The Basics of State Machines: What They Are and How They Work

Are you curious about state machines? Do you wonder how they work? If you're interested in learning about these exciting tools, then you've come to the right place! In this article, we'll explore the basics of state machines – what they are and how they work – so that you can begin to understand their power and potential.

What is a State Machine?

First things first: what exactly is a state machine? At its most basic level, a state machine is a device or algorithm that can change its behavior based on its current state. In other words, it's a tool that can respond differently to input depending on what has happened before.

This might seem like a simple concept, but it can actually be applied to a wide variety of situations. For example, a vending machine is a state machine: it changes its behavior (dispensing a specific item) based on the current state (the buttons that have been pressed and the money that has been inserted).

How Do State Machines Work?

So, how do state machines actually work? At their core, state machines are made up of two key parts:

  1. States: these are the different states that the machine can be in. For example, a traffic light might have states such as "green", "yellow", and "red".
  2. Transitions: these are the events or triggers that cause the machine to transition from one state to another. For example, when a traffic light is in the "green" state, it will transition to the "yellow" state after a certain amount of time has passed.

Together, these two parts create a powerful tool that can respond to a wide range of inputs and events. By defining the different states and transitions, you can create a machine that behaves exactly as you want it to.

Types of State Machines

There are two main types of state machines: finite state machines (FSMs) and hierarchical state machines (HSMs).

Finite State Machines

Finite state machines are the simplest type of state machine. They consist of a set of states and transitions between them, and they can be used to model simple systems with a limited number of states. For example, a traffic light or a vending machine could be modeled using an FSM.

Hierarchical State Machines

Hierarchical state machines are more complex than FSMs. They allow you to create nested states and sub-states, which can be useful for modeling more complex systems. For example, a system that has different modes (such as "normal" mode and "service" mode) might be better modeled using an HSM.

Why Use State Machines?

So, why would you want to use a state machine in the first place? There are a few key benefits that these tools offer:


State machines are highly modular, which means that you can break complex systems down into smaller, more manageable parts. By defining states and transitions, you can create modules that can be reused across different parts of your system.


State machines are also highly readable and easy to understand. Because they are based on simple, well-defined rules, it is easy to look at a state machine and understand how it works.


Finally, state machines are highly robust. Because they are based on a predictable set of rules, they are less likely to encounter unexpected behavior or edge cases. This makes them highly reliable and well-suited to safety-critical systems.


State machines are a powerful tool for modeling and controlling a wide range of systems. By defining states and transitions, you can create highly modular, easy-to-understand machines that are well-suited to a wide range of applications. Whether you're building a simple vending machine or a highly complex safety-critical system, state machines are an essential tool that you won't want to overlook. So why not give them a try today?

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