File Allocation Table 32 (FAT32)

FAT32 is a version of the File Allocation Table (FAT) file system that was introduced by Microsoft in 1996 with its Windows 95 OEM Service Releases 2 (OSR2) operating system. It is an extension of Microsoft’s FAT16 file system.

The purpose of FAT32 was to overcome the limitations of FAT16 and add support for larger media. The major enhancements introduced by FAT32 included support for much larger volumes, better performance and more flexibility and robustness.

The standard maximum volume size for FAT16 is 2GB, with a cluster size of 32K and sector size of 512 bytes. FAT32 increases this limit to a significant 2TB by increasing the number of bits used for cluster addressing. FAT32 reserves 32 bits for each cluster entry, of which the lower 28 bits are actually used for addressing the clusters.

Other points:

• All FAT systems are “little endian,” which refers to the order the addressing bytes are stored.
• A FAT file system contains four basic regions: (1) reserved, (2) FAT, (3) root directory and (4) file and data directory region.
• FAT32 uses 28 bits for addressing clusters and can address a maximum of 268,435,444 (228 - 12) clusters, as compared to 65,524 maximum addressable clusters by FAT16.
• Maximum file size on FAT32 is 4,294,967,295 (232-1) bytes.
• Directories cannot have more than 65,535 files and other directories.
• FAT directories are not sorted or indexed. This decreases efficiency for many operations like creation of new files, when the directory size becomes large.
• Unlike FAT12 and FAT16, the root directory in FAT32 can be of variable size and is a cluster chain, just like any other directory.