do not need to be predefined, and you can type instructions in upper, lower, or
mixed case. The few rules about REXX format are covered in “Syntax of REXX
Instructions” on page 9.
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 exec running in TSO/E encounters an error, messages describing
the error are displayed on the screen. In addition, you can use the REXX TRACE
instruction and the interactive debug facility to locate errors in execs.
Interpreted language
TSO/E implements the REXX language as an interpreted language. When a REXX
exec runs, the language processor directly processes each language statement.
Languages that are not interpreted must be compiled into machine language and
possibly link-edited before they are run. You can use the IBM licensed product, IBM
Compiler and Library for REXX/370, to provide this function.
Extensive parsing capabilities
REXX includes extensive parsing capabilities for character manipulation. This
parsing capability allows you to set up a pattern to separate characters, numbers,
and mixed input.
Components of REXX
The various components of REXX are what make it a powerful tool for
programmers. REXX is made up of:
v Instructions — There are five types of instructions. All but commands are
processed by the language processor.
– Keyword
– Assignment
– Label
– Null
– Command (both TSO/E REXX commands and host commands)
v Built-in functions — These functions are built into the language processor and
provide convenient processing options.
v TSO/E external functions — These functions are provided by TSO/E and interact
with the system to do specific tasks for REXX.
v Data stack functions — A data stack can store data for I/O and other types of
processing.
The SAA Solution
The SAA solution is based on a set of software interfaces, conventions, and
protocols that provide a framework for designing and developing applications.
The SAA Procedures Language has been defined as a subset of the REXX
language. Its purpose is to define a common subset of the language that can be
used in several environments. TSO/E REXX is the implementation of the SAA
Procedures Language on the MVS system.
Features of REXX
4
z/OS V1R1.0 TSO/E REXX User’s Guide
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