Character amnesia
It is difficult to establish exactly how many different Chinese characters are in use today; the new HSK, a widely used proficiency test for Standard Chinese as a second language, tests over 2,600 different characters, whilst in 1988 the People's Republic of China published the "List of Commonly Used Characters in Modern Chinese" which contains 7,000 different characters. In Japan, where a smaller set of characters are in general usage, the Japanese Ministry of Education prescribes the teaching of 2,136 kanji in primary and secondary school in a list called the jōyō kanji, meaning "regular-use Chinese characters".
History of printing in East Asia
Given that the Chinese language does not use an alphabet it was usually necessary for a set of type to contain 100,000 or more blocks, which was a substantial investment. Common characters need 20 or more copies, and rarer characters only a single copy. In the case of wood, the characters were either produced in a large block and cut up, or the blocks were cut first and the characters cut afterwards. In either case the size and height of the type had to be carefully controlled to produce pleasing results. To handle the typesetting, Wang Zhen used revolving tables about 2m in diameter in which the characters were divided according to the five tones and the rhyme sections according to the official book of rhymes. The characters were all numbered and one man holding the list called out the number to another who would fetch the type.