The operating system for the IBM System/360, introduced in 1964. OS/360 was later released in two versions: OS/MFT (Multiple Fixed Transactions) supported multiple programs that used fixed memory regions, and OS/MVT (Multiple Variable Transactions) supported varying program sizes. OS/MFT and OS/MVT were later enhanced for virtual storage and became OS/VS1 and OS/VS2. OS/VS2 evolved into MVS. See
System/360 and
MVS.