In fact not really, because Unicode DOES assign more precise semantics to a few of these controls, notably for those given whitespace and newline properties (notably TAB, LF, CR in C0 controls and NL in C1 controls, with a few additional constraints for the CR+LF sequence) as they are part of almost all plain text protocols ; NUL also has a specific behavior which is so common that it cannot be mapped to anything else than a terminator or separator of plain text sequences.
So even if the ISO/IEC 8859 standard does not specify a charecter mapping in C0 and C1 controls, the registered MIME types are doing so (but nothing is well defined for the C0 and C1 controls except NUL, TAB, CR, LF, NL, for MIME usages purpose). And then yes, the ISO/IEC 8859 standard is different (more restrictive) from the MIME charsets defined by the IETF in some RFC's (and registered in the IANA registry), simply because the ISO/IEC standard (encoded charset) was developed to be compatible with various encoding schemes, some of them defined by ISO, some others defined by other standard European or East-Asian bodies (including 7-bit schemes, using escape sequences, or shift in/out controls). By itself, the ISO/IEC 8859 is not a complete encoding scheme, it is just defining several encoded character sets, independantly of the encoding schme used to store or transport it (it is not even sufficient to represent any plain-text content). On the opposite, The MIME "charsets" named "ISO_8859-*" registered by the IETF in the IANA registry are "concrete" encoding schemes, based on the ISO/IEC 8859 standard, and suitable for representing a plain-text content, because the MIME charsets are also adding a text presentation protocol. In practice, almost nobody today uses the ISO/IEC 8859 standard alone : there's always an additional concrete protocol added on top of it (which generally makes use of the C0 and C1 controls, but not necessarily, and not always the same way). So plain-text documents never use the ISO/IEC 8859 standard, but the MIME charsets (plus a few specific or proprietary charsets that have not been registered in the IANA registry as they are bound to a non-open protocol). 2012/11/16 Whistler, Ken <[email protected]> > No Unicode doesn’t. But yes, is **does** follow that decoding C0/C1 > control codes produces a Unicode code point of equal value. RTFM. TUS 6.2, > p. 544:**** > > ** ** > > “There are 65 code points set aside in the Unicode Standard for > compatibility with the C0 and C1 control codes defined in the ISO/IEC 2022 > framework. … The Unicode Standard provides for the intact interchange of > these code points, neither adding to nor subtracting from their semantics. > The semantics of the control codes are generally determined by the > application with which they are used. However, in the absence of specific > application uses, they may be interpreted according to the control function > semantics specified in ISO/IEC 6429:1992.”**** > > ** ** > > --Ken**** > > ** ** > > latin1 explicitly doesn't define characters (or control codes) in those > ranges, but unicode does.**** > > It doesn't directly follow that decoding a byte in those undefined ranges > produces a unicode-point of equal value.**** > > ** ** >
