RPGLE Source Layout and Free Format Basics

Learning Objective

By the end of this lesson, you will understand the basic layout rules of free-format RPGLE source: the **free marker, semicolons, comments, and how free-format differs in spirit from older fixed-format RPG.

Simple Explanation

In the Introduction to RPGLE lesson, you learned that RPG has both an older, column-based fixed-format style and a newer free-format style, and that this lesson group focuses on free-format RPGLE. This lesson looks at the basic layout rules that make free-format source what it is.

A few simple rules define free-format RPGLE source:

• Source written in free-format traditionally begins with a **free line at the very top of the source member, marking everything below it as free-format.
• Every statement ends with a semicolon (;), rather than relying on fixed column positions to know where one instruction ends and the next begins.
• Comments start with two forward slashes (//) and run to the end of the line, used to explain what a piece of code does for anyone reading it later.
• Indentation and spacing are flexible and used for readability, not required by the compiler the way older fixed-format column positions were.

By contrast, older fixed-format RPG required specific pieces of information to start in specific, fixed column positions on the line, which made it far less forgiving to read and write. Free-format RPGLE was introduced to make RPG read more like other modern programming languages, while still running on the same IBM i platform and working with the same underlying data.

**free
ctl-opt dftactgrp(*no);

// Declare a variable to hold a customer's name
dcl-s custName char(30);

custName = 'Jordan Lee'; // Assign a simple value
dsply custName;

*inlr = *on;

Why It Matters

Understanding these basic layout rules matters immediately and practically: without knowing that statements must end in a semicolon, or that **free marks free-format source, simple typos can turn into confusing compiler errors for a beginner. Recognizing this basic structure also helps you tell, at a glance, whether a piece of RPG source you are looking at is free-format or older fixed-format.

Practical Example

Imagine a beginner copies an example from a free-format lesson but forgets to end a line with a semicolon. When they try to compile it, the compiler reports an error pointing at that line. Recognizing that free-format RPGLE requires a semicolon at the end of every statement lets them quickly spot and fix the missing punctuation, rather than assuming something more complicated is wrong with their code.

This is a simplified, illustrative example rather than a specific real error message, but it reflects a very common, easily fixed mistake beginners make when they are first getting comfortable with free-format RPGLE's layout rules.

Common Confusions

"Do I always need to type **free at the top of every RPGLE source member?" Traditionally, yes, to clearly mark a source member as free-format. This lesson keeps to this traditional, safe convention; some newer compiler versions handle certain cases without it, but including **free remains a clear, widely understood way to start a free-format program.

"Can I mix fixed-format and free-format in the same program?" Older RPG code bases sometimes do mix styles, since RPG has evolved so much over time, but this lesson group focuses entirely on writing clean, consistent free-format RPGLE, which is the recommended style for new code today.

"Does indentation matter to the compiler?" No. Indentation and spacing in free-format RPGLE are for human readability; the compiler relies on semicolons to know where statements end, not on how the code is visually indented.

Quick Recap

• Free-format RPGLE source traditionally begins with a **free line at the top of the source member.
• Every statement ends with a semicolon, rather than relying on fixed column positions.
• Comments start with // and run to the end of the line.
• Indentation is flexible and used for readability, not required by the compiler.

Try Asking the AI Tutor

Use the AI Tutor to ask follow-up questions about this lesson. For example, try asking:

• "What kinds of errors happen if I forget a semicolon in free-format RPGLE?"
• "Why did IBM introduce free-format RPGLE if fixed-format already existed?"