What is a file allocation table (FAT)?

A file allocation table (FAT) is a data structure used by file systems to organize and manage files on a storage device, such as a hard disk drive or a flash drive. It is a table that keeps track of the allocation status of each cluster (a fixed-size unit of storage) on the storage device.

The FAT contains entries for each cluster, indicating whether it is free or allocated to a specific file. Each entry in the FAT corresponds to a cluster and contains information about the next cluster in the file or if it is the last cluster in the file. This chain of clusters forms the file's logical structure.

The FAT is typically stored in a reserved area at the beginning of the storage device and is accessed by the file system to locate and manage files. It allows the file system to quickly find free clusters for new files and to retrieve the data of existing files by following the cluster chain specified in the FAT.

There are different versions of FAT, such as FAT12, FAT16, and FAT32, each with varying cluster sizes and maximum storage capacities. FAT file systems are widely used in various operating systems, including older versions of Windows, as they provide a simple and efficient method for organizing files on storage devices.