Is it bad practice to use C features in C++?

Question

For example printf instead of cout, scanf instead of cin, using #define macros, etc?

Answer 1

I would say the only ones that are truly harmful to mix are the pairings between malloc/free and new/delete.

Otherwise it's really a style thing...and while the C is compatible with the C++, why would you want to mix the two languages when C++ has everything you need without falling back?