The so-called left-top speedy radical system (zuo-shangwen kuaijian bushou 左上文快檢部首) is a graphical indexing system of Chinese characters developed by the linguist Liu Dah-ren (Liu Daren 劉達人) and exclusively used in his dictionary Liu's Chinese-English Dictionary, published in 1978.
Liu's intention was to provide his users with a system that should give quick access to Chinese characters via a radical system that was independent of the semantic content of the character. For many characters it is not easy to find out the traditional radical, like 目 for 相, 女 for 妝, 又 for 取, 口 for 和, only to tell a few simple examples. In Liu Renda's system the radicals were purely abstract and graphical. Liu was able to group all Chinese characters into 18 different types, according to the position of the radical. He abolished some rarely used or complicated radicals (邑, 阜， 辵， 匸， 干， 舛， 韭， 青 and 鹵) and introduced new, graphical radicals, coming to a total number of 215 radicals (see Liu Dah-ren's radical list).
Liu created the following new radicals:
He abolished the following traditional characters:
This large number is due to the fact that some traditional radicals appearing in different shapes depending on the position in a character were split into two (人 and 亻， 心 and 忄， 手 and 扌， 水 and 氵， 犬 and 犭， 艹， 阝， 火 and 灬, or 示 and 礻). Liu discerns the following types of characters:
In this pattern, simple, undividable characters like 人 or 文, are not mentioned. Liu Dah-ren also gives a simpler set of rules for discerning characters according to their composition, namely characters with radical standing to the left (like 亻, 氵, 扌 or 木), to the top (like 一, 亠, 乛, 冖 or 宀), to the right (like 頁or 鳥), at the bottom (like 皿, 里 or 鬲), half-enclosures (like 辶, 廴, 走, 風; , 气; 冂 or 匚), full enclosures (囗), characters consisting of a few crossing parts (like 中, 東, 失, 叉, 史, 吏 or 弗), and characters consisting of many different parts (like 囂, 纍, 毓 or 報).
For the position of a character in the dictionary, this classification of characters is not relevant. It is only a scholarly analysis of what graphic types of characters exist. In looking up a dictionary, the method is generally the same as with traditional radicals, only with a change of the radical system. Below the radical level, the characters are arranged according to the number of residual strokes. This method is also traditional.
The principles for determining a radical are the following: Because up to 85 per cent of characters have the left or upper left part as their radical, this part is to be preferred as the radical, if the character is composed of two parts. If it is composed of three parts or more, the upper left part is the decisive one, regardless if the traditional radical of the Kangxi zidian 康熙字典 is another part of the character. In characters that have a complex shape in which the components are not easily to separate, that part is to be chosen as the radical whose brush stroke reaches up highest. In characters that are enclosed on two, three or four sides, the enclosing component is to be chosen as the radical.
Liu Daren also invented a method to include the tone pitch into the transcription. He used the modern Hanyu pinyin transcription 漢語拼音. For the first tone, no change of the vowel was made, for the raising tone, an r is inserted after the vowel, for the falling-raising "third" tone, the vowel is doubled, and for the falling tone, an h is inserted after the vowel. This system is thus a combination of the Hanyu pinyin system and the Gwoyeu Romatzyh transcription system 國語羅馬字.