This subject makes an effort at detailed analysis of dynamic features of systems, both continuous and discrete ones. Linear systems are preferred. There are studied the problems of their various state description, their transform and their canonical forms. Relation between inner and external description is shown, as well as the conversion between their continuous and discrete models. The considerable part of subject is given to state estimation problem, both in full and reduce order Luenberger's variants. The very main problem is the practical design of optimal state controller, again in both modification continuous and discrete ones.