Display File Record Formats

Learning Objective

By the end of this lesson, you will understand what a record format means in the context of a display file, and how it differs from the single record format a physical file has.

Simple Explanation

In the Physical Files Explained in Depth lesson, you learned that a physical file has exactly one record format, describing every field in its records. A display file also uses record formats, but the idea works a little differently here: a display file commonly has more than one record format, and each one typically represents a distinct screen, or a distinct section of a screen, rather than a single, consistent shape every stored record follows.

For example, a single display file built for a customer inquiry application might have:

• One record format for the initial screen where a user enters a customer number.
• A separate record format for the results screen showing that customer's name and balance.
• Possibly another record format for an error screen shown if the customer number was not found.

Each of these record formats is defined separately within the same display file's DDS, and an RPGLE program chooses which record format to show at a given moment, depending on what the program needs the user to see next.

Why It Matters

Understanding that a display file can hold multiple record formats explains how a single display file object can support an entire, multi- screen interaction, an inquiry screen, a results screen, an error screen, rather than needing a completely separate display file for every distinct screen a user might see. This is a meaningful difference from physical files, where "exactly one record format" was a firm rule.

Practical Example

Imagine the customer inquiry screen flow described in earlier lessons in this group. One display file could define an INQFMT record format for the initial customer-number entry screen and a separate RESULTFMT record format for the results screen showing that customer's details. The RPGLE program driving this interaction shows INQFMT first, and, once it has looked up the customer, shows RESULTFMT instead, both coming from the same display file object.

This is a simplified, illustrative example rather than a specific real application, but it reflects a very common, practical way display files are organized to support a multi-screen interaction.

Common Confusions

"Does every display file need more than one record format?" No. A very simple display file might only need one record format, if it only ever shows a single, unchanging screen. Multiple record formats become useful once an interaction involves more than one distinct screen or screen state.

"Is this the same 'record format' idea covered for physical files?" It is the same general term, a named structure describing a set of fields, but the details differ meaningfully: a physical file's single record format describes stored data records, while a display file's record formats each typically describe a distinct screen or screen section, and a display file is not limited to only one.

"Does having more than one record format mean the display file stores more than one kind of data?" No. A display file does not store business data the way a physical file does at all; its record formats describe screen layout and the fields shown or entered on that screen, not stored records.

Quick Recap

• A display file commonly has more than one record format, each typically representing a distinct screen or screen section.
• This differs from a physical file, which has exactly one record format describing its stored data records.
• An RPGLE program chooses which of a display file's record formats to show at a given moment.
• Multiple record formats let one display file object support a full, multi-screen interaction.

Try Asking the AI Tutor

Use the AI Tutor to ask follow-up questions about this lesson. For example, try asking:

• "How does an RPGLE program actually choose which record format to show?"
• "Can two different record formats in the same display file share some of the same fields?"