1.3.1.3 File Allocation Table

Central to all FAT file systems is the concept of a file allocation table (FAT). A FAT is essentially a map of clusters. In other words, each cluster is represented by an integer that represents one of the following:

• cluster number of the ``next'' one in a chain
• end of file (EOF) flag
• bad cluster flag
• reserved cluster flag
• unused flag

FAT12 uses $2^{12}=4\mathrm{ki}$ entries for the entire partition. Combined with the fact that each cluster is 8kiB, a partition can be as large as 32MiB.

FAT16 uses $2^{16}=64\mathrm{ki}$ entries for the entire partition. Combined with 64kiB clusters, a partition can be as large as 4GiB.

FAT32, despite its name, uses $2^{22}=4\mathrm{Mi}$ entries for the entire partition. Combined with a maximum size of 32kiB per cluster, a partition can have up to $2^{22+15}=2^{37}=128\mathrm{GiB}$.