Carve the board into three parts, the upper and lower parts are used to block the beads and the middle part is used to locate them. Everyone has five beads. The upper bead and the lower four beads are distinguished by color.

The traditional abacus in our country is the upper two and the lower five beads, with the upper one indicating "5" and the next one indicating "1". When calculating with an abacus, the five-liter decimal system is adopted, that is, when each gear is "full of 5", it is represented by a bead, and when each gear is "full 10", it moves forward to the previous gear.

In ancient China, "16 two systems" was used to calculate the weight, that is, one catty was equal to sixteen taels. Modern people often say that two people are almost as bad, which means they are the same as each other. But half a catty is half a catty, and eight liang is eight liang. How can it be equal? It turns out that in China's ancient weight unit system, one catty was equal to sixteen taels, so half a catty was equal to eight taels. Every gear can be counted as "15", so "16" will advance to the next gear. Therefore, the traditional abacus calculation of "upper two and lower five balls" in China is formed to adapt to hexadecimal.