UNIT-1 FOUNDATIONS OF HCI

The Human: I/O channels – Memory – Reasoning and problem solving; The computer:
Devices – Memory – processing and networks; Interaction: Models – frameworks –
Ergonomics – styles – elements – interactivity- Paradigms.

SHORT ANSWERS

1) What is Human Computer Interaction?

Human computer interaction (HCI), alternatively man machine interaction (MMI) or
computer human interaction (CHI) is the study of interaction between people (users) and
computers. ―Human-computer interaction is a discipline concerned with the design,
evaluation and implementation of interactive computing systems for human use and with the
study of major phenomena surrounding them‖.

2) Elaborate the goals and purpose of HCI

A basic goal of HCI is to improve the interactions between users and computers by
making computers more usable and receptive to the user's needs.

A long term goal of HCI is to design systems that minimize the barrier between the
human's cognitive model of what they want to accomplish and the computer's understanding
of the user's task.

3) Why is HCI important?

 User-centred design is getting a crucial role.

 It is getting more important today to increase competitiveness via HCI studies
(Norman,
1990).
 High-cost e-transformation investments.
 Users lose time with badly designed products and services.
 Users even give up using bad interface – Ineffective allocation of resources.

4) Define User Interface.

User interface, design is a subset of a field of study called human-computer
interaction (HCI). Human-computer interaction is the study, planning, and design of how
people and computers work together so that a person's needs are satisfied in the most effective
way.

5) List out the factors that the HCI designers must consider.

 what people want and expect, physical limitations and abilities people possess,
 How information processing systems work, and what people find enjoyable and
attractive.
 Technical characteristics and limitations of the computer hardware and software must
also be considered.
6) Mention the essential components of user interface
Input Channel is how a person communicates his / her needs to the computer.
-Some common input components are the keyboard, mouse, trackball, one's finger, and one's
voice.
Output Channel is how the computer conveys the results of its computations and
requirements to the user.
–Today, the most common computer output mechanism is the display screen, followed by
mechanisms that take advantage of a person's auditory capabilities: voice and sound.

7) Define problem solving. Brief problem space theory

The Process of finding solution to unfamiliar task using knowledge.

Problem space theory

 problem space comprises problem states

 problem solving involves generating states using legal operators
 heuristics may be employed to select operators
e.g. means-ends analysis
 Operates within human information processing system
e.g. STM limits etc.
 Largely applied to problem solving in well-defined areas
e.g. puzzles rather than knowledge intensive areas.

8) Mention the ways in which the information stored in memory

There are three types of memory function: Sensory memories, Short-term memory
or working memory, Long-term memory. Selection of stimuli governed by level of arousal.

9) Brief Long Term Memory

 Repository for all our knowledge

 slow access ~ 1/10 second
 slow decay, if any
 huge or unlimited capacity
 Two types
 episodic – serial memory of events
 Semantic – structured memory of facts, concepts, skills.
 Semantic LTM derived from episodic LTM.

10) Explain different types of Reasoning with example.

 Deductive Reasoning
– derive logically necessary conclusion from given premises.
e.g. If it is Friday then she will go to work
It is Friday
Therefore she will go to work.
 Inductive Reasoning
– generalize from cases seen to cases unseen
– e.g. all elephants we have seen have trunks
therefore all elephants have trunks.
  Unreliable:
 - can only prove false not true… but useful!
 Humans not good at using negative evidence
e.g. Wason's cards.

 Abductive Reasoning
- reasoning from event to cause
e.g. Sam drives fast when drunk.
If I see Sam driving fast, assume drunk.
- Unreliable: can lead to false explanations.

11) Define Interaction and list out the different models of interaction.
Interaction may be defined as the communication between user and system. The various
models of interaction are Donald Norman‘s model, Abowd and Beale framework.

12) Mention the stages in Donald Norman’s model.

• Norman‘s model concentrates on user‘s view of the interface

• Seven stages
• user establishes the goal
• formulates intention
• specifies actions at interface
• executes action
• perceives system state
• interprets system state
• evaluates system state with respect to goal

13) What are the uses of Abowd and Beale’s Framework?

 translated into actions at the interface

 translated into alterations of system state
 reflected in the output display
 interpreted by the user

14) Demonstrate the general framework for understanding interaction.

 not restricted to electronic computer systems

 identifies all major components involved in interaction
 allows comparative assessment of systems
 an abstraction

15) Explain Ergonomics with examples

 Study of the physical characteristics of interaction

 Also known as human factors.
 Ergonomics good at defining standards and guidelines for constraining the way
we design certain aspects of systems.
Examples:
  arrangement of controls and displays
e.g. controls grouped according to function or frequency of use, or sequentially
 surrounding environment
e.g. seating arrangements adaptable to cope with all sizes of user
 health issues
e.g. physical position, environmental conditions (temperature, humidity), lighting,
noise,
 use of colour
e.g. use of red for warning, green for okay,
awareness of colour-blindness etc.

16) List out some common interaction styles.

 command line interface

 menus
 natural language
 question/answer and query dialogue
 form-fills and spreadsheets
 WIMP
 point and click
 three–dimensional interfaces

17) Mention some of the WIMP interfaces.

windows, icons, menus, pointers, buttons, toolbars, palettes, dialog boxes.

18) Explain paradigms of interactions with examples.

Predominant theoretical frameworks or scientific world views. e.g., Aristotelian,
Newtonian, Einsteinian (relativistic) paradigms in physics

New computing technologies arrive, creating a new perception of the

human—computer relationship. We can trace some of these shifts in the history of interactive
technologies. Examples are

• Batch processing
• Timesharing
• Networking
• Graphical display
• Microprocessor
• WWW
• Ubiquitous Computing

19) What is meant by dialogue boxes?

Information windows that pop up to inform of an important event or request information.
e.g: when saving a file, a dialogue box is displayed to allow the user to specify the filename and
location. Once the file is saved, the box disappears.

