The eCos Configuration Tool is used to tailor eCos at source level, prior to compilation or assembly, and provides a configuration file and a set of files used to build user applications. The sources and other files used for building a configuration are provided in a component repository, which is loaded when the eCos Configuration Tool is invoked. The component repository includes a set of files defining the structure of relationships between the Configuration Tool and other components, and is written in a Component Definition Language (CDL). For a description of the concepts underlying component configuration, see Chapter 24.