Four corner method

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The Four Corner Method (literal translation), (Traditional Chinese: 四角號碼檢字法; Simplified Chinese: 四角号码检字法; pinyin: sì jiǎo hào mǎ jiǎn zì fǎ) is used for encoding Chinese characters using four numerical digits per character. In many (if not most) situations—especially in large indexes and encyclopedias—an additional digit is used. The Four Corner Method is also known as the Four Corner System.

[edit] Origin

The Four Corner Method was invented in the 1920s by Wang Yunwu (王云五), the editor in chief at Commercial Press Ltd., China. Its development was based mainly on contributions by the Russian scholar Rosenberg in the 19th century, as well as experiments by Lin Yutang and others. Its original purpose was to aid telegraphers in looking up China Standard Telecode (CST) numbers in use at that time from long lists of characters. This was mentioned by Wang Yunwu in an introductory pamphlet called Sijiaohaoma Jianzifa in 1926 (Commercial Press, Shanghai). Introductory essays for this pamphlet were written by Cai Yuanpei (Ts'ai Yuan-p'ei) and Hu Shi (Hu Shih). Hu Shi also composed the following then-famous poem Bihuahaoma Ge as a "memory key" to the system:

一橫二垂三點捺，
點下帶橫變零頭，
叉四插五方塊六，
七角八八小是九。

一横二垂三点捺，
点下带横变零头，
叉四插五方块六，
七角八八小是九。

Yi heng, er chui, san dian, na;
Dian xia dai heng, bian ling tou;
Cha si, cha wu, fang kuai liu;
Qi jiao, ba ba, xiao shi jiu.

In the 1950s, lexicographers in the People's Republic of China changed the poem somewhat in order to avoid association with the (then) unmentionable Hu Shi (see the new version, with characters, below).

The first revised version was published in Shanghai in 1928. It was quickly adopted and popularized as a method for (amongst others):

Arranging and indexing Chinese characters in dictionaries
Indexing Chinese classical and modern books, libraries, and hospital and police records
Chinese typewriters
Military code making (for handling the characters quickly)

The Wang Yun-wu Da Cidian (Wang Yun-wu Ta Tz'u-tien) of 1928 was remarkable for its time, and although the pronunciations were very much in line with today's putonghua, the lack of a phonetic index diminished its overall usefulness. The northern Mandarin pronunciations were given in the then-new "Guoyu Luomazi", devised by linguist Zhao Yuanren, as well as in MPS characters with a dotted corner for tone. It also delineated parts of speech, and all compounds were listed by the four-corner method as well. It was extremely modern. It used some arcane styles of characters as a citation form, and had a few errors and some important omissions.

The famed lexicographer and author of Ci Yuan (T'zu Yuan), Lu Erkui (Lu Er-k'ui), as well as other lexicographers, became early proponents of the Four Corner Method. By 1931, it was used extensively by the Commercial Press to index virtually all classical reference works and collections of China, such as the Pei Wen Yun Fu and Si Ku Quan Shu, as well as many modern ones.

Hospital, personnel and police records were organized just like the biographical indexes and dynastic histories of former times. For a while (Nash, Trindex, 1930), it seemed that the Kang Xi Bushou (K'ang-hsi Pu-shou) 214 Radical System, left by the Qing (Ch'ing) Dynasty, was being replaced by the Four Corner Method.

Internationally, Harvard and other universities were using the method for their book collections, and the KMT Nanjing government seemed to have selected this numerical system as its standard. It was taught in primary schools to children in Shanghai and other locations during the late 1920s and throughout the 1930s, up to the outbreak of general war with Japan in 1937.

The Japanese militarists found the publishing activity and popularity of sijiaohaoma, as well as its academic, administrative and military uses threatening enough to destroy the Commercial Press building, shelling and burning it during the January 1932 Shanghai Incident. Books produced afterwards from damaged plates did not have such clarity and were marked "Guo Nan Hou Ban" (kuo-nan hou-pan) in the page margins. Sijiaohaoma was a way in which China, without a unified spoken language at that time, could draw upon the strength of its unified written language—old and new. Anything that helped unify China was anathema to the Japanese.

The Four Corner Method was extremely popular in government education circles until pronunciation-based systems, using the Mandarin phonetic symbols (the Guoyu Luomazi was thought to be too radical and difficult) in the GR phonetic chart's (labial-to-velar) "bo-po-mo-fo" order, became fashionable in the mid 1930s. It was used to promote spoken language unification.

The first such large-scale project in 1936 was Wang Li's 4 volume MPS-entry, Guoyu Cidian (Kuo-yu Tz'u-tien). In 1949 it was re-edited into the MPS Hanyu Cidian with Kang Xi 214 radical index, and a small Four Corner dictionary was available as the Xin Sijiaohaoma Cidian of c1953. After 1949, limited use of MPS and the original Four Corner Method continued under the People's Government, until the introduction of pinyin in 1958 (below) and after. Today's Chinese dictionaries still contain MPS characters below each Pinyin class entry and sometimes in a phonetics chart in tables (Xinhua Cidian), while main entries are all in Hanyu Pinyin order. There is one all-sijiaohaoma small dictionary (Third Revision, below).

A minor Second Revision was made during and just after World War II. This was used by most postwar lexicographers including Morohashi Testsuji, who created his 12-volume Dai Kanwa Jiten (Sino-Japanese dictionary) and included the Four Corner index among several other lookup methods. Olshanin (USSR) included a Four Corner index in his Chinese-Russian dictionary and in new China, an extraordinary project of the 25 Histories (Ershi wu shi) was published in the early 1950s with a Four Corner index volume containing the entire content.

