Introduction of Human Computer Interaction


Without a Human computer interaction is designs a design is useless, because poor designs can lead to unexpected problems. Before implement system first we have to make prototypes that prototypes we have follow best HCI pricncilpes for who are going to use system. The goals of HCI are to produce usable and safe systems, as well as functional systems. In order o produce computer systems with good usability, developers must attempt to: understand the factors that determine how people use technology. develop tools and techniques to enable building suitable systems.

What is HCI

it is focused on the interfaces between users and computers.Humans interact with computers in a many way mobile,tablets,laptops.HCI is different from UX-UI designers because UX-UI designers building new human-focused applications, products or services, but HCI practitioners are more concerned with the research. This means HCI is focused mainly on developing empirical understandings of users, which can then help to inform the work of on-the-ground UX designers. HCI can evolve accordingly, to create devices and machines that are ever more closely linked to our human psyches.

Design rules for interactive systems

Principles of Learnability

Learnability concerns the features of the interactive system that allow novice users to understand how to use it initially and then how to attain a maximal level of performance.

  • Predictability :- Users have previous knowledge then he can predict what can happen next and how to proceed.This assumes that the user has some mental model of how the system behaves
  • Synthesizability :- In building up some sort of predictive model of the system’s behavior, it is important for the user to assess the consequences of previous interactions in order to formulate a model of the behavior of the system. Synthesis, therefore, is the ability of the user to assess the effect of past operations on the current state.
  • Familiarity :- For a new user, the familiarity of an interactive system measures the correlation between the user’s existing knowledge and the knowledge required for effective interaction
  • Generalizability :- The generalizability of an interactive system supports this activity, leading to a more complete predictive model of the system for the user.
  • Consistency :- Consistency relates to the likeness in behavior arising from similar situations or similar task objectives. Consistency is probably the most widely mentioned principle in the literature on user interface design. ‘Be consistent!’ we are constantly urged. The user relies on a consistent interface.

Principles of Flexibility

Flexibility refers to the multiplicity of ways in which the end-user and the system exchange information.

  • Dialog initiative :- Allowing the user freedom from artificial constraints on the input dialog imposed by the system
  • Multi threading :- Ability of the system to support user interaction pertaining to more than one task at a time
  • Task migratability :- The ability to pass control for the execution of a given task so that it becomes either internalized by the user or the system or shared between them
  • Substitutivity :- Allowing equivalent values of input and output to be arbitrarily substituted for each other
  • Customizability :- Modifiability of the user interface by the user or the system


In a work or task domain, a user is engaged with a computer in order to achieve some set of goals. The robustness of that interaction covers features that support the successful achievement and assessment of the goals.

  • Observability :- Ability of the user to evaluate the internal state of the system from its perceivable representation
  • Recoverability :- Ability of the user to take corrective action once an error has been recognized
  • Responsiveness :- Responsiveness measures the rate of communication between the system and the user. Response time is generally defined as the duration of time needed by the system to express state changes to the user. In general, short durations and instantaneous response times are desirable.
  • Task conformance :-The degree to which the system services support all of the tasks the user wishes to perform and in the way that the user understands them .

Standards and Guideline for Interactive systems

Standards for interactive system design are usually set by national or international bodies to ensure compliance with a set of design rules by a large community. Standards can apply specifically to either the hardware or the software used to build the interactive system.

Shneidermans’s 8 Golden Rules

Ben Shneiderman, an American computer scientist consolidated some implicit facts about designing and came up with the following eight general guidelines

1. Strive for consistency in action sequences, layout, terminology, command use and so on.

2. Enable frequent users to use shortcuts, such as abbreviations, special key sequences and macros, to perform regular, familiar actions more quickly.

3. Offer informative feedback for every user action, at a level appropriate to the magnitude of the action.

4. Design dialogs to yield closure so that the user knows when they have completed a task.

5. Offer error prevention and simple error handling so that, ideally, users are prevented from making mistakes and, if they do, they are offered clear and informative instructions to enable them to recover.

6. Permit easy reversal of actions in order to relieve anxiety and encourage exploration, since the user knows that he can always return to the previous state.

7. Support internal locus of control so that the user is in control of the system, which responds to his actions.

8. Reduce short-term memory load by keeping displays simple, consolidating multiple page displays and providing time for learning action sequences.

These rules provide a useful shorthand for the more detailed sets of principles described earlier. Like those principles, they are not applicable to every eventuality and need to be interpreted for each new situation. However, they are broadly useful and their application will only help most design projects.

