FAT16

FAT16 is a file allocation table (FAT) filesystem developed by Microsoft as an extension of FAT12 for MS-DOS and early Windows systems. It uses 16-bit cluster numbers to address data clusters, allowing larger storage volumes than FAT12 while keeping a simple, lightweight design. Like other FAT variants, a FAT16 volume stores file metadata in directory entries and uses a table to describe how clusters are linked to form files.

A FAT16 volume layout typically includes a boot sector, a reserved area, one or more File Allocation Tables, a root directory with a fixed size, and a data region divided into clusters. The root directory for FAT16 is not located in the data area like subsequent directories; it has a limited capacity defined by the volume format (often around 512 directory entries). File data is accessed by following a chain of clusters described in the FAT. The 8.3 naming convention was standard, but long filenames became possible later through the VFAT extension.

Limitations and characteristics: FAT16 does not support built-in journaling, permissions, or hard links. The root directory is fixed in size, which limits the number of entries. The maximum practical volume size is constrained by the 16-bit cluster addressing, typically around 2 GB with common sector and cluster sizes, and larger volumes require FAT32. File names are simple by modern standards unless VFAT is used.

Compatibility and usage: FAT16 achieved broad interoperability across MS-DOS, Windows versions up to early Windows releases, Linux, macOS, and various embedded systems. It remains encountered on older media and some removable media formats, especially for smaller partitions or devices that require wide compatibility.