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 (710 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:
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•
•
•
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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
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•
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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.