Since the Chinese language uses a logographic script — that is, a script where one or more "characters" corresponds roughly to one "word" or meaning — there are vastly more characters, or glyphs, than there are keys on a standard computer keyboard.
Some Chinese input methods proposed for typewriters before 1950s, Lin Yutang spent much money on it.[1] Little or none is used before the computer age, then a variety of keyboard input method editors (IME) have been designed to allow the input of Chinese characters using standard keyboards.
Keyboard input methods can be classified in three main types:
by encoding
by pronunciation
by structure of the characters.
The following are just some samples of Chinese input methods. Many of those input methods have variations. Full Pinyin and Double Pinyin are variations of the pinyin input method. In addition, the methods which require the user to select a character from a menu generally have sophisticated methods for guessing which characters the user intends based on context.
Each standard has its strengths and weaknesses and usage varies between people. For example, for someone who is already familiar with pinyin, the pinyin method can be learned instantly. However, the maximum typing rate is limited, and learning the system can be difficult for those not familiar with pinyin. Wubi takes much effort to learn, but expert typists can enter text much faster with it than with the phonetic methods. Because of these factors, there is very little likelihood of a "standard" method evolving.
http://www.answers.com/topic/chinese-input-methods-for-computers
http://www.slate.com/id/2136726/
http://www.straightdope.com/columns/read/1138/how-can-the-chinese-use-computers-since-their-language-contains-so-many-characters
http://www.patentstorm.us/patents/6281884/claims.html