FAT12 (File Allocation Table 12-bit) is the earliest version of the FAT file system, introduced by Microsoft in 1977 for use with floppy disks. The “12” in FAT12 refers to the 12-bit entries in the file allocation table, which track the allocation of disk space. Though limited in capacity, FAT12 was revolutionary at the time and laid the foundation for subsequent versions like FAT16 and FAT32.

—

• **Key Features of FAT12**

   * **Optimized for Floppy Disks**  
     [[FAT12]] was designed specifically for floppy disks with small storage capacities, typically ranging from 360 KB to 1.44 MB.

 * **Simple Architecture**  
   The file system uses a file allocation table to map files across disk sectors, with a 12-bit entry representing each cluster.

 * **Single and Double-Sided Disk Support**  
   [[FAT12]] was compatible with both single-sided and double-sided floppy disks, enhancing flexibility during early computing.

 * **Legacy Compatibility**  
   Later operating systems, including early versions of [[MS-DOS]] and [[Windows]], maintained support for [[FAT12]] to enable access to floppy disks.

—

• **Limitations of FAT12**

   * **Limited Storage Capacity**  
     With a maximum of 4,084 clusters, [[FAT12]] is restricted to managing storage up to 32 MB, making it impractical for modern applications.

 * **No Support for Modern Features**  
   [[FAT12]] lacks journaling, compression, encryption, or file permissions, which are essential in contemporary file systems.

 * **High Fragmentation Risk**  
   The simple allocation strategy can lead to fragmented data, affecting performance even on small storage devices.

 * **Obsolete for Modern Usage**  
   While still used occasionally in retrocomputing and for compatibility with legacy devices, [[FAT12]] is generally obsolete for current computing needs.

—

• **Use Cases of FAT12**

   * **Floppy Disk Storage**  
     [[FAT12]] remains relevant in legacy systems and retrocomputing for accessing and preserving floppy disk data.

 * **Embedded Systems**  
   Some minimal embedded systems use [[FAT12]] due to its simplicity and low resource requirements.

 * **Compatibility with Legacy Software**  
   Vintage programs and operating systems, such as [[MS-DOS]], still rely on [[FAT12]] for data exchange via floppy disks.

—

• **Technical Overview**

   * **Cluster Management**:  
     Each cluster in [[FAT12]] is identified by a 12-bit entry, giving a maximum of 4,084 usable clusters.  
   * **Root Directory Limitation**:  
     [[FAT12]] supports a fixed-size root directory with a limited number of entries, usually capped at 224 entries on a 1.44 MB floppy disk.  
   * **File Size Limitation**:  
     Files on [[FAT12]] cannot exceed the size of the disk due to its small capacity.

—

• **Documentation and Resources**

   - Technical Overview: https://learn.microsoft.com/en-us/windows/win32/fileio/fat12-specifications  
   - GitHub Repository for FAT tools: https://github.com/msbentley/fattools  

—

FAT12 was a crucial innovation in early computing, providing a foundation for subsequent developments in file systems. While it is now largely obsolete, it remains a key part of computing history and is still used in specific contexts, such as retrocomputing and legacy software environments. The simplicity of FAT12 ensured its success on floppy disks, but modern needs have long since outgrown its limited capacity and functionality.