IBM i
Also known as: OS/400, i5/OS, IBM i on Power
IBM's operating system for Power Systems, evolved from the AS400 OS/400. IBM i 7.5 is the current release, actively developed and supported by IBM.
IBM i is the operating system that runs on IBM Power Systems hardware, representing the direct evolution of the AS400's OS/400 and iSeries i5/OS. IBM i integrates the operating system, relational database (DB2 for i), security, and application runtime into a single coherent platform. The IBM i architecture uses a single-level storage model that treats persistent and volatile storage uniformly, which simplifies application development and contributes to the platform's exceptional reliability. IBM i is backward compatible across generations ... applications written for the original AS400 in RPG, COBOL, or CL continue to run on modern IBM Power11 hardware running IBM i 7.5 without modification. IBM i 7.5, the current release, introduces enhanced AI integration, improved open-source support, and modern DevOps tooling alongside its traditional strengths.