REXX: A Comprehensive Overview of the Restructured Extended Executor Programming Language
In the landscape of programming languages, there are those that emerge as revolutionary tools for specific niches, and others that quietly make their mark through long-term utility in particular environments. One such language is REXX (Restructured Extended Executor), a high-level interpreted language that, although not as widely recognized in the broader programming community, has earned a devoted following due to its simplicity, flexibility, and use in critical systems within certain industries. Developed by Mike Cowlishaw at IBM in 1979, REXX has had a long and varied history, carving out a niche for itself in the realms of system programming, scripting, and data processing.
Origins and Development of REXX
REXX was developed at IBM by Mike Cowlishaw, a British computer scientist, initially as a replacement for IBM’s earlier scripting and programming languages. The goal was to create a language that was structured, high-level, and easy to read and write, even for those who were not professional programmers. The language’s design philosophy was centered on simplicity, flexibility, and readability—features that would make it ideal for both beginner programmers and seasoned developers alike.
REXX was officially released in 1979 and has since been implemented across a wide variety of platforms. It was primarily designed for interactive use and system scripting. Unlike languages such as C or Fortran, which require more intricate memory management and lower-level system understanding, REXX was intended to make it easier to write and debug code for day-to-day tasks, such as processing data, generating reports, and performing automation in various environments.
Key Features of REXX
Over the years, REXX has accumulated a set of characteristics that set it apart from other programming languages. Below are some of its most notable features:
1. Simplicity and Readability
One of the most prominent features of REXX is its simplicity. The syntax is designed to be intuitive, and the language does not have complex constructs or obscure keywords. The readability of REXX makes it particularly attractive to non-programmers and system administrators who need to write scripts to automate tasks. For instance, REXX’s use of English-like keywords (such as IF, THEN, ELSE, DO, END) allows users to easily understand and write code, even with minimal programming experience.
2. Interpretive Nature
REXX is an interpreted language, meaning that code written in REXX is not compiled into machine language but is instead executed line-by-line by an interpreter. This provides rapid prototyping capabilities, as developers can test individual components of a program without needing to compile the entire code. The trade-off is performance, which can be slower compared to compiled languages, but this is often acceptable given the tasks REXX is typically used for.
3. Structured Programming
REXX supports structured programming principles, including clear program flow and the use of functions, which contributes to its readability and maintainability. While it does not require the complex type systems of other languages, REXX provides sufficient control structures like loops, conditionals, and subroutines, allowing developers to write modular, logical code.
4. Data Processing and Text Manipulation
REXX excels at processing text and data. It has robust support for string manipulation, making it an excellent tool for processing large volumes of text-based data. Many users employ REXX scripts for tasks such as log file analysis, text extraction, and report generation. This functionality makes REXX a popular choice for automation within legacy systems and environments where extensive data manipulation is necessary.
5. Portability
Another important characteristic of REXX is its portability. Initially developed on IBM systems, REXX has been adapted to run on a wide variety of platforms, from IBM mainframes to personal computers, including UNIX and Linux systems. This has made it an invaluable tool for environments where cross-platform functionality is required. Additionally, REXX interpreters are available for other operating systems, including Windows and OS/2.
6. Macro Language and Scripting
REXX is widely used as a macro language in various applications. It has been embedded into a number of software applications as a scripting interface, allowing users to automate tasks within those applications. For example, REXX is used in the KEDIT text editor and the ZOC terminal emulator. Its integration into these programs allows users to create complex scripts that extend the functionality of the software.
7. Error Handling and Debugging
REXX provides mechanisms for error handling, such as SIGNAL and EXIT statements, that allow programmers to gracefully handle runtime errors and clean up after execution. Furthermore, because it is interpreted, REXX allows developers to easily debug and trace their programs by stepping through each line of code. This simplicity makes it easier for developers to locate bugs in the script.
REXX’s Role in Computing History
REXX’s history is inextricably tied to IBM’s systems, and it played an important role in IBM’s Systems Application Architecture (SAA) in the late 1980s. It was adopted as the standard scripting language for IBM mainframes, and was referred to as “SAA Procedure Language REXX” within that context. Over time, REXX evolved to be an essential tool for systems programming and administration.
In the early days, REXX was primarily used on IBM’s VM/370 and MVS mainframe systems. It was used for tasks ranging from simple automation to more complex batch processing jobs. The ease of use and integration capabilities of REXX within IBM environments made it a valuable tool for administrators and developers working with IBM’s proprietary systems.
REXX in Modern Computing
While REXX’s popularity may have waned somewhat in the face of newer scripting languages like Python, Perl, and Bash, it is far from obsolete. In fact, REXX continues to play a critical role in certain sectors. It is still in active use in legacy IBM environments, where it is often employed for tasks like batch job processing, system automation, and data analysis.
Additionally, REXX has seen continued use in embedded systems and in specific applications that require lightweight, high-level scripting capabilities. Many IBM and third-party applications still rely on REXX as an embedded scripting language. It is also used in modern environments for tasks like text parsing and report generation.
REXX in Popular Operating Systems
REXX has long been the scripting language of choice for many proprietary operating systems. For example, OS/2, a now-legacy IBM operating system, came with REXX pre-installed as its primary scripting language. The language is also available on other platforms such as AmigaOS and PC DOS. Today, users can still run REXX on Windows systems through interpreters like Regina, which provides the ability to run REXX scripts in the Windows environment.
REXX in the Open Source Community
Although REXX has historically been associated with IBM, there is an active open-source community that maintains and develops REXX implementations for modern platforms. Tools like the Regina REXX interpreter are freely available and regularly updated, offering support for a wide range of operating systems. This open-source community ensures that REXX continues to have a place in modern computing, despite the emergence of more popular scripting languages.
Applications and Use Cases of REXX
The primary applications of REXX remain in the domains of system scripting, automation, data processing, and text manipulation. Below are some of the most common use cases:
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System Administration
REXX is widely used by system administrators to automate system tasks such as backups, software installations, and configuration management. Its readability and ease of use make it an attractive choice for those who need to write scripts to manage complex systems without extensive programming expertise. -
Data Processing and Report Generation
REXX excels at processing structured data, especially text data. This makes it an ideal choice for generating reports, transforming data formats, or even scraping information from files and databases. It has been used extensively in industries that rely on data-heavy operations, such as finance and healthcare. -
Scripting and Macros in Applications
As a macro language, REXX can be used to extend the functionality of applications like KEDIT and ZOC terminal emulators. It is also used for scripting in IBM’s proprietary software systems, allowing users to automate repetitive tasks. -
Integration with Legacy Systems
REXX remains integral to many legacy IBM mainframe systems. It is often employed in environments where modern programming languages cannot easily be deployed, particularly in legacy data centers where mainframes are still in use.
Conclusion
In the landscape of programming languages, REXX is often overlooked in favor of more widely recognized languages like Python, JavaScript, or C++. However, its enduring utility in specialized fields—particularly in system scripting, text processing, and automation within legacy systems—ensures its continued relevance. Developed by Mike Cowlishaw in 1979, REXX has maintained a unique place in computing history due to its simple syntax, portability, and ease of integration into diverse environments. While other languages have emerged to serve similar purposes, REXX remains an important tool for those working in legacy IBM systems, as well as for those who value its unique combination of features.