L1 HCI Introduction TO Human Computer Interaction PDF

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INTRODUCTION TO HUMAN COMPUTER INTERACTION Introduction Def. Human Computer Interaction (HCI) is the study of how people interact with computers and to what extent computers are or are not developed for successful interaction with human beings. Def. 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." Association for Computing Machinery Parts of HCI HCI consists of three parts:  The user,  The computer,  Interaction (the ways they work together ) User: the user is an individual user, a group of users or a sequence of users in an organization working together. Computer: computer refers to any technology ranging from desktop computers, to large scale computer systems. For example, if when discussing the design of a Website, then the Website itself would be referred to as "the computer". Devices such as mobile phones or VCRs can also be considered to be “computers”. Interaction: There are obvious differences between humans and machines. In spite of these, HCI attempts to ensure that they both get on with each other and interact successfully. In order to achieve a usable system, you need to apply what you know about humans and computers, and consult with likely users throughout the design process. In real systems, it is vital to find a balance between what would be ideal for the users and what is feasible in reality. Interaction styles a) Command line interface: This a way of expressing instructions to the computer directly using function keys, single characters, short abbreviations, whole words, or a combination. This interaction style is suitable for repetitive tasks, better for expert users than novices, offers direct access to system functionality. Examples includes command names/abbreviations should be meaningful! b) Menus: A list of options is presented to the user and the appropriate decision is selected by typing some code or selecting the option required. Selection of the options is done through use of numbers, letters, arrow keys, the mouse or a combination of this methods. The selection relies on the recognition of the options names, thus requiring that the names used should be meaningful. Visibility of options make it easier to use and it reduces the need for recall. The methods also allows for hierarchical grouping of the options c) Direct Manipulation: Direct manipulation is a style of interaction which features a natural representation of task objects and actions promoting the notion of people performing a task themselves (directly) not through an intermediary like a computer

d) Question/answer and query dialogue: In this kind of interaction questions are asked one at a time and the next question may depend on the previous answer. Question and answer dialogues are often used in tasks where information is elicited from users in a prescribed and limited form. This a type of interaction where the user is led through the interaction via series of questions. It is suitable for novice users but has restricted functionality. A Fourth Generation language often used in information systems e) Form-fills and spreadsheets. Used for data entry and retrieval and are based on paper form metaphor. They are used for both input and output f) WIMP: Most common interaction style on PCs. Uses;  Windows  Icons  Menus  point and click The Goals of HCI A basic goal of HCI is to improve the interactions between users and computers by making computers more usable (usability), and receptive to the user's needs (functionality). Specifically, the goal of HCI is to design a user interface that meets the following characteristics; a) Effectiveness: effective to use - Concerned with whether the system is doing what it generally says it will do b) Efficiency: efficient to use c) Safety: It involves protecting the users from dangerous conditions and undesirable situations ie save to use. Preventing the user from making serious error by reducing the risk of wrong keys/buttons being mistakenly activated (an example is not placing the quit or delete- file command right next to the save command on a menu.) Providing users with various means of recovery should they make errors. Save interactive systems should engender confidence and allow the users the opportunity to explore the interface to carry out new operations. The HCI should provide means of recovering from errors such as undo options, confirmation dialogs etc. d) Utility: It refers to the extent to which the system provides the right kind of functionality so that user can do what they need or want to do. HCI should have sufficient functionality to accommodate range of users tasks. An example of a system with high utility is an accounting software package providing a powerful computational tool that accountants can use to work out tax returns. e) Learnability: It refers to how easy a system is to learn to use. It is well known that people do not like spending a long time learning how to use a system. They want to get started straight away and become competent at caring out tasks without too much effort. f) Memorability: It refers to how easy a system is to remember how to use, once learned. This is especially important for interactive systems that are used infrequently. If users haven’t used a system or an operation for a few months or longer, they should be able to remember or at least rapidly be reminded how to use it. Users shouldn’t have to keep relearning how to carry out tasks.

