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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

. 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

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:


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
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

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.

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
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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

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

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


. 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



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

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

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

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.

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 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

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.


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
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
electron beam


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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