Unix computers use a protocol called X11 to provide windows-like functionality in Unix applications. This interface is commonly called a graphical user interface or GUI interface. Most Unix applications can be invoked by the user in either an X11 mode (GUI mode using an X-terminal) or a text-based mode that does not use the GUI. Text-based versions of applications will not render graphics, nor will they have the familiar pull-down menus associated with common MS windows applications.