HFS+

HFS Plus or HFS+ is a file system developed by Apple Inc. It serves as the primary file system of OS X. HFS+ was developed to replace the Hierarchical File System (HFS) as the primary file system used in Macintosh computers (or other systems running Mac OS). It is also one of the formats used by the iPod digital music player. HFS Plus is also referred to as Mac OS Extended (or, erroneously, "HFS Extended"), where its predecessor, HFS, is also referred to as Mac OS Standard (or, erroneously, as "HFS Standard"). During development, Apple referred to this file system with the codename Sequoia.