Process control is the regulation of designated process parameters to within a specified target range or to a set target value called the set point. Process control is most often used in refineries, because many materials, such as fuel, gasoline and kerosene, must be accurate for a product to be well made. Therefore, to implement a quality product, process control is used to monitor and correct process parameters by analyzing the state of dynamic variables. Dynamic variables are process characteristics, such as temperature, flow, and pressure that vary with time. Through its I/O interfaces, a controller can regulate these dynamic variables to a desired set point, thus implementing process control.