What is the purpose of a class in C++?

In C++, class is a user-defined data type used to encapsulate data and related operations. It can include member variables (data) and member functions (operations) and can be used by instantiating (creating objects).

The main functions are as follows:

1. Encapsulating data: Using classes allows for related data and operations to be encapsulated together to form an independent entity. By defining data members as private or protected, the implementation details can be hidden from external sources, providing only public interfaces to achieve information hiding and data security.
2. Inheritance: The class supports an inheritance mechanism, allowing the creation of new classes through inheritance. Subclasses can inherit attributes and methods from the parent class, enabling code reuse and extension.
3. Polymorphism: classes support polymorphism, which allows for runtime dynamic binding through virtual functions and pure virtual functions, enabling different objects of the same type to have different responses to the same message.
4. Data abstraction: classes can encapsulate data and its operations together, forming an abstract data type. By hiding implementation details and only exposing necessary interfaces to users, it enhances the maintainability and scalability of the program.

In conclusion, the role of a class is to provide a mechanism that allows programmers to encapsulate data and related operations together, forming an independent entity for the organization, reuse, and extension of code.