Directory system directories

ECS capabilities for disk files were created by the directory system. The directory system was implemented as a single subprocess within a user process. The directory system maintained each directory in a single disk file. Directory capabilities were another special kind of ECS system user capability, for which the capability-creating-authorization was retained by the directory system. These directory capabilities contained the same information in their data parts as disk file capabilities, but since they were of the wrong type they could not be used as disk file capabilities by user programs.