The installation program installs all code and executables to your selected directory, and creates a shortcut on the Window's desktop to /guicode/hysplit4.tcl with the "Start In" directory as your selected default. On Unix systems the link would appear in the /working directory. When the GUI is first started, it looks for the supplemental programs such as Ghostscript, Ghostview, ImageMagick, and Tcl/tk in certain standard directories, and writes those paths to a file called default_exec. If this file already exists, those locations are used instead of the default search paths. The directories specified in this file may be edited through the "Set Directories" menu tab.