OS / 360

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OS / 360 is an operating system with batch processing capability of IBM from the 1960s for the System / 360 - mainframe . OS / 360 was one of the first operating systems to enable mass storage devices with direct access (e.g. hard drives ).

history

OS / 360 was developed as a family of three control programs, with each new program both larger and more functional. The simplest version, the PCP ( Primary Control Program ), was able to execute one task at a time and therefore had to process the jobs sequentially . The next version, the MFT ( Multiprogramming with a Fixed Number of Tasks ), added limited multitasking to the range of functions . Only a fixed number of tasks could be executed at the same time, whereby the necessary memory allocations for the jobs had to be defined before they were started. The last version, the MVT ( multiprogramming with a variable number of tasks ), allowed the execution of any number of tasks as well as a dynamic memory usage by the tasks, i. H. the memory area allocated to a task could increase or decrease during execution. OS / 360 also introduced the Job Control Language (JCL).

OS / 360 was delayed due to a combination of organizational problems at IBM. The whole project was technically very demanding and IBM did not yet have the necessary experience with such large software projects . According to the announcement in 1964, the originally planned delivery dates in 1965 for the simplest version and 1966 for the other two versions could not be met. PCP could not be delivered until 1966, MFT and MVT could not be delivered until 1967.

MVS via Hercules emulator

OS / 360 evolved when hardware with virtual addressing capability became available for the System / 370 family . MFT became OS / VS1, MVT became OS / VS2; later OS / VS2 was renamed MVS ( Multiple Virtual Storage ) after its further development .

Today OS / 360 is in the public domain and can be downloaded for free. In addition to the original System / 360 hardware , OS / 360 can now also be run on Windows and Linux systems with the free Hercules emulator .

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