The RPG IV source specification layouts differ significantly from the System/38™ environment RPG III and the OPM RPG/400 layouts. For example, the positions of entries on the specifications have changed and the types of specifications available have also changed. The RPG IV specification layouts are not compatible with the previous layouts. To take advantage of RPG IV features, you must convert RPG III and RPG/400 source members in your applications to the RPG IV source format.
If you are in a hurry and want to get started, go to Converting Your Source and follow the general directions.