WordNet (r) 3.0 (2006):

scheduler
    n 1: computer hardware that arranges jobs to be done by the
         computer in an appropriate order

The Free On-line Dictionary of Computing (30 December 2018):

scheduling
scheduler

    The arrangement of a number of related operations
   in time.

   There are several kinds of scheduling related to computers:

   instruction scheduling - sequencing the instructions
   executed by the CPU

   multitasking ("process scheduling") - sharing a CPU between
   several processes

   application software to help organise your daily meetings
   etc.

   task scheduling - algorithms to solve the general problem
   of satisfying time and resource constraints between a number
   of tasks.

   Compare planning.

   (1998-04-25)