Implementation notes provide information about how API specifications are implemented on the Series 40 and Symbian platforms. For each API, the implementation notes document which optional parts of the API are supported, clarify vaguely defined features from the API specification, and point out where the platform implementation differs from the API specification. Implementation notes also provide information about implementation changes between platform releases. Some implementation notes include only Series 40 or Symbian information. This is indicated at the beginning of each such implementation note.