In this paper the problem of designing computer-assisted nonlinear control for continuously nonlinear systems with discrete measurements is addressed. Its framework allows one to establish the connections between the feedback linearization method and one-step-ahead prediction horizon, but its implementation does not require on-line optimization algorithms. Depending on the numerical calculation, the explicit control law with the high-gain feedback effect can reinforce the output regulation performance. Incorporating the nonlinear internal model control (IMC) strategy, the computer-assisted output feedback control is developed. Through numerical simulations on the composition control for an exothermic chemical reactor system, the comparative evaluation between the proposed control and the nonlinear model predictive control (NMPC) are given.