Design for Human Computer Interaction

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					Design for Human Computer
         Design Considerations
           Types of Interface
            Interface Choice
   [NOT Help Systems, HCI Evaluation]
• 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      • advantages
  space’                          • control
                                  • ease of learning
• manipulate model
                                  • immediate feedback
• immediate                  • disadvantages
• good for most classes of        • modelling
  user                            • keeping track
                                  • memory usage (eg MS
• examples wp, spread               software)
  sheets, mac o/s,                • speed of response
• selection from a           • advantages
  presented set of choices        • no need to memorise
• good for occasional             • little typing skill needed
  users                           • avoids some errors
• examples mac o/s,               • context obvious (to m/c)
                                    used with help
  windows, most program
  development                • disadvantages
                                  • menu structures
                                  • keeping track
                                  • speed of operation esp
                                    exprerienced users
• commands are typed in    • advantages
  using the keyboard            • ease of implementation
                                • use of natural language
• good for regular users
                                • commands can easily be
• examples MSDos, Unix,           combined
  VMS                           • 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,
• some systems have more than one interface
  – interfaces designed with specific sub-sets of user in
          Information Presentation
• same considerations as for paper and video
     •   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.

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