Pointer Type Attributes

The following attributes specify the characteristics of pointers.

Attribute	Usage
ptr	Designates a pointer as a full pointer, with all the capabilities of a C-language pointer, including aliasing.
ref	Designates the simplest type of pointer in MIDL—one that simply provides the address of some data. Reference pointers can never be null.
unique	Lets a pointer be null, but does not support aliasing.
pointer_default	Applied to an interface to specify the default pointer type for all pointers in that interface, except for top-level parameter pointers, which automatically default to ref pointers.
iid_is	Provides the interface identifier of the COM interface that is the object of the pointer.
string	Specifies that the pointer points to a string.