RPG
IBM's primary programming language for AS400 and IBM i. Report Program Generator, now evolved into a modern structured language (ILE RPG / RPGLE) still in active use.
RPG (Report Program Generator) is the primary application development language for the AS400 and IBM i platform. Originally designed for business report generation in the 1960s, RPG was adapted for the System/38 and AS400 in the 1980s as RPG III. IBM introduced RPG IV (also called ILE RPG or RPGLE) with OS/400 V3R2 in 1994, transforming RPG into a fully structured, free-format programming language with modern capabilities. ILE RPG supports free-format syntax (similar to modern languages), procedures, service programs, and integration with APIs, SQL, and web services. The language remains central to IBM i application development. Thousands of business applications running on IBM i today were written in RPG and have been maintained and extended across decades. Finding RPG developers is frequently cited as a workforce challenge for IBM i shops, as university computer science programs rarely include RPG in curriculum.