BKD File

What are BKD files and how to open them

Are you having problems opening a BKD file or are you simply curious about its contents? We're here to explain the properties of these files and provide you with software that can open or handle your BKD files.

What is a BKD file?

A .BKD file is an ANDOS Disk Image file.

ANDOS Disk Image files are full images of floppy disks used with the ANDOS operating system on the Electronika BK series of Soviet PDP-11 compatible home computers. These images are exact captures of ANDOS-formatted disks, preserving the file system, boot sector, directory, FAT tables, and data written in the MS-DOS-compatible FAT12 format, typically with 800 kilobyte capacity floppies. They allow disk content to be mounted, emulated or restored exactly as the original BK disk would function under ANDOS.

ANDOS is a disk operating system developed in the early 1990s for the BK-0010, BK-0010-01, BK-0011 and BK-0011M computers. It supports standard FAT12 floppy disks so that disks used in ANDOS can also be read or manipulated using IBM-PC compatible tools. The system can accommodate multiple physical disk drives or logical partitions, supports more than one disk format (including a read-only version of MicroDOS format), and includes utilities for formatting, copying, file name conversion, and virtual RAM disks.

ANDOS Disk Image files are produced by copying the raw sectors of a physical floppy disk formatted with ANDOS. Emulators and disk image utilities that support the Electronika BK platform can load, write, or convert these images. Among supported extensions are ".bkd", ".dsk", and sometimes ".img", each representing the same kind of raw disk sector image for use with emulation or archival.

Technically, ANDOS Disk Images include a boot sector (Boot Record) containing parameters like the number of sectors per track, number of heads, and cluster size (often 4 sectors per cluster ≈ 2 KiB by earlier versions), a FAT12 table, root directory, and data area. The cluster structure is used to manage file allocation. A specific byte signature has been recorded: at a particular offset (0xA0001E01414E444F53) the ASCII "…ANDOS" appears, which serves as an internal identifier.

How to open BKD files

Important: Different programs may use files with the BKD file extension for different purposes, so unless you are sure which format your BKD file is, you may need to try a few different programs.

While we have not verified the apps ourselves yet, our users have suggested three different BKD openers which you will find listed below.

Last updated: August 24, 2026

Various apps that use files with this extension

These apps are known to open certain types of BKD files. Remember, different programs may use BKD files for different purposes, so you may need to try out a few of them to be able to open your specific file.

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