C++ Data Abstraction

Object-oriented programming offers various features that help to minimize problems and increase flexibility in writing programs; one of the features of object-oriented programming is Data abstraction. In this tutorial, you will learn how to implement the concept of data abstraction in C++ programs.

What is Data Abstraction?

Data abstraction allows programs to ignore the details of how a data type is represented. The word Abstraction (derived from the Latin word "abs", meaning away from, and "trahere", meaning to draw) refers to the act of representing essential features without including background details or explanations. C++ classes use abstraction techniques and are defined as lists of abstract attributes, such as width, cost, size, and functions, to operate on these attributes. They put in a nutshell all the essential properties of an object that must be created. The attributes are therefore called data members as they hold information. The functions that operate on those data members are termed member functions. Since C++ classes use the data abstraction concept, they are also termed abstract data types.

Data members and member functions are expressed in code when classifying a class. But, when using an object (that is, an instance of a class), the built-in data type and class members are ignored; This process is known as data abstraction. It is a programming design technique that relies on separating interfaces from implementations. So while designing your component, you being a programmer, must keep the interface independent of the implementation because if you change the underlying implementation, the interface will remain intact. C++ provides an excellent level of data abstraction. In C++, we use classes to define our own abstract data types (ADT). Programmers can use the "cout" object of class ostream for data streaming to standard output like this:

Example:

#include <iostream>
using namespace std;

int main()
{
    cout << "Hello World" << endl;
}

What is Abstract Class?

Abstract class in C++ is not to create objects. These classes are designed only to treat like a base class (inherited by other classes). It is a developed technique for program development that allows making a base upon which other classes can be built.

Access Labels Enforce Abstraction

In C++ language, programmers can use access modifiers to define the abstract interface of the class. A C++ class may contain zero or more access labels:

• As you all know, the members defined in Public Access Specifier are accessible to certain program parts. Any data abstraction can be viewed or classified by its public members.
• When the access specifier is in private mode, members defined in the private mode are not accessible to code that uses the class. The private section explicitly hides code implementation within a C++ program.

There is no limitation on how access modifiers may appear within a program. The specific access modifier keeps its effect until the next access modifier is declared or the closing brace (i.e. "}") of the class body is seen.

Program to Show the Use of Data Abstraction in C++

Here is an example of declaring Public members of a C++ class:

Example:

#include <iostream>
using namespace std;

class sample {
public:
    int gl, g2;

public:
    void val()
    {
        cout << "Enter Two values : "; cin >> gl >> g2;
    }
    void display()
    {
        cout << gl << " " << g2;
        cout << endl;
    }
};

int main()
{
    sample S;
    S.val();
    S.display();
}

Output:

Enter Two values : 20
50
20 50

Here is a Private member example in which member data cannot be accessed outside the class:

Example:

#include <iostream>
using namespace std;

class sample {
public:
    int gl, g2;

public:
    void val()
    {
        cout << "Enter Two values : "; cin >> gl >> g2;
    }

private:
    void display()
    {
        cout << gl << " " << g2;
        cout << endl;
    }
};

int main()
{
    sample S;
    S.val();
    S.display();
}

If you execute the above program, the private member function will not be accessible, and hence the following error message will appear like this in some compilers:

Output:

error: 'void sample::display()' is private
     void display()
          ^

Advantages of Data abstraction

• Class internals get protected from inadvertent user-level errors
• The programmer does not have to write the low-level code
• Code duplication is avoided, so the programmer does not have to go over again and again fairly common tasks every time to perform a similar operation
• The main idea of abstraction is code reuse and proper partitioning across classes.
• This may not seem helpful for small projects, but for large projects, it provides conformity and structure as it provides documentation through the abstract class contract.
• It allows internal implementation details to be changed without affecting the users of the abstraction.