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The C++ language gives us a powerful OOP feature known as inheritance. Inheritance allows a class to use/inherit the features of another existing class. The class that wants to use the features of another class is called subclass or derived class, whereas the class whose features are to be used/inherited is referred to as base class. Hence, inheritance gives C++ the power of reusability.

What features a subclass inherits from its base class, through inheritance?

When a subclass inherits a base class, it inherits only the members of superclass that are marked with public, protected visibility modes, these members are -
• Properties of the base class.
• Functions of the base class.

Note - Base class members marked with private visibility mode are never inherited.

Syntax of Inheritance

Let us take a look at a general syntax of performing inheritance, using which we could define a derived class which is inheriting a base class.

class derived-class-name : visibility-mode base-class-name
{
//members of derived class
}

• In the syntax, The derived-class-name is the name of the derived class, which is being defined and it is going to inherit features of another class i.e. a base class with the name base-class-name.


• The colon : between derived-class-name and base-class-name indicates that inheritance is being performed.


• The visibility-mode is used to define whether the features of base class are publicly inherited, privately inherited or protected inherited, depending on the value of visibility-mode which could be either public, private or protected.
  
  Note : Defining visibility-mode when performing inheritance is optional, and if you don't specify it then the default visibility-mode value is private.

Publicly inheriting a class

Let us understand the syntax used to publicly inherit the feature of a class by another class.

class Y
{
public:
int a;
protected:
int b;
private:
int c;
}


class X : public Y
{
}

In the example above, the class named Y is publicly inherited another class named Y, which means that -

• The public member of class Y, such as a is inherited and have become public member in the derived class X.
• The protected member of class Y, such as b is inherited and have become protected member in the derived class X.
• The private member of any class are never inherited.

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Privately inheriting a class

Let us understand the syntax used to privately inherit the feature of a class by another class.

• class Y
  {
  public:
  int a;
  protected:
  int b;
  private:
  int c;
  }
  
  
  class X : public Y
  {
  }


In the example above, the class named X is privately inherited another class named Y, which means that -
• The public member of class Y, such as a is inherited and have become private member in the derived class X.
• The protected member of class Y, such as b is inherited and have become private member in the derived class X.
• The private member of any class are never inherited.





• class X : Y
  {
  }
  


When we don't define a value of visibility-mode, then the default visibility-mode value is private. Hence, in the example above, the class named X is privately inherited another class named Y, because which means that the public and protected members of class Y are inherited and have become private members in the derived class X.






Protected inheriting a class


Let us understand the syntax used to protected inherit the feature of a class by another class.



class Y
{
public:
int a;
protected:
int b;
private:
int c;
}


class X : protected public Y
{
}


In the example above, the class named Y is publicly inherited another class named Y, which means that -
• The public member of class Y, such as a is inherited and have become protected member in the derived class X, which means it is available for further inheritance.
• The protected member of class Y, such as b is inherited and have become protected member in the derived class X.
• The private member of any class are never inherited.







Types of Inheritance



• Single inheritance
• Multiple inheritance
• Multilevel inheritance
• Hybrid inheritance
• Hierarchical inheritance


As you can see, C++ provides many types of inheritance and in the upcoming tutorials we are going to discuss each type. So stay tuned for more!






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