State machines, or, Finite State Automata and the uses thereof

What is a state machine?

Example state machine:

Traffic lights!

I apologise in advance for my 'art'.

This is why I am not a graphic designer.

State Top

State Base

State Pedestrian

State Machine Diagram

State Pedestrian

Entry Action: turn pedestrian lights green.Delay 20 seconds.

Flash pedestrian lights red.Delay 40 seconds.

Exit Action: turn pedestrian lights red.Load State Base

State Base

Entry Action:Turn appropriate lights green.

Delay 40 seconds.Turn off green lights, turn on amber lights.

Delay 15 deconds.

Exit action:Turn off amber lights, turn on red lights.

Load State Top

State Top

Entry Action: as State Base

Input Action:If input, perform exit action and load State Pedestrian.

Otherwise, perform exit action and load State Base

Exit Action: turn all lights red, load next state.

A better way?

A more efficient way!