(1) See HFS.
(2) A file system that organizes data and program files in a top-to-bottom structure. All modern operating systems use hierarchical file systems, wherein access to the data starts at the top and proceeds downward throughout the levels of the hierarchy. In Windows, the top of the hierarchy is the Desktop, as seen in an Explorer file view; however, the real top is actually drive C:. See file system, root directory and path.