OS360

OS/360 is IBM's operating system family for the System/360 line of mainframe computers. Announced in 1964 and released in 1966, it was designed to provide a single operating system across the System/360 hardware family, supporting batch processing, multiprogramming, and a range of I/O facilities.

Two major batch-oriented variants, MFT (Multiprogramming with a Fixed number of Tasks) and MVT (Multiprogramming with a Variable number of Tasks), were part of the OS/360 line. IBM also offered DOS/360, a simpler disk-operating system intended for smaller configurations. The Time Sharing Option (TSO) introduced interactive capabilities, allowing multiple terminals to share a single system. The OS included job control language (JCL) and tools for memory management, I/O control, and system services.

Development of OS/360 encountered significant delays and budget overruns. The initial releases were not feature-complete and required substantial updates. Through the late 1960s and early 1970s IBM extended and refined the system, adding capabilities and new variants. OS/360's architecture and naming conventions laid the groundwork for later IBM mainframe operating systems, most prominently MVS (Multiple Virtual Storage), introduced in the 1970s, which integrated virtual memory and improved scalability. The OS/360 family thus served as a transition from the early fixed-function batch systems to more modern mainframe environments and influenced IBM's software strategy for decades.