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

It depends on which features. Using define macros in C++ is strongly frowned upon, and for a good reason. You can almost always replace a use of a define macro with something more maintainable and safe in C++ (templates, inline functions, etc.)

Streams, on the other hand, are rightly judged by some people to be very slow and I've seen a lot of valid and high-quality C++ code using C's FILE* with its host of functions instead.

And another thing: with all due respect to the plethora of stream formatting possibilities, for stuff like simple debug printouts, IMHO you just can't beat the succinctness of printf and its format string.