dispatch — the dispatch framework

       The  dispatch  framework  allows blocks to be scheduled for asynchronous and concurrent execution via the
       core functions described in dispatch_async(3) and dispatch_apply(3).

       Dispatch queues are the basic units of organization of blocks. Several queues are created by default, and
       applications may create additional queues for  their  own  use.  See  dispatch_queue_create(3)  for  more
       information.

       Dispatch  groups  allow  applications to track the progress of blocks submitted to queues and take action
       when the blocks complete. See dispatch_group_create(3) for more information.

       The dispatch framework also provides functions to monitor  underlying  system  events  and  automatically
       submit event handler blocks to dispatch queues.

       dispatch — the dispatch framework

dispatch_after(3),    dispatch_api(3),   dispatch_apply(3),   dispatch_async(3),   dispatch_benchmark(3),
       dispatch_group_create(3),      dispatch_object(3),      dispatch_once(3),       dispatch_queue_create(3),
       dispatch_semaphore_create(3), dispatch_source_create(3), dispatch_time(3)

Darwin                                             May 1, 2009                                       dispatch(3)

#include<dispatch/dispatch.h>