CJK Compatibility Ideographs

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)
 * 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.
 * One is a kyūjitai form of a kokuji whose extended shinjitai form exists in the URO . Both are hyōgai kanji, and are 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.
 * The remaining 12 are kokuji characters which are actually unified ideographs (with the Unified_Ideograph 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 "CJK COMPATIBILITY IDEOGRAPH", 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 as follows:

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