Abstract: Novel controllers have been discovered which permit control of the outputs of a system with minimal knowledge of the system's internal dynamics, and with no knowledge of the values of disturbances on the system, or of the effects of the disturbances on the system. Very rapid convergence of the actual outputs to selected desired outputs is possible. The systems controlled may have multiple inputs and multiple outputs; may be linear or nonlinear; may be expressed in input-output form, state space form, or mixed form; and may be implemented with analog circuit elements, digital circuit elements; or a hybrid of both analog and digital circuit elements. Both general and special cases of such controllers are disclosed.