Chapter 5. Internationalization
We’ve told you that XML documents contain text, but we haven’t
yet told you what kind of text they contain. In this chapter we rectify
that omission. XML documents contain Unicode text. Unicode is a character set large enough to
include all the world’s living languages and a few dead ones. It can be
written in a variety of encodings, including UCS-2 and the ASCII
superset UTF-8. However, since Unicode text editors are not ubiquitous,
XML documents may also be written in other character sets and encodings,
which are converted to Unicode when the document is parsed. The encoding
declaration specifies which character set a document uses. You can use
character references, such as θ
, to insert Unicode characters
like that aren’t available in the legacy character set in which a
document is written.
Computers don’t really understand text. They don’t recognize the Latin letter Z, the Greek letter γ, or the Han ideograph
. All a computer understands are numbers such as 90, 947, or 40,821. A character set maps particular characters, like Z, to particular numbers, like 90. These numbers are called code points. A character encoding determines how those code points are represented in bytes. For instance, the code point 90 can be encoded as a signed byte, a little-endian unsigned short, a 4-byte, two’s complement, a big-endian integer, or in some still more ...
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