To meet these characteristics, HCI is thus concerned with a) 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) b) Methods for implementing interfaces c) Techniques for evaluating and comparing interfaces d) Developing new interfaces and interaction techniques e) Developing descriptive and predictive models and theories of interaction HCI Usability ISO defines usability as the effectiveness, efficiency and satisfaction with which specified users can achieve specified goals in particular environments Usability is one of the key concepts in HCI. It is concerned with making systems easy to learn and use. It involves optimizing the interactions people have with interactive product to enable them to carry out their activities at work, school, and in their everyday life. Characteristics of a usable system a) Easy to learn: It refers to how easy a system is to learn to use. It is well known that people do not like spending a long time learning how to use a system. They want to get started straight away and become competent at caring out tasks without to much effort. b) Easy to remember how to use (memorability): It refers to how easy a system is to remember how to use, once learned. This is especially important for interactive systems that are used infrequently. If users haven’t used a system or an operation for a few months or longer, they should be able to remember or at least rapidly be reminded how to use it. Users shouldn’t have to keep relearning how to carry out tasks. c) Effective to use: the general goals and refers to how good a system at doing what it is supposed to do. d) Efficient to use: refers to the way a system supports users in carrying out their tasks. e) Safe to use: involves protecting the users from dangerous conditions and undesirable situations. f) Enjoyable to use g) Have good utility: refers to the extent to which the system provides the right kind of functionality so that user can do what they need or want to do. Factors Affecting HCI Usability The main factors affecting usability are: a) Format of input b) Feedback There is need to continuously inform the user about the system’s state, how it is interpreting the user’s input. The user should at all times be aware of what is going on c) Visibility This is the mapping between a control and its effect. For example, controls in cars are generally visible – the steering wheel has just one function, there is good feedback and it is easy to understand what it does. Mobile phones and VCRs often have poor visibility – there is little visual mapping between controls and the users‟ goals, and controls can have multiple functions.

d) Affordance The affordance of an object is the sort of operations and manipulations that can be done to it. A door affords opening, a chair affords support. Important types includes;  Perceived Affordances are the actions a user perceives to be possible. For example, does the design of a door suggest that it should be pushed or pulled open?  Real Affordances are the actions which are actually possible. Usability Principles There are several historical principles of usability that are evolving into new usability paradigms each day. Usability paradigms reveal how humans interact with computers in contemporary applications, while usability principles describe how these paradigms work. In their book Usability Paradigms and Principles in Human-Computer Interface, Dix, Finally, Abowd and Beale proposes three principles of usability design a) Learnability – the ease with which new users can begin effective interaction and achieve maximal performance. Learnability is supported by the following principles Predictability  determining effect of future actions based on past interaction history  operation visibility Synthesizability  assessing the effect of past actions immediate vs. eventual honesty Familiarity  how prior knowledge applies to new system  guessability; affordance Generalizability  extending specific interaction knowledge to new situations Consistency  likeness in input/output behaviour arising from similar situations or task objectives b) Flexibility – the multiplicity of ways in which the user and system exchange information. Flexibility is supported by the following priciples Dialogue initiative  freedom from system imposed constraints on input dialogue  system vs. user pre-emptiveness Multithreading  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 Substitutivity  allowing equivalent values of input and output to be substituted for each other  representation multiplicity; equal opportunity Customizability

 modifiability of the user interface by user (adaptability) or system (adaptivity) c) Robustness – the level of support provided to the user in determining successful achievement and assessment of goals. Observability  ability of user to evaluate the internal state of the system from its perceivable representation  browsability; defaults; reachability; persistence; operation visibility Recoverability  ability of user to take corrective action once an error has been recognized  reachability; forward/backward recovery; commensurate effort Responsiveness  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  it ensures task completeness; task adequacy Jacob Nielsen also proposed other ten general principles for user interface design. They are called "heuristics" because they are more in the nature of rules of thumb than specific usability guidelines. 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 the real world: The system should speak the users' language, with words, phrases and concepts familiar to the user, rather than systemoriented 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: 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. Disciplines Contributing to HCI The field of HCI covers a wide range of topics, and its development has relied on contributions from many disciplines. Some of the main disciplines which have contributed to HCI are: 1. Computer Science  Technology  Software design, development & maintenance  User Interface Management Systems (UIMS) & User Interface Development Environments (UIDE)  Prototyping tools 2. Cognitive Psychology  information processing  capabilities  limitations  cooperative working  performance prediction 3. Social Psychology  social & organizational structures 4. Ergonomics/Human Factors  hardware design  display readability 5. Linguistics  natural language interfaces 6. Artificial Intelligence  intelligent software 7. Philosophy, Sociology & Anthropology  Computer supported cooperative work (CSCW) 8. Engineering & Design  graphic design  engineering principles...