To finish plugging in the concrete factory, you must create the instance function, defined in <env>OS.cpp, which returns a pointer to the concrete operating system factory. The instance method creates a single instance of the OMOSFactory. It is defined as follows:
static OMOSFactory* instance();
For example, in VxWorks, the declaration is as follows:
OMOSFactory* OMOSFactory::instance()
{
static VxOSFactory theFactory;
return &theFactory;
}