..
  Copyright 1988-2021 Free Software Foundation, Inc.
  This is part of the GCC manual.
  For copying conditions, see the GPL license file

.. _btest:

BTEST --- Bit test function
***************************

.. index:: BTEST

.. index:: BBTEST

.. index:: BITEST

.. index:: BJTEST

.. index:: BKTEST

.. index:: bits, testing

.. function:: BTEST(I,POS)

  ``BTEST(I,POS)`` returns logical ``.TRUE.`` if the bit at :samp:`{POS}`
  in :samp:`{I}` is set.  The counting of the bits starts at 0.

  :param I:
    The type shall be ``INTEGER``.

  :param POS:
    The type shall be ``INTEGER``.

  :return:
    The return value is of type ``LOGICAL``

  :samp:`{Standard}:`
    Fortran 90 and later, has overloads that are GNU extensions

  :samp:`{Class}:`
    Elemental function

  :samp:`{Syntax}:`

  .. code-block:: fortran

    RESULT = BTEST(I, POS)

  :samp:`{Example}:`

    .. code-block:: fortran

      program test_btest
          integer :: i = 32768 + 1024 + 64
          integer :: pos
          logical :: bool
          do pos=0,16
              bool = btest(i, pos) 
              print *, pos, bool
          end do
      end program test_btest

  :samp:`{Specific names}:`
    =================  ====================  ==============  ====================
    Name               Argument              Return type     Standard
    =================  ====================  ==============  ====================
    ``BTEST(I,POS)``   ``INTEGER I,POS``     ``LOGICAL``     Fortran 95 and later
    ``BBTEST(I,POS)``  ``INTEGER(1) I,POS``  ``LOGICAL(1)``  GNU extension
    ``BITEST(I,POS)``  ``INTEGER(2) I,POS``  ``LOGICAL(2)``  GNU extension
    ``BJTEST(I,POS)``  ``INTEGER(4) I,POS``  ``LOGICAL(4)``  GNU extension
    ``BKTEST(I,POS)``  ``INTEGER(8) I,POS``  ``LOGICAL(8)``  GNU extension
    =================  ====================  ==============  ====================