Song people said in a book: "Tatar has nothing to say. Every time he sends his troops, he makes a promise, which makes people convey and yearn for sparks." This is to transfer troops with grass and convey the number of people to be transferred! Others, such as Tibetans and Yi people, have written characters, but this method has been used for a long time among illiterate people. Minzu University of China collects a pair of knots of Gaoshan people, which are composed of two ropes: each rope has two knots, and then the two ropes are tied together. Interestingly, we tied ropes not only in the East, but also in the West. It seems that our planet has long been like a global village, but there were no telegrams and telephones at that time. Legend has it that the king of ancient Persia once fought a war and ordered his soldiers and horses to guard a bridge for 60 days. In order to keep the soldiers on guard for one more day, the king of Persia used a long pimp and tied 60 buttons on it. He said to the officers and men guarding the bridge, "After I leave, you can unbutton one button every day, and then you can go home."

See another interesting thing later. In the ancient Oracle Bone Inscriptions of China, the mathematical "number" was a right hand and a wooden stick with many knots tied on the left:-"number" means to tie a rope, remember it. Therefore, at the entrance of the Institute of Mathematics, it is best to tie a few knots with a wooden stick as a sign of "remembering", and even the signboard need not be hung.

A counting method almost at the same time or later than knotting rope is a kind of book contract. Book deed is carving and drawing, leaving notches and "marks" on bamboo, wood, tortoise shell or bone and clay board. The book "Ming Shi" says: "Qike, several times." It means to carve some symbols on something to count.

1974 Among the tombs excavated in Ledu County, Qinghai Province, 49 pieces of bone were found in China, all of which were similar in size and shape, and they were all slender rectangles the size of a child's little finger. There are notches on both sides of the middle of the bone block, some with three notches, some with five notches, and many with one notch. If a gap represents a number, then these 40 bone fragments can express any natural number from one to fifty or sixty. Of course, these small bone fragments can also be used to calculate. Interestingly, in A.D. 1937, westerners discovered a 400,000-year-old bone, which was the calf bone of a wolf cub. Very long, with 55 deep marks on it. This is the earliest historical witness that scored 20 13. So if you find a few bone fragments in the wild in the future, you must be careful not to miss the opportunity to be an amateur archaeologist.

With the development of engraving technology, pure digital symbols appear gradually. This is a glorious and great achievement.