IBM TSO/E REXX User Manual

Although the buffer does not prevent the PULL instruction from accessing elements
placed on the stack before the buffer was created, it is a way for an exec to create
a temporary extension to the stack. The buffer allows an exec to:
1. Use the QUEUE instruction to insert elements in FIFO order on a stack that
already contains elements.
2. Have temporary storage that it can delete easily with the DROPBUF command.
An exec can create multiple buffers before dropping them. Every time MAKEBUF
creates a new buffer, the REXX special variable RC is set with the number of the
buffer created. Thus if an exec issues three MAKEBUF commands, RC is set to 3
after the third MAKEBUF command.
Note: To protect elements on the stack, an exec can create a new stack with the
NEWSTACK command. For information about the NEWSTACK command,
see “Protecting Elements in the Data Stack” on page 147.
Creating a Buffer with the MAKEBUF Command
To create a buffer on the data stack before adding more elements to the stack, use
the TSO/E REXX MAKEBUF command. All elements added to the data stack after
the MAKEBUF command are placed in the buffer. Below the buffer are elements
placed on the stack before the MAKEBUF command.
Instructions that could be used to create the illustrated buffer are as follows:
'MAKEBUF'
PUSH 'newX'
QUEUE 'newY'
Removing Elements from a Stack with a Buffer
The buffer created by MAKEBUF does not prevent an exec from accessing
elements below it. After an exec removes the elements added after the MAKEBUF
command, then it removes elements added before the MAKEBUF command was
issued.
Using the previous illustration, when the exec issues three PULL instructions, the
following elements are removed from the data stack.
newX
newY
old1
Creating a Buffer on the Data Stack
Chapter 11. Storing Information in the Data Stack 143

IBM TSO/E REXX Specifications

General

Brand	IBM
Model	TSO/E REXX
Category	Computer Hardware
Language	English

Summary

Part 1. Learning the REXX Language

Chapter 1. Introduction

Explains the REXX programming language, its features, and suitability for various users.

Chapter 2. Writing and Running a REXX Exec

Details the process of writing, running, and understanding REXX execs, including syntax rules and common issues.

Chapter 3. Using Variables and Expressions

Covers REXX variables, expressions, operators, and tracing techniques for data manipulation and calculations.

Chapter 4. Controlling the Flow Within an Exec

Explains how to alter REXX exec execution using conditional, looping, and interrupt instructions.

Chapter 5. Using Functions

Describes REXX functions, including built-in, user-written, and packages, and how to use them.

Chapter 6. Writing Subroutines and Functions

Guides on writing, calling, and passing information to REXX subroutines and functions.

Chapter 7. Manipulating Data

Covers REXX data manipulation using compound variables, stems, and various parsing techniques.

Part 2. Using REXX

Chapter 8. Entering Commands from an Exec

Explains how REXX execs can interact with the operating system by issuing TSO/E and host commands.

Chapter 9. Diagnosing Problems Within an Exec

Details techniques for diagnosing and debugging REXX execs using tracing and special variables.

Chapter 10. Using TSO/E External Functions

Describes TSO/E external functions available for interacting with the system and performing specific tasks.

Chapter 11. Storing Information in the Data Stack

Explains how to use the REXX data stack for temporary storage, passing information, and managing buffers.

Chapter 12. Processing Data and Input/Output Processing

Covers dynamic REXX expression modification and processing data to/from data sets using EXECIO.

Chapter 13. Using REXX in TSO/E and Other MVS Address Spaces

Explains how to run REXX execs in TSO/E and non-TSO/E MVS address spaces and available services.

Part 3. Appendixes

Appendix A. Allocating Data Sets

Guides on creating and allocating data sets, including checklists for ISPF/PDF and ALLOCATE commands.

Appendix B. Specifying Alternate Libraries with the ALTLIB Command

Details using the ALTLIB command to specify and manage alternative libraries for implicit execution.

Appendix C. Comparisons Between CLIST and REXX

Compares REXX and CLIST languages, highlighting similarities and differences in features and capabilities.

Appendix D. Notices

Provides legal notices, warranty disclaimers, copyright, and trademark information.

Bibliography

TSO/E Publications

Lists IBM publications related to TSO/E, including administration, CLISTs, and general information.

Related Publications

Lists IBM publications related to z/OS MVS and ISPF, covering system programming and administration.

Index