Mini Project: Customer Inquiry Program

What We Are Building

A small, complete interactive RPGLE program: a 5250 screen where a user types a customer number and sees that customer's name and balance. This project combines a display file, a native keyed lookup, and basic error handling into one working program, CUSTINQR.

Business Scenario

Imagine a customer service representative on the phone with a customer who wants to know their current balance. Rather than paging through a report, the representative types the customer's number into a simple inquiry screen and sees the answer immediately. This is one of the most common, everyday shapes of an IBM i business program.

Concepts Used

This project brings together, without re-explaining any of them in depth:

• Display files and record formats, from the Display Files lesson group.
• dcl-f and exfmt, from the RPGLE Program Calling a Display File lesson.
• CHAIN and %FOUND, from the CHAIN for Keyed Access and Understanding %FOUND after CHAIN lessons.
• Function keys and indicators, from the Function Keys and Response Indicators in Display Files lesson.

Files and Programs Involved

• CUSTMAST, the existing keyed physical file used throughout this path, with CUSTNBR, CUSTNAME, and CUSTBAL.
• CUSTDSPF, a new display file with one record format, INQFMT, containing an input field for the customer number and output fields for the customer's name and balance.
• CUSTINQR, the RPGLE program tying CUSTDSPF and CUSTMAST together.

Step-by-Step Build Outline

1. Design CUSTDSPF's INQFMT record format: an input field for customer number, output fields for name and balance, and an "F3=Exit" function key indicator, exactly the shape covered in the Basic Inquiry Screen Pattern lesson.
2. Declare both CUSTDSPF and CUSTMAST in CUSTINQR with dcl-f.
3. Loop calling exfmt INQFMT, reading the customer number the user typed.
4. Use CHAIN to look up that customer number in CUSTMAST.
5. Check %FOUND: if found, the shared field names already populate the screen's output fields automatically; if not, set a message indicator, as covered in the Displaying Error Messages on 5250 Screens lesson.
6. Check the F3 indicator each time through the loop to exit cleanly.

Example Code

dcl-f CUSTDSPF workstn;
dcl-f CUSTMAST disk keyed;

dcl-s exitRequested ind;

dow not exitRequested;
  exfmt INQFMT;

  if *in03;
    exitRequested = *on;
  else;
    chain CUSTNBR CUSTMAST;
    if %found(CUSTMAST);
      *in50 = *off;
    else;
      *in50 = *on;
    endif;
  endif;
enddo;

*inlr = *on;

Here, *in50 is a message indicator tied to an error message constant in CUSTDSPF's DDS, shown only when %FOUND comes back false, exactly the pattern covered in the Displaying Error Messages on 5250 Screens lesson.

How to Test It

Test with three cases: a customer number that exists, confirming the name and balance display correctly; a customer number that does not exist, confirming the error message appears instead of stale or blank fields; and pressing F3 immediately, confirming the program exits cleanly without attempting a lookup at all.

Common Mistakes

• Forgetting to check %FOUND before trusting the screen's output fields, covered in the Understanding %FOUND after CHAIN lesson.
• Forgetting keyed on CUSTMAST's dcl-f, which CHAIN requires.
• Checking the F3 indicator only once, outside the loop, instead of on every pass.

Debugging Checklist

If this program does not behave as expected, apply the Basic Troubleshooting Flow for IBM i Developers lesson's flow: check the job log first, then, if it is a runtime problem, use STRDBG and a breakpoint right after the CHAIN, using EVAL to confirm %FOUND's actual value and whether CUSTNBR holds what you expect.

Possible Extensions

A natural next step is adding an update capability, letting the representative change the customer's balance directly from this screen, using UPDATE after a successful CHAIN, exactly as covered in the Updating Records with UPDATE lesson.

Quick Recap

• CUSTINQR combines a display file, CHAIN, and %FOUND into one small, complete inquiry program.
• Checking %FOUND and the F3 indicator on every pass through the loop are both essential.
• Testing should cover a found customer, a not-found customer, and immediate exit.

Try Asking the AI Tutor

Use the AI Tutor to practice extending or troubleshooting this project. For example, try asking:

• "How would I add a second input field to CUSTDSPF for the user to search by customer name instead of number?"
• "What would happen in this program if CUSTMAST were declared without the keyed keyword?"