Then, in 1958, with the introduction of Pinyin, a small "Xin Sijiaohaoma Cidian" was produced by the Beijing Commercial Press, but the rapid Han character simplification of the following years made the small (30,000 compound) book obsolete in China. Overseas and in Hong Kong, it remained popular for a number of years as a high speed key to phonetic dictionaries and indexes. It was used by those partly literate in Chinese or—in some areas—unfamiliar with Putonghua, especially Hanyu Pinyin.

Wang Yunwu produced a "Xiao Cidian" and "Zonghe Cidian" in the late 1940s. In Taiwan, "Zonghe Cidian" remains in print with an auxiliary section of rare characters. The telecode number, radical and stroke counts are shown for each character in a convenient size, but a phonetic index is still lacking. Also, all is traditional Chinese and it contains a lot of obsolete information. Still, it is convenient for reading old Republic-period materials and literature, and as a handy finder for pronunciations.

During the Great Proletarian Cultural Revolution, the Four Corner Method underwent a radical Third Revision during the compilation of the experimental volume of the Xiandai Hanyu Cidian, Commercial Press, Beijing, 1972. Another medium sized dictionary, the Xinhua Cidian, appeared with this index as well, but in the late 1990s the four corner index disappeared from newer editions. Both works now use use only the Pinyin main entry and multi-door radical index systems that make it possible to look up a character with perhaps a wrong radical (ie, characters appear redundantly under different radicals) and the number of strokes and variant forms are greatly reduced, and many more people are literate and capable of transcribing standard Chinese with Pinyin. The use of stroke counting and radicals puts memorization of the character ahead of sheer speed in handling it (utility). This method is more supportive of mass literacy, a more important priority than classical scholarship or processing and filing names or characters for the majority in China today. The four-corner method is ultimately for readers, researchers, editors and fileclerks, not for writers who seek a character that they know in speech or recitation. In China today, a new version of the excellent small "Xin Sijiaohaoma Cidian, soft cover from from Commercial Press, Beijing, has been available since the late 1970s, updated in several new editions and printings. It uses the Third Revision (above) and enjoys some popularity.

A new alpha-numerical shape system called Wubi, "Five Brushes", one of several such new systems generating one discreet number for each character, is being promoted by the People's Government today for computer use. I recently personally observed Chinese hospital clerks and some members of the general public fairly skillful at this input method.

The main purpose of the original four-corner system today is in doing academic research or handling large numbers of characters or terms, index cards, names etc, quickly, as opposed to browsing long lists, and in computer entry, where a smaller list is created to browse from than with other systems. Many beginning users find the rules for the fifth number in all three revisions to be a bit contrary; it is like language itself, a bit chaotic but one becomes fluent in it. The Xinhua Zidian large type edition is available with a four corner index for those whose failing eyesight precludes browsing and counting strokes.

In China today, many famous KMT period reference books and collections with four corner indexes are being reprinted for sale to scholars and those interested in Old Chinese language, historical studies etc.

The four digits used to encode each character are chosen according to the "shape" of the four corners of each character, i.e. the upper left, upper right, lower left and lower right corners. The shapes can be memorized using a Chinese poem; this version, from the 1958 Xin Sijiaohaoma Cidian, is reworded to avoid the stigma (at that time) of Hu Shi's original poem, (above). The 1950s version is as follows:

横一垂二三點捺，
叉四插五方框六，
七角八八九是小，
點下有横變零頭。

横一垂二三点捺，
叉四插五方框六，
七角八八九是小，
点下有横变零头。

Heng yi, chui er, san dian, na;
Cha si, cha wu, fang kuang liu;
Qi jiao, ba ba, jiu shi xiao;
Dian xia you heng, bian ling tou.

In short, the number 1 represents a horizontal stroke, 2 represents a vertical or diagonal stroke, 3 a dot stroke, 4 two strokes in a cross shape, 5 three or more strokes in which one stroke intersects all others, 6 a box-shape, 7 where a stroke turns a corner, 8 the shape of the Chinese character 八 and its inverted form, and 9 is used for the shape of the Chinese character 小 and its inverted form. Zero is used where there is either nothing in a corner, the part in a corner is already represented by a previous corner, or where a corner has a dot stroke followed by a horizontal stroke.

Several other notes:

A single stroke can be represented in more than one corner, as is the case with many curly strokes. (eg. the code for 乙 is 1771)
If the character is fenced by 囗, 門(门), or 鬥, the lower corners are used to denote what is inside the radical, instead of 00 for 囗 or 22 for the others. (eg. the code for 回 is 6060)

There have been scores, maybe hundreds, of such numerical and alpha-numerical (such as Lin Yutang's "Instant Index", Trindex, Head-tail, Wang An's Sanjiahaoma, Halpern etc) systems proposed or popularized; some Chinese refer to these generically as "sijiaohaoma" though this is not correct.

The Four-Corner Method or system, in its three revisions, is the one that was most widespread and actually supported by the Chinese state for a while, and is found in numerous older reference works (and some, like the Morohasi Daikanwa, and Kou Kanwa, Taishukan, Tokyo, and the Dictionaire Francaise de le Langue Chinoise, (Insitute Ricci, Taibei) still in publication) The later uses the First revision of 1928. The small Kangorin Sino-Japanese Dictionary by Yoneyama et al, Taishukan, Tokyo, had a four-corner index when it was introduced in the 1980s, but it has been since deleted. The four corner method is not in common usage in China today, including Taiwan, although dictionaries with it (above) are available in many bookshops and libraries for those who need or desire to learn or use it. It is identified, in public opinion, with the time when many Chinese were illiterate and the language was not yet unified; more Chinese today use the dictionary to help them write, not read. But it is useful for scholars, clerks, editors, compilers, and especially for foreigners who read Chinese. In recent years it has achieved a new usage as a character input system for computers, generating very short lists to browse.