string and math.h are not classes, but header-files and can be provided by the compiler or not, depends on your compiler and version.
C::B isnot a compiler, but an IntegratedDevelopmentEnvironment.
You seem to miss the absolute basics of programming.
You should try to find a website/forum, that supports basic programming questions or (better) buy yourself a good book about programming.
This forum/site is not such a site and your question is violating our forum rules therfore.
If you have questions related to C::B or how to set special parameters in C::B, feel free to start a new topic.
Topic locked !