A dialog box is a window that appears on top of a main application or other window (or occasionally no window at all) requesting user input. Dialog boxes are characterized by one or more input fields, such as edit boxes, check boxes, selection lists and others, an “OK” or equivalent button, and a “Cancel” button. Dialog boxes may or may not have title bars across the top, and while usually movable, they are most often not resizable.
If presented by an application, a dialog box is typically smaller than the application window, so as to appear to be a part of that application.
The term “dialog” refers to the metaphor that the computer is having a conversation or dialog with the user, and is asking for some form of input and processing that input when supplied.
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The dialog box (also called dialogue box (non-U.S. English) or just dialog) is a graphical control element in the form of a small window that communicates information to the user and prompts them for a response.
Dialog boxes are classified as "modal" or "modeless", depending on whether they block interaction with the software that initiated the dialog. The type of dialog box displayed is dependent upon the desired user interaction.
The simplest type of dialog box is the alert, which displays a message and may require an acknowledgment that the message has been read, usually by clicking "OK", or a decision as to whether or not an action should proceed, by clicking "OK" or "Cancel". Alerts are also used to display a "termination notice"—sometimes requesting confirmation that the notice has been read—in the event of either an intentional closing or unintentional closing ("crash") of an application or the operating system. (E.g., "Gedit has encountered an error and must close.") Although this is a frequent interaction pattern for modal dialogs, it is also criticized by usability experts as being ineffective for its intended use, which is to protect against errors caused by destructive actions, and for which better alternatives exist.
An example of a dialog box is the about box found in many software programs, which usually displays the name of the program, its version number, and may also include copyright information.