DEV Community: Rainierio.dev

Your free IBM i lab in 30 minutes: PUB400 + VS Code + Code for IBM i

Rainierio.dev — Sun, 25 Oct 2026 15:27:36 +0000

You do not need to buy hardware to learn IBM i. PUB400 gives you a free account on a real system, and VS Code with the Code for IBM i extension gives you a modern editor. This takes about 30 minutes, mostly waiting for your account.

Rules of PUB400 first

PUB400 is run by volunteers, so respect its terms:

Free profile with about 250 MB of storage (verify current limit on the site).
No commercial use. Learning and personal projects only. Do not put employer or customer code or data on it.
One account per person.
Runs IBM i 7.5 as far as I know; check the site.
Do not store anything you cannot lose. There are no guarantees.

Sign up: Get a PUB400 profile by email
Install VS Code: Add the Code for IBM i extension
Connect over SSH: Host pub400.com, your profile
Create a library and source file: Your workspace on the system
Write hello world: A short **FREE program
Compile and run: CRTBNDRPG, then CALL

Step 1: Sign up

Go to pub400.com and follow the sign-up link.
Fill in the form with a real email address. The password arrives by email, so check spam.
Your profile name will be uppercase, up to 10 characters.
On first sign-on you will be asked to change the password.

Approval is not always instant. Verify the exact process on the site; it may change.

Step 2: Install VS Code and the extension

Install VS Code from code.visualstudio.com.
Open Extensions (Ctrl+Shift+X), search for Code for IBM i (by Halcyon / Liam Allan and contributors), and install it.
Documentation lives at codefori.github.io/docs.

An "IBM i" icon appears in the left activity bar.

Step 3: Connect over SSH

Code for IBM i uses SSH to the IBM i. In the IBM i panel:

Choose New Connection.
Host: pub400.com. Port: 2222 (PUB400 uses a non-standard SSH port; verify on the site).
Username: your profile. Password: yours.
Connect.

If it works, you will see your connection and the panels for Object Browser, IFS Browser and Library List.

To check SSH outside VS Code:

ssh -p 2222 YOURUSER@pub400.com

Step 4: Create a library and a source file

On the IBM i command line (Code for IBM i has a terminal, or use the 5250 session below):

CRTLIB LIB(MYLIB) TEXT('My learning library')
CRTSRCPF FILE(MYLIB/QRPGLESRC) RCDLEN(112) TEXT('RPG source')
ADDLIBLE LIB(MYLIB)

On PUB400 you may not be allowed to create libraries with arbitrary names, and your home library may already exist. Use your own name-based library if CRTLIB is refused (verify).

Alternatively, work from the IFS (a Linux-like folder tree). /home/YOURUSER is yours, and Code for IBM i can edit source stream files there. For beginners I suggest the IFS; compiled programs still go in a library.

Step 5: Write hello world in `**FREE`

Create hello.pgm.rpgle in /home/YOURUSER/ (or a member HELLO in MYLIB/QRPGLESRC):

**FREE
ctl-opt dftactgrp(*no) actgrp(*new);

dcl-s who varchar(30) inz('IBM i');

dsply ('Hello from ' + who);
return;

Step 6: Compile and run

In Code for IBM i, use the Compile action on the file (command palette: Run Action then choose a compile action). Or in a terminal, using CRTBNDRPG for a source member:

CRTBNDRPG PGM(MYLIB/HELLO) SRCFILE(MYLIB/QRPGLESRC) SRCMBR(HELLO)
CALL PGM(MYLIB/HELLO)

For an IFS stream file, use CRTBNDRPG PGM(MYLIB/HELLO) SRCSTMF('/home/YOURUSER/hello.pgm.rpgle').

DSPLY writes to the job's message queue; in a 5250 session you see Hello from IBM i on screen. Press Enter to dismiss it.

