THE COMPUTER: INPUT DEVICES, TEXT ENTRY DEVICES, POSITIONING, POINTING AND DRAWING

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Human Computer Interaction (CS408)

Lecture

Lecture 13. The Computer

Learning Goals

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.

Input devices

13.1

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.

Text entry devices

13.2

There are many text entry devices as given below:

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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2 3 45 6

890

x bmwv

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 human-

computer interaction! With the recent increase of repetitive strain injury (RSI) to

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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 left-

handed 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.

Positioning, Pointing And Drawing

13.3

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, palm-

sized 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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Display devices

13.4

Cathode ray tube

electron beam

The cathode ray tube is the television-like

computer screen still most common as we electron gun

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,

focussing and

which is then focused and directed by

deflection

magnetic fields. As the beam hits the

phosphor-coated screen, the phosphor is

phosphor-

excited by the electrons and glows. The

coated screen

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.

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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.

Touch, feel and smell

13.5

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.

Physical controls

13.6

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.

Environment and bio sensing

13.7

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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