The exFAT file system uses a directory tree approach to manage the file system structures and files which exist in the Cluster Heap. Directories have a one-to-many relationship between parent and child in the directory tree.

The directory to which the FirstClusterOfRootDirectory field refers is the root of the directory tree. All other directories descend from the root directory in a singly-linked fashion.

Each directory consists of a series of directory entries (see Table 13).

One or more directory entries combine into a directory entry set which describes something of interest, such as a file system structure, sub-directory, or file.

Table 13 Directory Structure

Field NameOffset(byte)Size(byte)Comments
DirectoryEntry[0]032This field is mandatory and Section 6.1 defines its contents.
DirectoryEntry[N–1](N – 1) * 3232This field is mandatory and Section 6.1 defines its contents.N, the number of DirectoryEntry fields, is the size, in bytes, of the cluster chain which contains the given directory, divided by the size of a DirectoryEntry field, 32 bytes.