5250 emulator option

You can use the traditional green screen as well. Two options:

A TN5250 client, such as tn5250j or the one in Access Client Solutions (IBM's free tool), pointed at pub400.com. The telnet port and TLS port are on the PUB400 site (verify).
PUB400's own web access, if listed on the site.

Learn at least the basics of 5250: WRKACTJOB, WRKSPLF, DSPJOBLOG. You will meet these in every real job. See the roadmap, stage 1.

Troubleshooting

Connection refused / timeout: check you used the SSH port from the PUB400 site, not 22. Corporate networks often block outgoing ports; try from home.
Login fails: profile names are uppercase; passwords are case-sensitive. Passwords expire; reset via the site if you are locked out.
CPF2105 Object not found: the library is not on your library list. Run ADDLIBLE MYLIB.
CPF9801 / not authorized: you tried to create or write something outside your own library. Use your own.
Compile fails with errors: open the joblog or the Code for IBM i error panel. A common cause is the first line; **FREE must start in column 1 with nothing before it.
Extension can't find tools: Code for IBM i needs some open source packages on the server (like git, bash); it normally offers to install them. If that fails, check the extension docs.
Source file record length: QRPGLESRC members compile fine at 112; if you copy long lines they truncate. Keep lines short.

Before you go deeper, the roadmap shows where this lab fits, and AS400 vs iSeries vs IBM i explains what you just signed on to. Once hello world compiles, read the library and job mental model, then write something real in your first free-format RPG program.

Try it on PUB400

Make these three small changes and recompile each time:

Change the greeting and the variable.
Add a loop that prints 1 to 5 using dsply.
Introduce a deliberate typo and find the error in the compile output.

That cycle (edit, compile, fix, run) is the daily work. Do it ten times and you are no longer a beginner on tools.

Best resources

PUB400: free public IBM i; read the rules here
Code for IBM i docs: install and connection guide
IBM RPG Cafe beginner tutorial: what to write next
K3S RPG tutorial: practice exercises
RPGPGM.com: short examples when you get stuck

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.

AS400 vs iSeries vs IBM i: one page to settle it

Rainierio.dev — Sun, 25 Oct 2026 15:27:32 +0000

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

Free IBM i lab: PUB400 + VS Code

Originally published on rainierio.dev. The full Learn IBM i track, with an Indonesian version, is at rainierio.dev/learn.

The IBM i learning roadmap: from zero to modern RPG developer

Rainierio.dev — Sun, 25 Oct 2026 15:27:27 +0000

I work on IBM i core banking for a living, and the question I get most from newcomers is "where do I start, and in what order?" Most people lose months jumping between tutorials. This is the order I would follow if I started again today, using free resources only.

The hour estimates are my own rough guesses for someone studying part-time. They are not benchmarks. Your pace will differ.

The roadmap at a glance

The interactive roadmap diagram is on the original post: https://rainierio.dev/learn/start-here/ibm-i-learning-roadmap

Total: roughly 190 hours to be useful, longer to be good. Stages 2 to 4 overlap in practice; do not wait to "finish" one.

The 12 articles, in order

The roadmap is a map; these are the articles that go with it, in reading order.

The IBM i learning roadmap: Start here: the staged path
AS400 vs iSeries vs IBM i: Why the names differ and what to call it
Free IBM i lab: PUB400 + VS Code: PUB400 account and VS Code setup
Libraries, objects and jobs mental model: Libraries, library list, objects, jobs
Your first free-format RPG program: Write and compile modern RPG
Reading fixed-format RPG you inherited: Read the legacy code you will meet
CL programming essentials: Chain and schedule jobs
Embedded SQL in RPGLE, done properly: SQL inside RPG programs
DDS to SQL DDL migration: Move DDS files to SQL tables
ILE modules, service programs and the binder: Modules, service programs, binding
Expose RPG as a REST API with IWS: Call RPG from REST clients
Core banking on IBM i: what it does: The domain that makes you valuable

Stage 0: Orientation (~3h)

Learn: what IBM i is, how it relates to AS/400 and Power hardware, what kind of work exists (banking, insurance, retail, logistics), and what a modern day looks like (VS Code, Git, SQL).

