Chinese is a language build up by morphemes(word element).It's claimed that it had so much characters that no exhaustive list of character ever existed on earth.
Still, from many dictionaries and reference books, we can figure out the course of its development.
In Qin (Chin) Dynasty, a book named Canjie encompassed about 3300 characters. Later, in Shuo Wen Jie Zi(literally means explaining the Characters) by Xu Shen,a linguist in Eastern Han Dynasty, there are 9353 characters.After Jin and Song Dynasty, Chinese hold a vocabulary of 12824 collected in Zi Lin (Literally means woods of characters) by Lu Chen, linguist of Jin Dynasty.
When Dictionary of Kangxi(Name after The Emperor of Kangxi who in charge of the compilation) published in Qing Dynasty, it contained more than 47000 character.
In 1971, Zhang Qiyun compiled another big dictionary called Zhongwen Da Zidian(Big dictionary of Chinese) consists of 49888 characters.
In 1959, Morohashi Tetsuji, A Japanese Linguist,compiled a Big Chinese-Japanese dictionary,
which has 49964 characters.
Then, how many characters should a non-native speaker know in order to comunicate with native speakers?
After years of statistical research, the language authority published a 3500-character list called commonly used Chinese characters(download here), which should cover 99.48% usage in all kinds of publications.
That's what you should know about.
testing comment!