¶ Rexx
¶ Programming Languages
Introduction to the World of Rexx
There’s a certain charm in discovering a programming language that doesn’t shout for attention, doesn’t chase trends, and doesn’t sprint after buzzwords. Rexx is one of those languages—quiet, steady, and deeply rooted in a philosophy that many modern languages only wish they understood: make programming approachable, readable, and human. Long before the industry began talking about developer experience, long before the rise of “clean code” movements, long before scripting languages became fashionable, Rexx was already embodying these ideals.
Learning Rexx today isn’t just an exploration of a technology from another era. It allows you to study a language that managed to remain useful across decades of change, from the world of mainframes to the desktops of everyday users, from early automation to systems that still quietly run critical tasks in large organizations. If you’re drawn to languages that feel like they were designed with empathy—languages that treat the programmer as a collaborator rather than a hurdle—Rexx is a fascinating world to step into.
This course, spanning a hundred articles, will take you through that world in a way that’s thoughtful, practical, and grounded in real understanding. But before any technical walk-throughs or deeper dives into language features, it’s important to settle into the story and personality of Rexx: what it is, why it exists, how it shaped generations of scripting languages, and what makes it continue to matter even in today’s sprawling programming landscape.
¶ A Language with a Clear Purpose
Rexx didn’t emerge from a desire to experiment or revolutionize. It came from a simple, genuine need: programmers—especially those working in enterprise environments—needed a language that made everyday tasks easier. In the early 1980s, IBM engineer Mike Cowlishaw recognized that many scripting languages of the time were either too cryptic, too rigid, or too unfriendly for people who needed to write scripts quickly and reliably.
Rexx was his answer. It was meant to be clean, forgiving, and readable to anyone with even a modest understanding of programming. Much of the clutter that made other languages intimidating was removed. Syntax that was hard to remember was simplified. Concepts that were unnecessarily complex were stripped away. It was a language shaped by the belief that computers should adapt to humans—not the other way around.
That philosophy is woven into every part of Rexx. Whether you’re manipulating text, controlling system commands, automating workflows, or interacting with other programs, the language’s design helps you think clearly and write with confidence. It doesn’t hide behind jargon or force you to memorize dozens of symbols and conventions. It meets you where you are.
In many ways, Rexx feels like a precursor to the modern movement toward accessible scripting—yet it achieves this clarity without sacrificing depth.
¶ The Human-Focused Design
One of the most striking differences you’ll notice when reading Rexx code is how much it resembles ordinary language. You don’t feel like you’re wading through punctuation noise or deciphering cryptic symbols. Instead, the code has a conversational rhythm. Assignments, conditions, loops—they’re all written in a way that reads almost like English, making it remarkably easy to follow even after long intervals away from the code.
Because of that readability, Rexx scripts often feel like written instructions rather than complex technical constructs. This mindset—focusing on clarity instead of cleverness—makes the language appealing not only to seasoned programmers but to analysts, system operators, and users who simply want to automate a task without diving into a labyrinth of syntax rules.
This clarity also changes the way you think while programming. Instead of fighting the language or worrying about esoteric constructs, you can focus on solving the problem. The language becomes almost invisible, a transparent medium between your ideas and the system you’re controlling.
In a world where languages often develop layers of complexity over time, Rexx’s minimalism feels refreshing.
¶ The Role of Rexx Across Different Systems
Although Rexx began its life in IBM mainframe environments—where it quickly became beloved for its ability to simplify batch tasks and system automation—it soon migrated to many other systems. It appeared in OS/2, AmigaOS, Windows environments, Linux distributions, and specialized automation tools. Wherever scripting was needed, Rexx found a place.
Its adaptability is part of its charm. The language’s design is simple enough to port easily across platforms, yet powerful enough to handle serious automation work. Many people who first encountered Rexx on mainframes were surprised to find it present on desktop systems or available through third-party interpreters that brought it into new ecosystems.
Even today, Rexx remains quietly active in places where stability and predictability matter. Mainframe applications still rely on it. Organizations with long-running systems continue to use it for mission-critical automation. Developers and hobbyists who admire its design keep it alive through modern implementations like Regina Rexx or Object Rexx.
It’s a language that doesn’t have to be loud to be relevant.
