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Reading the Wikipedia article on UTF-8, I've been wondering about the term overlong. This term is used various times but the article doesn't provide a definition or reference for its meaning.
I would like to know if someone can explain the term and its purpose.
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The Difference Between Unicode and UTF-8Unicode is a character set. UTF-8 is encoding. Unicode is a list of characters with unique decimal numbers (code points).
The code point is a unique number for a character or some symbol such as an accent mark or ligature. Unicode supports more than a million code points, which are written with a "U" followed by a plus sign and the number in hex; for example, the word "Hello" is written U+0048 U+0065 U+006C U+006C U+006F (see hex chart).
UTF-8 (UCS Transformation Format 8) is the World Wide Web's most common character encoding. Each character is represented by one to four bytes. UTF-8 is backward-compatible with ASCII and can represent any standard Unicode character.
The most common encoding schemes are : UTF-8. UTF-16. UTF-32.
It's an encoding of a code point which takes more code units than it needs to.
For example, U+0020 is represented in UTF-8 by the single byte 0x20. If you decode the two bytes 0xc0 0xa0 in the normal fashion, you'll still end up back at U+0020, but that's an invalid representation.
The Unicode Corrigendum #1 has more information, particularly around table 3.1B.
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UTF-8 theoretically allows for different representations of characters that also have a shorter one. For example, you could encode an ASCII character in two bytes by setting the MSBs to zero. The UTF-8 specification explicitly forbids this.
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