The main purpose of this work is to determine the forward and backward solution space of a nonregular discrete time AR-representation i.e. A(σ )ξ(k) = 0, in a finite time horizon where A(σ ) is a polynomial matrix and σ is the forward shift operator. The construction of the behavior is based on the structural invariants of the polynomial matrix that describes the AR-representation i.e. the finite and infinite elementary divisors and the right and left minimal indices of A(σ Let R, C denote the fields of real and complex numbers respectively, R[σ ] the ring of polynomials with real coefficients and R(σ ) the field of rational functions. By R(σ ) p×m , R pr (σ ) p×m and R[σ ] p×m we denote the sets of p × m rational, proper rational and polynomial matrices respectively with real coefficients and indeterminate σ . Consider a system of linear homogeneous difference and algebraic equations described in matrix form by A(σ )ξ(k) = 0,(1) *