Human Computer Interaction (HCI)

22 min readDec 26, 2020


Hi everyone👋,this time i will Share some Informations about Human Computer Interaction(HCI).it is a field of science that studies the design and use of computer technology , this is a the study of how people intract with computers and to what extent computers are or are not developed for successful interaction with human beings.HCI focus on interface between user and computer and how to design, evaluate and implement interactive computer systems that satisfy the user.

Why programmers and analysts give more importance to this HCI. Because Interface are something we do at the end of software development. We want to make the system look nice for the end user. If we build poor interfaces we might find The quality of life of the users who use your system is reduced and Disastrous and possibly fatal errors happen in systems that are critical.So programmers give most importance to this HCI.

1.Design rules for interactive Systems

The principles to support Usability we present are first divided into three main categories Learnability,Flexibility and Robustness.


Learnability is defined as the capability of a product to enable the user to learn how to use it.The main reason learnability sometimes gets overlooked is due to the fact it’s relatively hard to test or quantify. In many cases, the only accurate way of testing whether a product is learnable is over a long period of time, using the same users testing the interface multiple times at regular intervals. This is the type of testing that sometimes gets neglected, as it can be time and money consuming.

So how do we make a product learnable? In the majority of cases, product design in particular relies on the following simple concepts

Predictability — This is often referred to as operation visibility, and is concerned with showing the availability of operations which can be performed next by the user. Eg-Menus Vs command shell,grayed menu items.

Synthesizability —Support for user in Assessing the effect of past operations on current system state. Eg- Moveing a file in command-line vs WIMP interface.

Familiarity — It is concerned with the ability of an interactive system to allow a user to map prior experiences, either real world or gained from interaction with other systems, onto the features of a new system.

Generalizability —This is provides support for users to extend knowledge of specific interaction within, and across applications, to new, but similar situations. Eg-cut and pastte in different applications.

Consistency — To support generalisability, consistency is essential and is probably one of the most widely applied design principle in user interface design. Eg-


The multiplicity of ways the user and system exchange information. there are few concepts hrlp to Flexibility Dialogue initiative, Multithreading, Task migratability, Subsitutivity, Customizability.

Dialogue initiative — User freedom from artificial constraints on the input dialog imposed by the system

Multithreading — The ability of the system to support user interaction for more than one task at a has two type first one is Concurrent(input to multible tasks simultaneously),next one is Interleaved(Many tasks,but input to one at the time).

Task migratability — The ability to transfer control for execution of tasks between the system and the user.Eg- Spell-Checking task

Subsitutivity — The extent to which an application allows equivalent input and output values to be substituted for each other.Eg- Give Values via slider or by typing

Customizability — The ability of the user or the system to modify the user interface.Eg- Style in word


The level of support provided to the user in determining successful achievement and assessment of goal-directed behavior.there are some functions Observability, Recoverability, Responsiveness and Task conformance are clearly define what i said.

Observability — The extent to which the user can evaluate the internal state of the system from the representation on the user interface.Eg- When we move some folders into our computers We can see MoreDetails button.

Recoverability — The extent to which the user can reach the intended goal after recognizing an error in the previous interaction.

Responsiveness — A measure of the rate of communication between the user and the system.

Task conformance — The extent to which the system services support all the tasks the user would wish to perform and in the way the user would wish to perform.

1.4.Standards for interactive system design

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.

Standardization in interface design offers the following benefits:

  • Promotes health and safety of users who will be less likely to experience stress or surprise due tounexpected system behaviour
  • Provides a common terminology, so that designers know that they are discussing the same concept.
  • Facilitates program maintenance and allows for additional facilities to be added.
  • Reduces training needs because knowledge can be transferred between standardized systems.

1.5.Guideline for Interactive systems

The majority of design rules for interactive systems are suggestive and more general guidelines.guidelines can also be automated to some extent, providing a direct means for translating detailed design specifications into actual implementation.Several books and technical reports contain huge catalogs of guidelines. A classic example was a very general list compiled by Smith and Mosier in 1986.The basic categories of the Smith and Mosier guidelines are

  1. Data Entry
  2. Data Display
  3. Sequence Control
  4. User Guidance
  5. Data Transmission
  6. Data Protection

Each of these categories is further broken down into more specific subcategories which contain the particular guidelines.