Read: AS400 vs iSeries vs IBM i, Free IBM i lab: PUB400 + VS Code

Why: you need to know the platform is alive and what you are signing up for. Also get a free place to practise now, not later. See AS400 vs iSeries vs IBM i and the lab article below.

Resources:

IBM i product page: official overview of the platform
PUB400: free public IBM i system for practice
Barrett Otte, IBMi-Book: a developer-written book that covers the platform end to end

Stage 1: Platform concepts (~12h)

Learn: everything is an object; libraries (like schemas/folders), source physical files, members, the IFS, jobs and subsystems, job logs, WRKACTJOB, WRKOBJ, DSPLIB, authority basics, library list.

Read: Libraries, objects and jobs mental model

Why: most beginner errors ("object not found", "not authorized") are platform errors, not RPG errors. If you understand the library list you will save yourself weeks.

Resources:

Barrett Otte, IBMi-Book: clear explanations of objects, libraries and jobs
IBM RPG Cafe beginner tutorial: walks through basics on a real system
nicklitten.com: long-running community site with many beginner explainers

Stage 2: RPG free-format (~40h)

Learn: **FREE fully free-format RPG: variable declarations, data structures, dcl-proc, built-in functions, dcl-f file access, READ/CHAIN/WRITE, error handling with monitor, debugging. Skip fixed-format columns for writing; learn to read them later because old code uses them.

Read: Your first free-format RPG program, Reading fixed-format RPG you inherited

Why: RPG is the language of the business logic on the platform. Free-format is what new code is written in and what teams expect from new hires.

A first taste:

**FREE
ctl-opt dftactgrp(*no) actgrp(*new);

dcl-s total packed(9:2) inz(0);
dcl-s i int(10);

for i = 1 to 3;
  total += i * 10.50;
endfor;

dsply ('Total: ' + %char(total));
return;

Resources:

COMMON RPG Bootcamp: structured course on modern RPG
K3S RPG tutorial: step-by-step RPG lessons
RPGPGM.com: hundreds of practical, short RPG articles by Simon Hutchinson
IBM RPG Cafe beginner tutorial: official starter tutorial

Stage 3: CL (~15h)

Learn: Control Language: variables, IF/DO, CALL, CHGVAR, MONMSG, OVRDBF, SBMJOB, DSPJOBLOG, writing small CL programs that run RPG programs.

Read: CL programming essentials

Why: CL is how jobs are chained and scheduled on IBM i. Every production batch cycle I have seen has CL in it.

PGM
  DCL VAR(&LIB) TYPE(*CHAR) LEN(10) VALUE('MYLIB')
  CALL PGM(&LIB/HELLO)
  MONMSG MSGID(CPF0000) EXEC(DO)
    SNDPGMMSG MSG('HELLO failed, check the job log')
  ENDDO
ENDPGM

Resources:

IBM i documentation, CL topic: the official command reference (verify exact page for your release)
nicklitten.com: practical CL walk-throughs
Barrett Otte, IBMi-Book: covers CL basics in context

Stage 4: Db2 for i SQL + SQLRPGLE (~30h)

Learn: SQL SELECT/INSERT/UPDATE, CREATE TABLE (instead of DDS), joins, embedded SQL in RPG (SQLRPGLE), cursors, SQLSTATE, SELECT INTO, and IBM i Services (SQL views like QSYS2.OBJECT_STATISTICS).

Read: Embedded SQL in RPGLE, done properly, DDS to SQL DDL migration

Why: modern shops move data access to SQL. It is also the most transferable skill on this list.

