The Trading System & Infrastructure

The Singapore Exchange Securities Trading Limited (SGX-ST) operates an order-driven market on an electronic trading engine. In an order-driven market, buy and sell orders entered by Trading Members are matched by the system according to price-time priority — the best-priced order takes precedence, and among orders at the same price the one entered earliest is filled first. There are no designated market-makers quoting two-way prices for ordinary equities; liquidity comes from the order book itself.

During continuous trading the market runs as a continuous auction: a new buy order that meets or exceeds the best existing sell order (or a sell order that meets the best buy) executes immediately at the resting order's price. Orders that do not match rest in the central order book, visible by price level, until matched, cancelled, or expired. This mechanism produces continuous price discovery throughout the trading session.

A trading day is divided into phases. The pre-open (pre-market opening) routine accepts order entry, amendment and cancellation but does not match trades; the system calculates and displays an indicative equilibrium price as orders accumulate. At the opening, a single opening call auction matches all crossable orders at one computed price that maximises executable volume. Continuous trading then follows for the main session.

Trading is split into a morning session and an afternoon session with a mid-day break in between (there is also a distinct opening and closing routine). Near the end of the day a pre-close period again accumulates orders without matching, followed by a closing call auction that establishes the official closing price. Understanding which phases match trades (the call auctions and continuous trading) versus which only accept orders (pre-open, pre-close) is frequently tested.