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Software components for data protection, secure storage and transfer

Callback File System® (CBFS®)

Create and manage virtual filesystems and disks from your Windows applications

Callback File System (CBFS) lets you create virtual file systems and disks that expose and manage remote data as if these data were files on the local disk.

Callback File System is an SDK (software development kit, component for use in software development) for Windows® platform.

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Latest version

Release:  6.1.184
21 September 2016

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Technical Specification


Callback File System - virtual file system SDK for Windows - technical description

Callback File System (CBFS®) is a software component (library) for presenting various data as files and directories of a local virtual disk. Regardless of where the actual data are kept: in files, in database records, memory, or elsewhere - they will be treated as if they were parts of a single file system.

Callback File System consists of the system-level driver and user-mode API.


File System driver creates a virtual device with application-provided file system and emulates a physical storage.
The driver works on the system level and turns a storage into a "real" disk device with its own file system. The "real disk device" is accessible in read-only and/or read-write mode by any application which uses system file management API.

The driver lets you make the mounted disk visible to the user or hide it from the user.
Unlike CallbackDisk, the driver of Callback File System provides a functionality to create not just your virtual disks, but your own file systems. The driver provides a callback mechanism, which lets you keep your files and file systems wherever you want (i.e. on remote computer, in memory or database tables etc.).

User-mode API

User-mode API is simple and introduces about ten functions, specific to driver management and storage mounting operations. Also the API includes about 20 callback functions (events) which your application must handle to effectively represent a full-featured file system.
The API is used for driver and storage manipulation and for security operations. All file operations can be performed using system file management API or framework-specific classes.

User-mode APIs are provided for .NET, VCL, Java and C++.

Security Features

Callback File System supports various security features. First of all, you can expose the virtual disk to the user by assigning it a drive letter, or you can keep the virtual disk hidden from user's eye (when no drive letter is assigned). Next, Callback File System lets you control what applications or users access the data. Finally, you can support NTFS security functions for files and directories stored within Callback File System.

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Supported platforms

  • Windows:
    • Windows 10
    • Windows 2012 Server R2
    • Windows 8.1 (32-bit and 64-bit)
    • Windows 2012 Server
    • Windows 8 (32-bit and 64-bit)
    • Windows 2008 Server R2
    • Windows 7 (32-bit, 64-bit x64 and 64-bit Itanium)
    • Windows 2008 Server (32-bit, 64-bit x64 and 64-bit Itanium)
    • Windows Vista (32-bit, 64-bit x64 and 64-bit Itanium)
    • Windows 2003 Server (32-bit, 64-bit x64 and 64-bit Itanium)
    • Windows XP (32-bit and 64-bit)
  • Microsoft .NET Framework on Windows:
    • .NET 4.6.x (32-bit, 64-bit x64)
    • .NET 4.5.1 (32-bit, 64-bit x64)
    • .NET 4.5 (32-bit, 64-bit x64)
    • .NET 4.0 (32-bit, 64-bit x64 and Itanium)
    • .NET 3.5 (32-bit, 64-bit x64 and Itanium)
    • .NET 3.0 (32-bit, 64-bit x64 and Itanium)
    • .NET 2.0 (32-bit, 64-bit x64 and Itanium)
  • Java on Windows:
    • Java SE/EE 1.6 and later

Development tools

  • .NET API:
    • Visual Studio 2015
    • Visual Studio 2013
    • Visual Studio 2012
    • Visual Studio 2010
    • Visual Studio 2008
    • Visual Studio 2005
    • CodeGear Prism
  • C++ API:
    • Visual Studio 2015
    • Visual Studio 2013
    • Visual Studio 2012
    • Visual Studio 2010
    • Visual Studio 2008
  • VCL API (VCL units are linked into the application without any external DLLs):
    • Embarcadero RAD Studio 10.1 Berlin
    • Embarcadero RAD Studio 10 Seattle
    • Embarcadero RAD Studio XE8
    • Embarcadero RAD Studio XE7
    • Embarcadero RAD Studio XE6
    • Embarcadero RAD Studio XE5
    • Embarcadero RAD Studio XE4
    • Embarcadero RAD Studio XE3
    • Embarcadero RAD Studio XE2
    • Embarcadero RAD Studio XE
    • Embarcadero RAD Studio 2010
    • CodeGear RAD Studio 2009
    • CodeGear RAD Studio 2007
    • Delphi 10.1 Berlin (Win32 platform)
    • Delphi 10 Seattle (Win32 platform)
    • Delphi XE8 (Win32 platform)
    • Delphi XE7 (Win32 platform)
    • Delphi XE6 (Win32 platform)
    • Delphi XE5 (Win32 platform)
    • Delphi XE4 (Win32 platform)
    • Delphi XE3 (Win32 platform)
    • Delphi XE2 (Win32 platform)
    • Delphi XE
    • Delphi 2010
    • Delphi 2009
    • Delphi 2007
    • Delphi 2006
    • Delphi 2005
    • Delphi 7
    • C++Builder 10.1 Berlin (Win32 platform)
    • C++Builder 10 Seattle (Win32 platform)
    • C++Builder XE8 (Win32 platform)
    • C++Builder XE7 (Win32 platform)
    • C++Builder XE6 (Win32 platform)
    • C++Builder XE5 (Win32 platform)
    • C++Builder XE4 (Win32 platform)
    • C++Builder XE3 (Win32 platform)
    • C++Builder XE2 (Win32 platform)
    • C++Builder XE

To request more details please use our feedback form or Web-based Helpdesk system.

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As of July 15, 2016 EldoS Corporation will operate as a division of /n software inc. For more information, please read the announcement.

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