How to use include + path syntax correctly?

[alleycat 28]

I would like to know how to use paths correctly in scripting.

For example when I try to include

foldername/include.hpp it wont work, however foldername\include.hpp appears to work. I also saw \foldername\include.hpp in some scripts and even absolute paths. Can someone explain when to use which?

[ceeeb 147]

https://community.bistudio.com/wiki/PreProcessor_Commands#.23include

[alleycat 28]

Thanks!