Editing Scheduling (computing) (section)

===OS/360 and successors===
IBM [[OS/360]] was available with three different schedulers.  The differences were such that the variants were often considered three different operating systems:

* The ''Single Sequential Scheduler'' option, also known as the ''Primary Control Program (PCP)'' provided sequential execution of a single stream of jobs.
* The ''Multiple Sequential Scheduler'' option, known as ''Multiprogramming with a Fixed Number of Tasks (MFT)'' provided execution of multiple concurrent jobs.  Execution was governed by a priority which had a default for each stream or could be requested separately for each job.  MFT version II added subtasks (threads), which executed at a priority based on that of the parent job.  Each job stream defined the maximum amount of memory which could be used by any job in that stream.
* The ''Multiple Priority Schedulers'' option, or ''Multiprogramming with a Variable Number of Tasks (MVT)'', featured subtasks from the start; each job requested the priority and memory it required before execution.

Later virtual storage versions of MVS added a ''[[Workload Manager]]'' feature to the scheduler, which schedules processor resources according to an elaborate scheme defined by the installation.