ANDOS is a Russian operating system for Electronika BK-0010, Electronika BK-0011 and Electronika BK-0011M series computers. It was created in 1990 and first released in 1992. Initially it was developed by Alexey Nadezhin (by whose name the system is named) and later also by Sergey Kamnev, who joined the project. It was the only widespread system on BK series computers that used MS-DOS-compatible file system format. ANDOS used the FAT12 filesystem on 800 Kb floppy disks. For Electronika BK-0011M and Electronika BK-0011 ANDOS provided Electronika BK-0010 emulation by loading BK-0010 ROM image into BK-0011(M) RAM. In minimal configuration the system was able to occupy less than 4 Kb of RAM.