Section 14.11: New Types Up Chapter 14: Extensions Section 14.13: Passing IDs  

14.12 Variable IDs

You can specify and reference all 4GL objects in the.
_variable (str) is used to replace hard coded identifiers. e.g for PREPARE statements or CURSOR names or WINDOW names
So
OPEN WINDOW w1 at at 1,1 WITH 10 ROWS, 10 COLUMNS
could be written as
LET lv_str="w1"
OPEN WINDOW _variable(lv_str) at at 1,1 WITH 10 ROWS, 10 COLUMNS
Might seem a little unnecessary at first - but what if you wanted to open 20 windows ?
 Section 14.11: New Types Up Chapter 14: Extensions Section 14.13: Passing IDs