If you create an unmanaged project where the sources have not been built and does not contain any debugging information, the IDE might have trouble configuring code assistance. In this case, you can specify in the Configure Code Assistance wizard to use a special mode, Search file system for C/C++ header files. In this mode, the IDE tries to resolve failed include directives by searching the file system for headers. The wizard asks you to enter the path to search for headers. By default, the path is the project source root.