RPGLE Learning Path: Beginner to Advanced

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This page lists every published RPGLE lesson on AS400Decoded in the order it was designed to be read. Each entry gives the lesson’s level and links to the lessons before and after it.

Start here: lesson 1, RPGLE for Beginners, gives the big picture. Then work down the page. Levels rise from Beginner to Intermediate as you go. Stages that are still being written are listed at the end, with existing articles you can read in the meantime.

Stage 1: Getting Started

Lessons 1 to 7. Starts at Beginner and ends at Beginner to Intermediate.

1. RPGLE for Beginners: A Practical IBM i Learning Path

The pillar overview: what RPGLE is, why it still matters, and how this path is organized.

2. What RPGLE Is and Where It Fits on IBM i

RPG, RPGLE, RPG IV, and ILE RPG terminology, and where the language sits on IBM i.

3. RPGLE Source Members, Compilers, and Build Flow

How RPGLE source becomes a compiled IBM i program object.

4. RPGLE Specifications: Fixed, Free, and Fully Free

The three RPGLE source styles you will see in real IBM i code.

5. RPGLE Development Environments and Tooling Basics

Editing tools and the edit, compile, diagnose, and run workflow.

6. How to Read an RPGLE Program From Top to Bottom

A strategy for reading RPGLE source in the right order.

7. RPGLE Naming Conventions and Code Organization

Clearer names and cleaner ordering for code that is easier to maintain.

Stage 2: Program Structure

Lessons 8 to 13. Starts at Beginner to Intermediate and ends at Intermediate.

8. RPGLE Program Structure Explained

The major sections of a typical RPGLE program and why each one exists.

9. RPGLE Control Specifications and Compiler Directives

Compiler directives, the **FREE directive, CTL-OPT, and program-wide control options.

10. RPGLE Input and Output Specifications Explained

Traditional input and output specifications and the modern fully free-form approach.

11. RPGLE Calculation Specs and Logic Blocks

How legacy C-specs express calculations, and how to map them to fully free-form logic.

12. RPGLE Indicators and Status Flags

How indicators and status flags drive legacy program flow, and clearer modern alternatives.

13. RPGLE Source Layout and Readability

Consistent sections, spacing, indentation, and comments that make fully free-form RPGLE easier to review.

Stage 3: Variables and Data

Lessons 14 to 18. Starts at Beginner to Intermediate and ends at Intermediate.

14. RPGLE Variables and Storage Types

Declaring variables with DCL-S, and how scope and storage type control visibility and lifetime.

15. RPGLE Data Types, Lengths, and Precision

Character, decimal, integer, date/time, and indicator types, and what length and precision mean.

16. RPGLE Data Structures Explained

Typed subfields, QUALIFIED access, LIKEDS reuse, and simple nested data structures.

17. RPGLE Constants and Literals

Variables versus named constants versus literals, including DCL-C and figurative constants.

18. RPGLE Passing Data by Value and by Reference

What default parameter passing, VALUE, and CONST do to the caller’s storage.

Stage 4: Decisions

Lessons 19 to 22. Starts at Beginner to Intermediate and ends at Intermediate.

19. RPGLE IF, ELSE, and ELSEIF Decisions

One-way, two-way, and ordered decisions with IF, ELSEIF, ELSE, and ENDIF.

20. RPGLE Select and When Logic

Readable multi-branch decisions with SELECT, WHEN, OTHER, and ENDSL.

21. RPGLE Nested Decisions and Guard Clauses

Using guard clauses and early exits to flatten nested conditions.

22. RPGLE Boolean Logic and Comparison Patterns

Comparison operators, AND/OR precedence, and readable compound conditions.

Stage 5: Loops

Lessons 23 to 26. Starts at Beginner to Intermediate and ends at Intermediate.

23. RPGLE DO Loops Explained

Counted DO loops: index setup, inclusive limits, and avoiding boundary mistakes.

24. RPGLE DOU Loops Explained

Post-test DOU loops that always run their body at least once.

25. RPGLE DOW Loops Explained

Pre-test DOW loops whose body can run zero times, and how to trace them.

26. RPGLE LEAVE, ITER, and Loop Control

Exiting a loop with LEAVE and skipping an iteration with ITER.

Stage 6: Arrays and Data Structures

Lessons 27 to 28. Starts at Beginner to Intermediate and ends at Intermediate.

27. RPGLE Arrays and Tables

Fixed-size arrays with DIM, one-based subscripts, and %ELEM.

28. RPGLE Varying-Dimension Arrays

Arrays that grow within a declared maximum, VAR versus AUTO, and guarded appends.

Still to come in this stage: RPGLE Data Structures for Related Fields; RPGLE Built-In Functions for Lists and Arrays.

Coming Next

These stages are planned. Where an existing article already covers the topic, it is listed so you can keep going.

Stage 7: Procedures and Prototypes

Planned lessons: RPGLE Procedures and Subprocedures; RPGLE Prototypes and Procedure Interfaces; RPGLE Procedure Overloading and Optional Parameters; RPGLE Recursive Procedures and Reentrancy; RPGLE Error Handling in Procedures.

Read now:

Stage 8: Modules and Service Programs

Planned lessons: RPGLE Modules and Compilation Units; RPGLE Service Programs and Exported Procedures; RPGLE Binding Directories and Signatures; RPGLE Reusable Code Packaging Patterns.

Read now:

Stage 9: Database File Operations

Planned lessons: RPGLE Native Database I/O with Files; RPGLE READ CHAIN SETLL and READE; RPGLE Update Delete and Write Operations; RPGLE Record Locks and Commitment Control.

Quick reference now:

Stage 10: Embedded SQL

Planned lessons: RPGLE Embedded SQL Basics; RPGLE SQL Cursor Patterns; RPGLE Host Variables and SQL Diagnostics; RPGLE SQL Performance and Error Handling.

Read now:

Stage 11: Error Handling and Debugging

Planned lessons: RPGLE Error Handling Patterns; RPGLE Debugging Tools and Techniques; RPGLE Logging Messages and Tracing.

Read now:

Stage 12: Modern RPG and Professional Practice

Planned lessons: RPGLE Modern Error-Free Coding Practices; Modern Fixed Free-Form RPGLE Coding Standards; RPGLE JSON XML and API Integration; RPGLE Testing Strategies and Unit Tests; RPGLE Interview Questions and Practice Scenarios.

Read now:

Quick reference now:

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