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To be covered:- What is HCI? Goal of HCI HCI - An Interdisciplinary Area Concerns in HCI Interface and interaction design Goals of interaction design Utility, Usability, Likeability Structured Process for Creating Usable Products Principles to support usability How to Achieve Usability.

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To be covered:-

    • What is HCI?
    • Goal of HCI
    • HCI - An Interdisciplinary Area
    • Concerns in HCI
    • Interface and interaction design
    • Goals of interaction design
    • Utility, Usability, Likeability
    • Structured Process for Creating Usable Products
    • Principles to support usability
    • How to Achieve Usability

Human Computer Interaction (HCI)

Human–computer Interaction (HCI) involves the study, planning, and design of the interaction between people (users) and computers. Interaction between users and computers occurs at the user interface (or simply interface), which includes both software and hardware.

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”


Human Computer Interaction (HCI)

Because human–computer interaction studies a human and a machine in conjunction, it draws from supporting knowledge on both the machine and the human side.

On the machine side, techniques in computer graphics, operating systems, programming languages, and development environments are relevant.

On the human side, communication theory, graphic and industrial design disciplines, linguistics, social sciences, cognitive psychology, and human factors such as computer user satisfaction are relevant.


Goal 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. Specifically, HCI is concerned with:
  • Methodologies and processes for designing interfaces (i.e., given a task and a class of users, design the best possible interface within given constraints, optimizing for a desired property such as learnability or efficiency of use).
  • Methods for implementing interfaces (e.g. software toolkits and libraries; efficient algorithms).
  • Techniques for evaluating and comparing interfaces.
  • Developing new interfaces and interaction techniques.
  • Developing descriptive and predictive models and theories of interaction.

In order to produce computer system with good usability;

Developers must attempt to

The long term goal:

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


HCI - An Interdisciplinary Area/

Disciplines that Contribute to HCI

  • Computer Science
  • Application design and engineering of human-computer
  • Interfaces
  • Psychology
  • The application of theories of cognitive processes and
  • the empirical analysis of user behavior
  • Sociology and Anthropology
  • Interactions between technology, work, and organization
  • Design and Industrial Design
  • Creating interactive products

Concerns in HCI

Science, Engineering, and Design Aspects

  • The joint performance of tasks by humans and machines
  • The structure of communication between human and
  • machine
  • Human capabilities to use machines (including the
  • learn ability of interfaces)
  • Algorithms and programming of the interface itself
  • Engineering concerns that arise in designing and
  • building interfaces
  • The process of specification, design, and implementation
  • of interfaces

Interface and interaction design

  • Interface design (ID)
  • • Primarily design of 2D/3D widgets
  • Designing interactive products to support people
  • in their everyday and working lives
  • • Sharp, Rogers and Preece (2002)
  • The design of spaces for human communication
  • and interaction
  • • Winograd (1997)

Goals of interaction design

  • Develop usable products
  • Usability means:
    • • easy to learn
    • • effective to use
    • • enjoyable experience
  • Usable products = successful products?
  • Involve users in the design process

Utility, Usability, Likeability

  • Utility
  • a product can be used to reach a certain goal or to
  • perform a certain task. This is essential!
  • Usability
  • relates to the question of quality and efficiency. E.g. how
  • well does a product support the user to reach a certain
  • goal or to perform a certain task.
  • Likeability
  • this may be related to utility and usability but not
  • necessarily. People may like a product for any other
  • reason…

What is Usability

“Usability is a quality attribute that assesses how easy user interfaces are to use. The word ‘usability’ also refers to methods for improving ease-of-use during the design process.”

  • Usability has five quality components:
  • Learn ability: How easy is it for users to accomplish basic tasks
  • the first time they encounter the design?
  • Efficiency: Once users have learned the design, how quickly
  • can they perform tasks?
  • Memorability: When users return to the design after a period of
  • not using it, how easily can they reestablish proficiency?
  • Errors: How many errors do users make, how severe are these
  • errors, and how easily can they recover from the errors?
  • Satisfaction: How pleasant is it to use the design?
why usability is important
Why Usability is Important?

How many systems are easy, effortless, and enjoyable to use?


Why is Usability Important?

  • Improving usability can
    • • increase productivity of users
    • • reduce costs (support, efficiency)
    • • increase sales/revenue (web shop)
    • • enhance customer loyalty
    • • win new customers

Why is Usability Important in the

  • Context of WWW and New Media?
  • Competition is very close (just another link…)
  • User Interface is often the central discriminating factor
  • Comparison is easily possible
  • Example – Online-Shop
  • Direct correlation between usability and sales is reported in many cases.
  • Users who can’t find the product in the shop can not buy it.
  • Users who are not able to fill in correctly the order form are not going to buy.

