By means of the theory of Galois fields and formal series, it is possible to develop an operational calculus for the finite sequence space of finite fields and rings, where group laws are modulo

sum and product; whether

is prime or not. The sequences that can be treated are ultimately periodic. Elementary properties of this calculus are given and application to linear sequential systems is made possible by the introduction of transfer functions. Examples are described where the proposed calculus can be used to advantage.