inheritance - Abstract class and pure method C++ -

i've read in book stephen prata - "c++ primer plus vi edition" in abstract class can write definition of pure method. understood can write example void pure() = 0 , can make definition of method in class. thought = 0 make class abstract , if make class inheriting class don't have overwrite (i don't know if word "overwrite" right, meant wan't hide method basic class writing method same name in secondary class).

i checked in compiler , warning "it has no overrider". if have overwrite pure virtual method (with definition in abstract class) in secondary class how can use definition basic class? useless?

are looking this:

class abstract { public:   virtual void f() = 0; };  // pure virtual function can still defined. // has defined out-of-class. void abstract::f() {   // }  class concrete : public abstract { public:   void f() {     abstract::f();  // call base class implementation     // more   } };