighted ball
faces upwards and is
rotated inside a static housing, the motion being detected in
the same way as for a
mechanical mouse, and the relative motion of the ball moves the
cursor. It is a very
compact device, as it requires no additional space in which to
operate. It is an indirect
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device, and requires separate buttons for selection. It is
fairly accurate, but is hard to
draw with, as long movements are difficult. Trackball now appear
in a wide variety of
sizes, the most usual being about the same as golf ball, with a
number of larger and
smaller devices available.
Thumbwheels are different in that they have two orthogonal dials
to control the cursor
position. Such a device is very cheap, but slow, and it is
difficult to manipulate the
cursor in any way other than horizontally or vertically. This
limitation can sometimes
be a useful constraint in the right application.
Although two-axis thumbwheels are not heavily used in mainstream
applications,
single thumbwheels are often included on a standard mouse in
order to offer an
alternative mean to scroll documents. Normally scrolling
requires you to grab the
scroll bar with the mouse cursor and drag it down. For large
documents it is hard to be
accurate and in addition the mouse dragging is done holding a
finger down which
adds to hand strain. In contrast the small scroll wheel allows
comparatively intuitive
and fast scrolling, simply rotating the wheel to move the page.
Joystick and trackpoint
The joystick is an indirect input device, taking up very little
space. Consisting of a
small palm-sized box with a stick or shaped grip sticking up
form it, the joystick is a
simple device with which movements of the stick cause a
corresponding movement of
the screen cursor. There are two type of joystick: the absolute
and the isometric.
In absolute joystick, movement is the important characteristic,
since the position of
the joystick in the base corresponds to the position of the
cursor on the screen.
In the isometric joystick, the pressure on the stick corresponds
to the velocity of the
cursor, and when released, the stick returns to its usual
upright centered position.
Trackpoint is a smaller device but with the same basic
characteristics is used on many
laptop computers to control the cursor. Some older systems had a
variant of this called
the keymouse, which was a single key. More commonly a small
rubber nipple
projects in the center of keyboard and acts as a tiny isometric
joystick. It is usually
difficult for novice to use, but this seems to be related to
fine adjustment of the speed
settings.
Touch screens
Touch displays allow the user to input information into the
computer simply by
touching an appropriate part of the screen or a touch-sensitive
pad near to the screen.
In this way the screen of the computer becomes a bi-directional
instrument in that it
both receives information from a user and displays output from a
system. Using
appropriate software different parts of a screen can represent
different responses as
different displays are presented to a user. For example, a
system giving directions to
visitors at a large exhibition may first present an overview of
the exhibition layout in
the form of general map. A user may then be requested to touch
the hall that he
wishes to visit and the system will present a list of exhibits.
Having selected the
exhibit of his choice by touching it, the user may then be
presented with a more
detailed map of the chosen hall.
The advantages of touch screens are that they are easy to learn,
require no extra
workplace, have no moving parts and are durable. They can
provide a very direct
interaction. Ease of learning makes them ideal for domains in
which use by a
particular user may occur only once or twice, and users cannot
be expected to spend a
time learning to use the system.
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They suffer from a number of disadvantages, however. Using the
finger to point is not
always suitable, as it can leave greasy marks on screen., and,
being a fairly blunt
instrument, it is quite inaccurate. This means that the
selection of small regions is very
difficult, as is accurate drawing. Moreover, lifting the arm to
point a vertical screen is
very tiring, and also means that the screen has to be within
about a meter of the user
to enable to be reached, which can make it too close for
comfort.
Stylus and light pen
For more accurate positioning, systems with touch-sensitive
surface often employ a
stylus. Instead of pointing at the screen directly, small
pen-like plastic stick is used to
point and draw on the screen. This is particularly popular in
PDAs, but they are also
being used in some laptop computers.
An old technology that is used in the same way is the light pen.
The pen is connected
to the screen by a cable and, in operation, is held to the
screen and detects a burst of
light from the screen phosphor during the display scan. The
light pen can therefore
address individual pixels and so is much more accurate than the
touchscreen.
Eyegaze
Eyegaze systems allow you to control the computer by simply
looking at it. Some
systems require you to wear special glasses or a small
head-mounted box, others are
built into the screen or sit as a small box below the screen. A
low-power laser is shone
into the eye and is reflected off the retinal. The reflection
changes as the angle of the
eye alters, and by tracking the reflected beam the eyegaze
system can determine the
direction in which the eye is looking. The system needs to be
calibrated, typically by
staring at a series of dots on the screen, but thereafter can be
used to move the screen
cursor or for other more specialized uses. Eyegaze is a very
fast and accurate device,
but the more accurate versions can be expensive. It is fine for
selection but not for
drawing since the eye does not move in smooth lines. Also in
real application it can
be difficult to distinguish deliberately gazing at some thing
and accidentally glancing
it.
