Alternate Character Sets

THO: Does not need an escape sequence. BIG-5 does not need an escape sequence. ASCII is a 7 bit character set, which means that the top bit of the byte is “0”. The parser knows that when the top bit of the byte is “0”, the character set is ASCII. When it is “1”, the following bytes should be handled as 2 bytes (or more). No escape technique is needed. However, since some servers do not correctly interpret when they receive a top bit “1”, it is advised, in internet RFC, to not use these kind of non-safe non-escape extension.

THO: Note that the code contains a space, i.e., “ISO IR87”. The JIS X 0208 needs an escape sequence. In Japan, the escape technique is ISO 2022. From basic ASCII, escape sequence “escape” $ B (in HEX, 1B 24 42) lets the parser know that following bytes should be handled 2-byte wise. Back to ASCII is 1B 28 42.

THO Usage: Available from The Unicode Consortium, P.O. Box 700519, San Jose, CA 95170-0519. See http://www.unicode.org/unicode/consortium/consort.html

THO: UTF-8 is a variable-length encoding, each code value is represented by 1,2 or 3 bytes, depending on the code value. 7 bit ASCII is a proper subset of UTF-8. Note that the code contains a space before UTF but not before and after the hyphen. Since UTF-8 represents the full UNICODE character set, the following restriction apply to its use: 1. UTF-8 must be the default encoding of the message, UTF-8 cannot be specified as an additional character set in MSH-18 2. There are no other character sets allowed in a message where UTF-8 is the default encoding in the message. In other words, UNICODE UTF-8 can only be specified as a single value in MSH-18 3. A message encoded in UTF-8 must not use a Byte Order Mark (BOM).