Your work with the Microsoft Foundation Class (MFC) Library framework is based largely on a few major classes and several Visual C++ tools. Some classes encapsulate a large portion of the Win32 application programming interface (API). Other classes encapsulate application concepts such as documents, views, and the application itself. Still others encapsulate OLE features and ODBC and DAO data-access functionality. (DAO is supported through Office 2013. DAO 3.6 is the final version, and it is considered obsolete.)
For example, Win32's concept of window is encapsulated by MFC class
CWnd. That is, a C++ class called
CWnd encapsulates or "wraps" the
HWND handle that represents a Windows window. Likewise, class
CDialog encapsulates Win32 dialog boxes.
Encapsulation means that the C++ class
CWnd, for example, contains a member variable of type
HWND, and the class's member functions encapsulate calls to Win32 functions that take an
HWND as a parameter. The class member functions typically have the same name as the Win32 function they encapsulate.