Cursor keys
Cursor keys are available on most keyboards.
Four keys on the keyboard are used to control
the cursor, one each for up, down, left and
right. There is no standardized layout for the
keys. Some layouts are shown in figure but the
most common now is the inverted ‘T’.
Cursor keys used to be more heavily used in
character-based systems before windows and mice were the norm.
However, when
logging into remote machines such as web servers, the interface
is often a virtual
character-based terminal within a telnet window.
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13.4 Display devices
Cathode ray tube
The cathode ray tube is the television-like
computer screen still most common as we
write this, but rapidly being displaced by flat
LCD screens. It works in a similar way to a
standard television screen. A stream of
electrons is emitted from an electron gun,
which is then focused and directed by
magnetic fields. As the beam hits the
phosphor-coated screen, the phosphor is
excited by the electrons and glows. The
electron beam is scanned from left to right,
and then flicked back to rescan the next line, from top to
bottom.
Black and white screens are able to display grayscale by varying
the intensity of the
electron beam; color is achieved using more complex means. Three
electron guns are
used, one each to hit red, green and blue phosphors. Combining
these colors can
produce many others, including white, when they are all fully
on. These three
phosphor dots are focused to make a single point using a shadow
mask, which is
imprecise and gives color screens a lower resolution than
equivalent monochrome
screens.
The CRT is a cheap display device and has fast enough response
times for rapid
animation coupled with a high color capability. Note that
animation does not
necessarily means little creatures and figures running about on
the screen, but refers in
a more general sense to the use of motion in displays: moving
the cursor, opening
windows, indicating processor-intensive calculations, or
whatever. As screen
resolution increased, however, the price rises. Because of the
electron gun and
focusing components behind the screen, CRTs are fairly bulky,
though recent
innovations have led to flatter displays in which the electron
gun is not placed so that
it fires directly at the screen, but fires parallel to the
screen plane with the resulting
beam bent through 90 degrees to his the screen.
Liquid Crystal Display
Liquid Crystal Displays are mostly used in personal organizer or
laptop computers. It
is a light, flat plastic screen. These displays utilize liquid
crystal technology and are
smaller, lighter and consume far less power than traditional
CRTs. These are also
commonly referred to as flat-panel displays. They have no
radiation problems
associated with them, and are matrix addressable, which means
that individual pixels
can be accessed without the need for scanning.
This different technology can be used to replace the standard
screen on a desktop
computer, and this is now common. However, the particular
characteristics of
compactness, lightweight, and low power consumption have meant
that these screens
have created a large niche in the computer market by
monopolizing the notebook and
portable computer systems side.
electron gun
focussing and
deflection
electron beam
phosphorcoated
screen
122
Digital paper
A new form of display that is still in its infancy is the
various forms of digital papers.
These are thin flexible materials that can be written to
electronically, just like a
computer screen, but which keep their contents even when removed
from any
electrical supply.
Physical controls and sensors
Sound output
Another mode of output that we should consider is that of
auditory signals. Often
designed to be used in conjunction with screen displays,
auditory outputs are poorly
understood: we do not yet know how to utilize sound in a
sensible way to achieve
maximum effect and information transference. Sounds like beeps,
bongs, clanks,
whistles and whirrs are all used for varying effect. As well as
conveying system
output, sounds offer an important level of feedback in
interactive systems. Keyboards
can be set to emit a click each time a key is pressed, and this
appears to speed up
interactive performance. Telephone keypads often sound different
tones when the
keys are pressed; a noise occurring signifies that the key has
been successfully
pressed, whilst the actual tone provides some information about
the particular key that
was pressed.
13.5 Touch, feel and smell
Sense of touch and feel is also used for feedback; tactile
feedback has its own
importance and is being used in many interactive devices. We
usually feel textures
when we move our fingers over a surface. Technology for this is
just beginning to
become available.
13.6 Physical controls
A desktop computer has to serve many functions and do has
generic keys and controls
that can be used for a variety of purpose. In contrast, these
dedicated controls panes
have been designed for a particular device and for a single use.
This is why they differ
so much.
Usually microwave a flat plastic control panel. The reason is
this, the microwave is
used in the kitchen whilst cooking, with hands that may be
greasy or have food on
them. The smooth controls have no gaps where food can accumulate
and clog buttons,
so it can easily be kept clean an hygienic.
When using the washing machine you are handling dirty clothes,
which may be
grubby, but not to the same extent, so the smooth easy-clean
panel is less important. It
has several major settings and the large buttons act both as
control and display.
13.7 Environment and bio
sensing
Although we are not always conscious of them, there are many
sensors in our
environment—controlling automatic doors, energy saving lights,
etc. and devices
monitoring our behavior such as security tags in shops. The
vision of ubiquitous
computing suggests that our world will be filled with such
devices. |
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