Creating a Module Object

A module is a nonrunnable object (type *MODULE) that is the output of an ILE compiler. It is the basic building block of an ILE program.

An ILE RPG module consists of one or more procedures, and the file control blocks and static storage used by all the procedures in the module. The procedures that can make up an ILE RPG module are:

• an optional cycle-main procedure which consists of the set of H, F, D, I, C, and O specifications that begin the source. The cycle-main procedure has its own LR semantics and logic cycle; neither of which is affected by those of other ILE RPG modules in the program.
• zero or more subprocedures, which are coded on P, D, and C specifications. Subprocedures do not use the RPG cycle. A subprocedure may have local storage that is available for use only by the subprocedure itself. One of the subprocedures may be designated as a linear-main procedure, if a cycle-main procedure is not coded.

The main procedure (if coded) can always be called by other modules in the program. Subprocedures may be local to the module or exported. If they are local, they can only be called by other procedures in the module; if they are exported from the module, they can be called by any procedure in the program.

Module creation consists of compiling a source member, and, if that is successful, creating a *MODULE object. The *MODULE object includes a list of imports and exports referenced within the module. It also includes debug data if you request this at compile time.

A module cannot be run by itself. You must bind one or more modules together to create a program object (type *PGM) which can then be run. You can also bind one or more modules together to create a service program object (type *SRVPGM). You then access the procedures within the bound modules through static procedure calls.

This ability to combine modules allows you to:

• Reuse pieces of code. This generally results in smaller programs. Smaller programs give you better performance and easier debugging capabilities.
• Maintain shared code with little chance of introducing errors to other parts of the overall program.
• Manage large programs more effectively. Modules allow you to divide your old program into parts that can be managed separately. If the program needs to be enhanced, you only need to recompile those modules which have been changed.
• Create mixed-language programs where you bind together modules written in the best language for the task required.

For more information about the concept of modules, refer to ILE Concepts.