Command and control is an interface between traders and the trading system. It can be a command-line system or a user interface receiving the commands from the traders and sending the messages to the appropriate components. Let's have a look at the following diagram:

As shown in the diagram, if we need to update the trading strategy parameters, the trader can use a text field on a web-based application to specify the risk tolerance the trading strategy can take. The number (corresponding to the tolerance limit) will be sent to the appropriate trading strategy.