Another tool is the Prolog Navigator. This tool can be started from PceEmacs using the command Browse/Prolog navigator, from the GUI debugger or using the programmatic IDE interface described in section 3.8. It is rooted at the common directory of all loaded source files and initially shows only these files. Collapsing and re-expanding a directory, or Show all files from its popup menu, adds the Prolog files that are not loaded. If the loaded files are spread over multiple Windows drives, the root is a virtual node holding these drives.