Design for Human Computer Interaction

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

2. Objective • objective • effective use of software • quick • accurate • selling of software • problems • different users • assessment of capabilities

3. 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

4. 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

5. 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

6. Interface Types • direct manipulation • menu • command

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

8. 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 Menus • selection from a presented set of choices • good for occasional users • examples mac o/s, windows, most program development environments

9. 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 Command • commands are typed in using the keyboard • good for regular users • examples MSDos, Unix, VMS

10. 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

11. 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

12. 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.