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# C++ Data Encapsulation Data Encapsulation is a fundamental concept in Object-Oriented Programming (OOP) that is achieved by bundling data and the functions that operate on that data within a class. This encapsulation ensures the privacy and integrity of the data, preventing external code from directly accessing and modifying it. All C++ programs have the following two basic elements: * **Program Statements (Code):** This is the part of the program that performs actions; they are called functions. * **Program Data:** Data is the information of the program that is affected by the program functions. Encapsulation is a concept in OOP that binds data and the functions that operate on that data together, thereby protecting it from outside interference and misuse, thus ensuring safety. Data encapsulation leads to another important OOP concept, namely **Data Hiding**. **Data Encapsulation** is a mechanism that bundles data and the functions that operate on that data together, while **Data Abstraction** is a mechanism that exposes only the interface to the user and hides the implementation details. C++ supports encapsulation and data hiding (public, protected, private) by creating **classes**. We already know that a class can contain private members, protected members, and public members. By default, all items defined in a class are private. For example: class Box{public: double getVolume(void){return length * breadth * height; }private: double length; // length double breadth; // width double height; // height}; The variables length, breadth, and height are all private (private). This means they can only be accessed by other members within the Box class, and not by other parts of the program. This is a way to implement encapsulation. To make the members of a class public (i.e., accessible by other parts of the program), you must declare them using the **public** keyword. All variables or functions defined after the public identifier can be accessed by all other functions in the program. Defining a class as a friend class of another class exposes implementation details, thereby reducing encapsulation. Ideally, each class should hide its implementation details from the outside as much as possible. **Access Modifiers:** * **private**: Private members can only be accessed within the class itself and cannot be directly accessed by external code. * **public**: Public members can be directly accessed by external code. * **protected**: Protected members can be accessed by the class and its derived classes. ## Example of Data Encapsulation