More information about the REXX language

The System Product Interpreter (SPI), a component of the z/VM® operating system, processes procedures, XEDIT macros, and programs written in the REXX™ language. The REXX interpreter operates directly on the program as it executes, line-by-line and word-by-word.

There is no mechanism for declaring variables. Variables may be documented and initialized at the start of a program and implicit declarations occur during execution. The only true declarations are the markers (labels) that identify points in the program that may be used as the targets of SIGNAL instructions or internal routine calls.

Input and output functions in REXX are defined only for simple character-based operations.

Instructions written in any high level language, such as REXX, must be prepared for execution. The two types of programs that can perform this task are:

An interpreter, which parses and executes an instruction before it parses and executes the next instruction.
A compiler, which translates all the instructions of a program into a machine code program. It can keep the machine code program for later execution. It does not execute the program.

The input to a compiler is the source program that you write. The output from a compiler is the compiled program and the listing. The process of translating a source program into a compiled program is known as compilation.