The first time you run Source Insight, it automatically creates a project named Base. The Base project is the last place that Source Insight will search for symbols. It is implicitly at the end of the project symbol path. In other words, if Source Insight is looking up a symbol, and it can’t find it in either an open file, the current project, or any of the projects in the project symbol path, then it looks in the Base project for the symbol.
Note: You do not have to add the Base project to the project symbol path. Source Insight automatically searches it as though it were in the list.
This gives you a convenient place to save common symbols. Any symbol stored in the Base project is visible from any other project. For example, you could add all of the standard C/C++ include files to the Base project. The Base project is also a good place to add your favorite Source Insight editor macro files.