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 2.5: Critical bug fixes and performance enhancements - fixed division by zero crashes, nil reference errors, memory leaks, and optimized file system operations.