Dialog Box

In a graphical user interface of computers, a dialog box is a type of window used to enable reciprocal communication or "dialog" between a computer and its user. It may communicate information to the user, prompt the user for a response, or both. A dialog box is most often used to provide the user with the means for specifying how to implement a command, or to respond to a question or an "alert" (see below).

Dialog boxes are classified as "modal" or "modeless", depending on whether or not 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.