Web site: (not active)
Origin: Russia
Category: Workstation
Desktop environment: CLI
Architecture: ZX Spectrum clones
Based on: unknown
Wikipedia: iS-DOS
Media: Install Floppy
The last version | Released: 1992

iS-DOS – an operating system for Russian ZX Spectrum-compatible home computers. Developed in the early 1990s (1990-92) by Iskra Soft from Leningrad. Supports floppy disks (double-sided, double-density), hard disks, CD-ROM drives.

The system was developed as an alternative to the standard TR-DOS disk system for Russian ZX Spectrum clones. The main disadvantages of TR-DOS were the absence of subdirectories (later bypassed by the TRDN file manager), a limitation on the number of files on the disk (no more than 128), a limitation on the length of one file of 64 KB (later removed thanks to the standard for satellite files), which was also present and a number of others.

When developing iS-DOS, the MS-DOS ideology was used, and the restrictions listed above were absent. In addition, there was a file-based two-panel shell, similar to Norton Commander, built into the system level, as well as a set of software necessary for operation. However, the system was incompatible with TR-DOS, and did not allow running programs adapted for TR-DOS – this required their serious modification.

A number of software have been written and adapted for iS-DOS. Since the system architecture provided the ability to create device drivers, there was support for any type of expanded memory, various external devices, and IDE controllers (for working with hard drives).

The disadvantages of iS-DOS are:
– impossibility of changing the file system, which results in a limited partition size (16 MB) and non-transparent CD-ROM support;
– limited amount of lower memory (not paged) available for user programs;
– lack of upper memory management interface (fixed in TASiS).

The development company, having started with sales of linoleum in 1993, and later finishing materials, became one of the leaders in this segment, and then went bankrupt in 2011.

– iS-DOS’99 Classic is a version that runs on any ZX Spectrum, as it only uses 48 kB of RAM anyway.
– iS-DOS’99 Chic differs from iS-DOS’99 Classic in that when loaded into the computer’s memory, it disables the BASIC-48 ROM and places the operating system kernel in “shadow” RAM. This doubles the size of the transit area (from 8-15 KB to 20-27 KB). Works only on ZX Spectrum, which allows you to place RAM at address 0, that is: KAY-256/1024, SCORPION ZS 256 (Chic ZS option), PROFI and their analogues). Additional memory (of almost any volume addressable by a computer) can be used as an electronic disk.
– iS-DOS’2000 – directory extensions and SMUC controller drivers (for hard drive support) appear in Scorpion ZS.
– TASiS is a modern version developed by the NedoPC group for ATM Turbo 2+ computers in 2006. It supports text mode and the upper memory of these computers. Based on iS-DOS Chic. Also, with the help of special ROM firmware – xBIOS – the problem of compatibility with programs for TR-DOS has been solved. xBIOS contains vTR-DOS, a program that simulates TR-DOS at the system call level and works with a floppy disk image loaded into the computer’s extended memory. In 2019, the system was adapted to ZX-Evolution.

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