What Is Data Structure in AS400?


Larry Thompson

Data structure is a fundamental concept in AS400, which plays a crucial role in organizing and storing data efficiently. It provides a way to represent complex data types and relationships between various elements. Understanding data structures is essential for AS400 programmers to design and develop robust applications.

What is Data Structure?

Data structure refers to the way data is organized, stored, and managed in a computer system. It defines the relationship between different data elements, their organization, and the operations that can be performed on them. In AS400, data structures are used to define the layout of records or files.

Types of Data Structures in AS400

In AS400, there are various types of data structures available:

  • Flat Data Structure: A flat data structure consists of individual fields or variables without any hierarchical relationship.
  • Arrays: An array is a collection of elements of the same type that are accessed by an index or subscript.
  • Data Structures: A data structure can contain multiple fields or variables grouped together under a single name.
  • Files: Files are used to store related records in a structured manner.

Data Structure Definition

In AS400, you can define a data structure using the DCL-DS (Declare Data Structure) keyword. This keyword allows you to specify the name of the data structure and its components along with their attributes.

The syntax for defining a data structure is as follows:

DCL-DS DataStructureName;
   Field1 DataType;
   Field2 DataType;
   FieldN DataType;

Here, DataStructureName is the name of the data structure, and Field1, Field2, etc., are the individual fields or variables within the data structure.

Working with Data Structures in AS400

Data structures provide a convenient way to group related data elements together. They can be used to pass multiple values as parameters to subroutines or functions. Data structures can also be used to define the layout of files and records.

To access individual fields within a data structure, you can use dot notation. For example, if you have a data structure named Employee with fields Name, Age, and Salary, you can access them as Employee.Name, Employee.Age, and Employee.Salary.

You can also define nested data structures where one data structure is included within another. This allows for more complex relationships between data elements.

The Importance of Data Structures in AS400 Programming

Data structures play a critical role in AS400 programming as they provide a structured way to organize and manipulate data. By using data structures, programmers can improve code readability, maintainability, and efficiency.

  • Better Organization: Data structures help in organizing related data elements together, making it easier to understand and maintain the code.
  • Data Integrity: By defining the layout of files using data structures, programmers ensure that the stored data is consistent and accurate.
  • Easier Maintenance: With well-defined data structures, it becomes simpler to modify or extend existing code without affecting other parts of the program.
  • Efficient Memory Usage: Data structures optimize memory usage by grouping related data elements together, reducing the overall memory footprint.

Overall, data structures are an essential aspect of AS400 programming, enabling developers to build robust and efficient applications.


Data structures in AS400 provide a way to organize and manage data efficiently. They help in defining the relationship between different data elements and improve the readability and maintainability of code. By using various types of data structures, programmers can design robust applications that make optimal use of system resources.

So, next time you work on an AS400 project, remember to leverage the power of data structures to streamline your code!

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