xrpn

https://github.com/isene/XRPN

A full programming language and environment extending the features of the venerable HP calculator programmable calculators. With XRPN you can accomplish a wide range of modern programming tasks as well as running existing HP-41 FOCAL programs directly. XRPN gives modern life to tens of thousands of old HP calculator programs and opens the possibilities to many, many more. New in 1.9: Added functions 'lastpage' and 'load' and also added 'pprgtofile' in version 1.9.1 (see GitHub wiki). 1.9.5: Comments are now removed when loading programs (comments start with a tab and a semicolon and a space and whatever)