Use function Keys without Response Indicators:

A lot of programmers standardize on indicator usage for function keys within display file programs, e.g. *IN01 for F1, *IN03 for F3, etc, which is fine and readable if weare aware of the convention being used.
However, if we want to cut down on the number of indicators used in the program and make it easier to read and maintain then weshould code the display files not to use response indicators and make use of the device dependent I/O feedback area of the File Information Data Structure instead.
Position 369 of the File Information Data Structure for display files contains a hex byte that represents the function key (or other grey key) pressed by the user.
By coding field @FNKEY in this position of the INFDS and then defining text constants for the appropriate function key value, we can test for the use of function keys within the programs by using:
@FNKEY IFEQ $F5
...
...
ENDIF

as opposed to:

*IN05 IFEQ *ON
...
...
ENDIF
The source snippets below show the coding needed within the RPG/400 program to use this technique.
Code
RPG SOURCE SNIPPET
==================

FWORKSTN CF E WORKSTN KINFDS INFDS
F* Display File
F*----------------------------------------------------------------
IINFDS DS
I 369 369 @FNKEY
I* Function key values
I X'31' C $F1
I X'32' C $F2
I X'33' C $F3
I X'34' C $F4
I X'35' C $F5
I X'36' C $F6
I X'37' C $F7
I X'38' C $F8
I X'39' C $F9
I X'3A' C $F10
I X'3B' C $F11
I X'3C' C $F12
I X'B1' C $F13
I X'B2' C $F14
I X'B3' C $F15
I X'B4' C $F16
I X'B5' C $F17
I X'B6' C $F18
I X'B7' C $F19
I X'B8' C $F20
I X'B9' C $F21
I X'BA' C $F22
I X'BB' C $F23
I X'BC' C $F24
I X'BD' C $CLEAR
I X'F1' C $ENTER
I X'F3' C $HELP
I X'F4' C $RLLDN
I X'F5' C $RLLUP
I X'F4' C $PAGUP
I X'F5' C $PAGDN
I X'F6' C $PRINT
I X'F8' C $BCKSP
I X'3F' C $AUTO
I*----------------------------------------------------------------
C ...
C ...
C EXFMTxxxxxxxx
C*
C* Process function keys...
C*
C SELEC
C @FNKEY WHEQ $F1
C EXSR HELP
C @FNKEY WHEQ $F3
C ..
C ...
C @FNKEY WHEQ $ENTER
C ...
C ENDSL
C*----------------------------------------------------------------

DDS SOURCE SNIPPET
==================
A R DSPFMAT
A CF01
A CF03
A PAGEDOWN
A etc...