Since 1960,process control systems utilizing Direct Digital Control (DDC) have been treated by many investigators and several reports about the assignment of the parameters have been presented. Recently, the appearance of Micro-computers is going to change the status of all hierachy systems. The advantage of the DDC algorithm rests in its inherent flexibility and these profit never reached by the customary analog devices. In this report, we investigated i) PID algorithm by use of micro-processor ii) the influence to the indicial response of each parameter of the DDC system.