shared memory. Although it is common to allocate one task per physical or logical processor, the terms "task" and "processor" are not interchangeable. An activity that has business value, is initiated by a user, and is performed by software. In z/OS specifically, it is defined precisely as: "In a multiprogramming or multiprocessing environment, one or more sequences of instructions treated by a control program as an element of work to be accomplished by a computer." The term task in OS/360 through z/OS is roughly equivalent to light-weight process; the tasks in a job step share an address space. However, in MVS/ESA through z/OS, a task or Service Request Block (SRB) may have access to other address spaces via its access list. Linux kernel The term task is used in the Linux kernel (at least since v2.6.13, up to and including v4.8) to refer to a unit of execution, which may share various system resources with other tasks on the system. Depending on the level of sharing, the task may be regarded as a conventional thread or process. Tasks are brought into existence using the clone() system call, where a user can specify the desired level of resource sharing. History The term task for a part of a job dates to multiprogramming in the early 1960s, as in this example from 1961: The term was popularized with the introduction of OS/360 (announced 1964), which featured Multiprogramming with a Fixed number of Tasks (MFT) and Multiprogramming with a Variable number of Tasks (MVT). In this case tasks were identified with light-weight processes, a job consisted of a number of tasks, and, later, tasks could have sub-tasks (in modern terminology, child processes). Today the term "task" is used very ambiguously. For example, the Windows Task Manager manages (running) processes, while Windows Task Scheduler schedules programs to execute in future, what is traditionally known as a job scheduler, and uses the .job extension. By contrast, the term "task queue" is commonly used in the sense of "units of work". See also Task parallelism Task queue References Computing terminology