CJK Compatibility Ideographs is a Unicode block created to contain mostly Han characters that were encoded in multiple locations in other established character encodings, in addition to their CJK Unified Ideographs assignments, in order to retain round-trip compatibility between Unicode and those encodings. However, it also contains 12 unified ideographs sourced from Japanese character sets from IBM.

The block has dozens of ideographic variation sequences registered in the Unicode Ideographic Variation Database (IVD). These sequences specify the desired glyph variant for a given Unicode character.

Character sources

Sources for the original collection of CJK Compatibility Ideographs include:

South Korean KS X 1001 (U+F900–U+FA0B, 268 characters; see that page for the explanation) Taiwanese Big5 (U+FA0C–U+FA0D, 2 characters) "IBM 32": 32 Japanese characters from IBM (U+FA0E–U+FA2D; see below)

In ensuing versions of the standard, more characters have been added to the block from:

South Korean KS X 1001 (U+FA2E–U+FA2F, 2 characters) Japanese JIS X 0213 (U+FA30–U+FA6A, 59 characters) Japanese ARIB STD-B24 (U+FA6B–U+FA6D, 3 characters) North Korean KPS 10721-2000 (U+FA70–U+FAD9, 106 characters)

The "IBM 32" characters IBM Japanese double-byte EBCDIC includes several kanji which do not exist in, or do not round-trip from, JIS X 0208. These were included as gaiji in extensions to Shift JIS and EUC-JP from IBM (e.g. code page 942), NEC, the Open Software Foundation, and Microsoft (e.g. Windows code page 932). However, they were not used as a source for the original Unified Repertoire and Ordering (URO). Instead, 32 of the IBM extension kanji, those which had not been included in the URO from other sources, were included in the CJK Compatibility Ideographs block in the range U+FA0E–U+FA2D.

Of these 32 characters:

19 are unifiable with characters in the URO, and are therefore compatibility ideographs in the strict sense. 12 are kokuji characters which are actually unified ideographs (with the property, and which do not change upon normalisation). In spite of their inclusion in the CJK Compatibility Ideographs block and their algorithmically generated character names beginning with "", they are not duplicates of characters in the original CJK Unified Ideographs block in any respect; 11 of these 12 are completely non-duplicate, while was later unintentionally duplicated in CJK Unified Ideographs Extension B as . They are placed there because they do not have a URO encoding, yet IBM 32 is one of the encodings where duplicate encodings are of concern. All of them are rarely used or are variants of common kanji. They are as follows:

Uniquely, () is intended to be encoded as the kyūjitai form of a kokuji which received a separate encoding for a variant that is straightforwardly the (extended) shinjitai form . The URO only encoded the shinjitai form, and uses its stroke count to place it in this position. It is furthermore one variant of the many variants of the jinmeiyō kanji (i.e. Kummerowia). U+FA20 was assigned a normalisation to U+8612, even though the 龜 and 亀 components, while both forms of radical 213, are not usually considered unifiable.

Block

History The following Unicode-related documents record the purpose and process of defining specific characters in the CJK Compatibility Ideographs block:

Version Count L2 ID WG2 ID IRG ID Document 1.0.1 U+F900..FA2D 302 N782 N2667 N3525 N3590 N4111 N4103 3.2 U+FA30..FA6A 59 N1935 N2003 N2095 N2142 N710 N2103 N2197 N2221 N2221R txt) N2273 N2295 4.1 U+FA70..FAD9 106 N2253 N2375 N2403 N2478 N2493 N2541 N2540 N2566 N2572 N2573 N2569 N2569R N2776 N1062 N2924R N3899 N4111 N4103 5.2 U+FA6B..FA6D 3 doc) appendix) doc) 6.1 U+FA2E..FA2F 2 N3747 doc)

See also CJK Compatibility Ideographs Supplement

References