This section gives a brief overview of the classes and methods Rexx defines.
Rexx provides the following classes belonging to the object class:
(The classes are in a class hierarchy with subclasses indented below their superclasses.)
Note that there might also be other classes in the system, depending on the operating system. Additional classes may be accessed by using an appropriate ::requires directive to load the class definitions.
The following figures show Rexx built-in classes.
The chapters that follow describe the classes and other objects that Rexx provides and their available methods. Rexx provides the objects listed in these sections and they are generally available to all methods through environment symbols (see Environment Symbols).
In the method descriptions in the chapters that follow, methods that return a result begin with the word "returns".
For  and = methods, the syntax diagrams include the index or indexes within the brackets. These diagrams are intended to show how you can use these methods. For example, to retrieve the first element of a one-dimensional array named Array1, you would typically use the syntax:
When the argument of a method must be a specific kind of object (such as array, class, method, or string) the variable you specify must be of the same class as the required object or be able to produce an object of the required kind in response to a conversion message. In particular, subclasses are acceptable in place of superclasses (unless overridden in a way that changes superclass behavior), because they inherit a suitable conversion method from their Rexx superclass.
The isA method of the Object class can perform this validation.