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Rexx - the practical programming language

Another legacy language which still has supporters today

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Comment What is it with old languages? I only have to mention REXX while talking about Mumps and someone (the sort of person who remembers that the original, circa 1970-80, MUMPS was actually a O/S, language and integrated DBMS all in one – I can relate to that, perhaps why I like iSeries too) jumps up to say how much they liked it.

I liked REXX partly because (like many other much-loved languages), it actually had a personality attached to it – Mike Cowlishaw.

REXX was first developed by Mike between 1979-82 at IBM Hursley in the UK and the T. J. Watson Research Centre in the USA. In 1987, it became the Procedures Language for IBM’s System application Architecture (SAA) and in 1989 IBM Austria developed a REXX compiler.

Back when I first met REXX, you could even chat with Mike on the UK-based CIX conferencing system (another legacy that is still useful).

Mike valued user feedback. As he says (in “The REXX Language, a practical approach to programming”, M.F. Cowlishaw, Prentice Hall, ISBN 0-13-779067-8, which unfortunately seems to be out of print - the Rexx Programmer's Reference by Howard Fosdick is a possible alternative): "The language user is usually right ... It is impossible to overestimate the value of the direct feedback from users that was available while REXX was being designed”.

So, given that we had Visual Basic and MSDOS macros and so on when I met it, just what was so good about programming REXX? Back when Visual Basic books were 5cm thick and you argued around the coffee machine about what some lump of VB code actually did, REXX was powerful, compact and readable - and available as Personal REXX on the PC. In a language described in a 1 cm slim book (op. cit.), you could write comprehensible, properly-structured programs invoking all the power of the utilities/commands on an IBM mainframe.

Rather than trying to do everything itself, it was designed to encourage linking to external environments and reuse of the facilities there. Like Visual Basic on Windows (REXX was also designed as an interpreted language), perhaps, but REXX was fully-designed from scratch, it didn't just grow as people came up with neat ideas (perhaps VB.NET, after all these years, is a better comparison). I suspect that IBM still has a lot of REXX legacy code, since it was extensively used for tailoring the CMS component of IBM VM/SP - originally a “stopgap” Virtual Machine mainframe operating system that eventually made it to the strategic mainstream.

REXX was also wonderful for string handling – except for one foible – converting text to upper-case was dead easy, as I remember it, because that was what IBM big iron expected, but lower or mixed case was trickier. Still, its features for parsing input for processing according to a defined pattern were pretty neat back then.

No doubt they seem less neat today, when sophisticated scripting languages are commonplace, but REXX is not dead – neither has it stood still (there’s an open source community here and it is interesting that uppercase REXX itself seems to have transmogrified into mixed case Rexx).

Object Rexx is alive and well and there's a brief introduction to it here. If you want to learn more about its features (such as accurate decimal arithmetic for business calculations instead of binary floating-point arithmetic) visit the OO Rexx site. ®

David Norfolk is the author of IT Governance, published by Thorogood. More details here.

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