- <B>o</B> Shading is used to identify <I>X/Open</I> <I>Enhanced</I> <I>Curses</I> material,
- relating to interfaces included to provide enhanced capabilities
- for applications originally written to be compiled on systems
- based on the UNIX operating system. Therefore, the features
- described may not be present on systems that conform to <B>XPG4</B> <B>or</B>
- <B>to</B> <B>earlier</B> <B>XPG</B> <B>releases</B>. The relevant reference pages may
- provide additional or more specific portability warnings about
- use of the material.