AIX Version 4.3 Differences Guide

Note: The terms UCS-2 and Unicode will be used interchangeably throughout
this documentation.
The Unicode 2.0 standard (ISBN 0-201-48345-9) is the basis for the AIX
implementation and is used as the primary reference.
Further information is also available at the Unicode URL: http://www.unicode.org
10.3.1 UTF-8
For file systems to be able to work with Unicode, a UCS Transformation Format
was developed by the X/Open Internationalization (also known as I18N, because
there are 18 letters between the I and the N) working group. This transformation,
called UTF-8, provides a way of transforming Unicode into an ASCII
representation.
The UTF-8 transformation is important when considering that the majority of file
systems are ACSII-based. When using the UTF-8 Transformation Format, you
are assured of a file system-safe way of using Unicode to store files.
The UTF-8 transformation format is a multi-byte code set capable of encoding the
same set of characters of UCS-2 in 1 to 3 bytes or UCS-4 in 1 to 6 bytes. It has
the following characteristics:
• ASCII (7-bit code) is a proper subset.
• It preserves the semantics of the portable character set.
• It preserves the semantics of a null octet for the C programming language.
Note: It is expected that UTF-8 will be a dominant transformation method where
the UCS is not practical.
10.3.2 ULS
ULS, or Universal Language Support, refers to a toolkit of functions that enable
applications to work with UCS. The ULS is designed to be operating
system-independent, so the functions can be ported to any system.
The Universal Language Support specification describes a set of functions and
utilities for addressing a wide range of national language support (NLS)
problems. In summary, it provides:
• A universal coded character set capable of encoding most of today's
languages and scripts.
• A set of universal language support functions for the processing of input and
output of supported characters.
• A set of universal locale objects that describe processing of text on a global
scope.
• A set of universal layout objects that describe processing of text on a global
scope.
• A set of universal conversion objects for import/export of traditional data into
the ULS environment.
This specification identifies the level of support expected for the Universal Coded
Character Sets in the AIX operating system and all future releases of it. Without
National Language Support 243