data encapsulation in c++ is an Object Oriented Programming concept that binds together the data and functions that manipulate the data, and that keeps both safe from outside interference and misuse.

it led to the important OOP concept of data hiding.

encapsulation in cpp

Data encapsulation is a mechanism of bundling the data, and the functions that use them and
The data abstraction is a mechanism of exposing only the interfaces and hiding the implementation details from the user.

C++ supports the properties of encapsulation and data hiding through the creation of user defined types, called classes. We already have studied that a class can contain private,
protected and public members. By default, all items defined in a class are private. For example:

class Box
double getVolume(void)
return length * breadth * height;
double length; // Length of a box
double breadth; // Breadth of a box
double height; // Height of a box

The variables length, breadth, and height are private. This means that they can be accessed only by other members of the Box class, and not by any other part of your program. This is one way encapsulation is achieved.

To make parts of a class public i.e , accessibletootherpartsofyourprogram, you must declare them after the public keyword. All variables or functions defined after the public specifier are accessible by all other functions in your program.

Making one class a friend of another exposes the implementation details and reduces
encapsulation. The ideal is to keep as many of the details of each class hidden from all other
classes as possible.

Example of Data Encapsulation
#include <iostream>
using namespace std;
class Adder{
// constructor
Adder(int i = 0)
total = i;
// interface to outside world
void addNum(int number)
total += number;
// interface to outside world
int getTotal()
return total;
// hidden data from outside world
int total;
int main( )
Adder a;
cout << "Total " << a.getTotal() <<endl;
return 0;
Total 60

Above class adds numbers together, and returns the sum. The public members addNum and
getTotal are the interfaces to the outside world and a user needs to know them to use the class. The private member total is something that is hidden from the outside world, but is needed for the class to operate properly.

Designing Strategy

Most of us have learned through bitter experience to make class members private by default
unless we really need to expose them. That’s just good encapsulation.