HCI is Central to the Design and Development Process

  • … even if done unconsciously. Decisions made
  • in the development process are likely to influence how a product can be used.
  • thinking about the user interface when a first
  • version of a product is finished is to late!
  • good user interfaces – and often good products
  • – are a joined effort of all participants in the
  • design and development process

Structured Process for Creating Usable Products

  • Precondition
    • • Understanding how people interact with their environment
    • • Understanding the capabilities and limitations of users
    • • Basic ergonomics
  • Analyze what interaction is required and what technical
  • options are available in a user centered way, evaluate
  • the results of the analysis
  • Design and prototype user interfaces with user
  • involvement, evaluate prototypes
  • Implement an interactive digital product
  • Test and study the product created
  • Usability Engineering is a part of the overall development
  • The process is iterative (overall and at each step)

How it does NOT work

  • Usability tests at the end when the product is
  • ready and needs to be shipped.
  • Designing a new and pretty skin to a product.
  • Introducing HCI issues after the system
  • architecture and the foundations are completed.
  • Comparison: An interior designer can not make
  • a great house if the architect and engineers forgot windows, set the doors at the wrong locations, and created an unsuitable room layout.
principles to support usability
Principles to support usability


the ease with which new users can begin effective interaction and achieve maximal performance


the multiplicity of ways the user and system exchange information


the level of support provided the user in determining successful achievement and assessment of goal-directed behaviour

principles of learnability
Principles of learnability


  • determining effect of future actions based on past interaction history
  • operation visibility


  • assessing the effect of past actions
  • immediate vs. eventual honesty
principles of learnability ctd
Principles of learnability (ctd)


  • how prior knowledge applies to new system
  • guessability; affordance


  • extending specific interaction knowledge to new situations


  • likeness in input/output behaviour arising from similar situations or task objectives
principles of flexibility
Principles of flexibility

Dialogue initiative

  • freedom from system imposed constraints on input dialogue
  • system vs. user pre-emptiveness


  • ability of system to support user interaction for more than one task at a time
  • concurrent vs. interleaving; multimodality

Task migratability

  • passing responsibility for task execution between user and system
principles of flexibility ctd
Principles of flexibility (ctd)


  • allowing equivalent values of input and output to be substituted for each other
  • representation multiplicity; equal opportunity


  • modifiability of the user interface by user (adaptability) or system (adaptivity)
principles of robustness
Principles of robustness


  • ability of user to evaluate the internal state of the system from its perceivable representation
  • browsability; defaults; reachability; persistence; operation visibility


  • ability of user to take corrective action once an error has been recognized
  • reachability; forward/backward recovery; commensurate effort
principles of robustness ctd
Principles of robustness (ctd)


  • how the user perceives the rate of communication with the system
  • Stability

Task conformance

  • degree to which system services support all of the user's tasks
  • task completeness; task adequacy

How to Achieve Usability

  • Identify what utility and usability for the product means
    • • main purpose of the product
    • • anticipated users, target audience
    • • compare with similar/competing products (if applicable)
  • Common effort in the design and development process
  • • trade-offs between design, engineering, and usability
  • Iterative evaluation
  • • usability testing with different methods at various stages of the
  • development process
  • Improvement after product release
    • • monitoring user behavior.
    • • evaluation of changes to the product (e.g. adding a new feature
    • to a web shop)

Design Principles of

Human-Computer Interaction



  • Design process
    • What is design?
    • Traditional Waterfall Model vs. User-Centered Design
  • Design principles, guidelines, rules and standards
    • Know the users and their tasks
    • Choose the right interaction model
    • Psychological principles of design
    • Norman’s Seven Principles of interface design
    • Shneiderman’s Eight Golden Rules of interface design
    • Nielsen’s Heuristics of interface design
    • User interface guidelines

What is Design?

  • In general...
    • “Finding the right physical components of a physical structure.”
    • “A goal-directed problem-solving activity.”
    • “A creative activity – it involves bringing into being something
    • new and useful that has not existed previously.”

Design is a process...

“Engineering design is the use of scientific principles, technical information and imagination in the definition of a mechanical structure, machine of system to perform pre-specified functions with the maximum economy and efficiency.”


Problems with the Waterfall Model

  • Unrealistic: requirements are often incomplete and ambiguous.
  • In practice, the stages overlap and there is feedback from a
  • stage to the previous stage(s).
  • The software process is not a simple linear model but involves a
  • sequence of iterations of the development activities.
  • Maintenance is an important stage, up to 60% of the total effort.
  • Main problem: not user-centered
  • It is impossible to completely understand and express user
  • requirements until a large amount of design has already been done.

Designing HCI

  • HCI design model should:
    • be user-centered and involve users as much as possible
    • so that they can influence the design,
    • integrate knowledge and expertise from the different
    • disciplines that contribute to HCI design,
    • be highly iterative so that testing can be done to check
    • that the design does indeed meet users’ requirements.

