NTFS Documentation: Bitmap Attribute

Definition

This file attribute is a sequence of bits where each bit represents the status of an entity.

As far as we know, this file attribute is currently used in two ways:

for indexes (e.g. directories). Each bit represents a VCN of the index allocation attribute, starting at VCN 0. The bit is set when the VCN is used by an index buffer.
for the MFT. Each bit is a copy of the in-use flag of a FILE record, starting at FILE record number 0.

Last modified: Sun Feb 14 15:34:15 PST 1999