presentstate

Present state is the current configuration of a system at a specific time. In mathematical modeling and engineering, it is the minimal set of variables needed to determine future behavior given inputs, without recourse to the full past history. The present state, together with future inputs, uniquely determines the system’s evolution, while the past is implicit in how the present state was arrived at.

Many formal models describe present state in different ways. In automata theory, a deterministic finite automaton uses the present state and an input symbol to select the next state and, in some formulations, the output. Moore and Mealy state machines illustrate how outputs can depend on the present state or on the combination of present state and input.

In continuous- or discrete-time control theory, the present state is captured by a state vector x, and the system is described by state-space equations x' = f(x, u) and y = g(x, u). The present state thus contains the information needed to predict the future trajectory of the system under known inputs.

Often the true present state cannot be measured directly; estimators or observers reconstruct it from available measurements. Kalman filters or particle filters provide probabilistic estimates of the present state in noisy environments.

Practically, the concept applies to everyday mechanical systems, robotics, process control, and software simulations. Examples include a thermostat with present-state variables for temperature and heater status, or a robot whose present state comprises position, velocity, and battery level.

In programming, presentstate may be used as a variable name to store the current state of an object or system during a simulation or game loop.