  Constant Rank (CR) state machines play an important role in the general
structure theory of Finite State Machines. A machine is of constant rank if
each input and input-sequence maps the state set onto the same number of next
states. CR-machines are analysed via their sequential closure (semigroup),
which is a simple semigroup, thus: a semi- direct product (L \times R)*G of a
left- and a right-copy semigroup, and a group. . . . So in general a CR-machine
is a composition of: a branch-, a reset- and a permutation machine, which are
three of the five basic types of state machines, to be derived.
