Sustainability of Digital Formats: Planning for Library of Congress Collections

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Microsoft Compound File Binary File Format, Version 4

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Format Description Properties Explanation of format description terms

Identification and description Explanation of format description terms

Full name Microsoft Compound File Binary File Format, Version 4
Description

The Microsoft Compound File Binary (CFB) file format is used for storing storage objects and stream objects in a hierarchical structure within a single file.  See CFB_3 for a full description of the file system structure.

There are two active versions of CFB, version 3 and version 4. One major distinction between the versions is that the sector size for version 3 is of 512 bytes and the sector size for version 4 is 4096 bytes.

The minimum size of a compound file three sectors: one header, one FAT sector and one directory sector.

  • 4096-byte sector compound files can have 64-bit file and user-defined datastream sizes, up to slightly less than 16 terabytes.
  • The maximum number of directory entries (storage objects and stream objects) is roughly 4 billion. This corresponds to a maximum directory sector chain length of slightly less than 512 GB for a 4096-byte sector compound file.
Relationship to other formats
    Has earlier version CFB_3, Microsoft Compound File Binary File Format, Version 3
    Has subtype MSG, Microsoft Outlook Item
    Affinity to AAF_1_1, Advanced Authoring Format (AAF) Object, Version 1.1.

Early versions of the AAF format detailed use of the structured storage systems outlined in CFB to store the objects on disk.


Local use Explanation of format description terms

LC experience or existing holdings  
LC preference  

Sustainability factors Explanation of format description terms

Disclosure See CFB_3
    Documentation See CFB_3
Adoption See CFB_3
    Licensing and patents See CFB_3
Transparency See CFB_3
Self-documentation See CFB_3
External dependencies See CFB_3
Technical protection considerations See CFB_3

Quality and functionality factors Explanation of format description terms


File type signifiers and format identifiers Explanation of format description terms

Tag Value Note
Filename extension See related format.  See CFB_3
File signature Hex: D0 CF 11 E0 A1 B1 1A E1
Hex: 0x0004 (version 4)
From specification. This specification applies to the all Microsoft content types that share the general CFB structure.

Notes Explanation of format description terms

General

In addition to the Major Version field value declaration of the version number in the header, the Sector Shift field specifies the sector size depending on the version declaration. If Major Version is 4, then the Sector Shift must be 0x000C, specifying a sector size of 4096 bytes.

History  

Format specifications Explanation of format description terms


Useful references


Last Updated: 02/27/2017