When converting a C program to a C++ class, you can follow these steps to encapsulate the functionality of the C program within a class structure:

1. Identify the Functions: Identify the functions in your C program that need to be encapsulated within the class. These functions typically represent the main functionality of the program.
2. Create a Class: Create a class declaration, including a header file (.h) and an implementation file (.cpp). The class should have member variables and member functions that correspond to the relevant data and functionality in your C program.
3. Move Functions to Member Functions: Move the functions from the C program into member functions of the class. Adjust the function definitions to make use of the member variables of the class where necessary.
4. Modify Function Signatures: Modify the function signatures to include the class name as a qualifier. For example, if you have a function named calculateSum() in the C program, change it to MyClass::calculateSum() in the class definition.
5. Encapsulate Data: Encapsulate any relevant data from the C program as member variables within the class. This allows you to maintain the state of the data and encapsulate its access and modification within the class methods.
6. Handle Global Variables: If your C program relies on global variables, consider encapsulating them as private member variables within the class and providing appropriate accessor and mutator methods.
7. Instantiate the Class: In your main function, instantiate an object of the class and utilize its member functions to perform the desired functionality.
8. Handle Additional Class Features: Consider adding additional features to the class, such as constructors, destructors, overloaded operators, and access specifiers, to improve the design and functionality of the converted program.

Note that this conversion process may involve additional considerations depending on the complexity of your C program. It's important to carefully analyze the existing C code and structure it appropriately within the C++ class to ensure proper encapsulation and maintainability.

Remember to make use of C++ features like classes, constructors, destructors, and encapsulation to leverage the benefits of object-oriented programming.