Macintosh File System
Encyclopedia
Macintosh File System (MFS) is a volume
format (or disk file system
) created by Apple Computer
for storing files on 400K floppy disk
s. MFS was introduced with the Macintosh 128K
in January 1984.
MFS was notable both for introducing resource fork
s to allow storage of structured data, and for storing metadata needed to support the graphical user interface
of Mac OS
. MFS allows file names to be up to 255 character
s in length, although Finder
does not allow users to create names longer than 63 characters (31 characters in later versions). MFS is called a flat file system because it does not support a hierarchy of directories
.
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 box
es. 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 megabyte
s in size, or about 1,400 files. While this is small by today's standards, it seemed very expansive when all Apple Macintosh computers at the time had a 400 kilobyte
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 http://developer.apple.com/technotes/tn/tn1096.html, and in Mac OS 8.0 support for MFS volumes was removed altogether. Although Mac 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.
Volume (computing)
In the context of computer operating systems, volume is the term used to describe a single accessible storage area with a single file system, typically resident on a single partition of a hard disk. Similarly, it refers to the logical interface used by an operating system to access data stored on...
format (or disk file system
File system
A file system is a means to organize data expected to be retained after a program terminates by providing procedures to store, retrieve and update data, as well as manage the available space on the device which contain it. A file system organizes data in an efficient manner and is tuned to the...
) created by Apple Computer
Apple Computer
Apple Inc. is an American multinational corporation that designs and markets consumer electronics, computer software, and personal computers. The company's best-known hardware products include the Macintosh line of computers, the iPod, the iPhone and the iPad...
for storing files on 400K floppy disk
Floppy disk
A floppy disk is a disk storage medium composed of a disk of thin and flexible magnetic storage medium, sealed in a rectangular plastic carrier lined with fabric that removes dust particles...
s. MFS was introduced with the Macintosh 128K
Macintosh 128K
The Macintosh 128K machine, released as the "Apple Macintosh", was the original Apple Macintosh personal computer. Its beige case contained a monitor and came with a keyboard and mouse. An indentation in the top of the case made it easier for the computer to be lifted and carried. It had a selling...
in January 1984.
MFS was notable both for introducing resource fork
Resource fork
The resource fork is a construct of the Mac OS operating system used to store structured data in a file, alongside unstructured data stored within the data fork. A resource fork stores information in a specific form, such as icons, the shapes of windows, definitions of menus and their contents, and...
s to allow storage of structured data, and for storing metadata needed to support the graphical user interface
Graphical user interface
In computing, a graphical user interface is a type of user interface that allows users to interact with electronic devices with images rather than text commands. GUIs can be used in computers, hand-held devices such as MP3 players, portable media players or gaming devices, household appliances and...
of Mac OS
Mac OS
Mac OS is a series of graphical user interface-based operating systems developed by Apple Inc. for their Macintosh line of computer systems. The Macintosh user experience is credited with popularizing the graphical user interface...
. MFS allows file names to be up to 255 character
Character (computing)
In computer and machine-based telecommunications terminology, a character is a unit of information that roughly corresponds to a grapheme, grapheme-like unit, or symbol, such as in an alphabet or syllabary in the written form of a natural language....
s in length, although Finder
Macintosh Finder
The Finder is the default file manager used on Mac OS and Mac OS X operating systems; it is responsible for the overall user-management of files, disks, network volumes and the launching of other applications...
does not allow users to create names longer than 63 characters (31 characters in later versions). MFS is called a flat file system because it does not support a hierarchy of directories
Directory (file systems)
In computing, a folder, directory, catalog, or drawer, is a virtual container originally derived from an earlier Object-oriented programming concept by the same name within a digital file system, in which groups of computer files and other folders can be kept and organized.A typical file system may...
.
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
Finder
Finder may refer to:* Finder , a core component of the Apple Macintosh operating system, is the graphical representation of the computer's file system* Finder , a comic book series by Carla Speed McNeil...
windows, but not in the open and save dialog box
Dialog box
In a graphical user interface of computers, a dialog box is a type of window used to enable reciprocal communication or "dialog" between a computer and its user. It may communicate information to the user, prompt the user for a response, or both...
es. 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 megabyte
Megabyte
The megabyte is a multiple of the unit byte for digital information storage or transmission with two different values depending on context: bytes generally for computer memory; and one million bytes generally for computer storage. The IEEE Standards Board has decided that "Mega will mean 1 000...
s in size, or about 1,400 files. While this is small by today's standards, it seemed very expansive when all Apple Macintosh computers at the time had a 400 kilobyte
Kilobyte
The kilobyte is a multiple of the unit byte for digital information. Although the prefix kilo- means 1000, the term kilobyte and symbol KB have historically been used to refer to either 1024 bytes or 1000 bytes, dependent upon context, in the fields of computer science and information...
floppy drive.
Apple introduced Hierarchical File System
Hierarchical File System
Hierarchical File System is a file system developed by Apple Inc. for use in computer systems running Mac OS. Originally designed for use on floppy and hard disks, it can also be found on read-only media such as CD-ROMs...
as a replacement for MFS in September 1985. In Mac OS 7.6.1
System 7 (Macintosh)
System 7 is a single-user graphical user interface-based operating system for Macintosh computers. It was introduced on May 13, 1991 by Apple Computer. It succeeded System 6, and was the main Macintosh operating system until it was succeeded by Mac OS 8 in 1997...
, Apple removed support for writing to MFS volumes http://developer.apple.com/technotes/tn/tn1096.html, and in Mac OS 8.0 support for MFS volumes was removed altogether. Although Mac OS X
Mac OS X
Mac OS X is a series of Unix-based operating systems and graphical user interfaces developed, marketed, and sold by Apple Inc. Since 2002, has been included with all new Macintosh computer systems...
has no built-in support for MFS, an example VFS plug-in from Apple called MFSLives provides read-only access to MFS volumes.
See also
- Comparison of file systemsComparison of file systems-General information:-Limits:-Metadata:-Features:-Allocation and layout policies:-Supporting operating systems:-See also:* Comparison of archive formats* Comparison of file archivers* List of archive formats* List of file archivers...
- MFSLives on Apple
External links
- Apple Tech Article 9502 - MFS volume support in Mac OS 7.x
- MacTech Volume 1, Issue 5: Disks - organization of the standard Macintosh disk (April 1985)
- Resurrecting MFS Macintosh Floppies
- Fred's Follies - HFS used in Macs with 128K ROMs different from MFS used in Macs with 64K ROMs
- Q&A: Mac Plus - limitation due to MFS on an external 400K floppy drive disk
- MFSLives - VFS read-only plug-in for MFS in Mac OS X