User Interface Design and Ergonomics - National Open University of ...

Advantages of Direct Manipulation
Visually presents task concepts.
Easy to learn.
Errors can be avoided more easily.
Encourages exploration.
High subjective satisfaction.
Recognition memory (as opposed to cued or free recall memory)
Disadvantages
May be more difficult to programme.
Not suitable for small graphic displays.
Spatial and visual representation is not always preferable.
Metaphors can be misleading since the “the essence of metaphor is understanding
and experiencing one kind of thing in terms of another”, which, by definition,
makes a metaphor different from what it represents or points to.
Compact notations may better suit expert users.
3.2 GRAPHIC DESIGN PRINCIPLES
The graphic design of an interface involves decisions about issues such as where to put
things on the screen, what size and font if type to use, and what colors will work best. For
these questions as for other, more substantive design issues, intelligent borrowing should
be your first approach. But that often leaves you with a lot of decisions still to be made.
Here are a few principles of graphic design that will not only make your interface more
attractive, but will also make it more usable. Each principle is accompanied by a
description of WHY it is important. So you will be able to consider the tradeoffs when
there is a conflict between two principles or between a design principle and a borrowed
technique.
a. The Clustering Principle: Organize the screen into visually separate blocks of
similar controls, preferably with a title for each block.
"Controls," as we use the word here, include menus, dialog boxes, on-screen buttons, and
any other graphic element that allows the user to interact with the computer. Modern
WIMP (Windows-Icons-Menus-Pointer) systems are a natural expression of the
Clustering Principle. Similar commands should be on the same menu, which places them
in close proximity visually and gives them a single title. Large numbers of commands
related to a given area of functionality may also show up in a dialog box, again a visually
defined block.
But the same principle should apply if you are designing a special control screen with
many buttons or displays visible, perhaps a touch-screen interface. The buttons for a
given function should be grouped together, then visually delineated by color, or a
bounding box, or surrounding space ("white space"). The principle should also be applied
within WIMP systems when you design a dialog box: If there is a subgroup of related
functions, put them together in the box.
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