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
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.
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.
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