Guidelines for routines in Add-On Instructions

Routines must be named according to what they represent. Name a logic routine Logic(), and name a prescan routine prescan().
Routines within add-on instructions cannot have parameters nor routine-scoped tags. Tags can only be defined in the AOI.
Routines within an AOI cannot have parameters even through the parentheses () are required for the routine declaration.
Routines within an AOI cannot contain routine-scoped tags. Tags can only be declared within the AOI itself.
You can declare a routine outside of the AOI in the same file or in another file.
To declare a routine as external to the AOI, add the
extern
keyword before the
routine
keyword.
External routines have two parts:
The declaration of the external routine within the AOI. For example:
The routine implementation itself. For example:

        extern routine [name] ();
        [aoi name].[routine name] () { 
          < content> 
        }