Let’s say our traffic lights start, when we reset them, at the green state. Let’s focus on 1 single traffic semaphore.Īs we said above, we have 3 states, which can call green, red, yellow. That’s another finite state machine, which contains multiple different finite state machines for each traffic lights device installed for each side of each road of an intersection, which work in sync.ĭon’t think about it now. Of course traffic lights do not exist in isolation. There are many more examples of finite state machines we could use:īut let’s stick to our traffic lights example, which is very simple and we can reason about it easily. We can’t define it in a finite number of states.īut traffic lights? That’s a simple thing, and it has 3 states, like we said above. Like the world ecosystem model, or the life of an insect. Some systems might have an infinite number of states. Our traffic lights state machine is said to be finite because we have a finite number of states. In a state machine, the state can only change (and we have a transition) in response to an input. Some semaphores have a button that pedestrian can press to cause the red to display to cars, and that would be another input. The timer in this case is the input of the system. The traffic semaphore will change state when it receives an input, typically just a fixed timer that decides how much time the traffic lights should be green, yellow and red.
In State Machines terminology, lights being on or off is called output.Įach of those 3 scenarios is called state. (Some semaphores are slightly different, but we don’t care for the sake of this example) as the yellow light on, and the other 2 lights off.has the red light on, and the other 2 lights off.has the green light on, and the other 2 lights off.The most popular and commonly found example is traffic lights.Īt any point in time, a traffic semaphore has a defined state. After reading this tutorial, I am sure you’ll point out objects in the real world saying to your friends “that’s a state machine” (depending on the nerdy level of your friends). You can see them everywhere, but perhaps you didn’t think of them as such. State Machinesīefore looking into what a Finite State Machine is, I want to first introduce what a State Machine is. I like to simplify things, and I decided to write a little explanation for normal human beings, not theoretical or anything made to pass an exam. I did find a lot of information, and of course being textbooks things are made more complex than needed (IMHO). I found the topic of Finite State Machines applied to Frontend Engineering pretty amazing, and I went back to my old books to see if I could find a good explanation of them. This Digital Design course was about encoding information, boolean algebra, combinatorial networks, sequential circuits, sequential state machines, arithmetical circuits, VHDL, and more. I have first met Finite State Machines and Automata back in High School, 20 years ago, then I met them again in my Digital Design course at the University. There’s this popular library called XState, with more than 11000 stars on GitHub, which I run into lately, and I keep reading about it on Twitter and other places.
There’s a lot of talk about Finite State Machines these days in JavaScript land. A quick overview of what State Machines are, with simple examples
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