Sybase 12.4.2 manual Language issues in client/server computing, 318

Understanding character sets in software

•Database servers, which sort characters (for example, list names alphabetically), use a collation. A collation is a combination of a character encoding (a map between characters and hexadecimal numbers) and a sort order for the characters. There may be more than one sort order for each character set; for example, a case-sensitive order and a case-insensitive order, or two languages may sort characters in a different order.

•Characters are printed or displayed on a screen using a font, which is a mapping between characters in the character set and their appearance. Fonts are handled by the operating system.

•Operating systems also use a keyboard mapping to map keys or key combinations on the keyboard to characters in the character set.

Language issues in client/server computing

Database users working at client applications may see or access strings from the following sources:

•Data in the database Strings and other text data are stored in the database. The database server processes these strings when responding to requests.

For example, the database server may be asked to supply all the last names beginning with a letter ordered less than N in a table. This request requires string comparisons to be carried out, and assumes a character set ordering.

The database server receives strings from client applications as streams of bytes. It associates these bytes with characters according to the database character set. Data in some IQ indexes is stored based on the sort order of the collation.

• Database server software messages Applications can cause

database errors to be generated. For example, an application may submit a query that references a column that does not exist. In this case, the database server returns a warning or error message. This message is held in a language resource library, which is a DLL or shared library called by Adaptive Server IQ.

•Client application The client application interface displays text, and internally the client application may process text.

•Client software messages The client library uses the same language library as the database server to provide messages to the client application.

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