When using a graphical user interface (or GUI) like the X Window System, one's display is typically occupied by a collection of windows associated with various applications, rather than a single stream of text associated with a single process. In this case, one may use a terminal emulator application within the windowing environment. This arrangement permits terminal-like interaction with the computer (for running a command-line interpreter, for example) without the need for a physical terminal device; it can even allow the running of "multiple" terminal emulators on the same device.