Dialog box

A dialog box (or simply "dialog") is an interactive element where an operating system running a graphical user interface is awaiting information from a user.

History
Dialog boxes were introduced in the Apple Lisa in 1983, followed in 1984 by Macintosh computers running classic Mac OS. Modal dialog boxes require a user to provide input before proceeding further on other tasks.

Simple dialog boxes
Simple dialog boxes can present a binary "yes-or-no" question. For example, when you quit Microsoft Word, the application may ask you whether or not you wish to save any unsaved documents. The default response, if available, will be indicated by the presence of color or a heavy outline and can be activated by the enter button as an alternative to a mouse click. The simplest dialog boxes, such as alerts, may present only one option requiring acknowledgement by the user before proceeding.

Complex dialog boxes
In more complex dialog boxes, the user can complete tasks other than simply answering multiple-choice options. For early Mac users, the Font/DA Mover was a dialog box where the user had to move fonts and desk accessories within the confines of a dialog box. Other common examples include open and save dialog boxes.

Dialog sheets
Introduced in Mac OS X (now mac OS) dialog sheets are a form of dialog box that is attached to a specific window, so that the user can more easily identify the source of the dialog query. Sheets are not modal, allowing the user to work on other tasks while awaiting a response.