What is a Printer File in IBM i?

Learning Objective

By the end of this lesson, you will understand what a printer file is, how it fits alongside the physical, logical, and display files you already know about, and what its output typically becomes.

Simple Explanation

You have already learned that a physical file stores business data, and that a display file, a kind of workstation file, describes a 5250 screen's layout. A printer file is a third kind of IBM i file object, type *FILE, that describes the layout of printed or report output instead: what appears on a printed page, line by line.

Like physical and display files, a printer file is defined using DDS, the same Data Description Specifications syntax covered in the DDS and SQL: Two Ways to Define Db2 for i Data lesson, though a printer file's DDS describes printed report lines rather than stored data or a screen. A printer file is declared with the device type PRINTER, just as a physical file uses DISK and a display file uses WORKSTN.

An RPGLE program does not format a printed page directly. Instead, it works with a printer file, which handles the actual layout, and the program's output generally becomes a spool file, the generated output artifact introduced in the Job Logs and Spool Files Basics lesson, rather than paper coming out of a printer immediately.

Why It Matters

Understanding that printed reports come from a printer file object, separate from the RPGLE program that writes to it, mirrors the same division of responsibility already covered for display files: the file object defines layout, while the program focuses on the business logic of what data to report. This separation is exactly why the same basic report pattern shows up across countless IBM i business applications.

Practical Example

Imagine a program that needs to print a daily list of customer balances, using the CUSTMAST physical file. A printer file object defines how each line of that report should look, headings, columns, and spacing. The RPGLE program reads through CUSTMAST's records and writes each one to the printer file, and IBM i produces a spool file containing the finished report, ready to be viewed or actually printed.

This is a simplified, illustrative example rather than a specific real report, but it reflects the basic shape of how printed reports are produced on IBM i.

Common Confusions

"Is a printer file the same thing as a physical file?" No. Both share the *FILE object type, but a physical file stores actual business data, while a printer file describes the layout of printed output. Neither one stores the other's kind of information.

"Does writing to a printer file immediately print something on paper?" Not directly. A program's output to a printer file generally becomes a spool file first, as covered in the Job Logs and Spool Files Basics lesson, and the Spool Files and Output Queues lesson later in this group covers what happens to that spool file next.

"Is a printer file the same kind of file as a display file?" Not quite. Both are defined with DDS and both describe output rather than storing business data, but a display file describes an interactive 5250 screen, while a printer file describes printed report output; they use different device types, WORKSTN and PRINTER, for exactly this reason.

Quick Recap

• A printer file is an IBM i object, type *FILE, that describes the layout of printed or report output, defined using DDS.
• A printer file uses the device type PRINTER, just as physical files use DISK and display files use WORKSTN.
• An RPGLE program works with a printer file rather than formatting a printed page directly itself.
• Writing to a printer file generally produces a spool file, rather than immediately printing on paper.

Try Asking the AI Tutor

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

• "Why would IBM i produce a spool file instead of printing immediately?"
• "Can one RPGLE program write to more than one printer file?"