Method of the four corners

The method of the four corners (四角號碼檢字法) is a method of research of the characters in the Chinese dictionaries according to a code of four digits determined by the C-W communication of the four corners of the character, from where its name. It is used as a basis for a method of encoding of Chinese on computer, with an additional figure in certain situations.

This method was imagined in the Années 1920 by Wang Yunwu (Y.W. Wong, 王雲五) 1888 - 1979, Editor association of the " Commercial Close Ltd." of China. An improved version was published by it in Shanghai in 1928. This new method of indexing of the Chinese characters for dictionaries was very popular until the massive use of the Pinyin. It for summer has developed for the encoding of Chinese natures on computers.

Coding

The method of the 4 corners allots to each Chinese character a combination of four digits and sometimes a fifth, in index.

A character is divided into four corners (the corners left superior, higher right, left inferior and lower right) to which one allots a number for each corner:

the number of the left higher corner is the first figure of the combination.
the number of the corner higher right is the second figure.
the number of the left lower corner is the third figure.
the number of the corner lower right is the fourth figure.

That forms a code of four digits for each sinogramme.

A fifth number, allotted according to the same graphic criteria and noted in index, relates to the feature of the corner lower right which is not crossed by the four features concerned previously. This fifth number is useful for data-processing coding because there are typically several characters corresponding to the same code of four digits. For research in the dictionary, the additional number is not necessary because a rapid glance is enough to find the character sought in the column of the of the same characters codes.

Values

The four keys used for the encoding of each character are selected according to the " forme" of the four corners. The correspondence forms/figure can be memorized by using a Chinese poem:

Briefly, number 1 accounts for an horizontal line, 2 a line vertical or diagonal, 3 a short feature, 4 a feature crossing another feature (the shape of cross), 5 a feature crossing two features or more, 6 a square, 7 an angle (right or acute), 8 the form of the Chinese character 八, 9 the form of the character 小 and or its reversed form, a 0 feature runs above an horizontal line.

Precise details

the attribution of a figure to each corners can raise difficulties. Thus, certain forms occupy two naturally or several corners, or are centered: in the character zi 字 (sinogramme) the forms 丶 and 十 being worth 3 and 4 respectively are centered. The determination of the code is done as follows: classification being done from left to right, the left corners are seen affecting the right figure-code and corners 0: 3040. For the character shi 十 (ten), there exists only one centered form, which is worth 4: this figure is affected with the first corner (higher left) and all the others take value 0: 4000. On the other hand, in the character yi 乙 (one of the celestial Branches) one distinguishes four corners well: 1771.
As of many characters is made of features included in 囗, 門 (门), or 鬥, to obtain a more precise code, the figures of the lower corners are given according to the internal features. Thus if one as envisaged considered the external corners according to the general rule, tuan 團 (group) and today 回 (return) would have the same code: 6000; by determining the last two numbers according to the internal corners, one obtains 6034 and 6060 respectively. In the same way, men 門 (carries) and wen 問 (to ask) would have both code 7722; for the second one uses the internal format for the last two figures and one obtains 7760.

In spite of its speed, the method of the four corners is not everyday usage. Indeed, the children learn in class especially the method of research by key which is accompanied by an analytical decomposition by the characters useful for their memorizing and the knowledge of the history of the language.

See too

Wiktionnaire: Sinogrammes - Index Method of the 4 corners|the index of the sinogrammes by the method of the 4 corners

External bonds

http://www.sungwh.freeserve.co.uk/sapienti/fourcinp.htm
''' Sino Input Method Online ''' (encoding of Chinese natures enligne, without installation of software on computer)

Zh-yue: 四角號碼

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