HFS was introduced by Apple in September 1985, specifically to support Apple's first hard disk drive for the Macintosh, replacing the Macintosh File System (MFS), the original file system which had been introduced over a year and a half earlier with the first Macintosh computer.
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Apple introduced HFS out of necessity with its first 20 MB hard disk offering for the Macintosh in September 1985.
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More importantly, HFS was hard-coded into new Plus' 128K ROM, freeing not only space from the system software disk, but also RAM.
The Hierarchical File System or HFS, 1985 until the release of Mac OS X, still supported as of 2007
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This was made possible as the SuperDrive now utilitized the same MFM (Modified Frequency Modulation) encoding scheme used by the IBM PC, yet still retained backward compatibility with Apple's variable-speed zoned CAV scheme and Group Code Recording encoding format, so it could continue to read Macintosh MFS, HFS and Apple II ProDOS formats on 400/800 KB disks.