C++ Abstract Base Class

What is Abstract Base Class?

• Allows the base class to provide only an interface for its derived classes.
• Prevents anyone from creating an instance of this class.
• A class is made abstract if atleast one pure virtual function defined.

EXAMPLE: Demonstrate the definition of a abstract base class

#include <iostream>

using namespace std;

class MyInterface {
    public:
       virtual void Display() = 0;
};

class MyClass1 : public MyInterface {
    public:
       void Display() {
          cout << "MyClass1" << endl;
       }
};

class MyClass2 : public MyInterface {
    public:
       void Display() {
           cout << "MyClass2" << endl;
       }
};

void main()
{
    // MyInterface obj;
    // Error E2352 Interface.cpp 26: Cannot create instance of abstract class 'MyInterace' in function main()
    // Error E2353 Interface.cpp 26: Class 'MyInterface' is abstract because of 'MyInterface::Display() = 0' in function main()
    // *** 2 errors in Compile ***

    MyClass1 obj1;
    obj1.Display();

    MyClass2 obj2;
    obj2.Display();
}

OUTPUT:

MyClass1
MyClass2