Multiple Inheritance in C++

This section will discuss the Multiple Inheritances in the C++ programming language. When we acquire the features and functionalities of one class to another class, the process is called Inheritance. In this way, we can reuse, extend or modify all the attributes and behaviour of the parent class using the derived class object. It is the most important feature of object-oriented programming that reduces the length of the program.

A class that inherits all member functions and functionality from another or parent class is called the derived class. And the class from which derive class acquires some features is called the base or parent class.

Multiple Inheritance is the concept of the Inheritance in C++ that allows a child class to inherit properties or behaviour from multiple base classes. Therefore, we can say it is the process that enables a derived class to acquire member functions, properties, characteristics from more than one base class.

Diagram of the Multiple Inheritance

Following is the diagram of the Multiple Inheritances in the C++ programming language.

In the above diagram, there are two-parent classes: Base Class 1 and Base Class 2, whereas there is only one Child Class. The Child Class acquires all features from both Base class 1 and Base class 2. Therefore, we termed the type of Inheritance as Multiple Inheritance.

Syntax of the Multiple Inheritance

class A
{
// code of class A
}
class B
{
// code of class B
}
class C: public A, public B (access modifier class_name)
{
// code of the derived class
}

In the above syntax, class A and class B are two base classes, and class C is the child class that inherits some features of the parent classes.

Let's write the various program of Multiple Inheritance to inherit the member functions and functionality from more than one base class using the derived class.

Example 1: Program to use the Multiple Inheritance

Program1.cpp

#include <iostream>
using namespace std;

// create a base class1
class Base_class
{
	// access specifier
	public: 
	// It is a member function
	void display()
	{
		cout << " It is the first function of the Base class " << endl;
	}
};

// create a base class2
class Base_class2
{
	// access specifier
	public: 
	// It is a member function
	void display2()
	{
		cout << " It is the second function of the Base class " << endl;
	}
};

/* create a child_class to inherit features of Base_class and Base_class2 with access specifier. */
class child_class: public Base_class, public Base_class2
{
	
	// access specifier
	public:
	void display3()	// It is a member function of derive class
	{
		cout << " It is the function of the derived class " << endl;	
	}
	
};

int main ()
{
	// create an object for derived class
	child_class ch;
	ch.display(); // call member function of Base_class1
	ch.display2(); // call member function of Base_class2
	ch.display3(); // call member function of child_class
}

Output

It is the first function of the Base class
 It is the second function of the Base class
 It is the function of the derived class

In the above program, we created two base classes and one child class. The child_class invoke member function display() and display2() from both parent classes Base_class and Base_class2 with the help of child class's object ch.

Example 2: Use Multiple Inheritance to perform the arithmetic operation

Let's create a derived class to inherit the member functions from multiple base classes in C++ programming.

Program2.cpp

#include <iostream>
using namespace std;

// create add class
class add
{
	public:
		int x = 20;
		int y = 30;
		void sum()
		{
			cout << " The sum of " << x << " and " << y << " is " <<x+y << endl;
		}
};

// create Mul class
class Mul
{
	public:
		int a = 20;
		int b = 30;
		void mul()
		{
			cout << " The Multiplication of " << a << " and " << b << " is " <<a*b << endl;
		}
};

// create Subclass
class Sub
{
	public:
		int a = 50;
		int b = 30;
		void sub()
		{
			cout << " The Subtraction of " << a << " and " << b << " is " <<a-b << endl;
		}
};

// create Div class
class Div
{
	// access specifier
	public:
		int a = 150;
		int b = 30;
		void div()
		{
			cout << " The Division of " << a << " and " << b << " is " <<a/b << endl;
		}
};

// create a derived class to derive the member functions of all base classes
class derived: public add, public Div, public Sub, public Mul
{
	// access specifier
	public:
		int p = 12;
		int q = 5;
		void mod()
		{			
			cout << "The Modulus of " << p << " and " <<q << " is " << p % q << endl;
		}
};

int main ()
{
	// create an object of the derived class
	derived dr;
	dr.mod(); // call derive class member function	
	// call all member function of class add, Div, Sub and Mul
	dr.sum();
	dr.mul();
	dr.div();
	dr.sub();
}

Output

The Modulus of 12 and 5 is 2
 The sum of 20 and 30 is 50
 The Multiplication of 20 and 30 is 600
 The Division of 150 and 30 is 5
 The Subtraction of 50 and 30 is 20

Example 3: Get the average marks of six subjects using the Multiple Inheritance

Let's create another program to print the average marks of six subjects using the multiple Inheritance in the C++ programming language.

