Control theory

Equation of state

State space (controls)

State diagram

State (physics)

State (computer science)

The state variable representing the current state of a discrete-time system (i.e. digital systems) is <math>x(n)\,</math>, where n is the discrete point at which the system is being evaluated. The discrete-time state equations are

State variable filter

State (functional analysis)

A state variable is any variable which represents the state of an object. Thermodynamic variables are sometimes called state variables.

In Control Engineering and other areas of science and engineering, state variables are used to represent the states of a general system. The state variables can be used to describe the state space (controls) of the system. The equations relating the current state and output of a system to its current input and past states are called the state equations. The state equations for a linear time invariant system are expressed with Coefficient matrices: <math>A\,\!</math> existing in dimension R^N*N <math>B\,\!</math> existing in dimension R^N*L <math>C\,\!</math> existing in dimension R^M*N <math>D\,\!</math> existing in dimension R^M*L