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YAMADA Nobuko
YAMADA Nobuko

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Story of Backslash, Yen and Yuan sign

This is the Summery of the articles:

https://en.wikipedia.org/wiki/Backslash
https://en.wikipedia.org/wiki/Yen_and_yuan_sign

And translation of my article: https://zenn.dev/e99h2121/articles/3baa5d9d878683

In JIS X 0201, the character set standard for Japanese, the Yen and Yuan signs are 0x5C.
In UNICODE, like Laten-1, 0x5C is a backslash. The Yen and Yuan signs are 0xA5.

The backslash is used under the European font, and the Yen and Yuan signs are used under the Japanese font. This is coming from the IBM Japan keyboard, a legacy which was designed as a mainframe terminal, and does not mean that the Yen sign and the backslash can coexist in today's general PC environment.

The directory separator in Windows is still 0x5C, and it needs to be re-recognized as a backslash instead of a Yen sign.

Integration into Unicode: The Unicode was created to conduct all of the world's character codes in a single system. So any language can be represented in Unicode.

The characters of the world's various character codes were mapped to Unicode characters to enable conversion from the various character codes to Unicode, but there was a problem with the handling of the Yen sign.

In the Japanese character code, the Yen sign is located at 0x5C and is treated as a control code. On the other hand, in ISO-8859-1 for Western European languages, the Yen sign is placed at 0xA5, which is a different address from 0x5C (backslash), and the Yen sign is not treated as a control code.

Therefore, if a document written in these character codes is converted to Unicode and any of the Yen signs are mapped to the Unicode circle symbol (U+00A5), it is not clear whether the converted Yen sign is the Japanese Yen sign, which should be regarded as a control code equivalent to the backslash (U+005C).

In this case, it is not possible to know whether the converted Yen sign is a Japanese Yen sign, which should be regarded as a control code equivalent to a backslash (U+005C), or a European Yen sign, which is just a character.

Practical solution: the Japanese yen sign is converted to Unicode backslash (U+005C) in most environments.

Microsoft Windows and other Microsoft operating systems use 005C in the Japanese font for the Yen sign to avoid the problem.

Also, many Japanese JIS keyboards have separate keys for the Yen sign and the backslash, but no matter which key is entered, 005C is entered.

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