iS-DOS

iS-DOS[1][2] is a disk operating system (DOS) for Soviet/Russian ZX Spectrum clones.

iS-DOS was developed in 1990 or 1991, by Iskra Soft, in Leningrad, Soviet Union, now Saint Petersburg, Russia.

Unlike TR-DOS, iS-DOS is resident in random-access memory (RAM), and thus reduces the amount of memory available for user programs.

iS-DOS Chic[2] is a version developed for the Nemo KAY.

TASiS[2], based on iS-DOS Chic, is a modern version developed by NedoPC for the ATM Turbo 2+ in 2006,[4][5] supports the enhanced text mode and larger memory of that model.