#include *.h file confused me...

Good day.

Is there any clear rule for how and when to include *.h ?

Sometime i found some of the *.h work well at A.h or at A.cpp.
Sometime i found if C.h was inclued by B.h, and i only need include B.h at A.h for the execute A.cpp. If i still included C.h at A.h. Does C.h will be compiled twice or not?

Thanks!

You are confusing me. Anyway, here's the gist of what I think you need to know:

• Use header inclusion guards for your own headers.
• If you need a definition from a header, include it.
• If you need a declaration from a header, consider a forward declaration instead.
• Do not rely on a header including another header since that fact may change under maintenance.

i guess i understand.

Thank you a lot!