Buy and sell orders are placed by ritualized hand gestures.
The tiny pool of "buy orders" on hand at the opening had dried up.
Two series of computer-guided "buy" orders helped lift stocks late in the day, adding 5 points to the Dow.
It is called market impact cost - in essence, the impact that buy or sell orders can have on stock prices.
Fidelity Investments will refuse buy orders if it believes the buyers are following a market-timing service.
Buy and sell orders are submitted by customers to brokers.
Over all, he said, there were only 10 or 15 percent more sell than buy orders.
These buy orders combined with substantial short-covering by domestic traders and investors.
The Dow benefited from two rounds of computer-guided "buy" orders in the afternoon.
According to an exchange official, the firm has offered to buy orders in return for 5 percent of the profit on the business.
