>> G=pck(A,B,C,D) % pack in partitioned form
>> seesys(G) % display G in partitioned format
>> [A,B,C,D] = unpck(G)
% unpack the system matrix
>> G = pck([],[],[],10) % create a constant system matrix
>> [y,x,t] = step(A,B,C,D,Iu) % Iu =i (step response of the i-th channel)
>> [y,x,t] = initial(A,B,C,D,x0)
% initial response with x0
>> [y,x,t] = impulse(A,B,C,D,Iu) % impulse response
>> [y,x]=lsim(A,B,C,D,U,T) % U is a length(T) column(B) matrix input; T is the sampling points.