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+## Copyright (C) 1996 Auburn University.  All rights reserved.
+##
+## This file is part of Octave.
+##
+## Octave is free software; you can redistribute it and/or modify it
+## under the terms of the GNU General Public License as published by the
+## Free Software Foundation; either version 2, or (at your option) any
+## later version.
+##
+## Octave is distributed in the hope that it will be useful, but WITHOUT
+## ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+## FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+## for more details.
+##
+## You should have received a copy of the GNU General Public License
+## along with Octave; see the file COPYING.  If not, write to the Free
+## Software Foundation, 59 Temple Place, Suite 330, Boston, MA 02111 USA.
+
+## -*- texinfo -*-
+## @deftypefn {Function File} {[@var{y}, @var{t}] =} step (@var{sys}@{, @var{inp},@var{tstop}, @var{n}@})
+## Step response for a linear system.
+## The system can be discrete or multivariable (or both).
+## If no output arguments are specified, @code{step}
+## produces a plot or the step response data for system @var{sys}.
+##
+## @strong{Inputs}
+## @table @var
+## @item sys
+## System data structure.
+## @item inp
+## Index of input being excited
+## @item tstop
+## The argument @var{tstop} (scalar value) denotes the time when the
+## simulation should end.
+## @item n
+## the number of data values.
+##
+## Both parameters @var{tstop} and @var{n} can be omitted and will be
+## computed from the eigenvalues of the A-Matrix.
+## @end table
+## @strong{Outputs}
+## @var{y}, @var{t}: impulse response
+##
+## When invoked with the output paramter y the plot is not displayed.
+## @end deftypefn
+## @seealso{impulse and stepimp}
+
+## Author: Kai P. Mueller <mueller@ifr.ing.tu-bs.de>
+## Created: September 30, 1997
+## based on lsim.m of Scottedward Hodel
+
+function [y, t] = step (sys, inp, tstop, n)
+
+  if((nargin < 1) || (nargin > 4))
+    usage("[y, u] = step(sys[, inp, tstop, n])");
+  endif
+
+  if(nargout > 2)
+    usage("[y, u] = step(sys[, inp, tstop, n])");
+  endif
+
+  if(!is_struct(sys))
+    error("step: sys must be a system data structure.");
+  endif
+
+  if (nargout == 0)
+    switch (nargin)
+      case (1)
+        stepimp(1, sys);
+      case (2)
+        stepimp(1, sys, inp);
+      case (3)
+        stepimp(1, sys, inp, tstop);
+      case (4)
+        stepimp(1, sys, inp, tstop, n);
+    endswitch
+  else
+    switch (nargin)
+      case (1)
+        [y, t] = stepimp(1, sys);
+      case (2)
+        [y, t] = stepimp(1, sys, inp);
+      case (3)
+        [y, t] = stepimp(1, sys, inp, tstop);
+      case (4)
+        [y, t] = stepimp(1, sys, inp, tstop, n);
+    endswitch
+  endif
+
+endfunction