Norman’s 7 Principles

To assess the interaction between human and computers, Donald Norman in 1988 proposed seven principles. He proposed the seven stages that can be used to transform difficult tasks. Following are the seven principles of Norman

  • Use both knowledge in world & knowledge in the head.
  • Simplify task structures.
  • Make things visible.
  • Get the mapping right (User mental model = Conceptual model = Designed model).
  • Convert constrains into advantages (Physical constraints, Cultural constraints, Technological constraints).
  • Design for Error.
  • When all else fails − Standardize.

Evaluation techniques for interactive systems

Evaluation techniques for interactive systems

What is evaluation

evaluation should not be single process., ideally evalution should occur throughout the design life cycle with the results of the evaluation feeding back into modifications to the design.Clearly, it is not usually possible to perform extensive experimental testing continuously throughout the design, but analytic and informal techniques can and should be used.

Goals of evaluation

it has 3 main goals. to assess the extent and accessbility of the system’s functionality, to assess users’ experience of the interaction, and to identify any specific problems with the system. The system functionality is important in that it must record with user’s requirments. In other words , the design of the system should enable users to perform their intended tasks more easily. This includes not only making the appropriate functionality available within the system, but making it clearly reachable by the user in terms of the actions that the user needs to take to perform the task. It also involves matching the use of the system to the user’s expectations of the task. Second goal is assess the user’s experience of the interaction and its impact upon him. This includes considering aspects such as how easy the system is to learn, its usability and the user’s satisfaction with it .The final goal of evaluation is to identify specific problems with the design. These may be aspects of the design which, when used in their intended context, cause unexpected results, or confusion amongst users. This is, of course, related to both the functionality and usability of the design (depending on the cause of the problem). However, it is specifically concerned with identifying trouble-spots which can then be rectified.

Evaluation through expert analysis

In particular, the first evaluation of a system should ideally be performed before any implementation work has started. A number of methods have been proposed to evaluate interactive systems through expert analysis. These depend upon the designer, or a human factors expert, taking the design and assessing the impact that it will have upon a typical user. The basic intention is to identify any areas that are likely to cause difficulties because they violate known cognitive principles, or ignore accepted empirical results. These methods can be used at any stage in the development process from a design specification, through storyboards and prototypes, to full implementations, making them flexible evaluation approaches. They are also relatively cheap, since they do not require user involvement. However, they do not assess actual use of the system, only whether or not a system upholds accepted usability principles.

  • Cognitive walkthrough :-The origin of the cognitive walkthrough approach to evaluation is the code walkthrough familiar in software engineering. Walkthroughs require a detailed review of a sequence of actions. In the code walkthrough, the sequence represents a segment of the program code that is stepped through by the reviewers to check certain characteristics .main focus of the cognitive walkthrough is to establish how easy a system is to learn. It is vital to document the cognitive walkthrough to keep a record of what is good and what needs improvement in the design. It is therefore a good idea to produce some standard evaluation forms for the walkthrough
  • Heuristic evaluation :- A heuristic is a guideline or general principle or rule of thumb that can guide a design decision or be used to critique a decision that has already been made. Heuristic evaluation can be performed on a design specification so it is useful for evaluating early design. But it can also be used on prototypes, storyboards and fully functioning systems. It is therefore a flexible, relatively cheap approach. Hence it is often considered a discount usability technique. The general idea behind heuristic evaluation is that several evaluators independently critique a system to come up with potential usability problems. It is important that there be several of these evaluators and that the evaluations be done independently.
  • Model based evaluation :- it is a third expert-based approach is the use of models. Certain cognitive and design models provide a means of combining design specification and evaluation into the same framework. Design methodologies, such as design rationale (see Chapter 6), also have a role to play in evaluation at the design stage. Design rationale provides a framework in which design options can be evaluated. By examining the criteria that are associated with each option in the design, and the evidence that is provided to support these criteria, informed judgments can be made in the design. Dialog models can also be used to evaluate dialog sequences for problems, such as unreachable states, circular dialogs and complexity. Models such as state transition networks are useful for evaluating dialog designs prior to implementation.
  • Using previous studies in evaluation :-Experimental psychology and human–computer interaction between them possess a wealth of experimental results and empirical evidence. Some of this is specific to a particular domain, but much deals with more generic issues and applies in a variety of situations. Examples of such issues are the usability of different menu types, the recall of command names, and the choice of icons. A final approach to expert evaluation exploits this inheritance, using previous results as evidence to support (or refute) aspects of the design. It is expensive to repeat experiments continually and an expert review of relevant literature can avoid the need to do so. It should be noted that experimental results cannot be expected to hold arbitrarily across contexts. The reviewer must therefore select evidence carefully, noting the experimental design chosen, the population of participants used, the analyses performed and the assumptions made.

