The ObjectARX classes with an AcEd prefix include classes for defining and registering new AutoCAD commands that operate in the same manner as built-in AutoCAD commands. The new commands you define are referred to as "native" commands because they reside in the same internal structure (the AcEdCommandStack) as built-in commands. The AcEd classes also include AcEditorReactor, which monitors the state of the AutoCAD editor and notifies the application when specified events occur, such as starting, ending, or canceling a command. Global functions with the AcEd prefix allow applications to interact with AutoCAD.
For information on registering new AutoCAD commands using ObjectARX, see ObjectARX Application Basics. For an example of using an editor reactor, see Notification.