CATS is an automated exchange system developed for the Toronto Stock Exchange

Toronto Stock Exchange

Toronto Stock Exchange is the largest stock exchange in Canada, the third largest in North America and the seventh largest in the world by market capitalisation. Based in Canada's largest city, Toronto, it is owned by and operated as a subsidiary of the TMX Group for the trading of senior equities...

 in 1977. CATS was one of the first technologies allowing for a full automation of the price-setting process in a stock exchange. This technology was implemented in several other stock exchanges in the 1980s. In some cases, it was used as an assistance to open-outcry

Open outcry

Open outcry is the name of a method of communication between professionals on a stock exchange or futures exchange. It involves shouting and the use of hand signals to transfer information primarily about buy and sell orders...

, but in others it allowed for a full dismantlement of the open-outcry institution. The Paris Bourse

Paris Bourse

The Paris Bourse is the historical Paris stock exchange, known as Euronext Paris from 2000 onwards.-History and functioning:...

 purchased this system in the early 1980s and implemented it as CAC (Cotation Assistée en Continu

Cotation Assistée en Continu

Cotation Assistée en Continu was an electronic trading system used at the Paris Bourse, the French stock exchange, in the 1980s and 1990s. It was introduced in 1986 for trading less liquid equities, and in 1989 it was operational for all listed stocks. The acronym is also used to refer to the CAC...

).

CATS handled the process of order matching and price setting through a "double auction

Double auction

A double auction is a process of buying and selling goods when potential buyers submit their bids and potential sellers simultaneously submit their ask prices to an auctioneer, and then an auctioneer chooses some price p that clears the market: all the sellers who asked less than p sell and all...

" algorithm

Algorithm

In mathematics and computer science, an algorithm is an effective method expressed as a finite list of well-defined instructions for calculating a function. Algorithms are used for calculation, data processing, and automated reasoning...

. It is credited for having been the first system to allow for a full automation

Automation

Automation is the use of control systems and information technologies to reduce the need for human work in the production of goods and services. In the scope of industrialization, automation is a step beyond mechanization...

of the price setting process in a centralized, order-driven stock market.