<Li> Output (y) - The output is the metric used to determine the behavior of the system . The control output can be classified as measured, unmeasured, or unmonitored . </Li> <P> Processes can be characterized as one or more of the following forms: </P> <Ul> <Li> Batch--Some applications require that specific quantities of raw materials be combined in specific ways for particular duration to produce an intermediate or end result . One example is the production of adhesives and glues, which normally require the mixing of raw materials in a heated vessel for a period of time to form a quantity of end product . Other important examples are the production of food, beverages and medicine . Batch processes are generally used to produce a relatively low to intermediate quantity of product per year (a few pounds to millions of pounds). </Li> <Li> Continuous--Often, a physical system is represented through variables that are smooth and uninterrupted in time . The control of the water temperature in a heating jacket, for example, is an example of continuous process control . Some important continuous processes are the production of fuels, chemicals and plastics . Continuous processes in manufacturing are used to produce very large quantities of product per year (millions to billions of pounds). Such controls use feedback such as in the PID controller A PID Controller includes proportional, integrating, and derivative controller functions . </Li> <Li> Hybrid - Applications having elements of batch and continuous process control are often called hybrid applications . </Li> </Ul> <Li> Batch--Some applications require that specific quantities of raw materials be combined in specific ways for particular duration to produce an intermediate or end result . One example is the production of adhesives and glues, which normally require the mixing of raw materials in a heated vessel for a period of time to form a quantity of end product . Other important examples are the production of food, beverages and medicine . Batch processes are generally used to produce a relatively low to intermediate quantity of product per year (a few pounds to millions of pounds). </Li>

What are control systems write two basic characteristics of the process related to control