Program3.cpp

#include <iostream>
using namespace std;

// create base class1
class student_detail 
{
	// access specifier 
	protected:
		int rno, sum = 0, i, marks[5];
	
	// access specifier	
	public:
		void detail()
		{
			
			
			cout << " Enter the Roll No: " << endl;
			cin >> rno;

			cout << " Enter the marks of five subjects " << endl;
			// use for loop
			for (i = 0; i < 5; i++)
			{
				cin >> marks[i];
			}
			
			
			for ( i = 0; i < 5; i++)
			{
				// store the sum of five subject
			sum = sum + marks[i];
			}
		}
			
};

// create base class2
class sports_mark 
{
	protected:
		int s_mark; 
	
	public:
		
		void get_mark()
		{
			cout << "\n Enter the sports mark: ";
			cin >> s_mark;
			}	
};

/* create a result as the child class to inherit functions of the parent class: student_detail and sports_mark.*/
class result: public student_detail, public sports_mark
{
	int tot, avg;
	public:
		
		// create member function of child class
		void disp ()
		{
			tot = sum + s_mark;
			avg = tot / 6; // total marks of six subject / 6
			cout << " \n \n \t Roll No: " << rno << " \n \t Total: " << tot << endl;
			cout << " \n \t Average Marks: " << avg;
		}
};

int main ()
{
	result obj; // create an object of the derived class

	// call the member function of the base class
	obj.detail();
	obj.get_mark();
	obj.disp();
}

Output

Enter the Roll No:
25
 Enter the marks of five subjects
90
85
98
80
75

 Enter the sports mark: 99


         Roll No: 25
         Total: 527

         Average Marks: 87

Ambiguity Problem in Multiple Inheritance

In Multiple Inheritance, when a single class is derived from two or more base or parent classes. So, it might be possible that both the parent class have the same-named member functions, and it shows ambiguity when the child class object invokes one of the same-named member functions. Hence, we can say, the C++ compiler is confused in selecting the member function of a class for the execution of a program.

Program to demonstrate the Ambiguity Problem in Multiple Inheritance

Let's write a simple to invoke the same member function of the parent class using derived class in C++ programming.

Program4.cpp

#include <iostream>
#include <conio.h>

using namespace std;

// create class A
class A
{
	public: 
	void show()
	{
		cout << " It is the member function of class A " << endl;
	}
 }; 
 
 // create class B
 class B
{
	public: 
	void show()
	{
		cout << " It is the member function of class B " << endl;
	}
 };
 
 
 // create a child class to inherit the member function of class A and class B
 class child: public A, public B
 {
 	public:
 		void disp()
 		{
 			cout << " It is the member function of the child class " << endl;
		 }
 };
 
 int main ()
 {
 	// create an object of the child class to access the member function
 	child ch;
 	ch.show(); // It causes ambiguity 
ch.disp();
 	return 0;
 } 

When the above program is compiled, it throws the show() member function is ambiguous. Because of both the base class A and B, defining the same member function show(), and when the derived class's object call the shows() function, it shows ambiguity in multiple inheritances.

Therefore, we need to resolve the ambiguous problem in multiple Inheritance. The ambiguity problem can be resolved by defining the class name and scope resolution (::) operator to specify the class from which the member function is invoked in the child class.

Syntax of the Ambiguity Resolution

Derived_obj_name.parent_class_name : : same_named_memberFunction ( [parameter] );

For example,

ch.A:: show(); // class_name and scope resolution operator with member function
ch.B::show();

After making some changes, now we again execute the above program that returns the given below Output.

It is the member function of the child class
 It is the member function of class A
 It is the member function of class B

Next TopicC++ Bitwise XOR Operator

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Multiple Inheritance in C++

Diagram of the Multiple Inheritance

Syntax of the Multiple Inheritance

Example 1: Program to use the Multiple Inheritance

Example 2: Use Multiple Inheritance to perform the arithmetic operation

Example 3: Get the average marks of six subjects using the Multiple Inheritance

Ambiguity Problem in Multiple Inheritance

Program to demonstrate the Ambiguity Problem in Multiple Inheritance

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