This is the calculator that should have come with your PalmPilot. Parens is a complete general-purpose calculator which provides proper order of operations (1+2*3=7, not 9), any number of parentheses, and 14 significant digits of precision displayed in floating point, fixed point, scientific notation, or engineering notation format. It includes a complete set of basic math keys such as exponents, roots, logarithms, and trigonometry in degrees, radians, or grads. It has simple statistics such as mean and standard deviation, with convenient data list editing. Parens also provides date & time calculations, and supports mixed-units calculation and conversion of weight, length, volume, or any other user-defined units. There are 10 memory registers, plus a user-definable list of mathematical constants. And if all that isn't enough, it also supports a plugin module interface to allow you to add in custom buttons created by yourself and others.