13. Procedures – ILE RPG in Easy Bytes

In this environment, the calling programs and the called programs are complete in themselves, having been individually compiled. This technique is called a dynamic program call. With this technique, when a program encounters the Callp operation to invoke another program, the system goes looking for the called program dynamically, during runtime, using an internal process known as resolution.

Dcl-proc proc-name {keywords}; … End-proc {proc-name}; Between these instructions, the subprocedure can include the following: A procedure interface Declarations Processing statements (calculations) To understand the basic coding requirements for a procedure, let’s look at an example. The following procedure converts a Fahrenheit temperature value into its Celsius equivalent:

A cycle main program has a main procedure implicitly specified in the main section of the program. In a cycle main program, the main procedure does not have a name; it is the main procedure by virtue of its location in the program code. A cycle main program includes a main source section (the main procedure), followed by zero or more subprocedure sections.

A linear main program explicitly names a procedure to be the main procedure for the program. A linear main program includes a Ctl-opt instruction with the Main keyword to name the main procedure: Ctl-opt Main(proc-name); You then code the main procedure just as any other subprocedure, starting with a Dcl-proc instruction and ending with an End-proc instruction.

They include a main procedure, along with all the other required subprocedures, coded within one source member, or compile unit. ILE also enhances modular programming concepts by allowing you to code a source member that consists of a segment of a program without a main procedure. The resulting Nomain module contains only subprocedures (one or more) that you can combine with other modules to create a program.

The CRTBNDRPG command combines the two program-creation steps: Compile—translate the ILE RPG source member into a machine language module (*Module) object Bind—copy and organize the module to produce a program (*Pgm) object With the introduction of ILE, the system now allows, and sometimes requires, you to separate the compile and binding steps by using two CL commands: CRTRPGMOD (Create RPG Module) CRTPGM (Create Program) When you compile source code with the CRTRPGMOD command, the compiler creates a *Module object, rather than an executable program (*Pgm) object.

pass by reference and pass by read-only reference. You can also use these two methods to pass parameters between procedures. In addition, procedures afford a third method:

Learn how to write ILE RPG IV procedures. Code Nomain procedures; pass parameters by value; use a binding directory and conditional compilation directives.

Every procedure begins with a P-spec and ends with a P-spec. As you might expect, the P-spec has a P in position 6. You name the procedure in positions 7–21 (Name+++++++++++).