User Interfaces

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					User Interfaces
Good interface design
 A good interface design can help to ensure that users carry out
   their tasks:
    – Safely - in the case of a jumbo jet pilot, for example
    – Effectively - users don’t find they have video’d two hours of Bulgarian
      clog dancing instead of the Cup Final
    – Efficiently - users don’t spend 5 minutes trying to find the correct way to
      insert their cash card and type in their PIN and the amount of cash, and
      then leave without remembering to extract their card
    – Enjoyably - a primary school pupil using a program to teach multiplication
 Well designed systems can improve the output of employees,
   improve the quality of life and make the world a safer and more
   enjoyable place to live in.
Design Considerations
 – Who will use the system?
    • Computer professionals or general public? For an educational
      program, will the users be primary school children or teenagers?
      Beginners or experienced? Or both?
 – What tasks is the computer performing?
    • Very repetitive? Requiring skill and knowledge? Do tasks vary
      greatly from one occasion to the next? A travel agent will require a
      different interface from an office worker
 – The computer environment
    • Hazardous (in a lifeboat), noisy (in a factory), or calm and quiet (some
 – What is technologically feasible
    • Is it possible to simply dictate a letter to a word processor instead of
      typing it in?
Interface styles
 Command line interface;
 Menus;
 Natural language;
 Forms and dialogue boxes;
 Graphical user interface (GUI).
 Several different kinds of menu interface:
   – Full screen menu
     • Typically the front-end of an application
  – Pull-down menu
     • As on menu bar at top of most Microsoft applications
  – Pop-up menu
     • As with short-cut menus available on right-click
Natural language dialogue
 Advantages:
  – Most natural form of dialogue for humans — no
    need for training in a specialised command
  – Extremely flexible and powerful;
  – The user is free to construct his own commands,
    frame his own questions, etc.
Natural language dialogue
 Disadvantages:
  – People find it difficult to stick to strictly
    grammatical English;
  – A well designed ‘artificial language’ can often
    say the same thing more concisely than ‘natural
  – A smooth, natural language can easily mislead
    the naive user into believing the computer is
    much more intelligent than it actually is.
Forms and dialogue boxes
 When the user is required to enter data:
  – Display should be given a title to identify it
  – The form should not be too cluttered
      • spaces and blanks in a display are important
   – It should give some indication of how many
     characters can be entered in each field
   – User should be given a chance to go back and
     correct any field before the data is accepted
Forms and dialogue boxes
 – Items should appear in a logical sequence
 – Default values should be prewritten onto the
   form to minimise of data entry
 – Full exit and ‘help’ facilities should be provided
    • users could enter ‘?’ in a field if they require more
 – Lower-case is neater and easier to read than
 – ‘Attention-getting’ devices such as blinking
   cursors, high-intensity, reverse video,
   underlining etc should not be over-used
The WIMP Interface
 Windows, Icons, Mouse and Pull-down
  – Window is the area on screen through which
    program or data file is being viewed
  – Icon is a small picture representing a system item.
    May be a file, program, command or storage
    medium. Usually ‘clickable’
  – MS Windows allows more than one application to
    run at a time, and also to move or link data between
Advantages of a common user
 Increased speed of learning;
 Ease of use;
 Confidence building for novice users;
 Increased range of tasks solvable by
  experienced users;
 A greater range of software accessible to the
  average user
Speech Input
 Ultimate interface would be to be able to speak normally to
  issue instructions to your computer.
 Two distinct types of voice recognition systems are
   – Command and Control systems
       • Small, tightly-controlled vocab. of technical terms
   – Large vocabulary dictation system
       • Handle whole sentences – but need considerable processing power
         and RAM
       • Use probability to select the correct word from a possible set that
         system has ‘heard’. Considers context and placement in sentence.
       • 70 wpm and around 97% accurate after ‘training’
Speech/Sound output
 Speech synthesis systems
   – Words spoken into microphone are recorded by the
   – Once the words are in the ‘vocabulary’, output that
     would normally be printed can then be ‘spoken’
   – Sometimes words that are not recognised are spelt
   – Limited use, but possible use in telephone banking
     or other telecommunications applications
Human-computer Interaction
Computers in the workplace
 Applying ergonomics to the office environment:
   – Lighting
     chosen for brightness, contrast, glare, blinds etc
   – Furniture
     must be comfortable and adjustable
   – Environmental considerations
     energy-efficient computer systems
 Psychological factors
 Vision
   –   important information should not be displayed in blue text - the
       eye is less sensitive to blue
   –   8% of males and 1% of females are colour-blind
   –   no interface should depend on everyone being able to distinguish
 Hearing
   –   Sound is commonly used for warnings e.g. illegal operation; Mac
       SonicFinder uses ‘auditory icons’
 Touch
   –   important in keyboard and mouse design.
 Movement
   –   users may find it difficult to manipulate small objects so targets
       should be reasonably large
 Memory
   –   present information intuitively, in easily-memorised portions
Designing good software
 Study software design to see what makes it good:
   – observe people interacting with computers
   – what do they find easy
   – which parts lead them to make more errors
 Human-Computer Interaction (HCI) design cycle
                Talk to and                          Participate
                 observe                                  in

       HCI                                                          testing

   Studied by

                       Design                         Design
                    Improvements   Contributes to   Weaknesses
Good User Interfaces
 Provide:
   – Help for novice users
   – Short cuts for experts
   – Meaningful images
   – Consistent behaviour
   – Clear, helpful error messages
   – Uncluttered screens with effective use of colour and text
      that is easy to read.
 Text vs Graphics
   – GUIs are generally easier to use
   – Sometimes it is quicker for an expert to type commands
   – Overuse of GUIs can slow the system down