Creating RPGLE Modules with CRTRPGMOD

Learning Objective

By the end of this lesson, you will be able to compile free-format RPGLE source into a module using CRTRPGMOD, and explain exactly what that command does and does not produce.

Simple Explanation

CRTRPGMOD (Create RPG Module) compiles RPGLE source into a *MODULE object. It behaves like any other RPGLE compile in terms of checking your syntax and reporting compile errors, but the object it produces is a module, not a program: the result cannot be called or run on its own, exactly as covered in the previous lesson.

**free
ctl-opt nomain;

dcl-proc isValidCustNbr export;
  dcl-pi *n ind;
    custNbr packed(6:0) const;
  end-pi;

  return custNbr > 0;
end-proc;

This small module contains one procedure, isValidCustNbr, that returns whether a customer number looks valid. Notice ctl-opt nomain; at the top: it tells the compiler this module has no main procedure of its own, since its only purpose is to offer isValidCustNbr to whatever binds it in later. The export keyword is covered in depth in the Internal Procedures vs Exported Procedures lesson later in this batch.

To compile this into a module:

CRTRPGMOD MODULE(MYAPPLIB/CUSTVAL) SRCFILE(MYAPPLIB/QRPGLESRC)

Why It Matters

Compiling to a module first, rather than straight to a program, is what makes the module reusable across more than one program later. Getting comfortable with CRTRPGMOD as its own distinct step is the foundation for the binding lessons that follow.

Practical Example

Imagine writing the isValidCustNbr logic once, compiling it with CRTRPGMOD into CUSTVAL, and knowing that this single compiled module can later be bound into a customer inquiry program, a customer maintenance program, or a shared service program, without ever needing to recompile the validation logic itself again for each one.

Common Confusions

"Can I call a module directly, like CALL PGM(CUSTVAL)?" No. A module is not a program, and there is no way to call it directly. It has to be bound into a program or service program first, using CRTPGM or CRTSRVPGM.

"Does CRTRPGMOD report compile errors differently from a normal RPGLE compile?" No. The compile listing and diagnostics work the same way you are already used to; the only real difference is the type of object produced at the end, *MODULE instead of *PGM.

"What happens if I compile a module and never bind it into anything?" Nothing runs it. It simply exists as an unused *MODULE object, taking up space, until something actually binds it into a program or service program.

Quick Recap

• CRTRPGMOD compiles RPGLE source into a *MODULE object.
• A module cannot be called or run directly; it must be bound into a program or service program afterward.
• ctl-opt nomain; marks a module as having no main procedure of its own, appropriate for a module meant purely to be bound in and called by something else.
• Compile errors and diagnostics work the same as any other RPGLE compile.

Try Asking the AI Tutor

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

• "What would happen if I left out ctl-opt nomain on a module meant to be bound into a program?"
• "Can one QRPGLESRC source file contain the source for more than one module?"