programming-for-dummies

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Designing a User Interface
User interfaces should tolerate and expect that the user will make a mistake
and then find a way to recover from these mistakes gracefully. This can be as
simple as having the program beep if the user tries to type his name instead
of his Social Security number, or having the program display a descriptive
error message that not only tells users what they did wrong but also tells
them what to do right.
By doing this, a user interface can give the user confidence to experiment
with a program and learn its features without reading a 300-page manual.
Instead, the user can gradually figure out how to use a program with the program
guiding him every step of the way.
Be consistent
One reason why franchise restaurants are so popular is because people
know what to expect when they eat there. User interfaces also need to make
a great first impression on users and then remain consistent so users generally
know what to expect from a program at any given time.
For example, suppose a program displays a toolbox of icons on the left side
of the screen. Now what happens if the user chooses a command and suddenly
the toolbox of icons either disappears or appears in another part of
the screen for no apparent reason at all?
Having the user interface suddenly change its appearance or behavior while
the program is running is certain to confuse and annoy users. By staying
consistent in appearance and behavior, a user interface can be predictable
so the user feels more comfortable using it (just as long as the user interface
was designed properly in the first place).
Focus on the task
Ultimately, the user interface must make it easy for the user to achieve a specific
result from the program, whether it involves creating greeting cards,
editing digital photos, or typing messages into a blog. If the user interface
doesn’t make the main purpose of the program clear and easy, users don’t
know or understand what to do.
The program in Figure 10-20 is designed to help people create stories, but
rather than display its various tools for story writing, this program forces
users to choose a file to open first. At this point, most users will wonder
which file to choose, where to find a file, and why they need to open a file if
they’re using the program for the first time?