20) List out different types of text entry devices.

 keyboards (QWERTY et al.)

 chord keyboards, phone pads
 handwriting, speech
DETAIL ANSWERS

1. Give a detailed comparison of the human and computer’s memory.

1. Memory
Memory is the second part of our model of the human as an information processing system. Memory
is associated with each level of processing. It is generally agreed that there are three types of memory
or memory function: sensory buffers, short-term memory or working memory, and long-term
memory. These memories interact, with information being processed and passed between memory
stores.

2.1 Sensory memory

The sensory memories act as buffers for stimuli received through the senses. A sensory memory exists
for each sensory channel: iconic memory for visual stimuli, echoic memory for aural stimuli and
haptic memory for touch. These memories are constantly overwritten by new information coming in
on these channels.
2.2 Short-term memory
Short-term memory or working memory acts as a ‗scratch-pad‘ for temporary recall of information. It
is used to store information which is only required fleetingly. Short-term memory can be accessed
rapidly, in the order of 70 ms. However, it also decays rapidly, meaning that information can only be
held there temporarily, in the order of 200 ms. Short-term memory also has a limited capacity. In
experiments where subjects were able to recall words freely, evidence shows that recall of the last
words presented is better than recall of those in the middle. This is known as the recency effect.
However, if the subject is asked to perform another task between presentation and recall (for example,
counting backwards) the recency effect is eliminated. The recall of the other words is unaffected. This
suggests that short-term memory recall is damaged by interference of other information. However, the
fact that this interference does not affect recall of earlier items provides some evidence for the
existence of separate long-term and short-term memories. The early items are held in a long-term
store which is unaffected by the recency effect. Interference does not necessarily impair recall in
short-term memory. Short-term memory is not a unitary system but is made up of a number of
components, including a visual channel and an articulatory channel. The task of sentence processing
used the visual channel, while the task of remembering digits used the articulatory channel, so
interference only occurs if tasks utilize the same channel. These findings led Baddeley to propose a
model of working memory that incorporated a number of elements together with a central processing
executive
2.3 Long-term memory
If short-term memory is our working memory or ‗scratch-pad‘, long-term memory is our main
resource. Here we store factual information, experiential knowledge, procedural rules of behaviour –
in fact, everything that we ‗know‘. It differs from short-term memory in a number of significant ways.
First, it has a huge, if not unlimited, capacity. Secondly, it has a relatively slow access time of
approximately a tenth of a second. Thirdly, forgetting occurs more slowly in long-term memory, if at
all. These distinctions provide further evidence of a memory structure with several parts. Long-term
memory is intended for the long-term storage of information. Information is placed there from
working memory through rehearsal. Unlike working memory there is little decay: long-term recall
after minutes is the same as that after hours or days.
Long-term memory structure
There are two types of long-term memory: episodic memory and semantic memory.
Episodic memory represents our memory of events and experiences in a serial form.
It is from this memory that we can reconstruct the actual events that took place at a
given point in our lives. Semantic memory, on the other hand, is a structured record of facts, concepts
and skills that we have acquired. The information in semantic memory is derived from that in our
episodic memory, such that we can learn new facts or concepts from our experiences. Semantic
memory is structured in some way to allow access to information, representation of relationships
between pieces of information, and inference. One model for the way in which semantic memory is
structured is as a network.
Items are associated to each other in classes, and may inherit attributes from parent classes. This
model is known as a semantic network. There are connections within the network which link into
other domains of knowledge, for example cartoon characters. This illustrates how our knowledge is
organized by association.
Long-term memory processes
There are three main activities related to long-term memory:
 Storage or remembering of information
 Forgetting
 Information retrieval.
Storage or remembering of information :
Information from short-term memory is stored in long-term memory by rehearsal. The repeated
exposure to a stimulus or the rehearsal of a piece of information transfers it into long-term memory.
This process can be optimized in a number of ways. Ebbinghaus performed numerous experiments on
memory. In these experiments he tested his ability to learn and repeat nonsense syllables, comparing
his recall minutes, hours and days after the learning process. He discovered that the amount learned
was directly proportional to the amount of time spent learning. This is known as the total time
hypothesis. However, experiments by Baddeley and others suggest that learning time is most effective
if it is distributed over time. This is known as the distribution of practice effect. The second theory is
that information is lost from memory through interference. If we acquire new information it causes
the loss of old information. This is termed Retroactive interference. Sometimes the old memory trace
breaks through and interferes with new information. This is called proactive inhibition.
Forgetting: Forgetting is also affected by emotional factors. In experiments, subjects given emotive
words and non-emotive words found the former harder to remember in the short term but easier in the
long term. Indeed, this observation tallies with our experience of selective memory. We tend to
remember positive information rather than negative and highly emotive events rather than mundane. It
is debatable whether we ever actually forget anything or whether it just becomes increasingly
difficult to access certain items from memory. There is evidence to suggest that we may not lose
information completely from long-term memory. First, proactive inhibition demonstrates the recovery
of old information even after it has been ‗lost‘ by interference. Secondly, there is the ‗tip of the
tongue‘ experience, which indicates that some information is present but cannot be satisfactorily
accessed.
Information Retrieval: Thirdly, information may not be recalled but may be recognized, or may be
recalled only with prompting. This leads us to the third process of memory: information retrieval.
Here we need to distinguish between two types of information retrieval, recall and recognition. In
recall the information is reproduced from memory. In recognition, the presentation of the information
provides the knowledge that the information has been seen before. Recognition is the less complex
cognitive activity since the information is provided as a cue.

