The seven-bead abacus is called the seven-bead abacus because it has two beads and five beads on it. The upper one stands for "5" and the lower one stands for "1". When calculating with an abacus, the five-liter decimal system is adopted, that is, when each file is "5", it is represented by a bead on it, and when each file is "10", it moves forward.
For example, the head reservation multiplication in 999×999 requires a top bead or a bottom bead. In division, if the quotient is returned, the top bead and bottom bead may be used, regardless of hexadecimal. China started to use decimal system in Shang Dynasty, and it was also the first country in the world to use decimal system.
The history of abacus:
Although we have entered the era of electronic computers, when we look at China's ancient abacus, we have to admire the great wisdom of our ancestors. Generally, abacus is mostly made of wood (or plastic products). Arranging a string of equal number of beads in a rectangular wooden frame is called the first gear. One beam divides the beads into upper and lower parts, with each bead in the upper part representing 5 and each bead in the lower part representing 1.
From right to left, each bead represents a decimal number, ten, hundred, thousand and ten thousand. Coupled with the software-a set of operating formulas for finger-playing rules, it can solve all kinds of complicated operations and even prescribe multiple prescriptions. Abacus is the predecessor of modern computer and the symbol of ancient computing technology in China.