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Esimerkit

• If your application works with MathML, or in various languages whose character sets gained support in Unicode 3.1 through the so-called Astral Planes, you will need to know that what Java calls a char is not really the same thing as a Unicode character or an XML character.
• The answer was UTF-16. Two blocks of 16-bit values were set aside for use as special values for encoding astral plane characters.
• UTF-16 encodes every character from O—65535 as 2 bytes; it then uses some dirty hacks if you actually need to represent the rarely used astral plane Unicode characters beyond 65535.
• The astral planes include some such characters, notably in the CJK extensions, without which it is impossible to write some people's names correctly.
• Such characters are in the so-called “Astral Planes,” with a code point above U+FFFF.
• But not all codepoints are used equally. Those in the "astral plane", for example, are used rarely, so the vast majority of the time you would be using twice as much memory as strictly necessary.
• Let's assume you want to display a Unicode character via JavaScript that is in an astral plane (obviously, there is a risk when doing so: not all fonts support all such characters).