Default class inheritance access

Solution 1:

From standard docs, 11.2.2

In the absence of an access-specifier for a base class, public is assumed when the derived class is defined with the class-key struct and private is assumed when the class is defined with the class-key class.

So, for structs the default is public and for classes, the default is private...

Examples from the standard docs itself,

class D3 : B { / ... / }; // B private by default

struct D6 : B { / ... / }; // B public by default

Solution 2:

You might have read something incomplete or misleading. To quote Bjarne Stroustrup from "The C++ programming Language", fourth Ed., p. 602:

In a class, members are by default private; in a struct, members are by default public (§16.2.4).

This also holds for members inherited without access level specifier.

A widespread convention is, to use struct only for organization of pure data members. You correctly used a class to model and implement object behaviour.

Solution 3:

The default inheritance level (in absence of an access-specifier for a base class )for class in C++ is private. [For struct it is public]

class Derived:Base

Base is privately inherited so you cannot do sth.Base::Do(); inside main() because Base::Do() is private inside Derived

Solution 4:

The default type of the inheritance is private. In your code,

class B:A

is nothing but

class B: private A