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Macintosh File System

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Title: Macintosh File System  
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Subject: Mac OS, Resource fork, Hierarchical File System, List of file systems, Macintosh file system
Collection: Disk File Systems, Mac Os
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Macintosh File System

Developer Apple Computer
Full name Macintosh File System
Introduced January 24, 1984 (System 1)
Partition identifier Apple_MFS (Apple Partition Map)
Directory contents Table
File allocation Linked list
Bad blocks No
Max. volume size 20 MiB
Max. file size 20 MiB
Max. number of files 4094
Max. filename length 255 characters
Allowed characters in filenames Any Apple codepage (such as MacRoman) character but ":"
Dates recorded Creation, modification
Date range January 1, 1904 - February 6, 2040
Date resolution 1s
Forks Only 2 (data and resource)
Attributes version, locked, type, creator, Finder window, location in Finder window, Finder flags
File system permissions No
Transparent compression No
Transparent encryption No
Supported operating systems System 1 — OS 7.6 (Write), Mac OS 8.0 (Read), OS X (Read with MFSLives)

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.

MFS was notable both for introducing resource forks 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 characters 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 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,[1] 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.


  • See also 1
  • References 2
  • Bibliography 3
  • External links 4

See also


  1. ^ "Technical Notes". Retrieved 2013-09-16. 


  • Apple Computer, Inc. (1985). Inside Macintosh Volume II. New York: Addison-Wesley. ISBN 0-201-17732-3.

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 OS X
  • MFSLives on Apple
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