Legacy Document
Important: The information in this document is obsolete and should not be used for new development.
Important: The information in this document is obsolete and should not be used for new development.
Programming With the Text Encoding Conversion ManagerWhen the Unicode Converter is able to convert a text string expressed in one text encoding to Unicode and back again to the original text encoding, with the final text string matching exactly the source text string--that is, without incurring any changes to the original--round-trip fidelity has been achieved.
For certain national and international standards that the Unicode Consortium used as sources for the Unicode coded character set, Unicode provides round-trip fidelity. Because the repertoires of those coded character sets have been effectively incorporated into the Unicode coded character set, conversion involving them will always produce round-trip fidelity. Text in one of those coded character sets can be mapped to Unicode and back again with no loss of information. Coded characters that were distinct in the source encoding will be distinct in Unicode.
However, perfect round-trip conversion is not always possible. Many character encodings include characters that do not have distinct representations in Unicode, or which may have no representation at all. For example, a source text string from a vendor coded character set might contain a ligature that is not represented in Unicode. In this case, that information may be lost during the round trip.
The Unicode Converter uses a variety of conventional methods to attempt to find some way to map the source coded representation of a character onto a sequence of Unicode coded representations in such a way as to preserve its identity and interchangeability.
Here are some of the methods used to map code representations of characters when high fidelity achieved through an exact or strict mapping is not possible: