With most calculators, you provide the data and the algorithm. To get the area of a circle, you enter the radius (the data, in this example), you square it, and then you multiply that by pi. Most of what you just did was algorithm input. With Calculator 2, you only provide the data and the app provides the algorithm. So now, instead of remembering algorithms, you just pick them from a list, insert your variables, and you're done. It's a "declarative" rather than an "imperative" calculator, if that makes sense.