IBM i

IBM i (formerly known as OS/400 and i5/OS) is the proprietary operating system that runs on IBM Power Systems hardware. It is the successor to the original AS400 (Application System/400) operating system introduced by IBM in 1988. IBM i is designed for business-critical applications and is known for its reliability, security, and object-based architecture. Many manufacturing, distribution, and financial services organizations run core business applications on IBM i that have been in continuous operation for decades. IBM i supports modern development languages and web services while maintaining backward compatibility with legacy applications. The combination of IBM Power hardware and IBM i OS is commonly referred to as AS400 in business settings, even when referring to current Power10 systems.