In China, if someone does not know how to read, they will be ridiculed as "Dou Da is illiterate in a basket", and the idiom "illiterate" also refers to this situation. Education is so developed in modern society that illiterate people are very rare, but there are still many in the old society. 
The Southern Song Dynasty poet Yang Wanli wrote in a poem, "Don't be ashamed to have an empty stomach without a T-character, and avoid killing people in the autumn sun"; In "Kindergarten Qionglin", it is said, "If the village man doesn't know a thing, the fool will not have anything." The meaning of "belly without Ding" here is the same as "illiterate", both are illiterate people. With the progress of society, people should use the idiom "illiterate" less and less frequently in the future. Idioms are a carrier of traditional culture, and many idioms have their allusions behind them. We can often say a concise and appropriate idiom casually, but we don't necessarily understand its origin. It's like being "illiterate". Some people will ask, why is this the T-character and not the other words? Indeed, this issue has been controversial since ancient times. 
"Illiterate" appeared relatively late in the literature, and its prototype is the aforementioned "illiterate". Probably before the Ming Dynasty, it was common to use the latter rather than the former. The story behind this idiom dates back to the Tang Dynasty. Zhang Hongjing, who served as the prime minister during the Yuanhe period of Tang Xianzong, was also a famous calligrapher and quite knowledgeable. When Zhang Hongjing served as the envoy of the Jiedu in Hebei, he lived a luxurious life and was very arrogant to his subordinates. Most of his staff members are frivolous and prodigal, who only know how to drink and have fun. Once, the imperial court handed Zhang Hongjing 1 million yuan, that is, 1 million guan, to reward the soldiers, but Zhang Hongjing honestly and unceremoniously deducted 200,000 guan. His aides also did the same, arbitrarily deducting military salaries. When the soldiers came to the door to theorize, Zhang Hongjing said disdainfully, "Today, under Taiping, Ru Cao can hold two stone bows, it is better to know a t-word!" ”
The word "stone" here is a measure word, pronounced "but", referring to the strength of the bow and crossbow. What Zhang Hongjing said is, if it is peaceful today, what is the use of you being able to pull a bow with two stones, it is better to recognize the word "Ding"! Without commenting on Zhang Hongjing's words and deeds, it was the sentence he said that gave rise to the idiom "ignorance", which later evolved into "illiterate." Due to the slight discrepancy in the records of Zhang Hongjing's original words in some ancient books, it has caused controversy among later scholars. Some people think that what Zhang Hongjing said is "It's better to know a word!" For example, Zhang Dai, a scholar in the Ming and Qing dynasties, said in "Night Sailing Boat", "Tang Zhang Hongjing said: There is nothing in the world, it is better to know one word if you hold two stone bows!" The word "one" is mistaken for the word "ding", and it is similar to its strokes. ”
Zhang Dai believes that what should be recorded in the history books should be the word "individual", which was mistakenly written as "ding", because the strokes of the two characters are similar. This is not that Zhang Dai wants to be different, some people have discovered this problem very early, such as the Song Dynasty scholar Wang Nan believes that the original version should be "not as good as knowing a word" after research. If you open the "Chinese Dictionary" and find the two entries "未語一丁" and "无丁字", you will find that the explanation is as follows, "Ding, the word for 'individual'." I don't know a word, which refers to an uneducated person. He is also illiterate and illiterate." It can be seen that the misrepresentation of the word "individual" as "ding" is the mainstream opinion in the academic circles. The scholars' point of view is reasonable, not to mention anything else, as long as we analyze the context of Zhang Hongjing's original words, he must mean that the martial artists do not know a word, not that they do not know the word "Ding". 
However, because there is also a variant of the character "Ding", the top is the word "person", and the bottom is a vertical hook, which is very similar to the word "individual", and ancient scholars have debated it endlessly. The word "Ding" also triggered a public case, and the great philosopher Zhuangzi "lay down the gun". Some people say that Zhuangzi was also "illiterate". Needless to say, Zhuangzi's knowledge is so great that his literary talent also looks at the ancient and modern, and some people even say that he is illiterate? Let's see what's going on. Ancient books such as the book "Shupin" by Yu Beiwu, a calligrapher of the Liang dynasty in the Southern Dynasty, and the "Sheng'an Collection" by Yang Shen, one of the three geniuses of the Ming Dynasty, all mention that Zhuangzi once said that "the T-character has a tail". Yu Beiwu and others made a discussion on this, which means that the lower half of the word "Ding" is a vertical hook, and the hook is facing right, which belongs to the "eight-point" body of the pre-Qin period. Yu Beiwu and Yang Shen only discussed the similarities and differences in the font, while the Ming dynasty writer and historian Wang Shizhen and another scholar, Xu Yingqiu, both pointed out that Zhuangzi was illiterate. Wang Shizhen is the author of "The Four Manuscripts of Yizhou", which has such a passage: "Those who are illiterate today are called 'illiterate and illiterate'......Zhuangzi said: The word Ding has a tail. Ding Wei is not the right to quote, but Zhuangzi can also be said to be ignorant! ”
Xu Yingqiu's "Yuzhitang Talks" also has such a statement. They think that the "tail" of the T-character is a hook to the left, and perhaps in the ancient book "Zhuangzi" they saw, the lower half of the T-character is a hook to the right, and they think that this is not right, so they say that Zhuangzi is illiterate. The author was deeply puzzled, and later found that some experts pointed out that Zhuangzi's original words were not "Ding characters have tails" at all, but "Ding Zi has tails". Sure enough, when talking about Hui Shi in "Zhuangzi", there is such a passage, "The egg has hair, the chicken has three legs, and the Ying has the world." Dogs can be sheep, horses have eggs, and cloves have tails. Zhuangzi's passage is about philosophy, and according to the context, the first part uses chickens, sheep, horses and other animals as analogies to talk about a situation that goes against nature, and the second part says that "the ding has a tail", which should also refer to an animal. So what is "Dingzi"? Tang Dynasty scholar Cheng Xuanying's annotated "Zhuangzi" said, "The Chu people call the shrimp toad Ding Ziye." The husband shrimp and toad have no tail, the world knows, this cover is not a matter of reason. "Shrimp toad" is a collective term for frogs and **. Zhuangzi's "Ding Zi has a tail" does not refer to Chinese characters, but to say ** or a frog will have a tail. Unexpectedly, Wang Shizhen and other scholars misunderstood Zhuangzi, probably because there was a mistake in the copying or printing of ancient books, and there was a big "oolong".