Macintosh File System

Macintosh File System (MFS) was the first file system used by Macintosh computers. It was a flat file system (all files were stored by the system on the root level of volumes), but had a mechanism that allowed users to create the cosmetic appearance of folders in the Finder by renaming the always-present folder "Empty Folder," which would then be re-created. Folders within folders were not supported.

MFS supported Macintosh files in two parts: a data fork for ordinary file data and a resource fork for collections of metadata, such as icon bitmaps, user interface elements, and other elements.

MFS was the native file system for System 1 and 2. It internally supported file names up to 255 characters, but the Finder only supported 63 characters. On September 17, 1985, it was superseded by the Hierarchical File System (HFS) in System 2.1, which reduced the file name limit to 31 characters. Support for 255 character file names returned in HFS Plus, which was introduced with Mac OS 8.1 on January 19, 1998. However, the Finder's 31-character limit was not revised until Mac OS X.