Folders existed as a concept on the original MFS-based Macintosh, but worked completely differently from the way they do on modern systems. They were visible in Finder windows, but not in the open and save dialog boxes. There was always one empty folder on the volume, and if it was altered in any way (such as by adding or renaming files), a new Empty Folder would appear, thus providing a way to create new folders. MFS stored all of the file and directory listing information in a single file. The Finder created the illusion of folders, by storing all files as a directory handle/file handle pair. To display the contents of a particular folder, MFS would scan the directory for all files in that handle. There was no need to find a separate file containing the directory listing.
The Macintosh File System did not support volumes over 20 mebibytes in size, or about 1,400 files. While this is small by today's standards, at the time it seemed very expansive when compared to the Macintosh's then-400 kibibyte floppy drive.
Apple introduced Hierarchical File System as a replacement for MFS in September 1985. In Mac OS 7.6.1, Apple removed support for writing to MFS volumes, and in Mac OS 8.0 support for MFS volumes was removed altogether. Although OS X has no built-in support for MFS, an example VFS plug-in from Apple called MFSLives provides read-only access to MFS volumes.