Design for Human Computer Interaction Design Considerations Types of Interface Interface Choice [NOT Help Systems, HCI Evaluation]

Objective objective –effective use of software quick accurate –selling of software problems –different users –assessment of capabilities

Human Characteristics small short-term memory huge, highly organised long-term memory difficult with handling large numbers of bits of information (7- 10 maximum) difficulty with handling unrelated bits of information intuitive, creative, pro-active liable to make errors distrust of systems about which it is not possible to theorise

Machine Characteristics large short-term memory (RAM) (almost) infinite, but not necessarily well organised, long-term memory (secondary storage - discs, etc.) can handle large amounts of information can handle handle unrelated bits of information make errors only if wrongly built reactive

HCI Design: Objective: use machine characteristics to support and enhance human characteristics HCI should: use the user’s language be consistent be predictable provide error recovery assist the user

Interface Types direct manipulation menu command

Direct Manipulation model of ‘information space’ manipulate model immediate good for most classes of user examples wp, spread sheets, mac o/s, windows advantages control ease of learning immediate feedback disadvantages modelling keeping track memory usage (eg MS software) speed of response

Menus selection from a presented set of choices good for occasional users examples mac o/s, windows, most program development environments advantages no need to memorise commands little typing skill needed avoids some errors context obvious (to m/c) used with help disadvantages menu structures keeping track speed of operation esp exprerienced users

Command commands are typed in using the keyboard good for regular users examples MSDos, Unix, VMS advantages ease of implementation use of natural language commands can easily be combined concise disadvantages learning langauge errors have to know commands even to use help

Interface Choice depends on profile of potential users often a mix of types eg: –menu + sort-cut commands (PDEs, CAE) –direct manipulation + menus or commands (WP, SSHEET) some systems have more than one interface –interfaces designed with specific sub-sets of user in mind

Information Presentation same considerations as for paper and video presentation static vs dynamic precise vs relative textual, numerical or graphical how often updated colour –number, changes, consistency, pairings

Poor interface design means that many software systems are never used. User-interface design will necessarily be a part of the overall system design, however if a system is broken down into smaller parts then the user-interface can be considered at that level. Diagram of the user-interface design process.