In previous releases of OLE, the primary mechanism used to create an object instance was the CoCreateInstance function. This function encapsulates the process of creating a class object, using that to create a new instance and releasing the class object. Another function of this kind is the more specific OleCreate, the OLE Compound Document helper that creates a class object and retrieves a pointer to a requested object.
To smooth the process of instance creation on distributed systems, COM has introduced three important new instance creation functions:
CoCreateInstanceEx extends CoCreateInstance to make it possible to create a single uninitialized object associated with the given CLSID on a specified remote machine. In addition, rather than requesting a single interface and obtaining a single pointer to that interface, CoCreateInstanceEx makes it possible to query for multiple interfaces and (if available) receive pointers to them in a single round trip, thus permitting fewer round trips between machines. This can make remote object interaction much more efficient. To do this, the function uses an array of MULTI_QI structures.
Creating an object through CoCreateInstanceEx still requires that the object be initialized through a call to one of the initialization interfaces (such as IPersistStorage:::Load). The two helper functions, CoGetInstanceFromFile and CoGetInstanceFromIStorage encapsulate both the instance creation power of CoCreateInstanceEx and initialization, the former from a file, and the latter from a storage.