1.6.Shneidermans’s 8 Golden Rules 

Ben Shneiderman, the founding director of the Human-Computer Interaction Laboratory, focuses on the studies of information and visualization. His “Eight Golden Rules of Interface Design” is a guide to the principles of good interface design and information modeling.

His rules are self explanatory and practical.

1. Strive for consistency.
2. Enable frequent users to use shortcuts.
3. Offer informative feedback.
4. Design dialog to yield closure.
5. Offer simple error handling.
6. Permit easy reversal of actions.
7. Support internal locus of control.
8. Reduce short-term memory load.

1.7.Norman’s 7 Principles

In 1988 Donald Norman proposed seven rules to simplify design work,He intended them to be used to transform difficult tasks into simple ones.

  1. Use both knowledge in world & knowledge in the head
  2. Simplify task structures.
  3. Make things visible
  4. Get the mapping right (User mental model = Conceptual Model = Designed Model)
  5. Convert constrains into advantages (Physical constraints, Cultural constraints, Technological constraints)
  6. Design for Error
  7. When all else fails — Standardize.

2.Evaluation techniques for interactive systems

2.1.What is evaluation?

The role of evaluation is However, even if such a process is used, we still need to assess our designs and test our systems to ensure that they actually behave as we expect and meet user requirements.evaluation should occur throughout the design life cycle, with the results of the evaluation feeding back into modifications to the design.simply say Evaluation is a tests usability and functionality of the occurs in laboratory, field and or in collaboration with users.this evaluates both design and implementation.

2.2.Goals of evaluation

Evaluation has three main goals there are assess the extent of system functionality,assess the effect of interface on user and identify specific problems.the first goal is not includes 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.

the second goal includes considering aspects such as how easy the system is to learn, its usability and the user’s satisfaction with it. It may also include his enjoyment and emotional response, particularly in the case of systems that are aimed at leisure or entertainment. It is important to identify areas of the design that overload the user in some way, perhaps by requiring an excessive amount of information to be remembered.

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.

2.3.Evaluation through expert analysis

We will consider four approaches to expert analysis: cognitive walkthrough, heuristic evaluation, the use of models and use of previous work.

2.3.1.Cognitive walkthrough

The origin of the cognitive walkthrough approach to evaluation is the code walkthrough familiar in software engineering.the main focus of the cognitive walkthrough is evaluates design on how well it supports user in learning usually performed by expert in cognitive psychology.Evaluators ‘step through’ design to identify potential problems using psychological principles.

For each task, walkthrough considers

  • what impact will interaction have on user?
  • what cognitive processes are required?
  • what learning problems may occur?

To do a walkthrough you need four things

  1. Description of the prototype of the system
  2. Description of the task the user is to perform on the system
  3. A complete written list of the actions needed to complete the task with the given prototype
  4. Who users are and what kind of experience and knowledge the evaluators can assume about them

the evaluators try to answer the following four questions for each step in the action sequence.

  • Will the users be trying to produce whatever effect the action has?
  • Will users be able to notice that the correct action is available?
  • Once users find the correct action at the interface, will they know that it is the right one for the effect they are trying to produce?
  • After the action is take

This information will help the designers to decide priorities for correcting the design, since it is not always possible to fix every problem.

2.3.2.Heuristic evaluation

Heuristic evaluation is the most popular of the usability inspection methods.Heuristic evaluation is done as a systematic inspection of a user interface design for usability.The goal of heuristic evaluation is to find the usability problems in the design so that they can be attended to as part of an iterative design process.this evaluation involves having a small set of evaluators examine the interface and judge its compliance with recognized usability principles (the “heuristics”).

Although Nielsen recommends the use of these 10 as providing the most effective coverage of the most common usability problems, other rules.Each evaluator assesses the system and notes violations of any of these heuristics that would indicate a potential usability problem.

