Penguin
The language that the HPCalculators use. It's based on Reverse Polish Notation, so you have to remember to enter everything backwards eg, instead of
6*(2+3)*4

you enter

6 2 3 + * 4 *

or maybe

2 3 + 6 * 4 *

or maybe

4 6 2 3 + * *

Note how you never need any parens because all operators are equal in precedence.