Hierarchical File System Plus (HFS+), also known as Mac OS Extended, is a journaling file system that was developed by Apple as an update to its aging Hierarchical File System. It was introduced with Mac OS 8.1 in 1998 and remained in use until it was deprecated with the release of the Apple File System with MacOS 10.13 in 2017.
HFS Plus replaced the 16-bit block addresses of HFS with 32-bit addresses, allowing for drive sizes up to 8 exabytes. The previous file name limit of 31 characters was extended to 255 characters, though the Finder was not updated to take advantage of it until Mac OS X. However, it carried over the 2040 date limit from HFS, which was not remedied until the release of APFS.
- Technical Note TN1150: HFS Plus Volume Format at Apple Developer Connection (2004-03-05)
- Volume size limits under HFS and HFS+ at 68k Macintosh Liberation Army (2016-03-28)
- HFS Plus at Wikipedia