Object-oriented extensions have been added to traditional REXX, but its existing functions and instructions have not changed. The Object REXX interpreter is actually an enhanced version of its predecessor, but with new support for:
Object REXX supplies the user with a base set of classes. These are ALARM, CLASS, ARRAY, LIST, QUEUE, TABLE, SET, DIRECTORY, RELATION, BAG, MESSAGE, METHOD, MONITOR, STEM, STREAM, STRING, and SUPPLIER. Object REXX is fully compatible with earlier versions of REXX that were not object-based.