An interface can be identified by a GUID. This is a 128-bit number, which is represented in a text representation (a string literal):
Each H character represents a hexadecimal number (0-9,A-F). The format contains 8-4-4-4-12 numbers. A GUID can also be represented by the following record, defined in the objpas unit (included automatically when in DELPHI or OBJFPC mode):
A constant of type TGUID can be specified using a string literal:
Normally, the GUIDs are only used in Windows, when using COM interfaces. More on this in the next section.