Chapter 1. Introduction; What Is Rexx; Features Of Rexx; Ease Of Use - IBM SC34-5764-01 Manual

Chapter 1. Introduction

This chapter describes the REXX programming language and some of its features.

What is REXX?

REXX is an extremely versatile programming language. Common programming structure, readability, and
free format make it a good language for beginners and general users. REXX is also suitable for more
experienced computer professionals because it can be intermixed with commands to host environments, it
provides powerful functions, and it has extensive mathematical capabilities.
REXX programs can do many tasks under CICS. These include issuing EXEC CICS commands, SQL
statements, as well as commands to the CEDA (Resource Definition Online Transaction) and CEMT
(Master Terminal Transaction) utilities.

Features of REXX

In addition to its versatility, REXX has many other features, some of which are:

Ease of use

The REXX language is easy to read and write because many instructions are meaningful English words.
Unlike some lower level programming languages that use abbreviations, REXX instructions are common
words, such as SAY, PULL, IF...THEN...ELSE..., DO...END, and EXIT.

Free format

There are few rules about REXX format. You need not start an instruction in a particular column. You can
skip spaces in a line or skip entire lines. You can have an instruction span of many lines, or have multiple
instructions on one line. You need not predefine variables. You can type instructions in upper, lower, or
mixed case. The few rules about REXX format are covered in section "Syntax of REXX Instructions" on
page 6.

Convenient built-in functions

REXX supplies built-in functions that perform various processing, searching, and comparison operations
for both text and numbers. Other built-in functions provide formatting capabilities and arithmetic
calculations.

Debugging capabilities

When a REXX program running in REXX/CICS encounters an error, REXX writes messages describing the
error. You can also use the REXX TRACE instruction and the interactive debug facility to locate errors in
programs.

Interpreted language

The REXX/CICS product includes the REXX/CICS interpreter. When a REXX program runs, the interpreter
directly processes each line. Languages that are not interpreted must be compiled into machine language
and possibly link-edited before they are run.

Extensive parsing capabilities

REXX includes extensive parsing capabilities for character manipulation. This parsing capability lets you
set up a pattern to separate characters, numbers, and mixed input.
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