For programming efficiency, similar objects in REXX are grouped into classes, forming a hierarchy. REXX gives you a basic class hierarchy to start with. All of the classes in the hierarchy are described in detail in the Object REXX Reference. But briefly, here are the classes REXX provides (there may be others in the system). The classes are indented to show subclassing. Classes in the list that are described later in this section are highlighted in bold type:
Object
Alarm
Class
Collection classes