function boo = isdt(sys)
%ISDT  Check if LTI model is discrete time.
%
%   ISDT(SYS) returns 1 (true) if the LTI model SYS is 
%   discrete, 0 (false) otherwise.  ISDT always returns 1 
%   for empty systems or static gains.
%
%   See also ISCT.

%   Author(s): P. Gahinet, 5-1-96
%   Copyright (c) 1986-98 by The MathWorks, Inc.
%   $Revision: 1.1 $  $Date: 1998/04/14 21:40:34 $

% SYS is discrete if it is a gain or Ts~= 0
if getst(sys.lti)~=0,
   boo = 1;
else
   boo = isstatic(sys);
end
