This thing is called "the abacus" in English. There is a Wikipedia article about that. Each row represents a magnitude of 10, if I recall. The way it works is that you move the beads for the original item from right to left. Then you move price for the next item and so on. The total number of beads moved represents the final number. You can use it for subtraction, too. Anything more sophisticated (like trigonometric functions) we used sliderule instead of abacus:-)

Can't believe they still use that!