A dialog is an equal exchange of information in real time between two partners or devices. Each dialog has a beginning, a series of actions, and an end. If one of the partners is a human, and the other is a computer, then the dialog takes place through the input of commands, by keystroke or mouse click, and the output is usually via a screen.
The dialog takes place in question-answer alternation, with the computer taking the active part and controlling the dialog. This is especially evident when working with dialog boxes, where the computer requests certain input and often only wants the following question to be answered when a corresponding entry is made.
In general, the person making the entry can follow each individual entry on the screen and thus modify or terminate his dialog part if necessary. For certain applications such as printing, authentication, saving files, and many more, there are predefined dialog boxes that limit the input options to meaningful entries.