Real-time System with Buffer Functions. Soviet RT-11 clone.

Russia

Embedded operating system for Soviet personal computers BK-0010 and BK-0010-01. The file system used is compatible with the RT-11 file system.

Alexander Ermakov, Russia

Another attempt at making an OS for x86 PCs from scratch. Now TTP.

Real-Time Batch Monitor. Capable of simultaneously performing multiple real-time processing tasks.

Xerox, Mitsubishi, Japan

Discontinued operating system developed for the RC 4000 minicomputer .

Regnecentralen, Denmark

Primary OS.

Hitachi, Japan

Real-time Disk Operating System. With variants: RTOS and DOS.

Data General, USA

x86 based OS written entirely in assembly. Provides protection with segmentation. Multithreaded with support for DOS, DPMI and Win32 console apps. Possible to add other emulated environments like UNIX.

Leif Ekblad, Sweden

Open source OS designed to be binary compatible with Windows NT and its variants (Windows XP, Windows 2000, etc.); currently in development phase.

Preemptive single-stack kernel.

OBP Research, Finland

Operating system for the RCA 3301 computer.

RCA, USA

Intelligent Micro Software (IMS) acquired a license to further develop Multiuser DOS from Novell in 1994 and renamed their product REAL/32.

Intelligent Micro Software, UK

Was IMS' attempt to create the "Next Generation" of REAL/32, also named "REAL/32 for the internet age". REAL/NG promised "increased range of hardware from PCs to x86 multi-processor server systems".

Intelligent Micro Software, UK

Early version of PICK.

USA

Linux for servers.

Red Hat, USA

Linux distribution.

Red Hat, USA

North Korean Linux distribution. Prior to its release, computers in North Korea typically used Red Hat Linux and Windows XP

Korea Computer Center, North Korea

Real-time operating system is designed specifically for mission-critical server and embedded applications.

Concurrent, USA

Written in Rust.

Modular, core-resident standard operating monitor designes dor use on small or very speclized real-time systems.

Control Data, USA

System III based Unix clone, with V6, V7, and SysV extensions.

Alcyon, USA

Operating system for personal computers. Alow PC users to run Android mobile apps on any compatible Intel-based PC.

Jide Technology, China

Free operating system (OS) based on the Android mobile platform that aims to replace all proprietary Android components with free-software counterparts.

Operating System for small PDP-11's attached to a host computer.

USA

Term used to refer to versions of the Unix operating system developed in the Bell Labs Computing Science Research Center.

Bell Labs, USA

FORTH-based OS and a prototype low-level infrastructure for the TUNES project.

Microkernel OS. Usually an embedded cell phone OS.

Qualcomm, USA

Operating system for 8080 and 8086.

Systems & Software, USA

Operating system for 8080 and 8086. Real-time executive that offers 16-bit microprocessing and coprocessing support.

Systems & Software, USA

Code name given to Apple Computer's next-generation operating system during the period of its development between Apple's purchase of NeXT in late 1996 and the announcement of Mac OS X (now called "macOS") in 1998.

Apple, USA

Rochester Intelligent Gateway. Network OS. Influenced Accent and Mach.

University of Rochester, UK

Network operating system for the ZNET.

USA

Small operating system for networked, memory-constrained systems with a focus on low-power wireless Internet of Things (IoT) devices.

FU Berlin, INRIA, HAW Hamburg, Germany

Discontinued Unix operating system designed to run on the Acorn Archimedes. Derived from BSD 4.3, by Acorn computers, for their ARM family of machines.

Acorn Computers, UK

Originally released in 1987 as Arthur 1.20. First release was to be called Arthur 2, but was renamed to RISC OS 2, and was first sold as RISC OS 2.00 in April 1989.

Acorn Computers, Castle Technology, RISCOS, UK

Formerly Arthur 2.

Latest version.

Port by MIPS for its MIPS-based computers.

MIPS Technologies, USA

Multiuser, multiprocessing OS for 68000. Cobol-based business environment for an abstract C-machine.

Ryan-McFarland, USA

Operating system for Datapoint computers.

USA

Real time operating system for 6809 and 68000 family.

Motorola, USA

Real-time operating system designed specifically for use with the Intel 8080 and Intel 8086 family of processors.

Intel / TenAsys Corporation, USA

USA

USA

Free and open-source software replacement for the OEM firmware in various forms of digital audio players (DAPs) with an original kernel.

Realtime Onboard Dependable Operating System. Real-time operating system for embedded systems and was designed for application domains demanding high dependability.

German Aerospace Center, Germany

Was SamOS. An OS with a virtual reality based UI.

Ramon van Handel, USA

Sometimes called Datalight DOS.

Datalight, USA

Research OS for Multimedia Engineering.

NEC USA, USA

Operating system for small-to-medium scale real-time processing.

Fujitsu, Japan

Operating system with Ada Support.

Telesoft, USA

Distributed OS for multiple identical processors (LSI-11s).

