Xcode linking files

I'm a C++ student and I would like to set up a project where I can store a host of .cpp's for reference. For example, a folder for vectors with a bunch of associated .cpp's, a folder for strings with a bunch of .cpp's, just to aid with learning this language. However, if I add more than one .cpp in a project, it will try to link these upon building and I will get errors. Is there anyway I can create separate folders in the same project to make everything look a bit more neat and more easily accessible?