Human Factors in Computing

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Human Factors in Computing
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Problems with Computers
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Learning Outcomes

• Understand the concept of usability in and its
  various sub-concepts in relation to computer
  software
• Identify and appreciate the functions of typical
  user-interface components and conventions of
  commonly used software

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Usability

• A concept in all man/machine interaction even
  down to the level of the opening and closing of
  doors
• How do we know whether to push or pull a door open

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Door at the End of the LB Corridor

• Elements of a Fire Exit
• Button for Wheelchair Users
• Sometimes the doors open sometimes not
• No intuitive sense of how the door works

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Door (2)

• No confusion about pushing or pulling
• No instructions on which door to push
• No feedback on actions
• Difficult to work out what does what

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Affordance

• Certain materials or the design of them afford
  certain actions with certain consequences
• Handle affords pulling
• Pushbutton affords pushing
• On a web page what affords clicking?
• Highlighted text, rollover images, change of
  cursor, 3d bevel of an image

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Visibility

• Difference between programming a digital display
  alarm clock and an analogue display alarm clock
• Knowledge in the head and in the world
• recognition vs recall
• Difference between using a command language to
  copy a file and a graphical interface

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Tube Map
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TV Sets
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Visibility Matrix
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Feedback

• Programming a VCR. Problems are
• difficulty remembering your place in the sequence
  of actions
• difficulty remembering what next needs to be done
• cannot check the information entered to see if it
  was what was intended
• Essentially a lack of feedback

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Feedback 2

• Sound as a form of feedback (rattle)
• Color to indicate different intensities of
  feedback

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Mapping

• The relationship between controls and their
  movements and results in the world

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Mental Models

• Mental models allow us to conjecture the
  functioning of a machine such that we can derive
  its behaviour from it
• My television
• Allows us to conjecture what might be the
  solution to a never-before-encountered problem
• How do I get from Bounds Green to Seven Sisters

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Constraints

• Cultural Constraints (going into restaurants)
• Strong constraints (I cannot switch on the
  microwave with the door open)
• Breaking glass to activate an alarm
• Graying out of menus in computer applications

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Standardisation

• Explicit conventions which are adopted
• In computers the position of the principle menus
  key commands

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Designing for Error

• If we explore - we will make errors
• To err is human to forgive is divine
• How can users make errors uncatastrophically?
• How does a computer stop us deleting files by
  accident?
• How does a computer allow us to retreat from our
  mistakes?

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Preventing Error

• Making choices exclusive
• Prohibiting certain choices at certain point

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Task Analysis

• Things do things
• Wide and shallow (choosing ice cream)
• Few levels, a multitude of choices
• Thin and deep
• Many levels, not many on each (doing a recipe)
• Taking an underground journey

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Models ? Metaphors

• The typewriter model works to the keyboard
• Think of various metaphors in use and how they
  work in the real world

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Icons - Graphical Metaphors

• Try to design icons for the following interface
  concepts
• a place to discard files
• to open
• to copy
• a place to store files

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Icons
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Manuals

• Place of last resort
• On-line help (context sensitive)

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How Things Work

• We understand how things work through
• affordances of materials, visibility of controls,
  natural mapping of controls, feedback to our
  actions, a coherent mental model of the thing
  used, constraints that prohibit us from doing
  undesirable things, adherence to standards and
  conventions in the operation of the thing
• We explore
• We read manuals

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Interaction Styles

• Command Entry
• Menus and Navigation

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Command Entry

• Normally the name of an executable file or system
  command followed by parameters
• copy a.txt b.txt (MS-DOS)
• cp a.txt b.txt (Unix)
• Parameters can be subdivided by switches (where
  there are a number of possible parameters)
• gcc processor.c -o processor.exe
• Wildcards can be used for multiple operations

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Pros Cons

• Can be very fast for expert users
• Commands can be combined into batch files
  (MS-DOS) or shell scripts (Unix) for running a
  particular sequence of commands or the same
  command many times
• Requires good memory or recourse to a manual if
  the command cannot be found

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Menu Driven Interaction

• Builds on a mental model of a system meaning you
  know more or less where you can do something then
  you just find it
• Can be pop-up or pull down
• Usually have accelerator keys attached (in case
  your mouse isnt working or for speed)
• Often used commands can be done with key
  combinations and via icons on the Toolbar

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Menu Conventions

• Now the first three menus on most applications
  are File, Edit ,View
• The last two are usually Window and Help
• What are typical commands you find within the
  File and Edit menus of most applications?

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Dialog Boxes

• Some operations are either too complex or
  specific to be accomplished by a single menu
  command

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Extended Dialog Boxes- (Wizards)
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Extended Dialog Boxes- (Tabbed)
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Natural Language Interaction

• Advantage - naturalness
• Disadvantage - comprehension
• of natural language still
• very poor by computer
• Mainly used for searching rather than doing

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Direct Manipulation

• Dragging/Drawing/Erasing
• Direct Manipulation interaction styles are
  characterised by
• visibility of the objects of interest
• rapid, reversible, incremental actions
• replacement of complex command language by direct
  manipulation of the object of interest

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Components

• Standardisation of User Interface components aids
  users making knowledge of one application help
  learning the next

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Buttons

• Push Buttons
• Grey 3d, Rollover
• Usually immediately produce and action when
  clicked
• Radio Buttons
• Used for a mutually exclusive choices
• Used for configuration - not action
• Check Boxes
• Used for inclusive choices (more than one of
  each)
• Used for configuration not action

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List Boxes/Combo Boxes

• Single Select List Box
• Multi Select List Box
• Combo Box/Drop Down Menu

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Menus

• Usually belong to Windowing Systems - not so
  common on web pages
• Menus and Submenus

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Text Fields

• Single Line Text Box
• Multi-Line Text Box

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Cursors

• Indicate both operations that are possible
• And state of the machine

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Widgets

• Sliders
• Scrollbars
• Spinner (Spin Buttons)

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Windows

• Client Area of Applications
• Can be tiled, maximised or minimised