function value = ch_is_alpha ( c )

%*****************************************************************************80
%
%% ch_is_alpha() is TRUE if C is an alphabetic character.
%
%  Licensing:
%
%    This code is distributed under the MIT license.
%
%  Modified:
%
%    22 February 2010
%
%  Author:
%
%    John Burkardt
%
%  Input:
%
%    character C, a character to check.
%
%  Output:
%
%    logical VALUE is TRUE if C is an alphabetic character.
%
  if ( ( 'a' <= c & c <= 'z' ) | ...
       ( 'A' <= c & c <= 'Z' ) )
    value = true;
  else
    value = false;
  end

  return
end
