Picking up user keyboard interactions in RPG is easy

But as usual there are many ways of doing it. Three main techniques are

(1) Assign a numeric value to the function keys

Probably the most common is to assign an indicator value to a function so that CMD01 sets on *IN01, CMD02 sets on *IN02 and so on.

(2) Leave the internal indicators for function keys

I see this a lot and I still sometimes use it if my program has simple function key handling. Basically, if you do not assign a numeric indicator to the function key, good ole’ IBM i will assign a free one for us. Namely CMD01 sets on *INKA, CMD02 sets on *INKB, CMD03 sets on *INKC and so on. But… but… beware of the missing alphabet letters 😉

(3) Indicators smell. Dont use them

Define an information data structre in a /copybook and then you can reuse this simple technique where you like. This is my preferred technique.

dcl-f dspf workstn infds(dspfinfo);

 // Use INFDS to pickup the AID value (hex value for keypresses)
 dcl-ds dspfinfo;
 pressedKey char(1) pos(369);
 end-ds;

 // Define Constants with HEX value of keypresses
 dcl-c PF1 const(x'31');
 dcl-c PF2 const(x'32');
 dcl-c PF3 const(x'33');
 dcl-c PF4 const(x'34');
 dcl-c PF5 const(x'35');
 dcl-c PF6 const(x'36');
 dcl-c PF7 const(x'37');
 dcl-c PF8 const(x'38');
 dcl-c PF9 const(x'39');
 dcl-c PF10 const(x'3A');
 dcl-c PF11 const(x'3B');
 dcl-c PF12 const(x'3C');
 dcl-c PF13 const(x'B1');
 dcl-c PF14 const(x'B2');
 dcl-c PF15 const(x'B3');
 dcl-c PF16 const(x'B4');
 dcl-c PF17 const(x'B5');
 dcl-c PF18 const(x'B6');
 dcl-c PF19 const(x'B7');
 dcl-c PF20 const(x'B8');
 dcl-c PF21 const(x'B9');
 dcl-c PF22 const(x'BA');
 dcl-c PF23 const(x'BB');
 dcl-c PF24 const(x'BC');
 dcl-c Clear const(x'BD');
 dcl-c Enter const(x'F1');
 dcl-c Help const(x'F3');
 dcl-c Up const(x'F4');
 dcl-c Down const(x'F5');
 dcl-c Print const(x'F6');
 
 Exfmt Screen;
 
 If pressedKey = Enter;
 // do some ENTER stuff
 else pressedKey = Help;
 // do some HELP stuff
 else pressedKey = PF03;
 // Exit or something?
 Else;
 // ... do other stuff for other keys
 EndIf;