A systematic method for the digital computer manipulation of the equations describing high-order linear processes into canonic state space form is briefly reviewed. The basic method is then extended to embrace system models which, it transpires, include input derivative terms. The paper concludes with a numerical example relating to a boiler dynamic model described by a set of 23 differential and algebraic equations. This example, in addition to illustrating the method of equation manipulation proposed brings out, quite simply, certain features of the boiler model in question which have not been discussed in previous papers.