IF / ELSE in RPGLE

Learning Objective

By the end of this lesson, you will be able to read and write a simple if / elseif / else block in free-format RPGLE, using the comparison operators covered in the previous lesson.

Simple Explanation

In the Expressions and Assignment in RPGLE lesson, you learned about comparison operators such as =, <, and >=. This lesson shows how those comparisons are used together with if to make a program's behavior depend on a condition.

A simple free-format if block looks like this:

dcl-s orderTotal packed(9:2);
dcl-s shippingFee packed(7:2);

orderTotal = 45.00;

if orderTotal >= 50;
  shippingFee = 0;
elseif orderTotal >= 25;
  shippingFee = 5.00;
else;
  shippingFee = 9.99;
endif;

Every if block starts with if, followed by a condition, and ends with endif. The elseif keyword lets you check an additional condition if the first one was false, and else covers whatever case is left when none of the earlier conditions matched. Both elseif and else are optional; a simple if / endif on its own is a complete, valid block.

Only one branch of an if block runs: IBM i checks each condition in order, top to bottom, runs the statements under the first one that matches, and skips the rest.

Why It Matters

Conditional logic is how a program makes decisions rather than always doing exactly the same thing regardless of the data it is working with. Practically every real business rule, applying different shipping fees based on order size, approving or rejecting a request, choosing which message to show, depends on if-style conditional logic at its core.

Practical Example

Imagine the shipping fee example above being used in an order-processing program. For an order total of 45.00, IBM i checks orderTotal >= 50 first, which is false, then checks orderTotal >= 25, which is true, so shippingFee is set to 5.00, and the else branch is skipped entirely.

If the order total had instead been 60.00, the very first condition would have matched, setting shippingFee to 0 and skipping both the elseif and else branches. This is a simplified, illustrative example rather than a specific real shipping policy, but it reflects a very common, everyday use of conditional logic in RPGLE.

Common Confusions

"Do I need an elseif or else in every if block?" No. A simple if / endif, with no elseif or else at all, is completely valid when you only need to handle one specific condition and do nothing otherwise.

"What happens if more than one condition would technically be true?" Only the first matching condition's branch runs. IBM i checks conditions in order, from the first if down through any elseif branches, and stops at the first one that matches, even if a later condition would also have been true.

"Do I need parentheses around the condition, like in some other languages?" No. Free-format RPGLE conditions, such as orderTotal >= 50, do not require surrounding parentheses, though you can use them within a condition to group parts of a more complex expression if needed.

Quick Recap

• An if block starts with if and a condition, and ends with endif.
• elseif checks an additional condition if earlier ones were false; else covers whatever is left; both are optional.
• Only the first matching branch of an if block runs; the rest are skipped.
• Conditional logic is how a program's behavior depends on the data it is actually working with.

Try Asking the AI Tutor

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

• "Can I nest one if block inside another in RPGLE?"
• "What is the difference between using multiple elseif branches and using SELECT / WHEN?"