Arrays in RPGLE

Learning Objective

By the end of this lesson, you will be able to declare a simple RPGLE array using dim, access an individual element by its index, and loop through an array's elements.

Simple Explanation

Every variable you have declared so far in this lesson group holds exactly one value. An array is a variable that holds a fixed number of values of the same data type, all sharing one name, distinguished from each other by a numbered position called an index.

An array is declared by adding dim(n) to a variable declaration, where n is how many elements the array holds:

dcl-s regionNames char(20) dim(4);

regionNames(1) = 'North';
regionNames(2) = 'South';
regionNames(3) = 'East';
regionNames(4) = 'West';

Each element is accessed by writing the array's name followed by its index in parentheses, such as regionNames(1) for the first element. RPGLE array indexes start at 1, not 0.

Arrays are commonly used together with the loops covered in the DO Loops and Basic Iteration in RPGLE lesson, to process every element without writing a separate line for each one:

dcl-s i int(10);

for i = 1 to 4;
  dsply regionNames(i);
endfor;

Why It Matters

Arrays let a program work with a whole group of related values using a single name and a changing index, rather than declaring a separate, individually named variable for every single value. This becomes especially useful together with a loop, letting you process every element with one small block of code instead of repeating the same statement many times by hand.

Practical Example

Imagine a program that needs to display four region names. Without an array, this would mean declaring four separate variables and writing four separate dsply statements. Using an array combined with a for loop, as shown above, the same four values are declared under a single name and displayed using one small loop, regardless of how many elements the array actually holds.

This is a simplified, illustrative example rather than a specific real program, but it reflects a genuinely common, practical reason RPGLE developers reach for arrays together with loops.

Common Confusions

"Does an array index start at 0, like in some other programming languages?" No. RPGLE array indexes start at 1. The first element is arrayName(1), not arrayName(0).

"Can an array hold more elements than its declared size?" No. An array's size, set with dim(n), is fixed when it is declared. Trying to access an index beyond that size, such as index 5 on an array declared with dim(4), is an error rather than something the array automatically expands to allow.

"Do all elements of an array have to be filled in before the array is used?" Not necessarily, but any element you have not explicitly assigned a value to will hold a default value based on its data type, such as blanks for character elements, rather than a value you have intentionally set.

Quick Recap

• An array is declared by adding dim(n) to a variable declaration, where n is the number of elements it holds.
• Individual elements are accessed using the array's name followed by an index in parentheses, such as regionNames(1).
• RPGLE array indexes start at 1, not 0.
• Arrays are commonly combined with loops to process every element without repeating the same statement for each one by hand.

Try Asking the AI Tutor

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

• "What happens if I try to access an array index beyond its declared size?"
• "Can I use %LEN or %TRIM on an individual array element the same way I would on a regular variable?"