US-ASCII is a 7-bit character set and encoding that covers the English-language alphabet. It is not large enough to cover the characters used in other languages, however, so it is not very useful for internationalization.

ISO-8859-1

ISO-8859-1 is the character set for Western European languages. It’s an 8-bit encoding scheme in which every encoded character takes exactly 8 bits. (With the remaining character sets, on the other hand, some codes are reserved to signal the start of a multibyte character.)

UTF-8

UTF-8 is an 8-bit encoding scheme. Characters from the English-language alphabet are all encoded using an 8-bit byte. Characters for other languages are encoded using 2, 3, or even 4 bytes. UTF-8 therefore produces compact documents for the English language, but for other languages, documents tend to be half again as large as they would be if they used UTF-16. If the majority of a document’s text is in a Western European language, then UTF-8 is generally a good choice because it allows for internationalization while still minimizing the space required for encoding.

UTF-16

UTF-16 is a 16-bit encoding scheme. It is large enough to encode all the characters from all the alphabets in the world. It uses 16 bits for most characters but includes 32-bit characters for ideogram-based languages such as Chinese. A Western European-language document that uses UTF-16 will be twice as large as the same document encoded using UTF-8. But documents written in far Eastern languages will be far smaller using UTF-16.

Note - UTF-16 depends on the system’s byte-ordering conventions. Although in most systems, high-order bytes follow low-order bytes in a 16-bit or 32-bit “word,” some systems use the reverse order. UTF-16 documents cannot be interchanged between such systems without a conversion.

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