Dialog box

In graphical user interface

Graphical user interface

A graphical user interface is a type of user interface item that allows people to interact with programs in more ways than typing such as computers; hand-held devices such as MP3 Players, Portable Media Players or Gaming devices; household appliances and office equipment with images rather than...

s, a dialog (or dialogue) box is a special window

Window (computing)

In computing, a window is a visual area containing some kind of user interface. It usually has a rectangular shape. It displays the output of and may allow input to one or more processes....

, used in user interfaces to display information

Information

Information as a concept has many meanings, from everyday usage to technical settings. The concept of information is closely related to notions of constraint, communication, control, data, form, instruction, knowledge, meaning, mental stimulus, pattern, perception, and representation.The English...

 to the user, or to get a response if needed. They are so-called because they form a dialog between the computer and the user—either informing the user of something, or requesting input from the user, or both. It provides controls that allow you to specify how to carry out an action.

Dialog boxes are classified as modal

Mode (computer interface)

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....

 or modeless, depending on whether they block interaction on the application

Application software

Application software is a computer program that functions and is operated by means of a computer, with the purpose of supporting or improving the software user's work. In other words, it is the subclass of computer software that employs the capabilities of a computer directly and thoroughly to a...

 that triggered the dialog.

In graphical user interface

Graphical user interface

A graphical user interface is a type of user interface item that allows people to interact with programs in more ways than typing such as computers; hand-held devices such as MP3 Players, Portable Media Players or Gaming devices; household appliances and office equipment with images rather than...

s, a dialog (or dialogue) box is a special window

Window (computing)

In computing, a window is a visual area containing some kind of user interface. It usually has a rectangular shape. It displays the output of and may allow input to one or more processes....

, used in user interfaces to display information

Information

Information as a concept has many meanings, from everyday usage to technical settings. The concept of information is closely related to notions of constraint, communication, control, data, form, instruction, knowledge, meaning, mental stimulus, pattern, perception, and representation.The English...

 to the user, or to get a response if needed. They are so-called because they form a dialog between the computer and the user—either informing the user of something, or requesting input from the user, or both. It provides controls that allow you to specify how to carry out an action.

Dialog boxes are classified as modal

Mode (computer interface)

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....

 or modeless, depending on whether they block interaction on the application

Application software

Application software is a computer program that functions and is operated by means of a computer, with the purpose of supporting or improving the software user's work. In other words, it is the subclass of computer software that employs the capabilities of a computer directly and thoroughly to a...

 that triggered the dialog. Different types of dialog boxes are used for different sorts of user interaction.

The simplest type of dialog box is the alert

Alert dialog box

An alert dialog is a colloquial term for a particular type of dialog box that occurs in a graphical user interface...

, which displays a message and requires only an acknowledgment (by clicking 'OK' usually) that the message has been read. Alerts are used to provide simple confirmation of an action, or include program termination notices or confirmation due to crashing

Crash (computing)

A crash or in computing is a condition where a program stops performing its expected function and also stops responding to other parts of the system. Often the offending program may simply appear to freeze...

 or intentional closing by user. Though this is a frequent interaction pattern

Interaction design pattern

Interaction design patterns are a way to capture optimal solutions to common usability or accessibility problems in a specific context. They document interaction models that make it easier for users to understand an interface and accomplish their tasks....

 for modal dialogs, it is also criticised by usability

Usability

Usability is a term used to denote the ease with which people can employ a particular tool or other human-made object in order to achieve a particular goal...

 experts as being ineffective for its intended use (protection against errors in destructive actions) and for which better alternatives exist.

Modeless

Non-modal or modeless dialog boxes are used when the requested information is not essential to continue, and so the window can be left open while work continues elsewhere. A type of modeless dialog box is a toolbar

Toolbar

In a graphical user interface on a computer monitor a toolbar is a GUI widget on which onscreen buttons, icons, menus or other input or output elements are placed....

 which is either separate from the main application, or may be detached from the main application, and items in the toolbar can be used to select certain features or functions of the application.

In general, good software design calls for dialogs to be of this type where possible, since they do not force the user into a particular mode of operation. An example might be a dialog of settings for the current document, e.g. the background and text colours. The user can continue adding text to the main window whatever colour it is, but can change it at any time using the dialog. (This isn't meant to be an example of the best possible interface for this; often the same functionality may be accomplished by toolbar buttons on the application's main window).

Application modal

Modal dialog boxes are those which temporarily halt the program in that the user cannot continue until the dialog has been closed: the program may require some additional information before it can continue, or may simply wish to confirm that the user wants to proceed with a potentially dangerous course of action. Modal dialogs are generally regarded as bad design solutions by usability practitioners since they are prone to produce mode errors. Dangerous actions should be undoable wherever possible; a modal alert dialog that appears unexpectedly or which is dismissed automatically (because the user has developed a habit

Habituation

Habituation is the psychological process in humans and animals in which there is a decrease in psychological response and behavioral response to a stimulus after repeated exposure to that stimulus over a duration of time.- Background :...

) will not protect from the dangerous action.

The main workflow

Workflow

A workflow consists of a sequence of connected steps. It is a depiction of a sequence of operations, declared as work of a person, a group of persons, an organization of staff, or one or more simple or complex mechanisms. Workflow may be seen as any abstraction of real work, segregated in...

 is interrupted when a modal dialog is shown. This effect has either been sought because it focuses on the completion of the task at hand or rejected because it prevents the user from changing to a different task when needed.

Window modal

Traditionally, modal dialogs have been either system or application modal - they either take over the whole system until they are dismissed, or just the application that displayed it. The concept of a document modal dialog has recently been used, most notably in Mac OS X

Mac OS X

Mac OS X is a line of computer operating systems developed, marketed, and sold by Apple Inc., and since 2002 has been included with all new Macintosh computer systems...

 where they are shown as sheets attached to a parent window. These dialogs block only that window until the user dismisses the dialog, permitting work in other windows to continue, even within the same application.
In OS X, dialogs appear to emanate from a slot in their parent window, and are shown with a reinforcing animation. This helps to let the user understand that the dialog is attached to the parent window, not just shown in front of it. No work can be done in the underlying document itself while the dialog is displayed, but the parent window can still be moved, re-sized, and minimized, and other windows can be brought in front so the user can work with them:

The same type of dialog box can be compared with the "standard" modal dialog boxes used in Windows and other operating systems.

Similarities include:

• the parent window is frozen when the dialog box opens, and one cannot continue to work with the underlying document in that window
• no work can be done with the underlying document in that window.

The differences are that

• the dialog box may open anywhere in the parent window
• depending on where the parent window is located, the dialog box may open virtually anywhere on screen
• the dialog box may be moved (in almost all cases), in some cases may be resizable, but usually cannot be minimized, and
• no changes to the parent window (cannot be resized, moved or minimized) are possible while the dialog box is open.
  

Both mechanisms have shortcomings:

• The Windows dialog box locks the parent window which can hide other windows the user may need to refer to while interacting with the dialog, though this may be mitigated since other windows are available through the task bar.
• The OS X dialog box blocks the parent window, preventing the user from referring to it while interacting with the dialog. This may require the user to close the dialog to access the necessary information, then re-open the dialog box to continue.