Geant4 has various built-in user interface commands, each of which corresponds roughly to a Geant4 category. These commands can be used interactively via a (Graphical) User Interface - (G)UI, in a macro file via /control/execute <command>, within C++ code with the ApplyCommand method of G4UImanager. The availability of individual commands, the ranges of parameters, the available candidates on individual command parameters vary according to the implementation of your application and may even vary dynamically during the execution of your job. List of built-in commands