By default the main window is split into three vertical panes (see below).
The menu bar contains the various commands to access the features of ProB. It includes the traditional "File" menu with a sub-menu "Recent Files" to quickly access the files previously opened in ProB. Notice the commands "Open\Save", "Reopen\Save" and "Reopen"; the latter reopens the currently opened file and reinitializes the state of the animation and the model checking processes completely. The "About" menu provides help on the tool and includes a command to check if an update is available on the ProB website.