![]() ![]() all have to decode the characters to unicode code points before such operations can be performed (there are some shortcuts, though).īoth the UCS standards and the UTF standards encode the code points as defined in Unicode. Multi-byte encodings (I should say multi-unit after the above explanation) have the advantage that they are relatively space-efficient, but the downside that operations such as finding substrings, comparisons, etc. Thus the most common (English) characters only occupy one byte in UTF-8 (two in UTF-16, 4 in UTF-32), but other language characters can occupy six bytes or more. If they're not set, this unit represents one character fully. The standard then defines a few of these bits as flags: if they're set, then the next unit in a sequence of units is to be considered part of the same character. All UTF encodings work in roughly the same manner: you choose a unit size, which for UTF-8 is 8 bits, for UTF-16 is 16 bits, and for UTF-32 is 32 bits. The other type of encoding uses a variable number of bytes per character, and the most commonly known encodings for this are the UTF encodings. They suffer from inherently the same problem as the ASCII and ISO-8859 standards, as their value range is still limited, even if the limit is vastly higher. Examples of these encodings would be UCS2 (2 bytes = 16 bits) and UCS4 (4 bytes = 32 bits). There are essentially two different types of encodings: one expands the value range by adding more bits. The ISO-8859 standards are the most common forms of this mapping ISO-8859-1 and ISO-8859-15 (also known as ISO-Latin-1, latin1, and yes there are two different versions of the 8859 ISO standard as well).īut that's not enough when you want to represent characters from more than one language, so cramming all available characters into a single byte just won't work. ASCII got extended by an 8th bit for other, non-English languages, but the additional 128 numbers/code points made available by this expansion would be mapped to different characters depending on the language being displayed. With 26 letters in the alphabet, both in capital and non-capital form, numbers and punctuation signs, that worked pretty well. English, into numbers ranging from 0 to 127 (7 bits). Old character encodings such as ASCII are from the (pre-) 8-bit era, and try to cram the dominant language in computing at the time, i.e. skipping a bit of history here and ignoring memory addressing issues, 8-bit computers would treat an 8-bit byte as the largest numerical unit easily represented on the hardware, 16-bit computers would expand that to two bytes, and so forth. Unicode assigns each character a unique number, or code point.Ĭomputers deal with such numbers as bytes. ![]() We've got lots of languages with lots of characters that computers should ideally display. To expand on the answers others have given: ![]()
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