A user function is a function specified for generators to monitor its values along curves and to detect its zeros along curves. It is treated like a test function, but are user-defined. "Detect" means to accurately locate points where the function changes sign and is sufficiently small. The function may use phase and parameter components of a point where it is evaluated. Names of the components are shown in a starter window.
You specify user functions with the user functions dialog box which is displayed by the Select|User functions command in the Main window.
Starter windows contain switches you use to set appropriate processing mode for each function.