Unlike other systems which use "paths" for locating commands, DCL requires commands to be defined explicitly, either via CLD (Command Language Definition) definitions or a "foreign symbol". Most OpenVMS-native commands are defined via CLD files; these are compiled by the CDU, the Command Definition Utility, and added to a DCL 'table' -- by default, although processes are free to use their own tables—and can then be invoked by the user. For example, defining a command FOO that accepts the option "/BAR" and is implemented by the image could be done with a CLD file similar to: