Ch. 2: User Interface

User interfaces
1. There must be some way for a person to command a computer, and to get its results: the user interface.
2. Early computers were strictly text-based.
  1. Impossible to use without doing a bunch of reading first.
  2. Often quite obscure and unintuitive.
3. Current computers have Graphical User Interfaces (GUIs).
  1. Designed for immediate use.
  2. Icons and menus let you select what to do from possibilities.
  3. Metaphors (virtual objects)
    1. Items on the screen look and act like real objects.
    2. Volume control, slider, music player, spreadsheet, &helip;
    3. Applies what we already know.
  4. Feedback.
    1. Immediate response (if possible).
    2. Spinner or progress bar.
  5. Consistent interface.
    1. Particular authors use consist-ant style.
    2. Fundamental items are consistent even between different makers.
    3. Avoids re-learning for every application.
  6. Common operations: New, copy, copy-paste, find-and-replace.
  7. Place-holder method.
Some History
1. Mouse invented by Douglas Engelbart at SRI (Stanford).
2. First commercial computer with a GUI: Alto from Xerox.
  Very expensive; not successful.
3. Steve Jobs visited Xerox PARC
  1. Apple created the Lisa, which was not popular.
  2. Then the Macintosh, which was.
4. Microsoft created Windows after the Mac success.
5. GUI created for office work: metaphor is the desktop.
GUI presenting the computer's contents. The GUI must represent the computer's objects in some comprehensible way.
1. The original GUI used the desktop metaphor
  1. Files are documents.
  2. The disk is a file cabinet where you can put documents.
  3. Deleting a file is moving it to the trash can.
2. Phones are leaving this.
  1. Author uses the term “Touch metaphor”
  2. But it doesn't seem to be a metaphor for anything.
  3. Which may just mean we no longer need our computer interface to look like something else.
Copying data. Why is this in this chapter? Don't know.
1. Traditional data recording is analog.
  1. To record a number, set some physical quantity proportional to it.
  2. This is the analog of the recorded quantity.
    1. Voltage in a wire (telephone or speaker wire).
    2. Amplitude or frequency of a carrier wave (AM or FM radio, analog TV).
    3. Grooves on a phonograph record.
    4. Amount of magnetization of a strip of tape.
2. Digital recording: Measure the number and record the number.
3. Experiment
  1. Draw a square, then make an exact copy.
  2. Write down the size, (say 4x5), then copy the size.
4. Copying
  1. The copied square will have some imperfection. The copied size does not have to look exactly the same to mean exactly the same thing.
  2. Copying an analog recording always introduces error. Repeated copying accumulates this error.
  3. Copying a digital recording makes a perfect copy.