There are books on how to use an abacus, but basically all it does is add and subtract, the rest you have to do in your head. Essentially, this is a proof by induction that a computer is more powerful than an abacus, since a computer program can contain an abacus. (But then again, you can simulate a computer within a computer, so what does that show). Actually, with a real abacus, one can move more than one row at a time with 10 fingers. But on the other hand, a real abacus does not have the current sum displayed as an integer.