Nielsen’s ten heuristics are:

  1. Visibility of system status — The system should always keep users informed about what is going on, through appropriate feedback within reasonable time.
  2. Match between system and real world — The system should speak the users’ language, with words, phrases and concepts familiar to the user, rather than system-oriented terms. Follow real-world conventions, making information appear in a natural and logical order.
  3. User control and freedom — Users often choose system functions by mistake and will need a clearly marked “emergency exit” to leave the unwanted state without having to go through an extended dialogue. Support undo and redo.
  4. Consistency and standards — Users should not have to wonder whether different words, situations, or actions mean the same thing. Follow platform conventions.
  5. Error prevention — Even better than good error messages is a careful design which prevents a problem from occurring in the first place. Either eliminate error-prone conditions or check for them and present users with a confirmation option before they commit to the action
  6. Recognition rather than recall — Minimize the user’s memory load by making objects, actions, and options visible. The user should not have to remember information from one part of the dialogue to another. Instructions for use of the system should be visible or easily retrievable whenever appropriate.
  7. Flexibility and efficiency of use — Accelerators- unseen by the novice user- may often speed up the interaction for the expert user such that the system can cater to both inexperienced and experienced users. Allow users to tailor frequent actions
  8. Aesthetic and minimalist design — Dialogues should not contain information which is irrelevant or rarely needed. Every extra unit of information in a dialogue competes with the relevant units of information and diminishes their relative visibility.
  9. Help users recognize, diagnose and recover from errors — Error messages should be expressed in plain language (no codes), precisely indicate the problem, and constructively suggest a solution.
  10. Help and documentation — Even though it is better if the system can be used without documentation, it may be necessary to provide help and documentation. Any such information should be easy to search, focused on the user’s task, list concrete steps to be carried out, and not be too large.

Once each evaluator has completed their separate assessment, all of the problems are collected and the mean severity ratings calculated. The design team will then determine the ones that are the most important and will receive attention first.

2.3.3.Model-based evaluation

A third expert-based approach is the use of is using a model of how a human would use a proposed system to obtain predicted usability measures by calculation or simulation. These predictions can replace or supplement empirical measurements obtained by user testing.then it Certain cognitive and designmodels provide a means of combining design specification and evaluation into the same framework.

2.4.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

2.4.1.Styles of evaluation

we will distinguish between two distinct evaluation styles,they are performed under the Laboratory,Field conditions.

Laboratory studies — Performed under laboratory conditions.this study advantages are specialist equipment available and uninterrupted environment. We have some disadvantages also there are difficult to observe several users cooperating and lack of context. if system location is dangerous or impractical for constrained single user systems to allow controlled manipulation of use,this condition is Appropriate.

Field studies —Conducted in the work environment or in the field.this study advantages are natural environment,context retained (though observation may alter it) and longitudinal studies possible. We have some disadvantages also there are Distractions, interruptions and noise distrub. where context is crucial for longitudinal studies,this condition is Appropriate.

2.4.2.Empirical methods: experimental evaluation

One of the most powerful methods of controlled evaluation of specific aspects of interactive behaviour.evaluator chooses hypothesis to be tested, which can be determined by measuring some attribute of participant behavior.a number of experimental conditions are considered which differ only in the value of some controlled variable.changes in behavioural measure are attributed to different conditions

Within this basic form there are a number of factors that are important to the overall reliability of the experiment, which must be considered carefully in experimental design. These include the participants chosen, the variables tested and manipulated, and the hypothesis tested.

Participants — who ,representative, sufficient sample.The choice of participants is vital to the success of any experiment.Participants should be chosen to match the expected user population as closely as possible.•If participants are not actual users, they should be chosen to be of a similar age and level of education

Variables — things to modify and has two type first one is Independent variable that means characteristic changed to produce different conditions(eg.interface style, number of menu items),the next one is Dependent variable that means characteristics measured in the experiment(eg.number of errors, user preference)

Hypotheses —what you had like to show.A hypothesis is a prediction of the outcome of an experiment,It is framed in terms of variables.The aim of the experiment is to show that this prediction is correct, this is done by disproving the null hypothesis

Experimental design — how you are going to do has two types first one is within groups design that means each subject performs experiment under each transfer of learning possible and less costly and less likely to suffer from user variation.the next one is between groups design that means each subject performs under only one no transfer of learning ,more users required and variation can bias results.

