A user interface of a machine tool includes a display that is divided into at least a first display region and a second display region. The first display region permanently displays a main menu, and the main menu includes a menu bar that provides a selection of different main modes of the user interface. Each main mode is associated with a main window that is opened in the second display region when a main mode is selected in the main menu. At least one of the main windows includes a permanently displayed submenu that provides selection of different submodes, with each submode being associated with a subwindow that is opened when an associated submode is selected. One or more of the main windows and the subwindows include input fields. The user interface also includes an input unit for selecting the individual modes and for processing the input fields provided in a window. The display permanently displays which one of the main modes is selected.