The Restructured Extended Executor (REXX™) language is a procedural language that allows programs and algorithms to be written in a clear and structural way. It is an interpreted and compiled language. An interpreted language is different from other programming languages, such as COBOL, because it is not necessary to compile a REXX command list before executing it. However, you can choose to compile a REXX command list before executing it to reduce processing time.

REXX is also used in the Java™ environment; for example, a dialect of REXX called NetRexx works seamlessly with Java. NetRexx programs can use any Java classes directly, and can be used for writing any Java class. This brings Java security and performance to REXX programs, and REXX arithmetic and simplicity to Java. Thus, a single language, NetRexx, can be used for both scripting and application development.

The structure of a REXX program is simple. It provides a conventional selection of control constructs. For example, these include IF... THEN... ELSE... for simple conditional processing, SELECT... WHEN... OTHERWISE... END for selecting from a number of alternatives, and several varieties of DO... END for grouping and repetitions. No GOTO instruction is included, but a SIGNAL instruction is provided for abnormal transfer of control such as error exits and computed branching.

The relationship between JCL and program files is the same for REXX as it is for COBOL and other HLLs.