Statistical measures — statistical analysis depends on the type of data and the questions we want to answer.The first two rules of statistical analysis are to look at the data and to save the data.It is easy to carry out statistical tests blindly when a glance at a graph, histogram or table of results would be more instructive.

2.4.3.Observational techniques

A popular way to gather information about actual use of a system is to observe users interacting with it.Simple observation is seldom sufficient to determine how well the system meets the users’ requirements since it does not always give insight into the their decision processes or attitude.there are some methods in this Techniques there are Think Aloud,Protocol analysis,Automated analysis and Post-task walkthroughs.

Think aloud and cooperative evaluation — In here user observed performing task.user asked to describe what he is doing and why, what he thinks is happening, etc.this method advantages are the user is encouraged to criticize the system, simplicity — requires little expertise,can provide useful insight and can show how system is actually use.although it has a disadvantage there is act of describing may alter task performance.

Protocol analysis — Methods for recording user actions include the following

  1. paper and pencil — cheap, limited to writing speed
  2. audio — good for think aloud, difficult to match with other protocols
  3. video — accurate and realistic, needs special equipment, obtrusive
  4. computer logging — automatic and unobtrusive, large amounts of data difficult to analyze
  5. user notebooks — coarse and subjective, useful insights, good for longitudinal studies

it Mixed use in this method Some automatic support tools available.ideally one uses specialized equipment that can automatically synchronize the different sources, possibly merging several video displays onto a single screen. Unfortunately, this sort of equipment is often only available in specialized laboratories.

Post-task walkthroughs — This method user reacts on action after the event.this method used to fill in intention.this method advantages are analyst has time to focus on relevant incidents ,avoid excessive interruption of task.But it has aom disadvantage there are lack of freshness ,may be post-hoc interpretation of events (people often can rationalize action with no relation to what they were really thinking at the time)

2.4.4.Query techniques

Interviews — it is Analyst questions user on one-to -one basis,Usually based on prepared questions.Advantages are Can be varied to suit context, Issues can be explored more fully, Can elicit user views and identify unanticipated problems.then disadvantages are Very subjective,Time consuming.

Questionnaires — it is Set of fixed questions given to users.these advantages are Quick and reaches large user group,Can be analyzed more rigorously.then disadvantages are Less flexible,Less probing.

2.5.Evaluation through monitoring physiological responses

Eye tracking for usability evaluation — head or desk mounted equipment tracks the position of the movement reflects the amount of cognitive processing a display requires.

measurements include

  1. fixations: eye maintains stable position. Number and duration indicate level of difficulty with display
  2. saccades: rapid eye movement from one point of interest to another
  3. scan paths: moving straight to a target with a short fixation at the target is optimal.

Physiological measurements — it will catch emotional response linked to physical changes.these may help determine a user’s reaction to an interface.

measurements include

  1. heart activity, including blood pressure, volume and pulse
  2. activity of sweat glands: Galvanic Skin Response (GSR)
  3. electrical activity in muscle: electromyogram (EMG)
  4. electrical activity in brain: electroencephalogram (EEG)

3.Universal Design for Interactive Systems

3.1.Universal Design Principles

The goal of Universal Design is to maximize usability by individuals with a wide variety of characteristics. Whether we are talking about learning strategies or physical space, Universal Design operates by a set of principles designed to maximize access by everyone.

Equitable Use — The design is useful and marketable to people with diverse abilities. For example, a counter space or desk surface may be raised or lowered to accommodate users of varying height, or an individual who uses a wheelchair.

Flexibility in Use — The design accommodates a wide range of individual preferences and abilities. For example, a captioned video will allow people to choose to listen or to read in order to understand content. This not only provides access to individuals with hearing impairments, but also accommodates those who would rather not use sound or who comprehend better through reading.

