My favorite calculator (got me through college). The HP-15C uses Reverse Polish Notation (RPN). In RPN, if you want to add 5 + 3, you type: 5 ENTER 3 +.
There used to be a complete HP-15C calculator in the App Store, but it stopped being supported, so I created this one for myself. It only includes the basics (no programming, matrix calculations, or complex numbers).