2. COMPUTER MEMORY
Like human memory, we can think of the computer‘s memory as operating at different levels, with
those that have the faster access typically having less capacity. The different levels of computer
memory are more commonly called primary and secondary storage. The details of computer memory
are not in themselves of direct interest to the user interface designer.
2.1 RAM and short-term memory (STM)
At the lowest level of computer memory are the registers on the computer chip, but these have little
impact on the user except in so far as they affect the general speed of the computer. Most currently
active information is held in silicon-chip random access memory (RAM). Different forms of RAM
differ as to their precise access times, power consumption and characteristics. Typical access times
are of the order of 10 nanoseconds, that is a hundred-millionth of a second, and information can be
accessed at a rate of around 100 Mbytes (million bytes) per second. Typical storage in modern
personal computers is between 64 and 256 Mbytes. Most RAM is volatile, that is its contents are lost
when the power is turned off. However, many computers have small amount of non-volatile RAM,
which retains its contents, perhaps with the aid of a small battery. This may be used to store setup
information in a large computer. Non-volatile RAM is more expensive so is only used where
necessary. Some also use flash memory, which is a form of silicon memory that sits between fixed
content ROM (read-only memory) chips and normal RAM. Flash memory is relatively slow to write,
but once written retains its content even with no power whatsoever.
2.2 Disks and long-term memory (LTM)
For most computer users the LTM consists of disks, possibly with small tapes for backup. The
existence of backups, and appropriate software to generate and retrieve them, is an important area for
user security. There are two main kinds of technology used in disks: magnetic disks and optical disks.
The most common storage media, floppy disks and hard (or fixed) disks, are coated with magnetic
material, like that found on an audio tape, on which the information is stored. Typical capacities of
floppy disks lie between 300 kbytes and 1.4 Mbytes, but as they are removable, you can have as many
as you have room for on your desk. Hard disks may store from under 40 Mbytes to several gigabytes
(Gbytes), that is several thousand million bytes. Optical disks use laser light to read and (sometimes)
write the information on the disk. There are various high capacity specialist optical devices, but the
most common is the CD-ROM, using the same technology as audio compact discs. CD-ROMs have a
capacity of around 650 megabytes, but cannot be written to at all.
2.4 Compression
Compression techniques can be used to reduce the amount of storage required for text, bitmaps and
video. Huffman encoding gives short codes to frequent words and run length encoding represents long
runs of the same value by length value pairs. Text can easily be reduced by a factor of five and
bitmaps often compress to 1% of their original size. For video, in addition to compressing each frame,
we can take advantage of the fact that successive frames are often similar. The decompression of the
image can be performed to any degree of accuracy, from a very rough soft-focus image, to one more
detailed than the original. The former is very useful as one can produce poor-quality output quickly,
and better quality given more time.
2.5 Storage format and standards
The most common data types stored by interactive programs are text and bitmap images, with
increasing use of video and audio.
 The basic standard for text storage is the ASCII character codes, which assign
to each standard printable character and several control characters an internationally recognized.
 With the exception of bare ASCII, the most common shared format is rich
text format (RTF), which encodes formatting information including style sheets.
 Documents can also be regarded as structured objects
There are ISO standards for document structure and interchange, which in theory could be used for
transfer between packages and sites, but these are rarely used in practice.
 Just as the PostScript language is used to describe the printed page, SGML
(standard generalized markup language) can be used to store structured text in a reasonably extensible
way.
2.6 Methods of access
Standard database access is by special key fields with an associated index. The user has to know the
key before the system can find the information. A telephone directory is a good example of this. In
fact, most database systems will allow multiple keys and indices, allowing you to find a record given
partial information. So these problems are avoidable with only slight foresight. Menu-based systems
make this less of an issue, but one can easily imagine doing the same with, say, file selection. Not all
databases allow long passages of text to be stored in records, perhaps setting a maximum length for
text strings, or demanding the length be fixed in advance.

2. Give a note on the thinking and problem solving skills of human being.
Humans are able to use information to reason and solve problems and indeed do these activities when
the information is partial or unavailable. Human thought is conscious and self-aware: while we may
not always be able to identify the processes we use. In addition, we are able to think about things of
which we have no experience, and solve problems which we have never seen before. Thinking can
require different amounts of knowledge. Some thinking activities are much directed and the
knowledge required is constrained. Others require vast amounts of knowledge from different domains
3.1 Reasoning
Reasoning is the process by which we use the knowledge we have to draw conclusions or infer
something new about the domain of interest. There are a number of different types of reasoning:
deductive, inductive and abductive.
 Deductive reasoning: Deductive reasoning derives the logically necessary conclusion from
the given premises.
For example,
If it is Friday then she will go to work
It is Friday
Therefore she will go to work.
It is important to note that this is the logical conclusion from the premises; it does
not necessarily have to correspond to our notion of truth. So, for example,
If it is raining then the ground is dry
It is raining
Therefore the ground is dry.
is a perfectly valid deduction, even though it conflicts with our knowledge of what is true in the
world.
Deductive reasoning is therefore often misapplied. We assume a certain amount of shared knowledge
in our dealings with each other, which in turn allows us to interpret the inferences and deductions
implied by others. If validity rather than truth was preferred, all premises would have to be made
explicit.
 Inductive reasoning: Induction is generalizing from cases we have seen to infer information
about cases we have not seen. In spite of its unreliability, induction is a useful process, which we use
constantly in learning about our environment. In an experiment first devised by Wason. You are
presented with four cards. Each card has a number on one side and a letter on the other. Which cards
would you need to pick up to test the truth of the statement ‗If a card has a vowel on one side it has an
even number on the other‘? A common response to this is to check the E and the 4. However, this
uses only positive evidence. In fact, to test the truth of the statement we need to check negative
evidence: if we can find a card which has an odd number on one side and a vowel on the other we
have disproved the statement. We must therefore check E and 7. (It does not matter what is on the
other side of the other cards: the statement does not say that all even numbers have vowels, just that
all vowels have even numbers.)

 Abductive reasoning
The third type of reasoning is abduction. Abduction reasons from a fact to the action or state that
caused it. This is the method we use to derive explanations for the events. In spite of its unreliability,
it is clear that people do infer explanations in this way, and hold onto them until they have evidence to
support an alternative theory or explanation. This can lead to problems in using interactive systems. If
an event always follows an action, the user will infer that the event is caused by the action unless
evidence to the contrary is made available. If, in fact, the event and the action are unrelated, confusion
and even error often result.