Simple and Intuitive Use — Use of the design is easy to understand, regardless of the user’s experience, knowledge, language skills, or current concentration level. For example, a website with that is well-organized with clear headings will facilitate access to information.

Perceptible Information — The design communicates necessary information effectively to the user, regardless of ambient conditions or the user’s sensory abilities. For example, a video includes a voiceover for individuals with visual impairments.

Tolerance for Error — The design minimizes hazards and the adverse consequences of accidental or unintended actions. For example, a hallway is free of protruding objects at a height where they would not be detectable by someone with a visual impairment who uses a cane.

Low Physical Effort — The design can be used efficiently, comfortably, and with a minimum of fatigue. For example, an automatic door opener can facilitate access to an office space or classroom.

Appropriate Size and Space for Approach and Use — Appropriate size and space is allotted for approach, reach, and manipulation regardless of physical characteristics such as size or mobility. For example, a classroom includes a range of seating options, including a table for someone who uses a wheelchair or wider chairs for individuals who are taller and/or larger.

3.2.Multi-modal interaction

it is use to more than one sensory channel or mode of interaction.this is depend on the 5 senses(Sight,Sound,Touch,Taste,Smell).We have Lot of multi-modal interface around us.Most interactive systems are predominantly visual.often WIMP based, they make use of simple sounds while adding more and more visual information to the screen.As systems become more complex, the visual channel may be overloaded if too much information is presented at once,this may lead to frustration or errors in use.Using multiple modes increases the bandwidth of the interaction.we should always remember that multi-modal interaction is not just about enhancing the richness of the interaction, but also about redundancy

Multimodal interaction is similar to any other interaction, but the user has multiple option to interact with again this comes at its own price designing and developing. The user could use any of the available modes to interact at his convenience, the main idea of multimodal interaction is to allow user with multiple option depending on user’s convenience. Consider you are in middle of an activity and you want to multitask without stopping something completely but continue both the activity. Consider your playing a chord on your guitar and want to go to next sheet or you are thinking aloud and dictating the report that you want to type.

Sound in the interface — Sound is an important contributor to usability.The Experimental evidences are Addition of audio confirmation of modes,in form of changes in key clicks,reduces errors and in video games Experts tend to score less well when the sound is turned off that when it is on.Dual Presentation of information through sound and vision supports universal design,by enabling access fr users with visual and hearing impairments.This has two general types there are speech,Non speech.Eg.Speech-based work processors,Telephone based System,Interactive Systems that give Feedback.

Touch in the interface —Touch is the only sense that can be used to both send and receive used of touch in the interface is known as haptic interaction.Haptics is generic term relating to touch, but it can be roughly divided into two areas there are Cutaneous Perception, it Concerned with tactile sensations through skin, and Kinesthetic perception of movement and position.In current usage Electronic Braille display,Force feedback devices in VR equipment these are some example of Tactile devices.

Handwriting recognition — This is Natural form of communication.Here Using digitizing tablet,refined by incorporating a thin screen on top to display the information,producing electric paper.Eg.Digitizing tablet, Electronic paper.

Gesture recognition — this Being able to control the computer with certain movement of the hand would be advantageous in many situations where there is no possibility of could also support communiction for people who have hearing loss.but this Technology of Capturing gestures is very expensive.this technology examples are DataGlove,Computer vision.

3.3.Designing Interfaces for diversity

In this part, we will consider briefly some of these factors and the particular challenges that each raises. We will consider three key areas: disability, age and culture.

3.3.1.Designing for users with disabilities

it uMaking the Web more accessible for users with various disabilities is to a great extent a matter of using HTML the way it was intended: to encode meaning rather than appearance.As long as a page is coded for meaning, it is possible for alternative browsers to present that meaning in ways that are optimized for the abilities of individual users and thus facilitate the use of the Web by disabled users.

Visual impairment

The rise in the use of graphical interfaces reduces the possibilities for visually impaired users.The sensory impairment that has attracted the most attention from researchers, perhaps because it is potentially also one of the most debilitating as far as interaction is concerned, is visual impairment.Examples are In text-based interaction, screen readers.using synthesized speech or braille output devices provided complete access to computers, input relied on touch-typing, with these mechanisms providing the output. However, today the standard interface is graphical.

