The first trader to use the system was Ralph W. Varney of Jones Gable, who also served on the development committee.
[1] CATS was introduced, piloted and developed by Harold B. Hofmann, then the Vice President of Operations at the Toronto Stock Exchange.
The Paris Bourse purchased this system in the early 1980s and implemented it as CAC (Cotation Assistée en Continu).
CATS handled the process of order matching and price setting through a "double auction" algorithm.
It is credited for having been the first system to allow for a full automation of the price setting process in a centralized, order-driven stock market.