.. _threads:

Multi-threaded Process
=======================

The simple model of a process containing only one thread is referred to as a
:term:`classic process`.  Modern operating systems also support processes with
multiple threads.  Each :term:`thread` of a single process can use the process'
global data with synchronization resources to easily communicate with other
threads.  Multi-threaded programs run more efficiently and use less resources
than a program that creates multiple processes to accomplish the same task.

.. figure:: thread.png
   :align: center

   Threads share global data and other resources, but each thread has it's own
   execution engine and stack for data that is local to each function in the
   program.

.. note::

    The scheduling of threads within a processes presents an interesting
    challenge, which we will later discuss.  Linux and Windows take completely
    different approaches to solve this problem.