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Jack Woehr

Dr. Dobb's Bloggers

Mainframe Programming vs. Woonix Programming

July 30, 2008

The differences between the Woonix (Windows and/or Unix) world and the world of classic IBM mainframe operating systems exist not because the mainframing world is clueless. Rather, it exists because the two different worlds often accomplish different missions in different ways.

Despite the differences at which some Woonix programmers bristle, mainframe programming is still computer programming, and it is deucedly interesting.

I've compiled a little chart of a few obvious contrasts between classic IBM mainframe opearting systems and Woonix. It's a subjective, impressionistic selection from a fan of both Mainframes and Woonix.

IBM Classic Mainframe Operating Systems
infinite flat storage
limited hierarchical storage
user utility application-based
rewards low-level programming
rewards high-level programming

In the above, the term "mainframe operating system" is used very loosely to mean:

  • i/OS
    • a.k.a. the Operating System Formerly Known As OS/400
  • z/OS
    • a.k.a. the Operating System Formerly Known As MVS and OS/390
  • z/VM
    • a.k.a. the Operating System Formerly Known As
      • VM
      • VM/370
      • VM/SP
      • VM/ESA
  • the Operating System Formerly Known As DOS/VSE and I am too lazy to figure out how IBM calls this one nowadays.

Let's examine the chart rows.


For business reasons, Mainframes took The Road Not Travelled some time ago. Woonixists might believe that this is perverse of the mainframe, but really, if you service the IRS, it makes quite a bit of sense.


If everything is a database instead of a stream file, you discover really cool ways of dealing with records and really cool things to do with records.


Screw interactive users. Mainframes are about running 24/7 for years without reboot. Users can visit the SaaS web application three steps downstream from the mainframe. Nonetheless, the command-line-only world of real mainframing is very cool. If you only have a command line, you learn how to make it work better than it does even in Unix.

infinite flat storage
limited hierarchical storage

"Data warehouse" is a figure of speech to most Woonix programmers. Burdensome acres of data storage devices is the norm in the mainframe world. It changes the way you look at things. When data got big in the Woonix world and we flattened out our hierarchical storage via YP and LDAP etc., the Mainframers were already there.

user utility application-based

If it has ever been done before in your Mainframe installation, there's a program to do it. If it hasn't been done before, you write a program to do it. You don't compose command lines: you write an exec and use the command line to launch the exec. Of necessity, secretary using email was, before the PC and at the height of corporate mainframing, a programmer him- or herself.

rewards low-level programming
rewards high-level programming

"Keep It Simple, Stupid" is the heartbeat of mainframe programming. Woonix programmers are used to their multi-GHz CPU's idling waiting for the mouse to move. Guess what? On a computer that costs five million dollars ($5*10^6) execution cycles are expected to be expended solely in the performance of useful work.

There are so many layers to Mainframe software, it leaves one breathless thinking of the number of bloggings necessary to express just an overview of the richness.

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