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This Wiki is intended to help average computer users (probably you) who also are curious about AS/400, iSeries, or IBM i to get started with the system. The platform is in parts dramatically different from many you've probably learned about before. This makes it hard to understand the underlying concepts. Additionally, there's a certain amount of slang. Without proper translation into terms we know, it's even more complicated to get going.

Fortunately, there's a wealth of online resources available in the web. Unfortunately, these are scattered around, sometimes providing insight to special topics while omitting basic information for helping novice users to just get started.

The intention of this information resource is trying to explain the platform in terms of, and comparison to, stuff you might be more familiar with.


The AS/400 is a huge area to explore. As you probably wouldn’t expect to learn everything Linux from reading three Wikipedia articles, you may possibly understand that this Wiki has a lot of content and is constantly growing and being filled with more information. Also, existing content is prone to being enhanced and corrected of errors. You may help with this by writing me to <>.

I had a hard time to learn and I want to make it easier for you to just get started.

Most content in this Wiki is based on my own experiences with an older 9401-150 machine, running OS/400 V4R5 with latest patches, that is from the early 2000’s. When I describe different machines or OS releases, I‘ll indicate that in the text.

Please read The Naming of the System for my thoughts regarding the regularly fought battle about It’s not an AS/400 anymore!.


But why should you care for V4? The current version is V7.something!

Every OS does evolve over time. So does OS/400, or IBM i, as it’s called today. Windows Server 2019 bears a certain resemblance to Windows 2000 (not counting the UI changes!). Much stuff you learned in the 2000’s era is outdated and never needed again in modern systems, though. Mac OS 9 from 2001 bears only a slight resemblance to today’s OS X (or macOS as it’s now called). Most conventional platforms don’t just evolve, they change, often in incompatible ways.

This is different with OS/400. Newer releases of OS/400 carry over almost all stuff you'd know from V4. Most knowledge you acquired with just V4 isn’t worthless with V7. V7 has additional capabilities to learn.

If you are interested in background information how and by whom the system was developed, see History.

Getting started

If you are interested in getting to know (more) about AS/400 basics, you may read About Green Screens and mouse-clickable UIs as well as about Features that separate the AS/400 from common computer systems to get a first glance what makes this platform so unique. This might provide a better decision-making about if you want to continue exploring the AS/400 beyond theoretical statements.

Want to dive deep? You should decide if you want your own machine or if it’s sufficient to have remote access to a machine to start exploring as an ordinary user, without administrative rights. You may start with the latter and get your own machine at a later point in time, though.

  • Holger Scherer has been providing free access to an IBM i installation hosted in his company’s bunker, for people to explore the system, learn and perhaps start programming.
  • If you decide having your own machine is the way to go, I encourage you to start looking at internet auction sites and companies with IBM i expertise for a used box to eventually call your own.

The ever growing UNIX-User's Cheater Table could probably be helpful in finding out a certain command when you know the command in UNIX, or Linux.

If you’re coming from the IBM mainframe world, you’ll be relieved that many concepts are borrowed from the predecessors of z/OS. If there’s demand, I’ll probably add an extra article for an overview of similarities and differences.

A word on virtualization

Currently there is no known way to run OS/400 on (virtual) x86 platforms. OS/400 can be virtualized – on appropriate hardware, driven by IBM POWER CPUs. That is, some kind of IBM POWER based system. But if you have this hardware in the first place, virtualization is probably superfluous.

OS/400 in recent versions can host LPARs for Linux, AIX, and itself, so it’s quite possible to have a good deal of integration the other way 'round.[1]

Further Reading

This selection of initial reading may be not applicable to your particular situation, maybe because you’re not (yet) owning an AS/400 or your box came with OS/400 preinstalled.

A little more advanced topics:

Regarding software development, it might be of interest to have a look at my GitHub Projects Page.

Links to IBM documentation

In the beginning of 2023 I was forced by IBM UK to take offline my publicly available IBM documents collection. No opportunity was given to challenge that decision. In addition, it proved to be impossible for me to find/identify a responsible person within IBM to overturn that decision.

Links in this Wiki thus point directly to the IBM Publications Center. If the list of results is empty, this means IBM doesn't publish the linked document any longer. Since I'm not allowed to publicly publish IBM copyrighted material, you probably need to find the linked documents elsewhere.

See also

Restrictions regarding this Wiki

This Wiki is read only for guest users because of frequent vandalism and spamming. Also, self-creating user accounts isn’t allowed for the very same reasons.

Volunteers are very welcome, especially for correcting my possibly numerous syntactic errors and misplaced commas. Feel free write an e-mail to <> and I’ll add an account for you.

I’m also happy with any feedback. Even if it’s only to say thank you.

Rules regarding this Wiki

Quality of the content comes before quantity. Also, to provide reasonable understandability and searchability for articles, please adhere to the following points:

  • Keep a high quality of language,
    • avoid spelling errors, slipshod procedure descriptions, and abstruse language.
  • Name articles concise and distinctly (Wikis don’t provide a hierarchy),
    • avoid repeating terms in several article names that are better used as a category name.
  • Always add category-tags at end of articles. This permits automatic grouping of related articles and better retrieval if the search function doesn’t provide expected results.
  • Add images sparsely and as additional reference only. Main explanation must be actual text, so
    • automatic translation services can actually translate content,
    • disabled persons can make better use of this Wiki.
  • Don’t flood/plaster articles with full-size pictures. It strains the eyes to read!
  • Adhere to Wikipedia Style when outlining articles:
    • Begin articles with a sentence or two that roughly describes what the article is about, highlight keywords also appearing in the article name,
    • Use separate sections for Weblink collections and footnotes at the very end of the article,
    • Don’t use the Single-Equals sign for sections, this is already implied by the article heading.
  • Be precise when mentioning actual products.

Please consult me before introducing new categories.


  1. POWER 8 is the first CPU with complete little endian support, which is required by most free and current Linux distros like Debian (ppc64el). For older machines you need to find an appropriately older distro version that still supports big endian (PPC64) CPUs. Currently, Debian PPC64 support is unofficial. See SupportedArchitectures in the Debian Wiki.