Function Keys and Response Indicators

Learning Objective

By the end of this lesson, you will understand how a display file connects a function key press to a numbered indicator, and how an RPGLE program uses that indicator to know what the user did.

Simple Explanation

In the Indicators in Modern RPGLE lesson, you learned that older, numbered indicators such as *IN03 were especially tied to controlling display file screen behavior, though that lesson did not go into the details. This lesson picks up exactly that thread.

A display file's DDS can associate a specific function key with a specific numbered indicator, so that when a user presses that key, IBM i turns the matching indicator on before control returns to the RPGLE program. Common DDS keywords for this include:

• CFxx (Command Function), which allows a function key to be pressed and passes control back to the program along with the matching indicator, without automatically validating the rest of the screen's input first.
• CAxx (Command Attention), similar in spirit to CFxx, generally used for function keys meant to interrupt the current screen immediately, such as a cancel action.

In both keywords, xx is the function key number, so CF03 associates function key F3 with an indicator, commonly *IN03 by convention, matching the indicator number to the function key number for clarity.

Once the RPGLE program regains control after the screen is submitted, it checks the relevant indicator, such as *IN03, to find out which function key the user actually pressed, and decides what to do next based on that.

Why It Matters

Function keys are one of the most common ways a user tells a 5250 screen what to do next, exiting, canceling, requesting help, or moving to another step. Understanding how a display file ties a function key to an indicator, and how an RPGLE program checks that indicator afterward, explains a core part of how interactive 5250 applications actually respond to what a user does.

Practical Example

Imagine the customer inquiry screen from earlier lessons in this group, where the display file's DDS includes CF03 on the inquiry record format, tying function key F3 to indicator *IN03. If the user presses F3 instead of entering a customer number, the RPGLE program, after the screen is submitted, checks if *in03; and recognizes that the user wants to exit, ending the program rather than trying to look up a customer number that was never entered.

This is a simplified, illustrative example rather than a specific real screen, but it reflects a very common, practical pattern for handling function keys in 5250 applications.

Common Confusions

"Does the RPGLE program decide which function keys are active on a screen?" No. Which function keys are active, and which indicator each one is tied to, is defined in the display file's DDS using keywords like CF03, not decided by the RPGLE program itself. The RPGLE program only checks the resulting indicator afterward.

*"Do I have to use IN03 specifically for F3?" No, not strictly, though matching the indicator number to the function key number, such as *IN03 for F3, is a very common, easy-to-follow convention. The specific indicator used is determined by what the DDS associates with that function key.

"What is the real difference between CFxx and CAxx?" Both associate a function key with an indicator, but they are generally used differently: CFxx is commonly used for function keys where the program may still want to see the rest of the screen's entered information, while CAxx is generally used for function keys meant to interrupt the screen immediately, without depending on other fields being filled in correctly.

Quick Recap

• DDS keywords like CF03 and CA03 associate a specific function key with a specific numbered indicator on a display file record format.
• When a user presses that function key, IBM i turns on the matching indicator before returning control to the RPGLE program.
• The RPGLE program checks the relevant indicator, such as *IN03, to find out which function key the user pressed.
• Matching the indicator number to the function key number, like *IN03 for F3, is a common, easy-to-follow convention.

Try Asking the AI Tutor

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

• "When would I choose CAxx instead of CFxx for a function key?"
• "Can more than one function key be active on the same record format at once?"