How Do You Define an External Data Structure in Rpgle Free Format?

How Do You Define an External Data Structure in Rpgle Free Format?

Defining an external data structure in RPGLE free format involves using the DCL-DS (Declare Data Structure) statement. This statement is used to define a data structure that maps to an externally described file or record format.

Let’s dive deeper into how you can define an external data structure in RPGLE free format.

1. Understanding External Data Structures

Before we go into the syntax and examples, let’s first understand what external data structures are. An external data structure is a way to define a complex data type that matches the layout of an externally described file or record format.

Using an external data structure allows you to work with multiple fields of different types as a single unit, making it easier to manipulate and access the data within the file or record format.

2. Syntax for Defining External Data Structures

To define an external data structure in RPGLE free format, you would use the following syntax:

DCL-DS DataStructureName EXTNAME(ExternalFileName);
  DataFields..
END-DS;

DataStructureName:

A unique name given to the external data structure.

ExternalFileName:

The name of the externally described file or record format.

DataFields:

The individual fields within the external data structure.

3. Example: Defining an External Data Structure

Let’s say we have an externally described file named “CUSTOMER” with the following layout:

     A          R CUSTOMER                   TEXT('Customer Record')
     A                                      TEXT('Customer ID')
     A            CUS_ID        5S 0
     A                                      TEXT('Customer Name')
     A            CUS_NAME     30A
     A                                      TEXT('Customer Address')
     A            CUS_ADDR1    30A
     A            CUS_ADDR2    30A

To define an external data structure that maps to this file, you would use the following RPGLE free format code:

DCL-DS CustomerDS EXTNAME('CUSTOMER');
  Cus_ID   Packed(5:0);
  Cus_Name Char(30);
  Cus_Addr1 Char(30);
  Cus_Addr2 Char(30);
END-DS;

In the above example, we declared an external data structure named “CustomerDS” using the EXTNAME keyword, which specifies that it matches the layout of the “CUSTOMER” file. The subsequent lines define the individual fields within the data structure, matching their types and lengths as defined in the file.

4. Using External Data Structures

Once you have defined an external data structure, you can use it just like any other data type in your RPGLE program. You can assign values to its fields, retrieve values from them, and perform operations using the defined data structure.

For example, you can assign a value to a field within the external data structure using syntax like this:

CustomerDS.Cus_ID = 1001;

You can also retrieve the value of a field within the external data structure using syntax like this:

CustID = CustomerDS.Cus_ID;

By using external data structures, you can simplify your RPGLE code and make it more readable and maintainable. They provide a convenient way to work with complex data types that match the layout of externally described files or record formats.

Conclusion

In RPGLE free format, defining an external data structure involves using the DCL-DS statement with the EXTNAME keyword. This allows you to create a complex data type that maps to an externally described file or record format.

By utilizing external data structures, you can enhance the readability and maintainability of your RPGLE code while working with complex data types.