Abacus
There is a common Chinese abacus. This abacus is split into two kinds of basic rows, the top is for the "5"s, and the bottom is for the "ones". There are one or two beads in the top rows, and four or five beads in the bottom ones. For example, 8 is one bead on top and 3 below, because 5 + 3 = 8. Every column represents a different digit.