Such physical process parameters as temperature pressure, and concentration can change spontaneously or as the result of lexternal influences. The primary objective of process control systems is the regulation of such dynamic parameters within a predefined range of values. Direct digital control refers to those cases in which digital logic circuits or a computer are an integral part of the feedback loop that controls dynamic variables. The indian textile industry cannot afford a complete replacement of existing production machinery with computer controlled equipment. It would be pragmatic, however, to develop computer based systems for selected processes and to use these systems to improve productivity and quality.