Definition
RPG (Report Program Generator) is the programming language most IBM i business applications were built in, and modern RPG IV, including its free-form syntax, remains actively supported and actively used. Decades of order processing, inventory, finance, and manufacturing logic live in RPG programs that have been tuned and corrected through years of real production use.
Buyers evaluating modernization or AI options often assume RPG is an obstacle to work around. In practice it is usually the opposite: RPG applications can be extended with web front ends, exposed through APIs, and connected to AI tools without touching the underlying logic, which is why so much IBM i modernization work leaves the RPG layer alone on purpose.