MFS (Macintosh File System)
MFS, or the Macintosh File System, was the original file system used on the first Apple Macintosh computers, introduced in 1984. It was designed for floppy disks and offered a flat file structure with minimal features compared to modern file systems. Here's a detailed look at MFS and its features:
Structure of the MFS File System
1. Volume Header:
The volume header contains basic metadata about the file system:
Volume Name:The name of the volume as displayed to the user.
Total Sectors:The total number of sectors on the disk.
Allocation Block Size:Defines the size of each block used for storage.
Directory Pointer:Points to the location of the file directory.
2. Flat File Structure:
MFS does not support a hierarchical directory structure:
Single-Level Directory:
All files are stored in a single directory, making organization simple but limited.
File Records:
Metadata for each file, including name, size, and location on disk.
3. Resource Forks and Data Forks:
MFS introduced the concept of forks for files:
Data Fork:
Stores the file’s main data.
Resource Fork:
Contains additional structured data, such as icons or settings.
4. Allocation Strategy:
MFS uses a bitmap to track storage blocks:
Fixed Block Allocation:
All blocks are the same size, leading to inefficient storage for small files.
Simple Bitmap:
Tracks used and free blocks for file storage.
Features of MFS
Flat File System:
A single-level directory simplifies file management for small disks.
Resource Forks:
Allows separation of file data and metadata, a concept carried forward into later Apple file systems.
Compact Design:
Optimized for floppy disks with limited capacity.
Limitations of MFS
No Hierarchical Directories:
All files are stored in a single directory, making organization difficult on larger volumes.
Limited Scalability:
Designed for floppy disks, with a maximum volume size of 20 MB.
Fragmentation:
Inefficient storage allocation for small files.
Obsolete:
Superseded by HFS in 1985, which introduced hierarchical directories and improved scalability.
Tools and Commands for MFS
Disk Initialization Tool:
Used to format floppy disks with MFS on early Macintosh systems.
Disk Copy:
Creates and restores disk images of MFS volumes.
Example Usage
On original Macintosh systems, MFS was used for basic file storage:
Insert a floppy disk:
MFS volumes were formatted and initialized using the built-in Disk Initialization Tool.
Store files:
Files were saved directly to the single-level directory on the disk.
MFS served as the foundation for Apple’s early file system development, introducing key concepts like resource forks. Its limitations, however, led to the development of HFS, which addressed scalability and organizational needs.