OS/360

OS/360 was an early operating system developed by IBM for their System/360 computer (announced in 1964). Other operating systems for this hardware included DOS/360 and TSS/360. Later IBM operating systems for their mainframe hardware include MVS and VM/CMS.

Originally based on IBM's operating system OS (IBM)[?], OS/360 developed three control programs, initially the single task PCP (Primary Control Program), then MFT (multiprogramming with a fixed number of tasks) and finally MVT (multiprogramming with a variable number of tasks) with JCL (Job control language). OS/360 was amongst the earliest OSs to need direct access storage devices.

After the virtual addressing hardware was developed, the systems were renamed. MFT became OS/VS1 and MVT became OS/VS2. OS/VS2 became MVS (Multiple Virtual Storage).

Frederick P. Brooks' book, The Mythical Man-Month, gives OS/360 as an example of the second-system effect.

OS/360 is in the public domain and can be downloaded freely. In addition to the System/360 hardware, it can also be run on the free Hercules emulator which runs under Linux and Windows.

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This article (or an earlier version of it) contains material from FOLDOC's article on OS/360 (http://wombat.doc.ic.ac.uk/foldoc/foldoc.cgi?OS%2F360), used with permission.