In relation to the Japanese language and computers many adaptation issues arise, some unique to Japanese and others common to languages which have a very large number of characters. The number of characters needed in order to write English is very small, and thus it is possible to use only one byte to encode one English character. However, the number of characters in Japanese is much more than 256, and hence Japanese cannot be encoded using only one byte, and Japanese is thus encoded using two or more bytes, in a so-called “double byte” or “multi-byte” encoding. Some problems relate to transliteration and romanization, some to character encoding, and some to the input of Japanese text.
For example, most Japanese emails are in ISO-2022-JP (“JIS encoding”) and web pages in Shift-JIS and yet mobile phones in Japan usually use some form of Extended Unix Code. If a program fails to determine the encoding scheme employed, it can cause mojibake (文字化け, “misconverted garbled/garbage characters”, literally “transformed characters”) and thus unreadable text on computers.There are several standard methods to encode Japanese characters for use on a computer, including JIS, Shift-JIS, EUC, and Unicode. While mapping the set of kana is a simple matter, kanji has proven more difficult. Despite efforts, none of the encoding schemes have become the de facto standard, and multiple encoding standards are still in use today.
The first encoding to become widely used was JIS X 0201, which is a single-byte encoding that only covers standard 7-bit ASCII characters with half-width katakana extensions. This was widely used in systems that were neither powerful enough nor had the storage to handle kanji (including old embedded equipment such as cash registers). This means that only katakana, not kanji, was supported using this technique. Some embedded displays still have this limitation.
The development of kanji encodings was the beginning of the split. Shift JIS supports kanji and was developed to be completely backward compatible with JIS X 0201, and thus is in much embedded electronic equipment.
However, Shift JIS has the unfortunate property that it often breaks any parser (software that reads the coded text) that is not specifically designed to handle it. For example, a text search method can get false hits if it is not designed for Shift JIS. EUC, on the other hand, is handled much better by parsers that have been written for 7-bit ASCII (and thus EUC encodings are used on UNIX, where much of the file-handling code was historically only written for English encodings). But EUC is not backwards compatible with JIS X 0201, the first main Japanese encoding. Further complications arise because the original Internet e-mail standards only support 7-bit transfer protocols. Thus RFC 1468 (“ISO-2022-JP“, often simply called JIS encoding) was developed for sending and receiving e-mails.