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Mode (user interface)

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This article is about a transient state in user interfaces. For modes in videogames, see Game mode. For other uses, see Mode (disambiguation).

In user interface design, a mode is a distinct setting within a computer program or any physical machine interface, in which the same user input will produce perceived different results than it would in other settings. The best-known modal interface components are probably the Caps lock and Insert keys on the standard computer keyboard, both of which put the user's typing into a different mode after being pressed, then return it to the regular mode after being re-pressed.

A precise definition is given by Jef Raskin in his book "The Humane Interface":

"An human-machine interface is modal with respect to a given gesture when (1) the current state of the interface is not the user's locus of attention and (2) the interface will execute one among several different responses to the gesture, depending on the system's current state." (Page 42).

An interface that uses no modes is known as a modeless interface.[1] Modeless interfaces intend to avoid mode errors[2] by making it impossible for the user to commit them.

Advantages

Modes offer many advantages to the user, including increased efficiency, convenience, and power. For instance in Vi, a modal text editor, many operations that would traditionally require moving the fingers from the homerow, or worse, removing a hand completely from the keyboard to use a mouse, can be executed by typically a few keystrokes.

Modes and Awareness

It is important to note that, in Raskin's sense, an interface is not modal as long as the user is fully aware of its current state. Raskin refers to this as 'locus of attention'. Typically a user is aware of a system state if the state change was purposefully initiated by the user, or if the system gives some strong signals to notify the user of the state change.

Problems occur if the state change happens unnoticed (initiated by the system, or by another person, such as the user who was previously using the machine), or if after some time the user forgets about the state change. Another typical problem is a sudden change of state that interrupts a user's activity. In such a situation it can easily happen that the user does some operations with the old state in mind, while the brain has not yet fully processed the signals indicating the state change.

A very frustrating type of modality is those modes where the user does not find a way out, or, in other words, where she cannot find how to restore the old system state.

Examples

There are several popular examples of software employing modes:

  • Microsoft Word - by default the program is in insert mode but can be toggled in and out of overstrike mode by pressing the Insert key.
  • vi - has one mode for inserting text, and a separate mode for entering commands. There is also an "ex" mode for issuing more complex commands (e.g. search and replace). Under normal circumstances, the editor automatically returns to the previous mode after a command has been issued; however, it is possible to permanently move into this mode using Shift-Q.
  • Emacs - has a special mode for issuing commands, which is entered by pressing the control key plus a letter key. This differs from vi in that the mode always ends as soon as the command is called. Emacs also has many "major and minor" modes that change the available commands, and are automatically invoked based on file type to more easily edit files of that type. Modes are written in Emacs Lisp, and all modes may not be included with all versions.
  • Cisco IOS - in order to execute certain commands, you must enter a certain "command mode" that allows you to execute that command.
  • Also, tools chosen from a palette in photo-editing and drawing applications are examples of a modal interface.

Criticism and mode errors

See also: User error

Modes are generally frowned upon in interface design because they inevitably lead to input errors, known as "mode errors", when the user forgets what state the interface is in, performs an action that is appropriate to a different mode, and gets an unexpected and undesired response.[3] A mode error can be quite startling and disorienting as the user copes with the sudden violation of his or her user expectations. Interface expert Jef Raskin came out strongly against modes, writing, "Modes are a significant source of errors, confusion, unnecessary restrictions, and complexity in interfaces." Later he notes, "'It is no accident that swearing is denoted by #&%!#$&,' writes my colleague, Dr. James Winter; it is 'what a typewriter used to do when you typed numbers when the Caps Lock was engaged'." Nevertheless, modal proponents may argue that this is not a fair criticism of the inherent modal paradigm, as many common activities are modal and users adapt or even prefer them. Motor vehicles are modal: A user may be surprised when pressing the acceleration pedal does not accelerate the vehicle in the forward direction, most likely because he or she had placed the vehicle in an operating mode like park, neutral, or reverse! Yet the majority of motor vehicles are modal. Modal interfaces require training and experience.

Larry Tesler, of Xerox PARC and Apple Computer, disliked modes sufficiently to get a personalized license plate for his car that reads: "NO MODES". He has used this plate from the early 1980s to the present, on various cars. Along with others, he has also been using the phrase "Don't Mode Me In" for years as a rally cry to eliminate or reduce modes. [4]

Bruce Wyman, the designer of a multi-touch table for a Denver Art Museum art exhibition [5] argues that interfaces for several simultaneous users must be modeless, in order to avoid bringing any single user into focus. [6]

Modes can be successful in particular usages to restrict dangerous or undesired operations, especially when the mode is actively maintained by a user. They can also work as well-understood conventions, such as painting tools.

Examples of mode errors

  • The most common source of mode errors may be the caps lock key.
  • A frequent example is the sudden appearance of a modal error dialog in an application while the user is typing; the user expects the typed text to be introduced into a text field, but the unexpected dialog discards all that input and may even interpret some keystrokes (like 'Y' or 'N' for 'yes' or 'no') incorrectly.
  • The Unix text editor vi can be notoriously difficult for beginners precisely because it uses modes, and earlier versions configured mode indication to be turned off by default.

Workarounds and alternatives

Small signs make explicit the mappings from signal to roads

HCI researcher Donald Norman argues that the best way to avoid mode errors, in addition to clear indications of state, is to construct an accurate mental model of the system for the user which will allow them to predict the mode accurately. This is demonstrated, for example, by some stop signs which show small diagrams describing which of the directions have a stop sign and which don't.

Quasimodes

In the book The Humane Interface, Jef Raskin championed what he termed "quasimodes", which are modes that are kept in place only through some constant action on the part of the user; such modes are also called "spring-loaded modes".[7] Modifier keys on the keyboard, such as the Shift key, the Alt key and the Control key, are all examples of a quasimodal interface.

The application enters into that mode as long as the user is performing a conscious action, like pressing a key and keeping it pressed while invoking a command. If the sustaining action is stopped without executing a command, the application returns to a neutral status.

The purported benefit of this technique is that the user doesn't have to remember the current state of the application when invoking a command: the same action will always produce the same perceived result. [8]

The name is a composite of the Latin prefix quasi (which means almost, to some degree) and mode (from Latin modus, manner, tune).

See also

Notes

  1. ^ Usability Glossary: modeless
  2. ^ Usability Glossary: mode error
  3. ^ Usability Glossary: modal
  4. ^ The Smalltalk Environment by Larry Tesler
  5. ^ Technology for Experience's Sake: Guest Post by Bruce Wyman
  6. ^ Bruce Wyman's post at the ixda.org mailing list
  7. ^ Usability Glossary: spring-loaded mode
  8. ^ Spring-Loaded Modes, Jakob Nielsen.

References

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