For normal text (not markup), there are no special characters: just
make sure your document refers to the correct encoding scheme for the
language and/or writing system you want to use, and that your computer
correctly stores the file using that encoding scheme. See the question
on non-Latin characters for a longer explanation. If your keyboard will
not allow you to type the characters you want, or if you want to use
characters outside the limits of the encoding scheme you have chosen,
you can use a symbolic notation called ‘entity referencing’. Entity
references can either be numeric, using the decimal or hexadecimal
Unicode code point for the character (eg if your keyboard has no Euro
symbol (€) you can type €); or they can be character, using an
established name which you declare in your DTD (eg ) and then use as €
in your document. If you are using a Schema, you must use the numeric
form for all except the five below because Schemas have no way to make
character entity declarations. If you use XML with no DTD, then these
five character entities are assumed to be predeclared, and you can use
them without declaring them:
The less-than character (<) starts element markup (the first character of a start-tag or an end-tag).
The ampersand character (>) starts entity markup (the first character of a character entity reference).
The greater-than character (>) ends a start-tag or an end-tag.
The double-quote character (") can be symbolised with this character
entity reference when you need to embed a double-quote inside a string
which is already double-quoted.
The apostrophe or single-quote character (') can be symbolised with
this character entity reference when you need to embed a single-quote
or apostrophe inside a string which is already single-quoted. If you
are using a DTD then you must declare all the character entities you
need to use (if any), including any of the five above that you plan on
using (they cease to be predeclared if you use a DTD). If you are using
a Schema, you must use the numeric form for all except the five above
because Schemas have no way to make character entity declarations.