Macintosh File System (MFS) is a volume format (or disk file system) created by Apple Computer for storing files on 400K floppy disks. MFS was introduced with the original Apple Macintosh computer in January 1984. The Macintosh File System does not support volumes over 20 MB 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 400 KB floppy drive.