The definition file is the last file needed to build the DLL. It lists the exported symbols. As an example, the definition file for a DLL containing only package API (where all the entities are exported with a C calling convention) is:
EXPORTS
count
factorial
finalize_api
initialize_api
If the C calling convention is missing from package API, then the definition file contains the mangled Ada names of the above entities, which in this case are:
EXPORTS
api__count
api__factorial
api__finalize_api
api__initialize_api