Radio Buttons - each set of radio buttons is counted as one DET. Only one radio button can be selected at a time.
Pick Lists - The actual pick list (also known as drop downs, lookups) could be an external inquiry, but the result of the inquiry may be a DET for an external input.
Check Box - Each check box that can be simultaneously checked is a unique DET.
Buttons - Buttons can be DETs. The OK button above would be a data element. If there was a series of buttons Add, Change and Delete. Each button would be counted as a DET for the associated transaction.
A single GUI "screen" may represent several transactional function types. For example, it is common for a GUI “screen” to have a series of external inquiries followed by an external input.
Error Messages - error messages are counted as data elements (DETs), not unique external inquiries. Count one DET for the entire input screen. Multiple Error Messages are similar to recursive values. An error message is part of another elementary process.
The number of error messages on a GUI screen is less than the number of error messages associated with traditional applications. If used correctly, radio buttons and pick lists can force users to select correct information; therefore, eliminating the need to do editing behind the scenes.
In practice the number of DETs do not make much of a difference in evaluating an EI, understanding error or confirmation messages help in the understanding of uniqueness.
Real Time and Embedded Systems - In real time and embedded systems communication between hardware and software is common and should not be overlooked when counting these types of systems. Other types of inputs for real time and embedded systems are: Operator Controls, Volume Controls, Sensor Readings, Radio Frequencies, Standards and Limit Settings (Alarms Settings, so on and so forth.)