RPGLE Basic Interview Questions

What This Lesson Prepares You For

This lesson works through common beginner-level RPGLE interview questions: the kind that check whether you understand program structure, variables, control flow, and built-in functions well enough to explain them clearly, not just recognize them on a screen.

Concepts to Revise First

• RPGLE program structure, from the RPGLE Program Structure lesson.
• Variables and data types, from the Variables and Data Types in RPGLE lesson.
• IF/ELSE and SELECT/WHEN/OTHER, from their respective lessons.
• DO loops and basic iteration, from the DO Loops and Basic Iteration in RPGLE lesson.
• Built-in functions, from the Built-in Functions in RPGLE lesson.

Common Interview Questions

• "What does free-format RPGLE look like compared to older fixed-format RPG?"
• "What is the difference between dcl-s and a data structure field?"
• "When would you use SELECT/WHEN instead of a chain of IF/ELSEIF statements?"
• "What does *INLR = *ON; actually do?"
• "What is a built-in function, and can you name one you have used?"

Good Beginner-Level Answers

For "what does *INLR = *ON; do?", a strong beginner answer is: "Setting *INLR on tells the system this program is done and its resources, like open files, should be closed when the program ends. Without it, the program can leave things in a state that causes problems the next time it is called." This shows you understand the purpose, not just that the line exists.

For "when would you use SELECT/WHEN instead of IF/ELSEIF?", a good answer is: "When I am checking the same variable against several possible values, SELECT/WHEN reads more clearly than a long chain of ELSEIFs checking the same thing over and over."

Scenario-Based Questions

• "You have a dcl-s packed field meant to hold a dollar amount, but a calculation is producing a value that looks truncated. What would you check first?"
• "A DOW loop that is supposed to process records until end-of-file never stops. What is the most common reason for that?"
• "You are asked to replace a long IF/ELSEIF chain that all checks one status code field. What would you change it to, and why?"

How to Explain Your Thinking

For the packed-field truncation scenario, a good structure for your answer is: name the likely cause first, then explain why. For example: "The most likely cause is the field's defined decimal precision, packed (9:2) for example, being too small for the actual result, so I'd check the field's declared length and decimal positions before assuming the calculation logic itself is wrong." This shows you check the data definition before assuming the logic is broken, a genuinely useful habit in real RPGLE work.

Common Weak Answers to Avoid

• Saying "I'd just look at the code" without naming what specifically you would look for first.
• Describing SELECT/WHEN and IF/ELSEIF as "basically the same thing" without explaining when one reads more clearly than the other.
• Forgetting that an infinite DOW loop is usually caused by the variable being checked never actually changing inside the loop, not by the loop syntax itself.

Practical Examples

dcl-s custStatus char(1);

select;
  when custStatus = 'A';
    // active customer handling
  when custStatus = 'H';
    // on-hold customer handling
  when custStatus = 'C';
    // closed customer handling
  other;
    // unexpected status value
endsl;

This is exactly the kind of small snippet worth being able to explain out loud: SELECT/WHEN here reads more clearly than three separate IF statements all checking custStatus, and the OTHER branch handles any status value that was not explicitly expected, rather than silently doing nothing.

Mini Practice Task

Write a short DOW loop, on paper or in a text editor, that reads through a list of five hard-coded status codes stored in an array and counts how many are 'A'. Then explain out loud, as if to an interviewer, why the loop eventually stops.

Quick Recap

• Beginner RPGLE interview questions usually test whether you understand program structure and control flow, not just whether you recognize syntax.
• Explaining why a piece of code works, not just what it does, is what separates a strong answer from a memorized one.
• The most common weak answer is skipping the "why" and only restating the "what."

Try Asking the AI Tutor

Use the AI Tutor to practice these questions out loud. For example, try asking:

• "Can you ask me a few beginner RPGLE interview questions about SELECT/WHEN and DO loops, one at a time?"
• "How would I explain the difference between dcl-s and a data structure field in an interview?"