C/C++ Programming interview questions and answers

What is multiple inheritance(virtual inheritance)? What are its advantages and disadvantages?
Ans- Multiple Inheritance is the process whereby a child can be derived from more than one parent class. The advantage of multiple inheritance is that it allows a class to inherit the functionality of more than one base class thus allowing for modeling of complex relationships. The disadvantage of multiple inheritance is that it can lead to a lot of confusion(ambiguity) when two base classes implement a method with the same name.

What are the access privileges in C++? What is the default access level?
Ans- The access privileges in C++ are private, public and protected. The default access level assigned to members of a class is private. Private members of a class are accessible only within the class and by friends of the class. Protected members are accessible by the class itself and it's sub-classes. Public members of a class can be accessed by anyone.



What is a nested class? Why can it be useful?
Ans- A nested class is a class enclosed within the scope of another class. For example:
  //  Example 1: Nested class
  //
  class OuterClass
  {
    class NestedClass
    {
      // ...
    };
    // ...
  };
Nested classes are useful for organizing code and controlling access and dependencies. Nested classes obey access rules just like other parts of a class do; so, in Example 1, if NestedClass is public then any code can name it as OuterClass::NestedClass. Often nested classes contain private implementation details, and are therefore made private; in Example 1, if NestedClass is private, then only OuterClass's members and friends can use NestedClass.
When you instantiate as outer class, it won't instantiate inside class.





What is a local class? Why can it be useful?
Ans- local class is a class defined within the scope of a function -- any function, whether a member function or a free function. For example:
  //  Example 2: Local class
  //
  int f()
  {
    class LocalClass
    {
      // ...
    };
    // ...
  };
Like nested classes, local classes can be a useful tool for managing code dependencies.



Can a copy constructor accept an object of the same class as parameter, instead of reference of the object? 
Ans- No. It is specified in the definition of the copy constructor itself. It should generate an error if a programmer specifies a copy constructor with a first argument that is an object and not a reference.