Attempt to recover a very old calculator project of mine. Almost certainly originally written for Java 1.1 around 2001 - I would do lots of things differently now.
A full RPN (Reverse Polish Notation) scientific calculator. Physically modelled after the HP 11c/12c/15c layout, but not programmable and without many of the special functions.
This was an early coding project of mine, to experiment with how a limited stack would work and also because I can't stand non-RPN calculators and the RPN calculators available were either too expensive, too complicated, or not cross platform.