Evaluation through user participation

User participation in evaluation tends to occur in the later stages of development when there is at least a working prototype of the system in place. This may range from a simulation of the system’s interactive capabilities, without its underlying functionality , some of the methods discussed can also contribute to the earlier design stages, such as requirements capture, where observation and surveying users are important

Styles of evaluation

distinguish between two distinct evaluation styles: those performed under laboratory conditions and those conducted in the work environment or ‘in the field’.

  • Laboratory studies :- users are taken out of their normal work environment to take part in controlled tests, often in a specialist usability laboratory A well-equipped usability laboratory may contain sophisticated audio/visual recording and analysis facilities, two-way mirrors, instrumented computers and the like, which cannot be replicated in the work environment. In addition, the participant operates in an interruption-free environment. However, the lack of context — for example, filing cabinets, wall calendars, books or interruptions — and the unnatural situation may mean that one accurately records a situation that never arises in the real world. It is especially difficult to observe several people cooperating on a task in a laboratory situation, as interpersonal communication is so heavily dependent on context
  • Field studies :- The second type of evaluation takes the designer or evaluator out into the user’s work environment in order to observe the system in action. Again this approach has its pros and cons. High levels of ambient noise, greater levels of movement and constant interruptions, such as phone calls, all make field observation difficult. However, the very ‘open’ nature of the situation means that you will observe interactions between systems and between individuals that would have been missed in a laboratory study. The context is retained and you are seeing the user in his ‘natural environment’. In addition, some activities, such as those taking days or months, are impossible to study in the laboratory (though difficult even in the field).

Empirical methods: experimental evaluation
One of the most powerful methods of evaluating a design or an aspect of a design is to use a controlled experiment. This provides empirical evidence to support a particular claim or hypothesis. It can be used to study a wide range of different issues at different levels of detail. The evaluator chooses a hypothesis to test, which can be determined by measuring some attribute of participant behavior. A number of experimental conditions are considered which differ only in the values of certain controlled variables

Observational techniques
In this method users are asked to complete a set of predetermined tasks, although, if observation is being carried out in their place of work, they may be observed going about their normal duties. The evaluator watches and records the users’ actions. Consequently users are asked to elaborate their actions by ‘thinking aloud’.

Query techniques
This relies on asking the user about the interface directly. Query techniques can be useful in eliciting detail of the user’s view of a system. They can be used in evaluation and more widely to collect information about user requirements and tasks. There are two main types of query technique: interviews and questionnaires.

Evaluation through monitoring physiological responses

Potentially this type of evaluation will allow the evaluators not only to see more clearly exactly what users do when they interact with computers, but also to measure how they feel. The two areas receiving the most attention to date are eye tracking and physiological measurement.

Universal Design for Interactive Systems

In the late 1990s a group at North Carolina State University in the USA proposed seven general principles of universal design [333]. These were intended to cover all areas of design and are equally applicable to the design of interactive systems. These principles give us a framework in which to develop universal designs. Universal design is the process of designing products so that they can be used by as many people as possible in as many situations as possible. In this case, this means particularly designing interactive systems that are usable by anyone, with any range of abilities, using any technology platform. This can be achieved by designing systems either to have built in redundancy or to be compatible with assistive technologies.

Universal Design Principles

Principle one is equitable use: the design is useful to people with a range of abilities and appealing to all. No user is excluded or stigmatized. Wherever possible, access should be the same for all. where identical use is not possible, equivalent use should be supported. Where appropriate, security, privacy and safety provision should be available to all.

Principle two is flexibility in use: the design allows for a range of ability and preference, through choice of methods of use and adaptivity to the user’s pace, precision and custom.

Principle three is that the system be simple and intuitive to use, regardless of the knowledge, experience, language or level of concentration of the user. The design needs to support the user’s expectations and accommodate different language and literacy skills. It should not be unnecessarily complex and should be organized to facilitate access to the most important areas. It should provide prompting and feedback as far as possible.