Hearing impairment

this impairment Compared with a visual disability where the impact on interacting with a graphical interface is immediately obvious, a hearing impairment may appear to have little impact on the use of an use To an extent this is true, and computer technology can actually enhance communication opportunities for people with hearing loss.Email and instant messaging are great levellers and can be used equally by hearing and deafusers alike.then Gesture recognition has also been proposed to enable translation of signing to speech or text, again to improve communication particularly with non-signers.

Physical impairment

Users with physical disabilities vary in the amount of control and movement that they have over their hands, but many find the precision required in mouse control difficult.although Speech input and output is an option for those without speech difficulties. An alternative is the eyegaze system which tracks eye movements to control the cursor, or a keyboard driver that can be attached to the user’s head.If the user is unable to control head movement, gesture and movement tracking can be used to allow the user control.If the user has limited use of a keyboard, a predictive system, such as the Reactive keyboard [157], can help, by anticipating the commands that are being typed and offering them for execution.

Speech impairment

For users with speech and hearing impairments, multimedia systems provide a number of tools for communication, including synthetic speech and text-based communication and conferencing systems.the Textual communication is slow, which can lower the effectiveness of the communication.Predictive algorithms have been used to anticipate the words used and fill them in, to reduce the amount of typing required.current system Conventions can help to provide context, which is lost from face-to-face communication, for example the ‘smilie’ :-), to indicate a joke. Facilities to allow turn-taking protocols to be established also help natural communication.


Users with cognitive disabilities such as dyslexia can find textual information difficult. In severe cases, speech input and output can alleviate the need to read and write and allow more accurate input and output. In cases where the problem is less severe, spelling correction facilities can help users. However, these need to be designed carefully.


Autism affects a person’s ability to communicate and interact with people around them and to make sense of their environment. This manifests itself in a range of ways but is characterized by the triad of impairments:

  1. Social interaction — problems in relating to others in a meaningful way or responding appropriately to social situations.
  2. Communication — problems in understanding verbal and textual language including the use of gestures and expressions.
  3. Imagination — problems with rigidity of thought processes, which may lead to repetitive behavior and inflexibility.

3.3.2.Designing for different age groups

We need to talk about other area of diversity that impact upon the way we design interface. One of these age. In particular part we have two different type of age people they are Children,Older people. they have specific needs when it comes to interactive technology.

Older people —But the requirements of the older population may differ significantly from other population groups, and will vary considerably within the population group. The proportion of disabilities increases with age: more than half of people over 65 have some kind of disability. Just as in younger people with disabilities, technology can provide support for failing vision, hearing, speech and mobility. New communication tools, such as email and instant messaging, can provide social interaction in cases where lack of mobility or speech difficulties reduce face-to-face possibilities. Mobile technologies can be used to provide memory aids where there is age-related memory loss.

Children — children have distinct needs when it comes to technology, and again, as a population, they are diverse. The requirements of a three year old will be quite different from those of a 12 year old, as will be the methods that can be used to uncover them. Children are, however, different from adults, and have their own goals and likes and dislikes. It is therefore important to involve them in the design of interactive systems that are for their use, though this in itself can be challenging as they may not share the designer’s vocabulary or be able to verbalize what they think. Information in Graphics, sound and text, Pen-based interfaces, touch or handwriting, may be easier for children than keyboard and mouse

3.3.3.Designing for cultural differences

Cultural difference is often used synonymously with national differences but this is too simplistic.The other factors such as age, gender, race, sexuality, class, religion and political persuasion, may all influence an individual’s response to a system.The designer practice universal design which include language, cultural symbols, gestures and use of colour that is colors are often used in interfaces to reflect ‘universal’ conventions, such as red for danger and green for go. But how universal are these conventions? In fact, red and green mean many different things in different countries. As well as danger, red represents life (India), happiness (China) and royalty (France). Green is a symbol of fertility (Egypt) and youth (China) as well as safety (Anglo-American).

-Thank you-






BSc.(Hons) Software Engineering Undergraduate -University of kelaniya-