Unicode Explained

Definitions of Characters Elsewhere

Characters were defined and used long before Unicode. Even in our times, characters

are often used without identifying them with a reference to any character code stand-

ards. This creates ambiguity and potential diversity when text data is represented in

computer-readable form.

For example, the standards that define the SI, the International System of Units (an

extension of the metric system), use several special characters such as µ, ×, and Ω. The

authoritative formats of the standards are printed documents, and since they do not

specify code numbers or Unicode names for the characters, we are left in some uncer-

tainty. Some characters can be identified rather unambiguously, but it is unclear what

the “raised dot” character is, for example. This character, used in notations like N·m

(for newton meter), is usually interpreted as the middle dot U+00B7, but it can be

argued that a more appropriate interpretation is the dot operator U+22C5.

Similarly, the International Phonetic Alphabet (IPA) was originally defined about a

century ago. When it later became relevant to use it on computers, the characters had

to be identified as Unicode characters. This was far from trivial, since many IPA char-

acters can be regarded as normal Latin letters, or treated as separate symbols.

Even relatively new standards on transliteration or transcription—i.e., on conversions ...