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The Convergent Technologies Operating System, also known variously as CTOS, BTOS and STARSYS, was a modular, message-passing, multi-process based operating system.

Contents 1 Overview 1.1 Programs 2 Usage 3 References 4 External links

[edit] Overview

CTOS had many innovative features for its time. The file system was hierarchical and allowed very long filenames. Security was also hierarchical. If one knew the password, for example, for a volume, one could access any file or directory on that volume (hard disk.) Each volume and directory were referenced with delimiters to identify them, and could be followed with a file name, depending on the operation, i.e. [VolumeName]<DirectoryName>FileName.

It was possible to custom-link the operating system to add or delete features.

There was a transparent peer-to-peer network running over serial RS-422 cables, and later over twisted pair with RS-422 adapters. Each workgroup, called a "cluster," was connected via a daisy-chain topology to a server, called a "master." The workstations, normally diskless, were booted over the cluster network from the master, and could optionally be locally booted from attached hard drives.

The Inter-process communication (IPC) is primarily based on the "request" and "respond" messaging foundation that enhanced the Enterprise Application Integration among services for both internal and external environments. Thus CTOS was well known for the message-based Micro-Kernel Architecture. Applications are added as services to the main server. The clients consume the services via its own mailbox called "exchange" and well published message formats. The communication works on "request codes" that are owned by the service. The Operating system maintains the exchanges, message queues, scheduling, control, message passing, etc while the service manages the messages at its own exchange using "wait", "check", and "respond" macros.

CTOS ran on Intel X86 computers, and could run concurrently with Windows NT.

The system API was presented to both high-level languages and assembly language.

[edit] Programs

The assembler was very advanced, with a Lisp-like pattern-matching macro facility unmatched by almost any other assembler before or since. There was an always-resident debugger.

Most of the system programs were written in PL/M, an ALGOL-like language from Intel which compiled directly to object code without a runtime library.

The word processor was one of the first screen-oriented editors with many high-powered features, such as multiple views of the same file, cut/copy/paste, unlimited undo/redo, no typing lost after a crash, user-selectable fonts, and much more.

A game included with the OS proved to be very popular, programmed using the font generator to do simple graphics: "Rats Of The Maze".

The system shell was extensible — it was possible to define new commands. To get the parameters, the system would display the form which was to be filled by the user.

[edit] Usage

Convergent Technologies' first product was the IWS (Integrated Workstation) based on the Intel 8086 processor, which had CTOS as its operating system. This was a modular operating system with built in local area networking. CTOS supports multiple processes or threads, and message-based inter-process communication.

Companies which licensed CTOS included Bull (STARSYS), and Burroughs (BTOS) and who latter merged with Sperry to become Unisys. Unisys was the single largest customer with whom Convergent Technologies merged to become one company in 1988. At its peak, CTOS had over 800,000 users worldwide. Diskless workstations (e.g. Bull) did use the Intel 80186 processor, which processor normally was not used for normal PCs.

Progress Software Corporation made a commercial database application for CTOS that was in 4GL. The United States Coast Guard used these databases for logistics administration for their vessels.

There was a port of CorelDRAW for CTOS running the Presentation Manager.

CTOS is no longer marketed to new customers; former major customers included police forces, banks, airlines, the U.S. Postal Service, the Drug Enforcement Administration, the U.S. Army and the United States Coast Guard. The Coast Guard used the operating system from approximately 1986 until 2000.

[edit] References

• Miller, Edna Ilyin; Jim Crook, June Loy (1991). Exploring CTOS. Prentice Hall. ISBN 0132973421. 

[edit] External links

• The CTOS FAQ October 1999
• CTOS Revealed, Byte, December 1994
• Paul Mooney's CTOS Central
• The CTOS FAQ Picture Archive
• Exhuming CTOS: The Convergent Technologies Project, Nadia Ilyin

This article was originally based on material from the Free On-line Dictionary of Computing, which is licensed under the GFDL.