On the Macintosh File System 

After listening to this week’s Hypercritical, on which John and Dan discuss file systems for about 17 hours, I realized that I didn’t know much about what came before the Hierarchical File System.

HFS, of course, is the grandfather of HFS+, which the Macintosh uses today. It was first released with the Hard Disk 20 for use with the Fat Mac in September 1985.

Apple dropped support for MFS in System 7.6.1.

The original Macintosh shipped with the Macintosh File System. Designed to run on the 400k floppy disks that Mac owners knew so well, it had several notable features:

Resource Forks

From Wikipedia:

A resource fork stores information in a specific form, such as icons, the shapes of windows, definitions of menus and their contents, and application code (machine code). For example, a word processing file might store its text in the data fork, while storing any embedded images in the same file’s resource fork. The resource fork is used mostly by executables, but every file is able to have a resource fork.

At first, the resource fork was used to store all graphic data for a file for being drawn on the screen of the Macintosh. These files helped the original Mac team run the machine with a measly 128 KB of RAM, down from the 1 MB the Lisa required for its GUI.

Today, resource forks are still a part of HFS+. They store icon information, program associations and more.

Character Limits

MFS supported file names with up to 255 characters. However, the Finder didn’t support file names longer than 63 characters. When Apple released HFS, the limit was dropped to 31 characters in the OS. With OS 8.1 (coupled with HFS+), 255 characters were supported, although Finder’s limit of 31 wasn’t changed until OS X.

Flat File System

The most dated feature of MFS is that it was a flat-file system.

The concept of folders existed under MFS, but they weren’t nested as we are used today — there was no hierarchy of directories on the original Macintosh.[1]

Here’s Wikipedia again:

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.

Good times.

  1. My pal Thomas Brand has clarified this on Twitter. Nested folders could be created, but were just an illusion built with metadata. Far out, right?  ↩