The CORBA specification defines the mapping of method interface definitions to C language procedure prototypes, hence SOM defines the same mapping. This mapping requires passing a reference to the target object and a reference to an implementation-specific Environment structure as the first and second parameters, respectively, in any method call.
The Environment structure is primarily used for passing error information from a method back to its caller. See also the topic "Exceptions and Error Handling" in Chapter 3, "Using SOM Classes in Client Programs," for a description of how to "get" and "set" error information in the Environment structure.