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IBM i rewards people who understand the platform before they write code. This guide collects every AS400Decoded article that explains how the system is organized, in the order most newcomers need it.
Read the first section to get the vocabulary straight, then work through objects, files, jobs, and security. Each section links to deeper material in the other pillars when you are ready.
Prefer a guided order? Follow the IBM i Beginner Roadmap on the IBM i Learning Paths page.
What Is IBM i?
- What Is AS400 (IBM i)? A Complete Beginner’s Guide
- History of AS400 and IBM Power Systems
- IBM i vs Mainframe: What’s the Difference?
- Why IBM i Is Still Relevant in 2026
Architecture, Libraries, and Objects
- IBM i Architecture Explained
- IBM i Libraries, Objects, and Members Explained
- How IBM i Uses Files, Libraries, and Data Access
- IBM i Data Areas, Data Queues, and User Spaces Explained
Files and the Integrated File System
- IBM i Integrated File System (IFS) Basics
- IFS and stream files on IBM i: the bridge to the outside world
- IBM i IFS in 2026: The Integrated File System, Stream Files, Git in the IFS, and Working with IFS from RPG and CL
Jobs and Subsystems
The basics are here; the IBM i Administration Guide goes deeper into work management.
- IBM i Subsystems and Job Descriptions Explained
- IBM i Job Scheduling and Batch Processing Explained
- IBM i Output Queues and Spool Files Explained
Security Basics
Your Development Environment
The Languages of IBM i
One introduction per language. Each pillar guide continues from here.
- RPGLE for Beginners: A Practical IBM i Learning Path
- CL Programming Explained
- Db2 for IBM i Explained
- SQL on IBM i for Beginners
Careers
Planned Topics
These topics are on the writing plan for this guide:
- Source physical files and source members, step by step
- Everyday IBM i commands for newcomers (WRK and DSP commands)
- Navigating 5250 green-screen menus and command prompts
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