In this module, we will explore how to handle files in RPG programming. File handling is a crucial aspect of any programming language, as it allows you to read from and write to files, which is essential for data storage and manipulation.

1. Types of Files:

   • Physical Files: These are the actual files that store data.
   • Logical Files: These are views or indexes on physical files, used to access data in different ways.

2. File Operations:

   • Reading Files: Extracting data from a file.
   • Writing Files: Adding or modifying data in a file.
   • Updating Files: Changing existing data in a file.
   • Deleting Files: Removing data from a file.

3. File Access Methods:

   • Sequential Access: Reading or writing data in a sequential manner.
   • Random Access: Accessing data at any position in the file.

In RPG, files are declared in the File Specification (F-spec) section. Here is an example of how to declare a file:

• F: Indicates a file declaration.
• MYFILE: The name of the file.
• I: Input file.
• F: Full procedural file.
• E: External file.
• K: Keyed file.
• DISK: The file is stored on disk.

To read data from a file, you use the READ operation code. Here is an example:

• READ MYFILE: Reads a record from the file MYFILE.
• %EOF(MYFILE): Checks if the end of the file has been reached.

To write data to a file, you use the WRITE operation code. Here is an example:

• WRITE MYFILE: Writes a record to the file MYFILE.

To update data in a file, you use the UPDATE operation code. Here is an example:

• UPDATE MYFILE: Updates the current record in the file MYFILE.

To delete data from a file, you use the DELETE operation code. Here is an example:

• DELETE MYFILE: Deletes the current record from the file MYFILE.

Let's create a simple program that reads from a file, processes the data, and writes the results to another file.

• FINPUTFILE: Declares the input file.
• FOUTPUTFILE: Declares the output file.
• READ INPUTFILE: Reads a record from the input file.
• DOW NOT %EOF(INPUTFILE): Loops until the end of the input file.
• Name = %TRIMR(Name) + ' Processed': Processes the data.
• Age = Age + 1: Increments the age.
• WRITE OUTPUTFILE: Writes the processed data to the output file.
• *INLR = *ON: Ends the program.

Write a program that reads data from a file and displays it on the screen.

Solution:

Write a program that writes a set of predefined records to a file.

Solution:

• Forgetting to Check for End of File: Always check for the end of the file to avoid infinite loops.
• Incorrect File Declaration: Ensure that the file is declared correctly in the F-spec section.
• *Not Setting INLR: Always set *INLR = *ON at the end of the program to close files properly.

In this section, we covered the basics of file handling in RPG, including how to read, write, update, and delete records in a file. We also provided practical examples and exercises to reinforce the concepts. Understanding file handling is essential for working with data in RPG programs, and mastering these skills will enable you to build more complex and functional applications.