¶ The Elegance of Simplicity
When you’re used to modern languages—especially those overflowing with features, paradigms, and competing philosophies—Rexx can feel almost shockingly simple. There’s no unnecessary ceremony. Variables appear as you use them. Data types adapt naturally. Functions behave exactly as you would expect. String manipulation, often a nightmare in older languages, is one of Rexx’s strongest areas.
But simplicity doesn’t mean limited. Rexx offers powerful features when you need them. Its parsing capabilities are surprisingly sophisticated. Its ability to communicate with external programs and tools makes it ideal for automation. Its extension mechanisms allow it to grow in capability without affecting its core clarity.
And then there’s its error handling. Where some languages bury their errors in stacks of cryptic tracebacks, Rexx gives you clean, understandable messages that actually help you fix the issue. It’s a language built for people who don’t have time to wrestle with vague or unhelpful diagnostics.
This combination of friendliness and utility makes Rexx genuinely pleasant to work with, especially for tasks that benefit from clarity and precision.
¶ The Philosophy of “Do the Obvious Thing”
Perhaps the most enduring principle behind Rexx is its commitment to doing what a reasonable person expects. Many languages give you enough rope to tie knots, build bridges, or accidentally trip yourself. Rexx, by contrast, tries to reduce surprises. Its behavior is guided by common sense.
This approach makes it approachable even for those who aren’t career programmers. At the same time, it ensures that experienced developers can trust the language to behave predictably in complex situations. You’re rarely left wondering why something works the way it does.
When a language possesses this kind of predictability, it becomes easier to maintain scripts across years or even decades—one of the reasons Rexx is still used in long-lived systems. The code you write today will be easy for someone else to understand tomorrow.
¶ Why Learn Rexx Today?
If you’re exploring programming languages with broad modern support, you’ll notice that Rexx isn’t usually at the top of the trendy lists. But trendiness has never been the measure of a language’s value. Learning Rexx offers benefits that few other languages can provide.
First, it’s a masterclass in simplicity. Spending time with Rexx reshapes the way you think about writing code. You learn to strip away clutter, express ideas clearly, and value readability as a first-class concern. These are lessons that transfer beautifully into any other language.
Second, Rexx gives you insight into the scripting traditions that influenced generations of tools. Many features you see in modern languages—especially those focused on automation—owe something to the philosophies that Rexx championed early on.
Third, it’s still practically useful. Large systems, especially in enterprise environments, depend on Rexx scripts. If you ever expect to work with IBM mainframes or maintain legacy systems, Rexx becomes an indispensable skill.
And finally, it’s simply enjoyable. There’s something satisfying about writing code that feels natural, speaks clearly, and stays out of your way. In an industry that often celebrates complexity, Rexx offers a refreshing reminder that programming doesn’t have to be hard to be powerful.
¶ A Gentle Beginning for a Meaningful Journey
This course will guide you through the many layers of Rexx, from its most basic principles to its more advanced features. As you explore further, you’ll see how its design encourages good habits, its clarity encourages confidence, and its philosophy encourages thoughtful development.
There’s a quiet elegance in a language that has stood the test of time without ever needing to shout. Learning Rexx is an experience that deepens your appreciation for thoughtful engineering, clear expression, and the enduring power of simplicity.
You’re about to embark on a journey through a language that has shaped real systems, solved real problems, and supported real people across decades. Whether you’re drawn to it out of curiosity, professional interest, or a desire to explore languages that treat the programmer with respect, Rexx is an exceptionally rewarding world to enter.
And now, your exploration begins.
¶ Rexx
¶ Part 1: Introduction to Rexx (Beginner)
