1.6 Systems Design

• Text Based Interfaces


  • Input to the computer is via typed text, probably via a command prompt
  • Text-based system can allow complex/unusual commands to be entered, which may not be available via a GUI
  • Text-based system may run more quickly than a GUI / requires fewer resources
  • May be very efficient for an experienced user
  • Likely to take a novice a longer time to learn
• Graphics User Interfaces (GUI)


  • GUI is an interface where most communication is via screen elements such as windows, icons, menus, pointers
  • GUI system is usually more intuitive to use/easier to learn
  • GUI may use icons relevant to the application / be more transparent to the user
  • May be similar to other packages (users are familiar)
  • There is no need to remember complex text commands
  • It is easier to cut and paste between applications
  • Usually good help / tutorial system
  • Users can customise desk-top, etc
• Speech Recognition Interfaces


  • Commands and/or text input are given to the computer via human speech
  • Speeds up text input / faster than typing
  • Can be used by someone doing another task with their hands eg pilot
  • Can be used by someone who is unable to type / not a skilled typist / disabled
  • Avoids RSI, etc
  • Can involve very heavy hardware performance requirements (once only)
  • Difficulty picking up / separating speech sounds
• Speech Recognition Interfaces


  • People have different accents / voices - computer may need to "learn" the speech style
  • Cannot usually be used without some tuition / may have to speak slowly
  • Affected by colds, throat infections / speech impediments etc
  • Problem of background noise / interference from/to other staff in office
  • Can overhear others' input
  • Can have difficulty with proper nouns
  • Can have difficulty with homophones
• Forms Dialogue Interfaces


  • Computer prompts for input into specific fields on a screen dialogue form
  • Cursor may move automatically to next input field
  • Allows change to be made while screen still visible
  • Intuitive to fill in - echoes familiar paper form / good for surveys etc
  • May include validation – only some entries allowed
• Free Format Dialogue Interfaces


  • A system which allows free form text to be entered into the interface
  • The user is not restricted by set fields / validation / syntax
  • Eg: Google search box; Windows help search box; pop up box asking for comments
• Handwriting Recognition Interfaces


  • Quicker / easier for user than typing
  • Avoids bulky keyboard
  • May not be very accurate - could easily "misread" user's handwriting
  • Difficult to use - needs constant visual checking
  • May not be possible for disabled users
  • User may need to learn writing style
  • Computer may need to "learn" a writer's handwriting
• Touchpad


  • A touchpad can more easily be fitted into a small device like a laptop computer or PDA
  • Does not require extended flat space to move the mouse over / allows multiple gestures, hand swipes etc
  • NOT just smaller / cheaper / faster / more precise / health issues / better for disabled user
• Dedicated Keys


  A dedicated key is a hardware button that has a fixed function in a user-interface
• Soft Keys


  A soft key is a hardware button whose function can be programmed to carry out different functions depending on the needs of the user interface
• Design Validation


  • A review of the design is undertaken to:
  • Check the correspondence between the actual design and its specification / user requirements / objectives / safety issues
  • Confirm that the most appropriate techniques have been used
  • Confirm the HCI is appropriate
• Errors made in the design stage will carry through to all further development stages of the new system
• If there were mistakes made at the design stage, a lot of work would be done in implementing a system which, at worst, did not work, or at best, did not do the job well
• Criteria To Evaluate A Computer-Based Solution

  • Requirements - have they been met?
  • Usability - can end users use it?
  • Robust - it should not crash or fail
  • Cost - has it come under budget?
  • Performance - does it respond quick enough?