This is a classified, alphabetic listing of most operating systems, past and present, that have been distributed commercially or reported in the English-language literature. This extensive catalog is included because we believe that for the serious student who wishes to understand OS implementation, there is no substitute for studying a variety of actual systems. Most of the systems in this catalog have something to teach, and in many cases the best explanations are given by designers or users in the published literaure.

The listing attempts to be as comprehensive as possible. However, it does not always distinguish closely-related versions or releases of the same OS, or reimplementations of substantially the same OS on different computers. Listed systems are limited to those which have actually been implemented (although perhaps only once), directly control the CPU hardware, and are general-purpose, at least within broad application areas (including business and real-time control).

The operating systems are classified roughly into fourteen categories. Each category is explained briefly at the beginning of the section. The classification is somewhat arbitrary; many OSs could reasonably be placed in several classes. Those that are difficult to classify are placed in the miscellaneous section at the end.

Each listing includes, where possible, a short characterization of the OS; the CPUs or computer types on which it runs; The approximate time it was first released or reported; The company or place where it was developed, and, if possible, at least one reference to a published description.

A catalog such as this is bound to have errors or omissions. The authors regret any that may be found here. We welcome comments, additions or corrections that could lead to an improved catalog in future editions.

Some of the material in this listing was gathered from a number of published surveys, including [Computerworld 1984], [Datapro 1974], [Goldberg 1974], [Hindin 1984], [Mini-Micro 1985], [Mini-Micro 1986], [Rosen 1969], [Rosen 1972], [Rosin 1969], [Weizer 1981], [Zarella 1981], and [Zarella 1982]. Useful information was also obtained from ongoing discussions on several computer conference systems, including USENET, BIX, and COMPUSERVE.

Many of the system names listed in this catalog are trademarks of the companies named in each listing.

Early Operating Systems

Batch Systems

Timesharing Systems

Minicomputer Operating Systems

Microcomputer Operating Systems

Workstation Operating Systems

UNIX and its Derivatives

Fault-Tolerant and Highly Secure Systems

Distributed Operating Systems

Real-Time Operating Systems

Virtual Machine Systems

Parallel and Multiprocessor Operating Systems

Educational Operating Systems

Miscellaneous Operating Systems