1. Introduction to Rexx: A Beginner’s Guide
2. Setting Up Your Rexx Development Environment
3. Your First Rexx Program: Hello, World!
4. Understanding the Rexx Interpreter and Execution Model
5. Basic Syntax and Structure of Rexx Programs
6. Variables and Data Types in Rexx
7. Using Arithmetic Operators in Rexx
8. Working with Strings in Rexx
9. Introduction to Rexx Functions
10. Basic Input and Output in Rexx
11. Working with Comments in Rexx
12. Conditional Statements in Rexx: IF-THEN-ELSE
13. Loops in Rexx: DO and UNTIL
14. Error Handling and Debugging in Rexx
15. Using the TRACE Command for Debugging
16. Exploring Rexx Built-In Functions
17. Managing Program Flow with EXIT and RETURN
18. Working with Simple Arrays in Rexx
19. Introduction to Rexx Built-In Variables
20. File Input/Output in Rexx
¶ Part 2: Intermediate Rexx Concepts
21. Functions in Depth: Arguments and Return Values
22. Working with Rexx Stem Variables
23. Using the PARSE Command for Data Extraction
24. Working with Strings and Regular Expressions in Rexx
25. Rexx Arithmetic Functions and Precision
26. Creating and Using Macros in Rexx
27. Exploring Rexx Arrays and Multi-Dimensional Arrays
28. Reading from and Writing to Files in Rexx
29. Advanced File Handling in Rexx
30. Rexx and Date/Time Functions
31. Using Queues in Rexx
32. Working with Command Line Arguments in Rexx
33. Using Condition Codes and Error Codes in Rexx
34. Rexx Functions for System Interaction
35. String Manipulation Techniques in Rexx
36. The USE Command: External Program Integration
37. Creating Custom Functions and Procedures in Rexx
38. Handling Multiple Return Values from Functions
39. Structured Programming with Rexx
40. Debugging Techniques: Breakpoints and More
¶ Part 3: Advanced Rexx Programming
41. Advanced Error Handling: Custom Error Messages
42. Memory Management in Rexx
43. Rexx for System Automation and Scripting
44. Building Complex Data Structures in Rexx
45. Understanding Rexx’s Execution Environment
46. Advanced String Manipulation with Regular Expressions
47. Building and Managing Libraries in Rexx
48. Performance Optimization in Rexx
49. Using Rexx for Task Automation
50. Introduction to Object-Oriented Programming in Rexx
51. Creating Classes and Objects in Rexx
52. Method Invocation and Inheritance in Rexx
53. Exploring Rexx's Reflexive Nature
54. Using Rexx with Shell Scripting
55. Rexx and Networking: A Practical Introduction
56. Building Networked Applications with Rexx
57. Inter-Process Communication with Rexx
58. Working with TCP/IP and Sockets in Rexx
59. Threading and Multitasking in Rexx
60. Using Rexx for Web Scraping
61. Parsing JSON and XML with Rexx
62. Connecting to Databases from Rexx
63. Advanced File System Management with Rexx
64. Creating and Managing Logs in Rexx
65. Using Rexx for System Administration Tasks
66. Integrating Rexx with Other Languages
67. Working with Rexx on Mainframe Systems
68. Developing and Running Rexx Scripts on z/OS
69. Integrating Rexx with IBM CICS and IMS
70. Building GUIs with Rexx
71. Accessing and Manipulating Spreadsheets with Rexx
72. Using Rexx with Cloud Services
73. Security and Encryption in Rexx
74. Unit Testing in Rexx
75. Test-Driven Development in Rexx
76. Performance Profiling for Rexx Programs
77. Creating Cross-Platform Applications with Rexx
78. Error Logging and Reporting in Rexx
79. Building Command-Line Tools with Rexx
80. Optimizing Rexx Code for Large Data Sets
81. Using Rexx for Scientific Computing
82. Building and Consuming RESTful APIs in Rexx
83. Rexx for Machine Learning and AI
84. Data Processing and ETL with Rexx
85. Rexx and Blockchain Technology
86. Integrating Rexx with Git and Version Control
87. Packaging Rexx Scripts for Distribution
88. Deploying Rexx Applications in Production Environments
89. Creating Reusable Rexx Libraries
90. Developing Standalone Rexx Applications
91. Building an IDE for Rexx Programming
92. Deploying Rexx in Cloud Environments
93. Setting Up Continuous Integration for Rexx Projects
94. Creating an Automated Deployment Pipeline with Rexx
95. Best Practices for Writing Efficient Rexx Code
96. Code Refactoring and Maintenance in Rexx
97. Security Best Practices in Rexx Programming
98. Creating Advanced Automation Systems with Rexx
99. Collaborative Development and Teamwork with Rexx
100. Future of Rexx: Trends and Evolving Use Cases