3.2 Problem solving

If reasoning is a means of inferring new information from what is already known, problem solving is
the process of finding a solution to an unfamiliar task, using the knowledge we have. Human problem
solving is characterized by the ability to adapt the information we have to deal with new situations.
However, often solutions seem to be original and creative. There are a number of different views of
how people solve problems.
Gestalt view: The earliest, dating back to the first half of the twentieth century, is the Gestalt view
that problem solving involves both reuse of knowledge and insight. This has been largely superseded
but the questions it was trying to address remain and its influence can be seen in later research. They
claimed, problem solving is both productive and reproductive.
Reproductive problem solving draws on previous experience as the behaviorists claimed, but
productive problem solving involves insight and restructuring of the problem. Although Gestalt theory
is attractive in terms of its description of human problem solving, it does not provide sufficient
evidence or structure to support its theories. It does not explain when restructuring occurs or what
insight is, for example. However, the move away from behaviorist theories was helpful in paving the
way for the information-processing theory that was to follow.
Problem Space Theory: A second major theory, proposed in the 1970s by Newell and Simon, was
the problem space theory, which takes the view that the mind is a limited information processor. Later
variations on this drew on the earlier theory and attempted to reinterpret Gestalt theory in terms of
information processing theories. Newell and Simon proposed that problem solving centers on the
problem space. The problem space comprises problem states, and problem solving involves
generating these states using legal state transition operators. The problem has an initial state and a
goal state and people use the operators to move from the former to the latter. Such problem spaces
may be huge, and so heuristics are employed to select appropriate operators to reach the goal. One
such heuristic is means–ends analysis. In means–ends analysis the initial state is compared with the
goal state and an operator chosen to reduce the difference between the two. An important feature of
Newell and Simon‘s model is that it operates within the constraints of the human processing system,
and so searching the problem space is limited by the capacity of short-term memory, and the speed at
which information can be retrieved. Within the problem space framework, experience allows us to
solve problems more easily since we can structure the problem space appropriately and choose
operators efficiently. Newell and Simon‘s theory, and their General Problem Solver model which is
based on it, have largely been applied to problem solving in well-defined domains.

3.3 Skill acquisition

The entire problem solving that we have considered so far has concentrated on handling unfamiliar
problems. However, for much of the time, the problems that we face are not completely new. Instead,
we gradually acquire skill in a particular domain area.
Skill Acquisition Models:
ACT Model: One model of skill acquisition is Anderson‘s ACT model. ACT identifies three basic
levels of skill:
1. The learner uses general-purpose rules which interpret facts about a problem.
This is slow and demanding on memory access.
2. The learner develops rules specific to the task.
3. The rules are tuned to speed up performance.
General mechanisms are provided to account for the transitions between these
levels.
Proceduralization is a mechanism to move from the first to the second. It removes the parts of the rule
which demand memory access and replaces variables with specific values.
Generalization, on the other hand, is a mechanism which moves from the second level to the third. It
generalizes from the specific cases to general properties of those cases. Commonalities between rules
are condensed to produce a general-purpose rule. Initially you may have a general rule to tell you how
long a dish needs to be in the oven and a number of explicit representations of dishes in memory. You
can instantiate the rule by retrieving information from memory.
IF cook[type, ingredients, time]
THEN
cook for: time
cook[casserole, [chicken,carrots,potatoes], 2 hours]
cook[casserole, [beef,dumplings,carrots], 2 hours]
cook[cake, [flour,sugar,butter,eggs], 45 mins]
Gradually your knowledge becomes proceduralized and you have specific rules for each case:
IF type is casserole
AND ingredients are [chicken,carrots,potatoes]
THEN
cook for: 2 hours
IF type is casserole
AND ingredients are [beef,dumplings,carrots]
THEN
cook for: 2 hours
IF type is cake
AND ingredients are [flour,sugar,butter,eggs]
THEN
cook for: 45 mins
Finally, you may generalize from these rules to produce general-purpose rules, which exploit their
commonalities:
IF type is casserole
AND ingredients are ANYTHING
 THEN
cook for: 2 hours
The first stage uses knowledge extensively. The second stage relies upon known procedures. The third
stage represents skilled behavior. Such behavior may in fact become automatic and as such be
difficult to make explicit. For example, think of an activity at which you are skilled, perhaps driving a
car or riding a bike. Try to describe to someone the exact procedure which you go through to do this.
You will find this quite difficult. In fact experts tend to have to rehearse their actions mentally in
order to identify exactly what they do. Such skilled behavior is efficient but may cause errors when
the context of the activity changes.

3.4 Errors and mental models

Human capability for interpreting and manipulating information is quite impressive. However, we do
make mistakes. Some are trivial, resulting in no more than temporary inconvenience or annoyance.
Others may be more serious, requiring substantial effort to correct. Occasionally an error may have
catastrophic effects, as we see when ‗human error‘ results in a plane crash or nuclear plant leak.
Avoiding mistakes: There are several different types of error
 If a pattern of behavior has become automatic and we change some aspect of it, the more
familiar pattern may break through and cause an error.
 Other errors result from an incorrect understanding, or model, of a situation or system.
Mental Models:
People build their own theories to understand the causal behavior of systems.
These have been termed mental models. They have a number of characteristics.
Mental models are often partial: the person does not have a full understanding of the working of the
whole system. They are unstable and are subject to change. They can be internally inconsistent, since
the person may not have worked through the logical consequences of their beliefs. They are often
unscientific and may be based on superstition rather than evidence. Often they are based on an
incorrect interpretation of the evidence.

