When you subclass an object, you create an object that inherits its functionality and appearance from another object.
Subclassing an object is similar to copying an object, except that the resulting subclassed object maintains a link to its source object. A subclassed object automatically inherits any changes that have been made to the source object when you open or recompile the module that contains the subclassed object unless both modules are open. If both modules are open, changes are inherited immediately.
Subclassing allows you to:
Subclassing, used in conjunction with the Object Library, can provide a powerful method for defining and enforcing look-and-feel requirements. Any object that is stored within the Object Library can be subclassed into form and menu modules to create independent instances of the parent class.