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Cabinet (file format)

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Design and Structure of CAB Files
– CAB archives can contain up to 65,535 folders, each of which can contain up to 65,535 files.
– Each folder is treated as a single compressed block, providing more efficient compression.
– Every entry in a folder has to be a file; empty folders cannot be stored in CAB archives.
– The structure of a CAB file includes folders and files.
– Paths in CAB files can be handled differently depending on the software implementation.

Implementations of CAB Files
Microsoft Windows supports creating and extracting CAB archives using various command-line utilities and tools.
– Other software like WinZip, WinRAR, and 7-Zip also support CAB archives.
– Linux systems have tools like cabextract and gcab for extracting and creating CAB archives.
– A full list of file archivers that support CAB format can be found in the Comparison of file archivers.
– Different tools have different capabilities, such as extracting only or both extracting and creating CAB archives.

Uses of CAB Files
– CAB format is used in various Microsoft installation technologies like Windows Installer and Setup API.
– It is also used in self-extracting programs like IExpress.
– CAB files can be embedded into other files like MSI and MSU files.
– Windows uses the cabinet format to archive its Component-Based Servicing (CBS) log.
– On Linux systems, CAB archives are used by fwupd for distributing firmware updates.

Related Formats and Extensions
– The .cab extension is also used by other installer programs for their proprietary archiving formats.
– InstallShield, for example, uses zlib for compression but has incompatible headers with Microsoft CAB files.
– Specialized utilities like Unshield can extract these proprietary formats.
– Windows CE installer uses a variant of Microsoft CAB format with a specific magic number.
– Microsoft Publisher has a Pack and Go feature that bundles documents into CAB files with a .PUZ extension.

References and Resources
– Microsoft provides a Cabinet Software Development Kit for working with CAB files.
– There are various tools and utilities available for working with CAB archives, both from Microsoft and third-party sources.
– The Microsoft Cabinet Format is documented in the Open Specifications Documentation.
– The compression algorithms used in CAB files include DEFLATE, Quantum compression, LZX, and NULL.
– References and resources for further information on CAB format and related topics.

Cabinet (or CAB) is an archive-file format for Microsoft Windows that supports lossless data compression and embedded digital certificates used for maintaining archive integrity. Cabinet files have .cab filename extensions and are recognized by their first four bytes (also called their magic number) MSCF. Cabinet files were known originally as Diamond files.

Filename extension
Internet media type
Uniform Type Identifier (UTI)
Magic numberMSCF
Developed byMicrosoft
Type of formatArchive file format
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