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

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.

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

Step 1: Sign up

1. Go to pub400.com and follow the sign-up link.
2. Fill in the form with a real email address. The password arrives by email, so check spam.
3. Your profile name will be uppercase, up to 10 characters.
4. 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

1. Install VS Code from code.visualstudio.com.
2. Open Extensions (Ctrl+Shift+X), search for Code for IBM i (by Halcyon / Liam Allan and contributors), and install it.
3. 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:

1. Choose New Connection.
2. Host: pub400.com. Port: 2222 (PUB400 uses a non-standard SSH port; verify on the site).
3. Username: your profile. Password: yours.
4. 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 [e-mail]

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:

1. Change the greeting and the variable.
2. Add a loop that prints 1 to 5 using dsply.
3. 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

Next

Libraries, objects and jobs mental model

Related

• The IBM i learning roadmap
• Libraries, objects and jobs mental model
• Your first free-format RPG program

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