Formerly an abbrev. for report program generator. A programming language used in commercial data processing for extracting information from files. The input to an RPG consists of a description of the file structure, a specification of the information required, and of its layout on the page. From this information, the RPG constructs a program to read the file, extract the desired information, and format it in the required manner. The current version is RPG IV, also called ILE RPG.
http://publib.boulder.ibm.com/infocenter/iseries/v5r4/topic/books/sc092507.pdf The ILE RPG Programmer's Guide