RPNcalc rpncalc is a Revese Polish logic scientific calculator application that is built using the GtkFortran libraries <https://github.com/vmagnin/gtk-fortran/wiki>. It should work equally well with late 2.x and the 3.0 versions of Gtk+. WARNING: On 24 Jan 2013, the executable name (and other name stems) were changed from "rpncalc" to "RPNcalc" to avoid a clash with an existing CLI calculator also called rpncalc. You are advised to uninstall the old version before updating your sources.