Convergent Technologies' first product was the IWS (Integrated Workstation) based on the Intel 8086, which had CTOS as its operating system. It is a modular operating system with built in local area networking. CTOS supports multiple processes or threads, and message-based inter-process communication.
Companies which have licensed CTOS include Burroughs (BTOS) and Bull (STARSYS). The largest customer was Unisys, with whom Convergent Technologies merged to become one company in 1988. CTOS now has over 800,000 users worldwide.
For some reason, CTOS is no longer marketted to new customers, although there is a support comittment for existing customers until 2001. Major customers include Police Forces, Banks, and Airlines.
["Exploring CTOS", Miller E., Crook J., Loy J. - Prentice Hall, ISBN 0-13-297342-1, 1991].