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OS/360 was a batch processing operating system developed by IBM for their then-new System/360 mainframe computer, announced in 1964. OS/360 was amongst the earliest operating systems to make direct access storage devices a prerequisite for its operation.1 Origins
OS/360 was developed as a family of three control programs, which increased in size as well as functionality. Initially, the single task PCP (Primary Control Program) processed jobs sequentially; the next, MFT (Multiprogramming with a Fixed number of Tasks) added multitasking, but only allowed a fixed number of concurrent tasks, each one having a preset memory allocation. Finally MVT (Multiprogramming with a Variable number of Tasks) allowed varying numbers of tasks whose memory size could change dynamically. OS/360 also introduced IBM's batch-scripting language JCL (Job Control Language).
OS/360 was late being delivered, due to a combination of organizational disarray inside IBM and lack of experience with the pitfalls of large software projects, as well as the significant technical challenges. Originally scheduled for delivery in 1965 (for the simplest versions) and 1966 (for the more complex ones), it ended up being a year late — it was not released in its first production versions until 1966 and 67 (PCP and MVT, respectively).
A family of simple alternative systems, BOS (Basic Operating System, for the smallest machines), TOS (Tape Operating System, for machines with only tape drives), and DOS (Disk Operating System), was therfore hurriedly put together to allow customers to use the new machines.
2 Later development
Although intended as a temporary interim tool, DOS survives today, having made the transition to virtual storage as DOS/VS , which later became DOS/VSE , then just VSE, and finally its current form, VSE/ESA .
When virtual addressing hardware was later developed for the System/370The System/370 is a line of IBM mainframes introduced in the early 1970s as the successor to the System/360 family. New architectural features distinct from the 360 range include dual-processor capability as standard, and full support for virtual memory p, the OS/360 systems were upgraded and renamed; MFT became OS/VS1 and MVT became OS/VS2. OS/VS2 was announced in two forms: OS/VS2 Release 1, aka SVS (Single Virtual Storage) and OS/VS2 Release 2, aka MVSMVS M ultiple V irtual S torage was the most commonly used operating system on the System/370 and System/390 IBM mainframe computers. It is unrelated to IBM's other mainframe operating system called VM/CMS. First released in 1974, MVS was later renamed by (Multiple Virtual Storage). SVS was intended as a stepping stone from MVT to MVS, and is only of historical interest today. MVS is still used on the latest members of the IBM 360 Series and its successors, the System/370The System/370 is a line of IBM mainframes introduced in the early 1970s as the successor to the System/360 family. New architectural features distinct from the 360 range include dual-processor capability as standard, and full support for virtual memory p, System/390 and zSeriesSince December, 2001, IBM designates all its mainframes with the name eserver zSeries with the e depicted in IBM's well-known red trademarked symbol. Nonetheless, the term zSeries now popularly refers only to IBM's newest line of 64-bit mainframes, starti, although it has been known by several other names as time went by, most recently OS/390OS/390 is an IBM operating system for the System/370 and System/390 IBM mainframe computers. It is basically a rebranded version of MVS with added Unix services. The OS/390 base includes a Communication Server that includes VTAM, the VTAM AnyNet feature,.
As of the turn of the millennium, the original OS/360 is in the public domainThe public domain comprises the body of all creative works and other knowledge—writing, artwork, music, science, inventions, and others—in which no person or organization has any proprietary interest. Proprietary interest is typically represented by a cop and can be downloaded freely. As well as being run on actual System/360 hardware, it can execute on the free Hercules emulatorThe Hercules emulator is an emulator for the IBM mainframe hardware: the System/370, System/390 and zSeries computers. It runs under Linux, Windows and Mac OS X and is released under the free software license QPL. It emulates the CPU and peripheral device which runs under GNU/Linux, Windows, and Mac OS X.
