# Finite State Machines

[Finite State Machines](<https://gameprogrammingpatterns.com/state.html#finite-state-machines-to-the-rescue >) are one of the most frequently used State patterns for games because they are one of the most **simple** ways to represent and implement logic for event-driven systems. A Finite State Machine is model of a dynamic, event-driven system. FSM's allow for simplification of the logic of complex event-driven systems. The simplification comes from the structure of the FSM which is specified below.\
\
**Finite State Machine** model specifies that the event-driven-system can be represented by:

* a finite **set of states - represented by nodes**
* a finite **set of events** that cause the system to change state&#x20;
* a well-defined set of **state-event transitions (event-arrows)**&#x20;
* **memory to keep track of the current state** of the system
* identification of the **starting state**
* at any point in time, the **system must be in one**, **and only one state** of the system.

The benefit of using an FSM to model a system is that once a system has been represented using a FSM format, then it is straightforward to write code to implement logic of the system. &#x20;

An FSM is often represented as a **diagram with nodes** to represent each state and **arrows between nodes to represent valid transition events**.  A table can also be used to represent the same logic.

## **Finite State Machines**&#x20;

The image below shows a **Finite State Machine** diagram for managing **Event-Driven changes in GameState** which correspond to **Level-Change Events** for the MiniGame used in Project 3.

![](/files/-MFWLzityMIwkP1nS5fN)

![Event-Driven Logic for Project 3, Corresponds to FSM Above](/files/-MFb1P01dPUfc2Ams3t-)

Throughout this course we will look at the fundamental computing structures associated with games and stories.  The online book listed below "Game Programming Patterns" is a resource we'll use throughout the course. &#x20;

In computer science, **programming patterns** are an important way to understand and communicate about common abstractions. &#x20;

### **The State Pattern defines the behavior of a dynamic object.**

> Allow an object to alter its behavior when its internal state changes. The object will appear to change its class.&#x20;

{% embed url="<https://gameprogrammingpatterns.com/state.html#finite-state-machines-to-the-rescue>" %}

As discussed in the book shown below, a useful way to think about games is to consider that they can be represented as a hierarchy of "looping systems."

**In Computer Science, such looping systems are called State Machines.** &#x20;

{% embed url="<https://gameprogrammingpatterns.com/game-loop.html>" %}

![Game-Loops: Image below from Michael Sellers, Advanced Game Design ](/files/-M1_bVgTGaCAfekp-L1c)

{% embed url="<https://learning.oreilly.com/library/view/advanced-game-design/9780134668185/ch2.xhtml#ch2>" %}


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