An external class defines the class properties, methods, and events for one or more external objects. An external class provides a wrapper for a single external object so that OpenROAD can use it seamlessly in your application. This wrapper provides display and storage space for the external object in your OpenROAD application. For instance, it allows a spreadsheet, word processor, or other application to be used within an OpenROAD application. OpenROAD can use a Microsoft Excel spreadsheet as an external object, read data from it, and use the data in OpenROAD code.