CWinApp( const char* pszAppName = NULL );
pszAppName
A null-terminated string containing the Windows application name for your application. If this argument is not supplied or is NULL, CWinApp uses the filename of the executable file by default.
Constructs a CWinApp object and passes pszAppName to be stored as the application name. This constructor is invoked by your global application object definition. You can have only one CWinApp object in your application. The constructor stores a pointer to the CWinApp object in a Microsoft Foundation-defined global variable. This is so the WinMain can call the object's member functions to initialize and run the application.