3. Explain the various devices available and also point out their significant
features.

1.1 Text Entry Devices

The most obvious means of text entry is the plain keyboard
1.1.1 The alphanumeric keyboard
The keyboard is still one of the most common input devices in use today used for entering textual data
and commands. The vast majority of keyboards have a standardized layout and are known by the first
six letters of the top row of alphabetical keys, QWERTY. These are of two forms: 26 key layouts and
chord keyboards.
26 key layout: A 26 key layout rearranges the order of the alphabetic keys, putting the most
commonly used letters under the strongest fingers, or adopting simpler practices. Examples of 26 key
layout are QWERTY, alphabetic and DVORAK. The QWERTY keyboard‗s layout of the digits and
letters is fixed but non-alphanumeric keys vary between keyboards. There is a difference between key
assignments on British and American keyboards. The standard layout is also subject to variation in the
placement of brackets, backslashes and suchlike. In addition different national keyboards include
accented letters and the traditional French layout places the main letters in different locations – the top
line starts AZERTY.
The QWERTY arrangement of keys is not optimal for typing, however. The reason for the layout of
the keyboard in this fashion can be traced back to the days of mechanical typewriters. Hitting a key
caused an arm to shoot towards the carriage, imprinting the letter on the head on the ribbon and hence
onto the paper. If two arms flew towards the paper in quick succession from nearly the same angle,
they would often jam – the solution to this was to set out the keys so that common
combinations of consecutive letters were placed at different ends of the keyboard, which meant that
the arms would usually move from alternate sides The electric typewriter and now the computer
keyboard are not subject to the original mechanical constraints, but the QWERTY keyboard remains
the dominant There is also a large investment in current keyboards, which would all have to be either
replaced at great cost, or phased out, with the subsequent requirement for people to be proficient on
both keyboards.
Chord keyboards Chord keyboards are significantly different from normal alphanumeric
keyboards.Only a few keys, four or five, are used and letters are produced by pressing one or more of
the keys at once. Such keyboards have a number of advantages. They are extremely compact and the
learning time for the keyboard is supposed to be fairly short . Moreover, they are capable of fast
typing speeds in the hands of a competent user. Chord keyboards can also be used where only one-
handed operation is possible, in cramped and confined conditions.

1.1.2 Phone pad and T9 entry

With mobile phones being used for SMS text messaging and WAP. 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 Most phones have at least two modes for the numeric buttons: one
where the keys mean the digits and one where they mean letters. Some have additional modes to make
entering accented characters easier. Also a special mode or setting is needed
1.1.3 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 handwriting recognition. Pen-based
systems that use handwriting recognition are actively marketed 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.
1.1.4 Speech recognition
Speech recognition is a promising area of text entry, but it has been promising for a number of years
and is still only used in very limited situations. There is a natural enthusiasm for being able to talk to
the machine and have it respond to commands, since this form of interaction is one with which we are
very familiar. Successful recognition rates of over 97% have been reported.

1.2 POSITIONING, POINTING AND DRAWING

Pointing devices allow the user to point, position and select items, either directly or by manipulating a
pointer on the screen. The mouse is still most common for desktop computers, but is facing challenges
as laptop and handheld computing increase their market share.
1.2.1 The mouse
The mouse is a major component of desktop computer systems sold today, and is the little box with
the tail connecting it to the machine. It is a small, palm-sized box housing a weighted ball – as the box
is moved over 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 relative motion information is passed to the computer via a wire attached to the
box, or in some cases using wireless or infrared, and moves a pointer on the screen, called the cursor.
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 a foot-operated device
1.2.2 Touchpad
Touchpads are touch-sensitive tablets usually around 2–3 inches square. 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.
1.2.3 Optical mice
Optical mice work differently from mechanical mice. A light-emitting diode emits a weak red light
from the base of the mouse. This is reflected off a special pad with a metallic grid-like pattern upon
which the mouse has to sit, and the fluctuations in reflected intensity as the mouse is moved over the
gridlines are recorded by a sensor in the base of the mouse and translated into elative x, y motion.
Some optical mice do not require special mats, just an appropriate surface, and use the natural texture
of the surface to detect movement. The optical mouse is less susceptible to dust and dirt than the
mechanical one
1.2.4 Trackball and thumbwheel
The 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. Because of this, the trackball requires no additional space
in which to operate, and is therefore a very compact device. 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.
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.
1.2.5 Joystick and keyboard nipple
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 from it, the joystick is a simple device with which
movements of the stick cause a corresponding movement of the screen cursor. There are two types of
joystick: the absolute and the isometric. In the 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.

1.2.6 Touch-sensitive screens (touchscreens)

Touchscreens are another method of allowing the user to point and select objects on the screen, much
more direct than the mouse, as they detect the presence of the user‘s finger, or a stylus, on the screen
itself. They work in one of a number of different ways: by the finger (or stylus) interrupting a matrix
of light beams, or by capacitance changes on a grid overlaying the screen, or by ultrasonic reflections.
Because the user indicates exactly which item is required by pointing to it, no mapping is required and
therefore this is a direct device. The touchscreen is very fast, and requires no specialized pointing
device. It is especially good for selecting items from menus displayed on the screen

1.2.7 Stylus and light pen

For more accurate positioning (and to avoid greasy screens), systems with touchsensitive surfaces
often emply a stylus. Instead of pointing at the screen directly a 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 older 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.

1.2.8 Digitizing tablet

The digitizing tablet is a more specialized device typically used for freehand drawing, but may also be
used as a mouse substitute. Some highly accurate tablets, usually using a puck (a mouse-like device),
are used in special applications such as digitizing information for maps. The tablet provides positional
information by measuring the position of some device on a special pad, or tablet, and can work in a
number of ways. The resistive tablet detects point contact between two separated conducting sheets. It
has advantages in that it can be operated without a specialized stylus – a pen or the user‘s finger is
sufficient. The magnetic tablet detects current pulses in a magnetic field using a small loop coil
housed in a special pen. There are also capacitative and electrostatic tablets that work in a similar
way. The sonic tablet is similar to the above but requires no special surface. An ultrasonic pulse is
emitted by a special pen which is detected by two or more microphones which then triangulate the pen
position.

1.2.9 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 retina. The reflection changes as the angle of the eye alters, and by tracking the
reflected beam the eyegaze system can determine thedirection in which the eye is looking. The system
needs to be calibrated, typically bystaring 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.

1.2.10 Cursor keys and discrete positioning

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. Small devices such as mobile phones, personal entertainment and television remote controls
often require discrete control, either dedicated to a particular function such as volume, or for use as
general menu selection.

1.3 Display Devices

1.3.1 Cathode ray tube
The cathode ray tube is the television-like computer screen that works in a similar way to a standard
television screen. A stream of electrons is emitted from an electron gun, which is then focussed 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. This is repeated at about 30 Hz per frame, although higher
scan rates are sometimes used to reduce the flicker on the screen. Another way of reducing flicker is
to use interlacing in which the odd lines on the screen are all scanned first, followed by the even lines.
Using a high-persistence phosphor, which glows for a longer time when excited, also reduces flicker,
but causes image smearing especially if there is significant animation. 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 focussed to make a single point using a shadow mask, which is imprecise and
gives color screens a lower resolution than equivalent monochrome screens.An alternative approach
to producing color on the screen is to use beam penetration. A special phosphor glows a different
color depending on the intensity of the beam hitting it.