User Centered Design

  • External analysis
    • Know the users,
    • Know their tasks.
  • Design and prototype
    • Design to fit the system to the users and their tasks.
  • Evaluate and iterate
    • Evaluate the design,
    • Iterate until a good design is achieved.

Know the Users and their Tasks

  • Know the users:
    • Novice and first time users,
    • Knowledgeable intermittent users,
    • Expert frequent users.
  • Know their tasks:
    • Tasks: sequence of operations.
    • Should be determined before the design proceeds.
    • Design or implementation convenience should not
    • dictate system functionality, features.

Choose the Interaction Style(s)

  • Interaction styles:
    • Direct manipulation,
    • Menu selection,
    • Form fill-in,
    • Command language,
    • Natural language.
  • When users and tasks are diverse, blend several interaction styles.

Design, Prototype, Evaluate

  • Create a design using:
    • Principles of interaction,
    • Graphics design principles,
    • Following guidelines.
  • Implement prototypes to:
    • Test the design,
    • Choose between alternatives,
    • Minimize the cost of experimentation.
  • Evaluate the usability requirements:
    • Learnability,
    • Speed of performance,
    • Rate of errors by users,
    • Retention over time,
    • Subjective satisfaction.

Design Principles

  • Sources of design principles:
    • Cognitive psychology,
    • Graphic design,
    • Designer’s knowledge and experience.
  • Types of design support:
    • Design principles
    • “High level” recommendations based on well established
    • knowledge about human behavior.
    • Design standards
    • Generally stated requirements, imposed in some formal way.
    • Design guidelines
    • Generally stated recommendations for user interface software,
    • adopted by agreement among practitioners.
    • Design rules
    • Explicit design specifications that do not require interpretation
    • by design practitioners.

Norman’s Seven Principles

  • “Seven principles for transforming difficult tasks into simple ones”:
  • 1. Use both knowledge in the world and knowledge in the head.
  • 2. Simplify the structure of tasks.
  • 3. Make things visible.
  • 4. Get the mappings right.
  • 5. Exploit the power of constraints, both natural and artificial.
  • 6. Design for error.
  • 7. When all else fails, standardize.

Shneiderman’s Eight Golden Rules

  • “Shneiderman’s eight golden rules of interface design”:
  • 1. Strive for consistency.
  • 2. Enable frequent users to use shortcuts.
  • 3. Offer informative feedback.
  • 4. Design dialogs to yield closure.
  • 5. Offer error prevention and simple error handling.
  • 6. Permit easy reversal of actions.
  • 7. Support internal locus of control.
  • 8. Reduce short-term memory load.


  • Many forms of consistency:
    • Consistent sequences of actions in similar situations.
    • Identical terminology across: prompts, menus, help screens.
    • Consistent color, layout, capitalization, fonts.


  • Enable frequent users to use shortcuts:
    • Abbreviations,
    • Special keys,
    • Hidden commands,
    • Macros,
    • Short response times,
    • Fast display rates.


  • Offer informative feedback:
    • For every user action, there should be system feedback.
    • For frequent and minor actions the response can be modest.
    • For infrequent and major actions the response should be more substantial.
    • Show changes on the visual representation of the objects of interest.

Design Dialogs to Yield Closure

  • Dialogs should have:
    • beginning, select “File->Open”
    • middle, complete the dialog
    • end. press “Open”

Error Prevention and Handling

  • Error prevention:
    • Design the system so that users cannot make a serious error.
    • Use menu selection instead of form fill-in.
    • When using forms, do not allow alphabetic characters in numeric
    • fields.
    • For command lines: correct matching pairs, complete sequences,
    • etc.
  • Error handling:
    • What happened?
    • Why did it happened?
    • How serious is it?
    • How can it be fixed?

Easy Reversal of Actions

  • Undo/Redo:
    • a single action,
    • a data-entry task,
    • complete group of actions, etc.

Locus of Control

  • Support internal locus of control:
    • Avoid a causality.
    • Users: initiators rather than the responders to actions.
  • Even the relatively simple process of adding or removing a file
  • becomes an interrogation:
    • What do you want to do?
    • What options do you want?
    • What name do you want to use?

Nielsen’s Heuristics

Nielsen’s ten usability heuristics:

1. Visibility of system status.

2. Match between system and the real world.

3. User control and freedom.

4. Consistency and standards.

5. Error prevention.

6. Recognition rather than recall.

7. Flexibility and efficiency of use.

8. Aesthetic and minimalist design.

9. Help users recognize, diagnose, and recover from errors

10. Help and documentation.



Microsoft Windows User Experience

Java Look and Feel Design Guidelines

Macintosh Human Interface Guidelines