- A word such as bat is ambiguous.
It can have different meanings
as in the zoo had many different bat species
versus I recently bought a new baseball bat.
The context helps us disambiguate the meaning of the word.
Same in a user interface.
It's possible that the same user action
has different effects,
depending on the context or the state
in which the system is in.
That's a mode.
Same input, different results.
Modes are pervasive in interfaces around us.
For example, here's my locked phone.
If I press the volume up button, nothing will happen,
but if I unlock my phone,
pressing the same button will raise the volume.
The same action, pushing the volume button,
has different effects,
depending on whether the phone is locked or not.
That's a mode.
Another classic example of a mode
is the use of the Caps Lock key on a typical keyboard.
With the Caps Lock key off,
pressing the key for the letter A in a text editor
will display a lowercase A.
With Caps Lock on, the same action
will result in an uppercase A.
Thus, the Caps Lock key is a mode switcher.
Now why do we need modes in user interfaces?
The answer is because usually
we don't have enough possible input actions.
In other words, our input vocabulary is limited.
A keyboard with keys for both upper and lowercase letters
will be too large.
But sometimes it's also because certain input actions
fit well with multiple functionalities.
For example, if on my phone I wanna sign a PDF document,
moving the finger on the screen is the most natural action
for drawing my signature.
But traditionally, moving the finger is used for scrolling.
Therefore, to allow for that gesture
to have different results,
a special edit mode will have to be defined.
Modes are often a source of user error,
usually because of the so-called hidden state problem.
People don't realize which state the system is in
and therefore, they expect that their actions
will have a different result.
It's probably happened to you to repeatedly get an error
while typing your password because Caps Lock was on
and you didn't realize it since the password was masked.
Because of that, often UX researchers don't like modes.
Larry Tesler, former VP at Apple, Amazon and Yahoo!
and a UX pioneer, famously had a no modes license plate.
Now a special type of mode is a modal.
A modal is a type of popup window.
What's special about a modal is that users cannot interact
with the background content until they dismiss the window.
Thus, modals put the system into a new mode.
When the modal is on,
clicking on any of the background visible links
doesn't do anything anymore.
Not every popup is a modal.
Some allow you to interact with the background
and those are called non-modal dialogs.
To summarize, modes are a way of dealing
with interface complexity.
Often the designer may have a limited input vocabulary
and a lot of possible functions
that a interface needs to support.
So they will end up reusing some of that input vocabulary
for two different commands.
Modes often lead to user errors
because people don't realize they are in the wrong mode
or sometimes don't know how to get to a mode
or out of a mode.
But in certain situations like drawing on a touchscreen,
modes may be the only reasonable solution
to a design problem.