A process control system includes a diagnostic monitoring and display functionality for viewing, in a coherent manner, diagnostic information relating to a process that operates over multiple devices and system components. Although the multiple devices and system components typically encompass widely different device types and operational standards, the process control system incorporates diagnostic information relating to all devices and presents this information to a system user in a uniform manner so that an operating control strategy and the diagnostic information are presented as though all control actions and diagnostic information were performed or generated at a single location. A user-defined diagnostic program is assembled as a set of function blocks and control modules and represented as a set of layers of interconnected control objects identified as modules which include informational structures accessed as attributes. Information is accessed using device hierarchy attribute addressing, supporting direct addressing of I/O signals from modules, bypassing the use of I/O function blocks and avoiding I/O function block behavior.