Using the strict definition of a data element provided by IFPUG’s Counting Practices Manual. "A data element is a user recognizable, non recursive field." Unfortunately this does not provide much guidance when counting real time or embedded systems. In fact, the IFPUG Counting Practices manual does not provide any detail on counting these types of systems.
Some traditional definitions can be applied directly to real time and embedded systems. The fields on a diagnostics file: time of diagnostics, hardware state during diagnostics, temperature, voltage, so on and so forth would all be examples of data elements.
Real Time Systems may not have any "traditional user interface." That is, the stimulus for the Real Time System may be it’s own output – or state. A real time or embedded systems can signal to determine current Hardware State (or location) and determine the appropriate adjustment (input) based on the current state.