These are the different versions of the evolution of the code. Over the years there have been improvements to the commands and operation codes to simplify the coding process. Over the years the L1, L2.. indicators became obsolete.. New commands have been added as well as API’s and built in functions ( BIF’s) that did things like sub-string, scan, trim to name a few. Then with the ability to run embedded SQL we have RPG Free to allow free form coding. Gone are the days of having to code in specific columns ans use a format like most other languages This make integration much easier..