The Volume Label is a Unicode string which enables end users to distinguish their storage volumes. In the exFAT file system, the Volume Label exists as a critical primary directory entry in the root directory (see Table 26). The valid number of Volume Label directory entries ranges from 0 to 1.

Table 26 Volume Label DirectoryEntry Structure

Field NameOffset(byte)Size(byte)Comments
EntryType01This field is mandatory and Section 7.3.1 defines its contents.
CharacterCount11This field is mandatory and Section 7.3.2 defines its contents.
VolumeLabel222This field is mandatory and Section 7.3.3 defines its contents.
Reserved248This field is mandatory and its contents are reserved.

7.3.1 EntryType Field

The EntryType field shall conform to the definition provided in the Generic Primary DirectoryEntry template (see Section 6.3.1).

7.3.1.1 TypeCode Field

The TypeCode field shall conform to the definition provided in the Generic Primary DirectoryEntry template (see Section 6.3.1.1).

For the Volume Label directory entry, the valid value for this field is 3.

7.3.1.2 TypeImportance Field

The TypeImportance field shall conform to the definition provided in the Generic Primary DirectoryEntry template (see Section 6.3.1.2).

For the Volume Label directory entry, the valid value for this field is 0.

7.3.1.3 TypeCategory Field

The TypeCategory field shall conform to the definition provided in the Generic Primary DirectoryEntry template (see Section 6.3.1.3).

7.3.1.4 InUse Field

The InUse field shall conform to the definition provided in the Generic Primary DirectoryEntry template (see Section 6.3.1.4).

7.3.2 CharacterCount Field

The CharacterCount field shall contain the length of the Unicode string the VolumeLabel field contains.

The valid range of values for this field shall be:

  • At least 0, which means the Unicode string is 0 characters long (which is the equivalent of no volume label)
  • At most 11, which means the Unicode string is 11 characters long

7.3.3 VolumeLabel Field

The VolumeLabel field shall contain a Unicode string, which is the user-friendly name of the volume. The VolumeLabel field has the same set of invalid characters as the FileName field of the File Name directory entry (see Section 7.7.3).