1.3.2 Liquid crystal display

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. Similar in principle to the digital watch, a thin
layer of liquid crystal is sandwiched between two glass plates. The top plate is transparent and
polarized, whilst the bottom plate is reflective. External light passes through the top plate and is
polarized, which means that it only oscillates in one direction. This then passes through the crystal,
reflects off the bottom plate and back to the eye, and so that cell looks white. When a voltage is
applied to the crystal, via the conducting glass plates, the crystal twists. This causes it to turn the plane
of polarization of the incoming light, rotating it so that it cannot return through the top plate, making
the activated cell look black.The LCD requires refreshing at the usual rates, but the relatively slow
response of the crystal means that flicker is not usually noticeable.

1.3.3 Special displays

There are a number of other display technologies used in niche markets The random scan display, also
known as the directed beam refresh, or vector display, works differently from the bitmap display, also
known as raster scan. Instead of scanning the whole screen sequentially and horizontally, the random
scan draws the lines to be displayed directly. By updating the screen at at least 30 Hz to reduce
flicker, the direct drawing of lines at any angle means that jaggies are not created, and higher
resolutions are possible, up to 4096 × 4096 pixels. Color on such displays is achieved using beam
penetration technology, and is generally of a poorer quality. The direct view storage tube is used
extensively as the display for an analog storage oscilloscope, which is probably the only place that
these displays are used in any great numbers.

1.3.4 Large displays and situated displays

There are several types of large screen display. Some use gas plasma technology to create large flat
bitmap displays. These behave just like a normal screen except they are big and usually have the
HDTV (high definition television) wide screen format which has an aspect ratio of 16:9 instead of the
4:3 on traditional TV and monitors. Where very large screen areas are required, several smaller
screens, either LCD or CRT, can be placed together in a video wall. These can display separate
images, or a single TV or computer image can be split up by software or hardware so that each screen
displays a portion of the whole and the result is an enormous image. This is the technique often used
in large concerts to display the artists or video images during the performance. For lectures and
meetings, display screens can be used in various public places to offer information, link spaces or act
as message areas. These are often called situated displays as they take their meaning from the location
in which they are situated. These may be large screens where several people are expected to view or
interact simultaneously, or they may be very small.

1.3.5 Digital paper

A new form of ‗display‘ that is still in its infancy is the various forms of digital paper. 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. There are various technologies being
investigated for this. One involves the whole surface being covered with tiny spheres, black one side,
white the other. Electronics embedded into the material allow each tiny sphere to be rotated to make it
black or white. When the electronic signal is removed the ball stays in its last orientation. A different
technique has tiny tubes laid side by side. In each tube is light-absorbing liquid and a small reflective
sphere. The sphere can be made to move to the top surface or away from it making the pixel white or
black. Again the sphere stays in its last position once the electronic signal is removed.
1.4 Devices For Virtual Reality and 3D Interaction
1.4.1 Positioning in 3D space
Virtual reality systems present a 3D virtual world. Users need to navigate through these spaces and
manipulate the virtual objects they find there. The move from mice to 3D devices usually involves a
change from two degrees of freedom to six degrees of freedom, not just three.
 Cockpit and virtual controls Helicopter and aircraft pilots already have to
navigate in real space. Many arcade games and also more serious applications use controls modeled
on an aircraft cockpit to ‗fly‘ through virtual space. However, helicopter pilots are very skilled and it
takes a lot of practice for users to be able to work easily in such environments. In many PC games and
desktop virtual reality the controls are themselves virtual. This may be a simulated form of the cockpit
controls or more prosaic up/down left/right buttons.
 The 3D mouse There are a variety of devices that act as 3D versions of a mouse.
Rather than just moving the mouse on a tabletop, you can pick it up, move it in three dimensions,
rotate the mouse and tip it forward and backward. The 3D mouse has a full six degrees of freedom as
its position can be tracked (three degrees), and also its up/down angle (called pitch), its left/right
orientation (called yaw) and the amount it is twisted abou its own axis (called roll)

 Data glove One of the mainstays of high-end VR the dataglove is a 3D input

device. Consisting of a lycra glove with optical fibers laid along the fingers, it detects the joint angles
of the fingers and thumb. As the fingers are bent, the fiber ptic cable bends too; increasing bend
causes more light to leak from the fiber, and the reduction in intensity is detected by the glove and
related to the degree of bend in the joint. Attached to the top of the glove are two sensors that use
ultrasound to determine 3D positional information as well as the angle of roll, that is the degree of
wrist rotation. people, but cost remains the limiting factor at present.The dataglove has the advantage
that it is very easy to use and is potentially very powerful and expressive.
 Virtual reality helmets The helmets or goggles worn in some VR systems
have two purposes: (i) they display the 3D world to each eye and (ii) they allow the user‘s head
position to be tracked.
 Whole-body tracking Some VR systems aim to be immersive, that is to make
the users feel as if they are really in the virtual world. In the real world it is possible. The user can
literally surf through virtual space. In the extreme the movement of the whole body may be tracked
using devices similar to the data glove, or using image-processing techniques.

