In the C++ programming language, a class consists of properties (or member data) and methods (or member functions). The properties are data elements, such as those contained in a structure. The methods are used for a variety of purposes, such as initialization, assignment, operations, and data access. You use a class declaration in the same way that you use a structure declaration. Memory is allocated for a class when you define a class object. Each class object has a data area for its properties and a table of pointers to the methods it supports.
In OLE, an object consists of data and methods, as it does in C++. However, an OLE object adheres to stricter rules. The data is strictly internal. An object only exposes interfaces. An interface is a set of related methods for an object. Each object can support multiple interfaces. All OLE interfaces support the IUnknown interface.