The Pre-Open Routine is a 30-minute session before regular trading starts at 0900 hrs. It comprises of the Pre-Open period and the Non-Cancel Period. During the Pre-Open Period (0830 - 0859 hrs), buy and sell orders can be entered, amended or withdrawn. However they will not be matched and executed during this period. The Non-cancel period can start any time between 0858 hrs to 0859 hrs, during which input, amendment and withdrawal of orders are not permitted. Orders that can be matched and executed at a single computed price, which will be the same as or better than the price at which the orders are entered. This computed price shall be the opening price for the day. Unmatched orders will be carried forward into the regular trading session. The Pre-Close Period starts at 1700 hrs and ends randomly within a one-minute window between 1704 2013 1705 hrs for full-day trading. For half-day trading, it starts at 1200 hrs and ends randomly within a one-minute window between 1204 2013 1205 hrs.