What is the predecessor of abacus?

China's modern abacus evolved from the ancient "calculation". "Planning" is to use a bamboo stick as a bargaining chip to calculate. By the end of the Tang Dynasty, people had improved the multiplication and division method, and by the Song Dynasty, China had produced folk songs for calculating division. By the middle of15th century, the ancient book "Luban Mu Jing" had written down the specifications for making abacus. Because abacus was very popular at that time, written works about abacus came into being. The most popular abacus book is The Arithmetic Unified Family written by Cheng Dawei in the Ming Dynasty in 1593. Because abacus calculation is simple and easy, it is widely used in China, and also spread to Japan, North Korea, India, the United States, Southeast Asia and other countries and regions. The appearance of abacus is called a major reform of calculator in human history. Now, although all kinds of electronic calculators and computers have been popularized, abacus still has its unique function.