1.4.2 Simulators and VR caves

In motorbike or skiing simulators in video arcades large screens are positioned to fill the main part of
your visual field. You can still look over your shoulder and see your friends, but while you are
engaged in the game it surrounds you. More general-purpose rooms called caves have large displays
positioned all around the user, or several back projectors. In these systems the user can look all around
and see the virtual world surrounding them.
1.5 Physical Controls, Sensors And Special Devices
1.5.1 Special displays
Apart from the CRT screen there are a number of visual outputs utilized in complex systems,
especially in embedded systems. These can take the form of analog representations of numerical
values, such as dials, gauges or lights to signify a certain system state. One visual display that has
found a specialized niche is the head-up display that is used in aircraft. The pilot is fully occupied
looking forward and finds it difficult to look around the cockpit to get information.
1.5.2 Sound output
Another mode of output that we should consider is that of auditory signals. 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.
1.5.3 Touch, feel and smell
In some VR applications, such as the use in medical domains to ‗practice‘ surgical procedures, the
feel of an instrument moving through different tissue types is very important. The devices used to
emulate these procedures have force feedback, giving different amounts of resistance depending on
the state of the virtual operation. These various forms of force, resistance and texture that influence
our physical senses are called haptic devices. Haptic devices are not limited to virtual environments,
but are used in specialist interfaces in the real world too. Electronic braille displays either have pins
that rise or fall to give different patterns, or may involve small vibration pins. Force feedback points
on the skin. Also, most of our senses notice change rather than fixed stimuli, Some arcade games also
generate smells, for example, burning rubber as your racing car skids on the track. These examples
both use a fixed smell in a particular location. Smell is a complex multi-dimensional sense and has a
peculiar ability to trigger memory, but cannot be changed rapidly.
1.5.4 Environment and bio-sensing
In a public washroom there are often no controls for the wash basins, you simply put your hands
underneath and (hope that) the water flows. Similarly when you open the door of a car, the courtesy
light turns on. The washbasin is controlled by a small infrared sensor that is triggered when your
hands are in the basin sometimes hard to find the ‗sweet spot‘. There are many different sensors
available to measure virtually anything: temperature, movement (ultrasound, infrared, etc.), location
(GPS, global positioning, in mobile devices), weight (pressure sensors). In addition audio and video
information can be analyzed to identify individuals and to detect what they are doing. Sensors can
also be used to capture physiological signs such as body temperature, unconscious reactions such as
blink rate, or unconscious aspects of activities such as typing rate, vocabulary shifts (e.g. modal
verbs).

4. Explain the various models and frameworks of Interaction

Interaction involves at least two participants- the user and the system.
The interface must effectively translate between them to allow the interaction to be successful. This
translation can fail at a number of points and for a number of reasons. The use of models of
interaction can help us to understand exactly what is going on in the interaction and identify the likely
root of difficulties.
1. Norman’s execution–evaluation cycle
The terms of interaction
 Traditionally, the purpose of an interactive system is to aid a user in accomplishing goals
from some application domain.
  A domain defines an area of expertise and knowledge in some real-world activity. A domain
consists of concepts that highlight its important aspects.
 Tasks are operations to manipulate the concepts of a domain. A goal is the desired output
from a performed task.
 An intention is a specific action required to meet the goal. Task analysis involves the
identification of the problem space for the user of an interactive system in terms of the domain, goals,
intentions and tasks. The concepts used in the design of the system and the description of the user are
separate, and so we can refer to them as distinct components, called the System and the User,
respectively.
 The System and User are each described by means of a language that can express concepts
relevant in the domain of the application. The System‘s language we will refer to as the core language
and the User‘s language.
 The core language describes computational attributes of the domain relevant to the System
state, whereas the task language describes psychological attributes of the domain relevant to the User
state.
2. The execution–evaluation cycle
Norman‘s model of interaction is perhaps the most influential in Human–Computer Interaction,
possibly because of its closeness to our intuitive understanding of the interaction between human user
and computer. The user formulates a plan of action, which is then executed at the computer interface.
When the plan, or part of the plan, has been executed, the user observes the computer interface to
evaluate the result of the executed plan, and to determine further actions. The interactive cycle can be
divided into two major phases: execution and evaluation.
These can then be subdivided into further stages, seven in all. The stages in
Norman‘s models of interaction are as follows:
1. Establishing the goal.
2. Forming the intention.
3. Specifying the action sequence.
4. Executing the action.
5. Perceiving the system state.
6. Interpreting the system state.
7. Evaluating the system state with respect to the goals and intentions.
Each stage is, of course, an activity of the user. First the user forms a goal. This is the user‘s notion of
what needs to be done and is framed in terms of the domain, in the task language. It is liable to be
imprecise and therefore needs to be translated into the more specific intention, and the actual actions
that will reach the goal, before it can be executed by the user. The user perceives the new state of the
system, after execution of the action sequence, and interprets it in terms of his expectations. If the
system state reflects the user‘s goal then the computer has done what he wanted and the interaction
has been successful; otherwise the user must formulate a new goal and repeat the cycle. Norman uses
this model of interaction to demonstrate why some interfaces cause problems to their users. He
describes these in terms of the gulfs of execution and the gulfs of evaluation. The gulf of execution is
the difference between the user‘s formulation of the actions to reach the goal and the actions allowed
by the system. If the actions allowed by the system correspond to those intended by the user, the
interaction will be effective. The interface should therefore aim to reduce this gulf. The gulf of
evaluation is the distance between the physical presentation of the system state and the expectation of
the user. If the user can readily evaluate the presentation in terms of his goal, the gulf of evaluation is
small. The more effort that is required on the part of the user to interpret the presentation, the less
effective the interaction.
Norman‘s model is a useful means of understanding the interaction, in a way that is clear and intuitive
but it does not attempt to deal with the system‘s communication through the interface.
3.The interaction framework
The interaction framework attempts a more realistic description of interaction by including the system
explicitly, and breaks it into four main components

