How Do You Define Data Structure in Rpgle?

How Do You Define Data Structure in Rpgle?

Data structures are an essential part of the RPGLE programming language. They provide a way to define and organize related data fields so that they can be easily accessed and manipulated.

In this tutorial, we will explore the concept of data structures in RPGLE and learn how to define and use them effectively.

Defining a Data Structure

To define a data structure in RPGLE, you need to use the DCL-DS (Declare Data Structure) keyword followed by the name of the data structure. The structure name should start with a letter and can contain letters, numbers, or underscores. Here’s an example:

DCL-DS Customer;
   ID CHAR(10);
   Name CHAR(50);
   Address CHAR(100);
END-DS;

In this example, we have defined a data structure named Customer with three fields: ID, Name, and Address. Each field is defined using the CHAR() keyword followed by the length of the field.

The fields are terminated with a semicolon.

Using a Data Structure

Once you have defined a data structure, you can use it to declare variables or as parameters for procedures or subroutines. To declare a variable using a data structure, you need to specify the name of the structure followed by the variable name. Here’s an example:

DCL-S CustomerRec LIKE(Customer);

In this example, we have declared a variable named CustomerRec using the LIKE() keyword, which tells RPGLE to create a variable with the same structure as the Customer data structure.

Accessing Data Structure Fields

To access the fields of a data structure, you can use dot notation. For example, to assign a value to the ID field of the CustomerRec variable, you can write:

CustomerRec.ID = 'C001';

You can also access the fields of a data structure using subfields. Subfields allow you to access specific parts of a field.

For example, if the Name field contains a full name in the format “First Last,” you can access the first name and last name separately using subfields. Here’s an example:

DCL-S FirstName CHAR(20) INZ;
DCL-S LastName CHAR(20) INZ;

FirstName = %SUBST(CustomerRec.Name: 1: %SCAN(' ': CustomerRec.Name)-1);
LastName = %SUBST(CustomerRec.Name: %SCAN(' ': CustomerRec.Name)+1);

In this example, we have defined two variables, FirstName and LastName, and used the %SUBST() and %SCAN() functions to extract the first name and last name from the Name field of the CustomerRec variable.

Nesting Data Structures

You can also nest data structures within other data structures to create more complex structures. This allows you to organize related data fields into hierarchical structures. Here’s an example:

DCL-DS Order;
   OrderID CHAR(10);
   OrderDate DATE;
   DCL-DS Customer LIKE(Customer);
   DCL-DS Items;
      ItemID CHAR(10);
      Quantity DEC(5, 0);
   END-DS;
END-DS;

In this example, we have defined a data structure named Order that contains fields for OrderID, OrderDate, and a nested Customer data structure. The nested Customer data structure contains fields for ID, Name, and Address.

Additionally, the Order data structure contains another nested data structure named Items, which has fields for ItemID and Quantity.

Closing Thoughts

Data structures in RPGLE provide a powerful way to organize and work with related data fields. By defining and using data structures effectively, you can improve the readability, maintainability, and efficiency of your RPGLE programs.

With the knowledge gained from this tutorial, you are well-equipped to start incorporating data structures into your RPGLE programs.