Now we need to define the component's public interface. To do this you must create an '''IDL file''' (see http://developer.mozilla.org/en/docs/XPIDL). The IDL file defines the component's public interface in a language neutral way. Mozilla uses the '''XPIDL''' format (Cross Platform Interface Definition Language) to define a component's public interfaces interface rather than doing it in C++ header files directly. Using IDL, these interfaces can be defined in a language- and machine-independent way. IDLs make it possible to define interfaces which can then be processed by tools to autogenerate language-dependent interface specifications. The IDL files are used to generate C++ header files.