A control class definition is generated for each defined production in the ASN.1 source file that is determined to be a Protocol Data Unit (PDU). By default, any type defined in an ASN.1 source file that is not referenced by any other type is a PDU. This default behavior can be overridden by using a configuration file setting (<isPDU/>) or a command-line option (-pdu) to explicitly declare that certain types are PDU’s.

The generated control class is derived from the ASN1CType base class. This class provides a set of common attributes and methods for encoding/decoding ASN.1 messages. It hides most of the complexity of calling the encode/decode functions directly.