Complex sentence: IBM i, formerly known as i5/OS is an operating system used on IBM Power Systems, descendant of the OS/400 operating system introduced with the AS/400 computer system in 1988.
Split into simpler sentences: IBM i, formerly known as i5/OS and OS/400, is an operating system used on IBM Power Systems. The OS/400 operating system was introduced with the AS/400 computer system in 1988.