Job ads say "AS400", IBM says "IBM i", and someone on a forum says "iSeries". They all mean the same lineage. By the end of this page you will know the dates of each rename, the difference between the operating system and the hardware, and what to write on your CV.
The short answer
IBM renamed one platform several times. In 2026, call the operating system IBM i and the hardware IBM Power. Say "AS/400" when you talk about history, or when you want to match what a recruiter types into a search box.
The naming timeline
Each step below is a rename, not a replacement. Version numbers carried straight through (V5R4, then 7.5), and programs written in the 1990s still run.
- 1988: AS/400. Application System/400 launches, successor to System/38 and System/36. The OS is called OS/400.
- 2000: iSeries. Rebrand to eServer iSeries during the e-business push.
- 2006: System i. Rebrand again, tied to the merger of the System p and System i hardware lines.
- 2008: IBM i. OS renamed IBM i; the hardware line becomes Power Systems, running IBM i, AIX and Linux.
The OS had its own names too: OS/400, then i5/OS, then IBM i. Check the dates against IBM's own history page before you quote them in a document; I wrote them from my own knowledge of the product history.
OS versus hardware
Most people miss this part.
- Hardware: IBM Power servers. The same physical family runs IBM i, AIX and Linux. Early AS/400s used a custom processor, later ones moved to PowerPC and then Power.
- Operating system: IBM i. This is what you log into and write programs on.
- Database: Db2 for i is built into the OS. You do not install it.
So "an AS/400" in 2026 is wrong twice: the box is a Power server and the OS is IBM i. Nobody at a bank will correct you, but now you know.
- Power server: The hardware you can rack, run by IBM or a hosting partner
- PowerVM partition (LPAR): One slice of the server, with its own OS and memory
- IBM i 7.5: The operating system you sign on to
- Db2 for i, ILE RPG, CL, COBOL, C: Database and compilers ship with the OS
- IFS and open source tools: Stream files, Node.js, Python, Git
Why job ads still say AS400
Recruiters search by the name they learned, and experienced developers type "AS400" into job boards, so the ads follow. Some companies have run the same system since the 1990s and the name stuck internally.
On your own CV, write "IBM i (AS/400)" once and use IBM i everywhere else. That matches both searches.
What to call it in 2026
| Thing | Say this | Notes |
|---|---|---|
| Operating system | IBM i | Also fine: "i", as in "the i" |
| Hardware | IBM Power | Or Power Systems |
| Main language | RPG (ILE RPG, RPGLE) | Free-format is the modern style |
| Casual talk with older colleagues | the AS400 | Common and fine |
| Writing for new readers | not iSeries, not System i | Retired names |
Current releases and hardware
| Release | Status | Hardware |
|---|---|---|
| IBM i 7.4 | Left standard support on 30 September 2026, so teams are upgrading or buying extended support | Check IBM's model list |
| IBM i 7.5 | The release most shops run or are moving to | Runs on a range of Power generations; check the model list for your box |
| IBM i 7.6 | General availability April 2025 | Power10 and Power11 only |
IBM's lifecycle page is the authority for exact end-of-support terms and supported models, so read it before you plan an upgrade.
PUB400, the free practice system, ran IBM i 7.5 when I last checked, which is a good target for learning.
Quick check on your own system
Once connected, ask the system which release it runs. This SQL view exists on current releases; verify on yours:
SELECT * FROM SYSIBMADM.ENV_SYS_INFO;
OS_VERSION and OS_RELEASE are in the result. The DSPPTF command and the sign-on screen show it too.
Does the old knowledge still apply?
Yes. Code written for the AS/400 in the 1990s often still runs on current IBM i, because IBM kept backward compatibility for decades. That is why banks keep these systems: the business logic is old and it works. It also means you will see fixed-format RPG, DDS-described files and green-screen menus sitting next to modern SQL, free-format RPG and REST services in the same shop. Learn the modern style first and learn to read the old one as you go.
Once you know the naming, set up a place to practise with the free PUB400 lab, then learn the platform's library and job mental model. The full order is in the learning roadmap. The old fixed-format code mentioned above is covered in reading fixed-format RPG you inherited.
Try it on PUB400
Sign on to PUB400 and run these at the command line:
DSPSYSVAL SYSVAL(QSRLNBR)
DSPPTF
WRKACTJOB
The first shows the serial number, the second lists installed fixes, and the third shows what the OS is doing right now. You are looking at IBM i on Power, not an AS/400, and you know why people still call it one.
Best resources
- IBM i product page: IBM's own current positioning
- Barrett Otte, IBMi-Book: introduction with platform history and concepts
- nicklitten.com: long-running IBM i community site with many platform explainers
- PUB400: free system to see IBM i for yourself
Next
Free IBM i lab: PUB400 + VS Code
Related
- The IBM i learning roadmap
- Free IBM i lab: PUB400 + VS Code
- Libraries, objects and jobs mental model
Originally published on rainierio.dev. The full Learn IBM i track, with an Indonesian version, is at rainierio.dev/learn.
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