University of Wisconsin, USA

Operating system of MikroTik RouterBOARD hardware based on Linux kernel.

Real-time Programming System. Real-time interactive operating system for the IBM Series/1, based on MSP/7 and MPX/1800.

IBM, USA

Experimental, network-wide operating system allowing access to resources distributed on various hosts on the ARPANET based principally on TENEX. The concept have been implemented in the National Software Works (NSW).

R.H. Thomas, USA

Resource System Time Sharing. Multi-user time-sharing operating system, initially developed by Evans Griffiths & Hart of Boston, and acquired by DEC for the PDP-11 series of 16-bit minicomputers.

DEC, USA

Resource System Time Sharing. The first commercial product name for RSTS.

Resource System Time Sharing/Enhanced. Multi-user time-sharing OS.

Realtime multitasking executive for DEC PDP-11. Based on RSX-15.

DEC, USA

Real-time multitasking executive for DEC PDP-15.

DEC, USA

Multi-user, multi-tasking, RSX-11M-like OS for Z80 and Z180 processors.

UNIX compatible OS for the PDP-11.

Human Computing Resources, USA

Base Line. An ultra compact version of the SJ monitor with minimal hardware requirements.

Foreground/Background. Supported two tasks: a high-priority, non- interactive "Foreground" job, and a low-priority, interactive "Background" job.

Single Job. Allowed only one task. This was the initial distribution.

Single Line. Single-tasking OS for machines with memory up to 64 KB.

Time Sharing. Multi-user multitasking OS with time sharing.

Provided support for systems with Separate Instruction and Data space.

Single user OS.

DEC, USA

eXtended Memory. Provided support for memory beyond 64kb.

True pre-emptive, multi-user, multi-tasking OS for 8086 chip and Hartley 3900 in particular.

Hartley, Australia

Open source scalable real-time operating system for embedded devices.

RT-Thread, China

Real-time application interface. Real-time extension for the Linux kernel, which lets users write applications with strict timing constraints for Linux.

Politecnico di Milano, Italy

Real-Time Exucutive. Realtime operating system for Hewlett-Packard HP-2000 series.

USA

Realtime virtual memory OS for dual HP-1000s, featuring high reliability.

USA

Realtime Executive for HP-1000 A-series.

USA

Real-Time Executive for Multiprocessor Systems. Formerly Real-Time Executive for Missile Systems, and then Real-Time Executive for Military Systems. Real-time operating system designed for embedded systems.

OAR, USA

Realtime executive for Interdata minicomputers.

USA

Hard realtime real-time operating system microkernel that runs the entire Linux operating system as a fully preemptive process. The hard real-time property makes it possible to control robots, data acquisition systems, manufacturing plants, and other time-sensitive instruments and machines from RTLinux applications.

New Mexico Institute of Mining and Technology, USA

Realtime executive for the AMC 95/4000.

USA

Free real-time microkernel OS sharing alot of ideas with Mach.

Johan Rydberg, Sweden

Real-Time Multiprogramming Operating System. 24-bit process control operating system that supported both real-time computing and multiprogramming.

General Electric, USA

Realtime multiprogramming OS for General Automation System 18/30.

USA

Real-Time Disk OS for Interdata Minicomputers.

USA

Real time operating system for Data General Nova.

USA

Real time multiprogramming OS for Prime 100, 200, 300.

USA

Real-time operating system.

Force10 Networks, USA

IBM's Real Time Operating System, ran on 5 NASA custom System/360-75s.

IBM, USA

OS for Randal office LINK computers.

Randal Data Systems, USA

OS for Randal office LINK computers.

Randal Data Systems, USA

Real-Time OS.

General Automation, USA

Successor to DMERT for the AT&T 3B20 Duplex computer, featuring high reliability.

USA

Open source real-time operating system for embedded devices.

Bernard Xiong & RT-Thread Team, China

Compact real-time operating system designed for the PDP-8 family of processors.

USA

Real Time Task Scheduler. OS for August Systems Can't Fail 300 with triple 8086s, featuring high reliability.

USA

Real time OS based on Unix for 68000 based systems. Multiprocessing, multitasking, message driven.

Emerge Systems, USA

Line of real-time operating system (RTOS) extensions. They are a software extension or abstraction layer that converts Microsoft Windows operating system into a RTOS. It was the first Windows real-time solution on the market.

IntervalZero, USA

Deterministic Real-Time Operating System designed for ARM and Cortex-M devices. Now part of Arm Holding.

Keil Elektronik, Germany

Realtime executive for General Automation System 18/30.

General Automation, USA

Quadros RTOS proprietary C-based RTOS used in embedded systems.

AT Barrett and Associates, Quadros Systems, USA

Soviet RT-11 clone.

Russia

IoT operating system, using JavaScript as its programing language.

Real time executive for the Texas Instruments TMS9900.

USA

See I-TRON.

NEC, Japan

See I-TRON.

NEC, Japan

Commercial DOS clone as described and available in the author's book "Dissecting DOS".

See Mustard.

NEC, Japan