The ‘r’ type descriptor defines a type as a subrange of another type. It is followed by type information for the type of which it is a subrange, a semicolon, an integral lower bound, a semicolon, an integral upper bound, and a semicolon. The AIX documentation does not specify the trailing semicolon, in an effort to specify array indexes more cleanly, but a subrange which is not an array index has always included a trailing semicolon (see Arrays).
Instead of an integer, either bound can be one of the following:
Subranges are also used for builtin types; see Traditional Builtin Types.