Micro PL/CS is a version of PL/CS developed for a single-user, interactive environment. A file system extension makes PL/CS self-sufficient for standalone file processing and secondary storage management. The basis of the file system extension is the Unrestricted File Organization which provides a free mixture of sequential, indexed and random file operations. The structure, operation, and system-interfaced procedures of the UFO are presented and explained. The Micro-PL/CS file extension implementation is then sketched in terms of the UFO primitives.