EECS20N: Signals and Systems

The Notion of State

A declarative model that is good for describing control logic is based on the notions of state and state transition. The state of a system is a summary of its history, and the state transition function describes how the state changes with input.

Here are some examples of state and state transition:



state transition

values in computer memory


assign new values to variables

your net worth

income and expenditures

changes when you save or spend

parking meter flag and timer positions

clock tick and coin insertion

changes with passage of time and coin insertion

customers present in a store

customers enter or leave

changes when customers enter or leave store

positions and velocities of masses


positions and velocities are changed according to Newton's laws


For some of these, the state changes discretely in response to discrete input events. We will focus first on such examples.