Hierarchical File System (
HFS) is a
proprietary file system developed by
Apple Inc. for use in computer systems running
Mac OS. Originally designed for use on
floppy and
hard disks, it can also be found on read-only media such as
CD-ROMs. HFS is also referred to as
Mac OS Standard (or, erroneously, "HFS Standard"), while its successor,
HFS Plus, is also called
Mac OS Extended (or, erroneously, "HFS Extended"). With the introduction of
OS X 10.6, Apple dropped support to format or write HFS disks and
images, which are only supported as read-only volumes.