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.