The IBM System/38 was introduced in November 1979 as a minicomputer for general business and departmental use. It was replaced by the AS/400 midrange computer in 1988 and later rebranded as the eServer iSeries in 2000. It was renamed in 2006 as the IBM System i until April 2008 when it was replaced by the IBM Power Systems line. It uses an object-based operating system called IBM i. The operating system has undergone name changes in accordance with the rebranding of the IBM server line. Initially, it was called OS/400 (following the name schema that gave birth to OS/2 and OS/390). Later on became known as i5/OS in line with the introduction of the eServer i5 servers featuring POWER5 processors. Finally, it was called just IBM i coinciding with the 6.1 release.

Features include a DBMS (DB2/400), a menu-driven interface, multi-user support, dumb terminal support (IBM 5250), printers, as well as security, communications and web-based applications, which could be executed either inside the (optional) IBM WebSphere application server or in PHP/MySQL[1] using a native port of the Apache web server.

While in Unix-like systems “everything is a file”, on the System i everything is an object, with built-in persistence and garbage collection. It also offers Unix-like file directories using the Integrated File System.[2] Java compatibility is implemented through a native port of the Java virtual machine.