If you're an existing ArcObjects SDK for Cross-platform C++ developer, get up to speed with What's new in version 10.
If you are new to the ArcObjects SDK for Cross-platform C++, start with the Concepts.
This web site is about the 10.0 version. For more information about the previous version see the 9.3.1 documentation for the ArcGIS Engine Windows and Solaris/Linux SDKs.
Use one of the supported widget sets to build GIS applications.