CREATE TABLE mylib.customer (
  cust_id   INTEGER NOT NULL PRIMARY KEY,
  cust_name VARCHAR(50) NOT NULL
);

**FREE
ctl-opt dftactgrp(*no);
dcl-s name varchar(50);
exec sql select cust_name into :name
         from mylib.customer where cust_id = 1;
if sqlcode = 0;
  dsply name;
endif;
return;

Resources:

IBM Db2 for i documentation: the SQL reference (verify the current page)
RPGPGM.com: many embedded SQL examples
Barrett Otte, IBMi-Book: SQL on IBM i chapter

Stage 5: ILE (~20h)

Learn: Integrated Language Environment: modules, programs, service programs, binding directories, activation groups, prototypes, exported procedures, binder language.

Read: ILE modules, service programs and the binder

Why: real systems are made of service programs, not single giant programs. You will not be able to read a modern codebase without this.

Resources:

COMMON RPG Bootcamp: covers procedures and modular design
IBM ILE documentation: official reference (verify the current page)
RPGPGM.com: service program and binder articles

Stage 6: Modernization, APIs, open source (~30h)

Learn: Git on IBM i, VS Code with Code for IBM i, Bob/build tooling, yum open source packages, Node.js/Python on IBM i, calling RPG from REST services, JSON in RPG (DATA-INTO, DATA-GEN), IBM i Services.

Read: Expose RPG as a REST API with IWS

Why: this is what makes a developer hireable in a modern team rather than a maintenance-only one.

Resources:

Code for IBM i docs: the VS Code extension for IBM i by Liam Allan
IBM ibmi-oss-examples: GitHub examples for open source on IBM i
Seiden Group learning resources: training material and modernization articles

Stage 7: Domain, core banking (ongoing)

Learn: the business, not the syntax: accounts, ledgers, interest, end-of-day batch, ISO 20022 / SWIFT messages, reconciliation, audit trails, decimal precision, and why packed is used for money.

Read: Core banking on IBM i: what it does

Why: at the banks I have worked in, the hardest part was understanding what the numbers mean. Language skill gets you in, domain knowledge makes you valuable. There is no single free course for this; read product documentation of any bank you can, and ask business analysts questions.

Try it on PUB400

Sign up for a free profile, open a source member and run the stage 2 program above. Each time you finish a stage, write one small program that uses it. Full setup is in the next article. Note PUB400 is for learning only; no commercial use.

Best resources

COMMON RPG Bootcamp: structured modern RPG course
K3S RPG tutorial: free step-by-step lessons
IBM RPG Cafe beginner tutorial: IBM's own starter
RPGPGM.com: deep archive of practical examples
nicklitten.com: community explainers
IBMi-Book: free book by Barrett Otte
Code for IBM i docs: your editor
PUB400: free practice system

AS400 vs iSeries vs IBM i

Originally published on rainierio.dev. The full Learn IBM i track, with an Indonesian version, is at rainierio.dev/learn.

DEV Community: Rainierio.dev

Your free IBM i lab in 30 minutes: PUB400 + VS Code + Code for IBM i

Rules of PUB400 first

Step 1: Sign up

Step 2: Install VS Code and the extension

Step 3: Connect over SSH

Step 4: Create a library and a source file

Step 5: Write hello world in **FREE

Step 6: Compile and run

5250 emulator option

Troubleshooting

Try it on PUB400

Best resources

Next

Related

AS400 vs iSeries vs IBM i: one page to settle it

The short answer

The naming timeline

OS versus hardware

Why job ads still say AS400

What to call it in 2026

Current releases and hardware

Quick check on your own system

Does the old knowledge still apply?

Try it on PUB400

Best resources

Next

Related

The IBM i learning roadmap: from zero to modern RPG developer

The roadmap at a glance

The 12 articles, in order

Stage 0: Orientation (~3h)

Stage 1: Platform concepts (~12h)

Stage 2: RPG free-format (~40h)

Stage 3: CL (~15h)

Stage 4: Db2 for i SQL + SQLRPGLE (~30h)

Stage 5: ILE (~20h)

Stage 6: Modernization, APIs, open source (~30h)

Stage 7: Domain, core banking (ongoing)

Try it on PUB400

Best resources

Next

Related

Step 5: Write hello world in `**FREE`