Abstract: A modular distributed I/O system that allows one or more modules of an island to be omitted without requiring reconfiguration of the system and a method for auto-addressing the system. The island includes a network interface module that is operably connected to a user interface. The user interface allows a user to indicate for each of the nodes of the island whether the node has an I/O module physically present or not physically present. This allows a constant process image in a system where the process image is dependent upon node ID's of modules, and modules are assigned addresses (i.e., ID's) automatically without using unique markers or signatures.