- User interfaces
- There must be some way for a person to command a computer, and to
get its results: the user interface.
- Early computers were strictly text-based.
- Impossible to use without doing a bunch of reading first.
- Often quite obscure and unintuitive.
- Current computers have Graphical User Interfaces (GUIs).
- Designed for immediate use.
- Icons and menus let you select what to do from possibilities.
- Metaphors (virtual objects)
- Items on the screen look and act like real objects.
- Volume control, slider, music player, spreadsheet, &helip;
- Applies what we already know.
- Immediate response (if possible).
- Spinner or progress bar.
- Consistent interface.
- Particular authors use consist-ant style.
- Fundamental items are consistent even between different makers.
- Avoids re-learning for every application.
- Common operations: New, copy, copy-paste, find-and-replace.
- Place-holder method.
- Some History
- Mouse invented by Douglas Engelbart at SRI (Stanford).
- First commercial computer with a GUI: Alto from Xerox.
Very expensive; not successful.
- Steve Jobs visited Xerox PARC
- Apple created the Lisa, which was not popular.
- Then the Macintosh, which was.
- Microsoft created Windows after the Mac success.
- 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
- The original GUI used the desktop metaphor
- Files are documents.
- The disk is a file cabinet where you can put documents.
- Deleting a file is moving it to the trash can.
- Phones are leaving this.
- Author uses the term “Touch metaphor”
- But it doesn't seem to be a metaphor for anything.
- 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.
- Traditional data recording is analog.
- To record a number, set some physical quantity proportional to it.
- This is the analog of the recorded quantity.
- Voltage in a wire (telephone or speaker wire).
- Amplitude or frequency of a carrier wave (AM or FM radio, analog TV).
- Grooves on a phonograph record.
- Amount of magnetization of a strip of tape.
- Digital recording: Measure the number and record the number.
- Draw a square, then make an exact copy.
- Write down the size, (say 4x5), then copy the size.
- The copied square will have some imperfection. The copied size
does not have to look exactly the same to mean
exactly the same thing.
- Copying an analog recording always introduces error. Repeated
copying accumulates this error.
- Copying a digital recording makes a perfect copy.