(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. See
file system,
root directory and
path.
Windows Hierarchy
Users often perceive the top of the hierarchy as their desktop; however, the real top is actually drive C:.