Printer File DDS Basics

Learning Objective

By the end of this lesson, you will understand how a printer file's DDS describes printed report lines, and how this compares to DDS used for physical and display files.

Simple Explanation

You already know that DDS describes a physical file's stored fields and a display file's screen layout. Printer file DDS uses the same underlying syntax, but describes something different again: the actual lines that will appear on a printed page.

Where a display file's DDS positions fields on a 24-by-80 screen grid, as covered in the Basic Display File DDS Keywords lesson, a printer file's DDS positions text and fields on printed lines instead, describing things like which column a piece of text or a field starts at, and how far down the page one line appears relative to the next. Fields on a printer file can be constant text, such as a column heading printed exactly the same way every time, or variable fields whose actual value the RPGLE program supplies when it writes that line.

Why It Matters

Recognizing that printer file DDS follows the same core DDS ideas already covered, fields, positioning, and record formats, means the DDS knowledge built up across physical and display files transfers directly to reading and understanding printed report layouts, rather than requiring an entirely new mental model.

Practical Example

Imagine the daily customer balance report introduced in the previous lesson. Its printer file DDS might describe a heading line with constant text like "Customer Balance Report" positioned near the top of the page, column headings such as "Customer Number," "Name," and "Balance" positioned above where the actual data will print, and then variable fields for each customer's actual number, name, and balance, positioned in aligned columns below those headings.

This is a simplified, illustrative example rather than exact real DDS syntax, but it reflects the kind of layout information printer file DDS is meant to describe.

Common Confusions

"Is printer file DDS a completely different syntax from physical or display file DDS?" No. It is the same underlying DDS syntax family, describing different things: physical file DDS describes stored fields, display file DDS describes a screen, and printer file DDS describes printed lines. The core idea of describing structure through DDS carries across all three.

"Can a printer file's DDS include constant text, like column headings?" Yes. Constant text that should print exactly the same way every time, such as a report title or column headings, is a normal, common part of printer file DDS, alongside variable fields whose value the program supplies.

"Do I need to specify exactly where every line and field goes on the page?" At a basic level, yes, printer file DDS describes specific positioning, similar in spirit to how display file DDS positions fields on a screen, covered in the Basic Display File DDS Keywords lesson. The full range of detailed positioning options is a more advanced topic beyond this introduction.

Quick Recap

• Printer file DDS uses the same core DDS syntax as physical and display files, but describes printed report lines instead of stored fields or a screen.
• A printer file's fields can be constant text, printed the same way every time, or variable fields whose value the RPGLE program supplies.
• Printer file DDS positions text and fields on the printed page, similar in spirit to how display file DDS positions fields on a screen.
• DDS knowledge from physical and display files transfers directly to reading printer file DDS.

Try Asking the AI Tutor

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

• "How does a printer file know when to start printing on a new page?"
• "Can the same field appear in more than one place on a printed report?"