Principle four is perceptible information: the design should provide effective communication of information regardless of the environmental conditions or the user’s abilities. Redundancy of presentation is important: information should be represented in different forms or modes (e.g. graphic, verbal, text, touch). Essential information should be emphasized and differentiated clearly from the peripheral content. Presentation should support the range of devices and techniques used to access information by people with different sensory abilities.

Principle five is tolerance for error: minimizing the impact and damage caused by mistakes or unintended behavior. Potentially dangerous situations should be removed or made hard to reach. Potential hazards should be shielded by warnings. Systems should fail safe from the user’s perspective and users should be supported in tasks that require concentration.

Principle six is low physical effort: systems should be designed to be comfortable to use, minimizing physical effort and fatigue. The physical design of the system should allow the user to maintain a natural posture with reasonable operating effort. Repetitive or sustained actions should be avoided.

Principle seven requires size and space for approach and use: the placement of the system should be such that it can be reached and used by any user regardless of body size, posture or mobility. Important elements should be on the line of sight for both seated and standing users. All physical components should be comfortably reachable by seated or standing users. Systems should allow for variation in hand size and provide enough room for assistive devices to be used.

Multi-modal interaction

More than one mode of interaction is an important principle of universal design. Such design relies on multi-modal interaction.However, it should always be remembered that multi-modal interaction is not just about enhancing the richness of the interaction, but also about redundancy. Redundant systems provide the same information through a range of channels, so, for example, information presented graphically is also captioned in readable text or speech, or a verbal narrative is provided with text captions. The aim is to provide at least an equivalent experience to all, regardless of their primary channel of interaction.

  • Sound in the interface Sound is an important contributor to usability. There is experimental evidence to suggest that the addition of audio confirmation of modes, in the form of changes in keyclicks, reduces errors [237]. Video games offer further evidence, since experts tend to score less well when the sound is turned off than when it is on; they pick up vital clues and information from the sound while concentrating their visual attention on different things. The dual presentation of information through sound and vision supports universal design, by enabling access for users with visual and hearing impairments respectively. It also enables information to be accessed in poorly lit or noisy environments.
  • Touch in the interface Touch is the only sense that can be used to both send and receive information. Although it is not yet widely used in interacting with computers, there is a significant research effort in this area and commercial applications are becoming available. The use of touch in the interface is known as haptic interaction. Haptics is a generic term relating to touch, but it can be roughly divided into two areas: cutaneous perception, which is concerned with tactile sensations through the skin; and kinesthetics, which is the perception of movement and position. Both are useful in interaction but they require different technologies.
  • Handwriting recognition Like speech, we consider handwriting to be a very natural form of communication. The idea of being able to interpret handwritten input is very appealing, and handwriting appears to offer both textual and graphical input using the same tools. There are problems associated with the use of handwriting as an input medium, however, and in this section we shall consider these. We will first look at the mechanisms for capturing handwritten information, and then look at the problems of interpreting it
  • Gesture recognition Gesture is a component of human–computer interaction that has become the subject of attention in multi-modal systems. Being able to control the computer with certain movements of the hand would be advantageous in many situations where there is no possibility of typing, or when other senses are fully occupied. It could also support communication for people who have hearing loss, if signing could be ‘translated’ into speech or vice versa. But, like speech, gesture is user dependent, subject to variation and co-articulation. The technology for capturing gestures is expensive, using either computer vision or a special dataglove .

Designing Interfaces for diversity

that, although we can make general observations about human capabilities, users in fact have different needs and limitations. Interfaces are usually designed to cater for the ‘average’ user, but unfortunately this may exclude people who are not ‘average’.

  • Designing for users with disabilities
  • It is estimated that at least 10% of the population of every country has a disability that will affect interaction with computers. Employers and manufacturers of computing equipment have not only a moral responsibility to provide accessible products, but often also a legal responsibility. In many countries, legislation now demands that the workplace must be designed to be accessible or at least adaptable to all — the design of software and hardware should not unnecessarily restrict the job prospects of people with disabilities.
  • Designing for different age groups
  • We have considered how people differ along a range of sensory, physical and cognitive abilities. However, there are other areas of diversity that impact upon the way we design interfaces. One of these is age. In particular, older people and children have specific needs when it comes to interactive technology.
  • Designing for cultural differences
  • The final area of diversity we will consider is cultural difference. Cultural difference is often used synonymously with national differences but this is too simplistic. Whilst there are clearly important national cultural differences, such as those we saw

@Thank you




Software Engineering undergraduate at University of Kelaniya

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Tharun varshanth

Tharun varshanth

Software Engineering undergraduate at University of Kelaniya

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