OS/400 - technical definition

The operating system for the iSeries family of midrange computers from IBM. Introduced in 1988 for the AS/400 (renamed iSeries in 2000), the OS/400 communicates with the hardware through the Licensed Internal Code (LIC) layer, which includes the device drivers. In 2004, OS/400 was renamed i5/OS to coincide with the eServer i5 models introduced in that same year. See i5/OS and iSeries.