A new and improved control system architecture using a combination of standard function blocks and new flexible function blocks eliminates the need for expensive and difficult to maintain custom control software and special I/O gateways for discrete/hybrid/batch and PLC applications. The end user builds application-specific flexible function blocks by configuring the number and type of inputs and outputs, and the block algorithm. Flexible function blocks and gateway flexible function block interconnect and interoperate with each other and with standard function blocks in a distributed control architecture.