The nodes represent the four major components in an interactive system – the System, the User, the
Input and the Output. Each component has its own language. In addition to the User‘s task language
and the System‘s core language, which we have already introduced, there are languages for both the
Input and Output components. Input and Output together form the Interface. As the interface sits
between the User and the System, there are four steps in the interactive cycle, each corresponding to a
translation from one component to another.
 The User begins the interactive cycle with the formulation of a goal and a task to achieve that
goal.
 The only way the user can manipulate the machine is through the Input, and so the task must
be articulated within the input language.
 The input language is translated into the core language as operations to be performed by the
System.
 The System then transforms itself as described by the operations; the execution phase of the
cycle is complete and the evaluation phase now begins.
 The System is in a new state, which must now be communicated to the User.
 The current values of system attributes are rendered as concepts or features of the Output.
 It is then up to the User to observe the Output and assess the results of the interaction relative
to the original goal, ending the evaluation phase and, hence, the interactive cycle.
There are four main translations involved in the interaction: articulation, performance, presentation
and observation.
 The User‘s formulation of the desired task to achieve some goal needs to be articulated in the
input language. The tasks are responses of the User and they need to be translated to stimuli for the
Input. The task is phrased in terms of certain psychological attributes that highlight the important
features of the domain for the User.
 At the next stage, the responses of the Input are translated to stimuli for the System. Of
interest in assessing this translation is whether the translated input language can reach as many states
of the System as is possible using the System stimuli directly. Once a state transition has occurred
within the System, the execution phase of the interaction is complete and the evaluation phase begins.
 The new state of the System must be communicated to the User, and this begins by translating
the System responses to the transition into stimuli for the Output component. This presentation
translation must preserve the relevant system attributes from the domain in the limited expressiveness
of the output devices.
 The response from the Output is translated to stimuli for the User which triggers assessment.
The observation translation will address the ease and coverage of this final translation.
3.2. FRAMEWORKS
The field of ergonomics addresses issues on the user side of the interface, covering the input and
output, as well as the user‘s immediate context. Dialog design and interface styles can be placed
particularly along the input branch of the framework, addressing both articulation and performance.
However, dialog is most usually associated with the computer and so is biased to that side of the
framework. Presentation and screen design relates to the output branch of the framework. The entire
framework can be placed within a social and organizational context that also affects the interaction.
Each of these areas has important implications for the design of interactive systems and the
performance of the user.

5. What are the various interaction styles available?

Interaction can be seen as a dialog between the computer and the user. The choice of interface style
can have a profound effect on the nature of this dialog.
There are a number of common interface styles including:
 command line interface
 menus
 natural language
 question/answer and query dialog
 form-fills and spreadsheets
 WIMP
 point and click
 three-dimensional interface
4.1 Command line interface
The command line interface was the first interactive dialog style to be commonly used. It provides a
means of expressing instructions to the computer directly, using function keys, single characters,
abbreviations or whole-word commands. In some systems the command line is the only way of
communicating with the system, especially for remote access using telnet.
Advantages:
Command line interfaces are powerful in that they offer direct access to system functionality and can
be combined to apply a number of tools to the same data. They are also flexible: the command often
has a number of options or parameters that will vary its behaviour in some way,
Disadvantages
Commands must be remembered, as no cue is provided in the command line to indicate which
command is needed. They are therefore better for expert users than for novices. This problem can be
alleviated a little by using consistent and meaningful commands and abbreviations. The commands
used should be terms within the vocabulary of the user rather than the technician. Unfortunately,
commands are often obscure and vary across systems, causing confusion to the user and increasing
the overhead of learning.
4.2 Menus

In a menu-driven interface, the set of options available to the user is displayed on the screen, and
selected using the mouse, or numeric or alphabetic keys. Since the options are visible they are less
demanding of the user, relying on recognition rather than recall. However, menu options still need to
be meaningful and logically grouped to aid recognition. Often menus are hierarchically ordered and
the option required is not available at the top layer of the hierarchy. The grouping and naming of
menu options then provides the only cue for the user to find the required option.
4.3 Natural language
Perhaps the most attractive means of communicating with computers, at least at first glance, is by
natural language. Users, unable to remember a command or lost in a hierarchy of menus, may long for
the computer that is able to understand instructions expressed in everyday words! Natural language
understanding, both of speech and written input, is the subject of much interest and research.
Unfortunately, however, the ambiguity of natural language makes it very difficult for a machine to
understand. Language is ambiguous at a number of levels.
4.4 Question/answer and query dialog
Question and answer dialog is a simple mechanism for providing input to an application in a specific
domain. The user is asked a series of questions and so is led through the interaction step by step. An
example of this would be web questionnaires. These interfaces are easy to learn and use, but are
limited in functionality and power. Query languages, on the other hand, are used to construct queries
to retrieve information from a database. They use natural-language-style phrases, but in fact require
specific syntax, as well as knowledge of the database structure.
4.5 Form-fills and spreadsheets
Form-filling interfaces are used primarily for data entry but can also be useful in data retrieval
applications. The user is presented with a display resembling a paper form, with slots to fill in. Often
the form display is based upon an actual form with which the user is familiar, which makes the
interface easier to use. The user works through the form, filling in appropriate values. The data are
then entered into the application in the correct place. Most form-filling interfaces allow easy
movement around the form and allow some fields to be left blank. They also require correction
facilities, as users may change their minds or make a mistake about the value that belongs in each
field. The dialog style is useful primarily for data entry applications and, as it is easy to learn and use,
for novice users.
4.6 Point-and-click interfaces
In most multimedia systems and in web browsers, virtually all actions take only a single click of the
mouse button. The point-and-click style is not tied to mouse-based interfaces, and is also extensively
used in touchscreen information systems. In this case, it is often combined with a menu-driven
interface. The point-and-click style has been popularized by World Wide Web pages, which
incorporate all the above types of point-and-click navigation: highlighted words, maps and iconic
buttons.

4.7 The WIMP interface

WIMP stands for windows, icons, menus and pointer and is the default interface style for the majority
of interactive computer systems in use today, especially in the PC and desktop workstation arena.
Examples of WIMP interfaces include Microsoft Windows for IBM PC compatibles, MacOS for
Apple Macintosh compatibles and various X Windows-based systems for UNIX.
4.8 Three-dimensional interfaces
There is an increasing use of three-dimensional effects in user interfaces. The most obvious example
is virtual reality, but VR is only part of a range of 3D techniques available to the interface designer.
The simplest technique is where ordinary WIMP elements, buttons, scroll bars, etc., are given a 3D
appearance using shading, giving the appearance of being sculpted out of stone. By unstated
convention, such interfaces have a light source at their top right. Where used judiciously, the raised
areas are easily identifiable and can be used to highlight active areas. Unfortunately, some interfaces
make indiscriminate use of sculptural effects, on every text area, border and menu, so all sense of
differentiation is lost. A more complex technique uses interfaces with 3D workspaces. Three-
dimensional workspaces give you extra space, but in a more natural way than iconizing windows.