http://lashwhip.com/grpn.html
(yes, I know that xcalc has an HP mode, but I only learned of that mode long after I'd begun using GPRN.
The calculator on my Android phone (I 'disabled' the maker installed one):
https://play.google.com/store/apps/details?id=org.efalk.rpnc...
And I've still got my original 80's HP-15C.
http://lashwhip.com/grpn.html
(yes, I know that xcalc has an HP mode, but I only learned of that mode long after I'd begun using GPRN.
The calculator on my Android phone (I 'disabled' the maker installed one):
https://play.google.com/store/apps/details?id=org.efalk.rpnc...
And I've still got my original 80's HP-15C.