In this module, we will delve into the concept of service programs and procedures in RPG IV. Service programs are a powerful feature in RPG IV that allow you to modularize your code, making it more reusable and maintainable. Procedures, on the other hand, are blocks of code that perform specific tasks and can be called from other parts of your program.

1. Service Programs:

   • Definition and purpose
   • Benefits of using service programs
   • Creating and managing service programs

2. Procedures:

   • Definition and purpose
   • Types of procedures (subprocedures and main procedures)
   • Creating and calling procedures

3. Binding Directories:

   • Definition and purpose
   • Creating and using binding directories

4. Practical Examples:

   • Step-by-step guide to creating a service program
   • Example of defining and calling procedures

5. Exercises:

   • Practical exercises to reinforce the concepts

A service program in RPG IV is a collection of procedures that can be used by other programs or service programs. It allows you to encapsulate functionality in a modular way, promoting code reuse and easier maintenance.

• Modularity: Break down complex programs into smaller, manageable pieces.
• Reusability: Share common functionality across multiple programs.
• Maintainability: Easier to update and maintain code.

To create a service program, you need to follow these steps:

1. Define the Procedures: Write the procedures that will be included in the service program.
2. Create a Module: Compile the source code into a module.
3. Create the Service Program: Bind the module(s) into a service program.
4. Use Binding Directories: Optionally, use binding directories to manage the service program.

A procedure is a block of code that performs a specific task. Procedures can be defined within a program or in a service program and can be called from other parts of the program.

• Subprocedures: Procedures defined within a module or service program.
• Main Procedures: The main entry point of a program.

Example: Defining a Procedure

Example: Calling a Procedure

A binding directory is a list of modules and service programs that can be used during the binding process. It simplifies the management of dependencies.

Example: Creating a Binding Directory

Example: Using a Binding Directory

1. Write the Procedures: Create a source file with the procedures.
2. Compile the Module: Use the CRTRPGMOD command to compile the module.
3. Create the Service Program: Use the CRTSRVPGM command to create the service program.
4. Use the Service Program: Call the procedures from other programs.

Example: Creating a Service Program

1. Write the Procedures:

2. Compile the Module:

3. Create the Service Program:

4. Use the Service Program:

1. Write a procedure that multiplies two numbers.
2. Compile the procedure into a module.
3. Create a service program from the module.
4. Write a program that calls the procedure from the service program.

Solution

1. Write the Procedure:

2. Compile the Module:

3. Create the Service Program:

4. Write the Program:

1. Create a binding directory.
2. Add the service program to the binding directory.
3. Use the binding directory in a program.

Solution

1. Create a Binding Directory:

2. Add the Service Program:

3. Use the Binding Directory:

In this module, we explored the concepts of service programs and procedures in RPG IV. We learned how to create and manage service programs, define and call procedures, and use binding directories to manage dependencies. By modularizing your code with service programs and procedures, you can create more maintainable and reusable applications. In the next module, we will delve into integrating RPG with modern technologies, such as web services and APIs.