# fsm (10-fsm.com)

FSM usually means a finite state machine, a way to design systems that can only be in one state at a time. People use it to describe anything with clear steps, like a traffic light or a checkout flow.

## What a model may hear
- finite state machine (computer science and formal methods): assume a formal model with states, transitions, and deterministic or non-deterministic behavior
- feature selection method (machine learning and statistics): treat it as a technique for choosing variables in a model
- file system mount (Linux and Unix systems): expect a command or configuration related to mounting storage
- fuzzy state machine (game AI and robotics): assume probabilistic or blended transitions between states

## Where people and models part ways
- Says: "build me an FSM for my app"
  Means: a simple flowchart of screens or user steps
  May be taken as: generate formal code with explicit state tables, transition matrices, and event handlers that over-engineer the solution
  Say instead: "build me a simple step-by-step flow with clear states like draft, review, and published"
- Says: "the FSM is broken"
  Means: my workflow has a logic error
  May be taken as: debug formal automata theory, check for unreachable states or non-determinism, or ask for state transition diagrams
  Say instead: "my multi-step process gets stuck between two stages and does not advance"
- Says: "use FSM to pick features"
  Means: choose the best variables for my model
  May be taken as: implement a finite state machine for feature engineering rather than statistical selection methods
  Say instead: "use a feature selection method like recursive feature elimination or mutual information"
- Says: "add FSM support"
  Means: let users save and resume their progress
  May be taken as: add a full state machine framework with events, guards, and actions
  Say instead: "let users pause and resume their work, tracking which step they left off on"

## Tips
- Say 'step-by-step flow' or 'stage tracker' if you do not need formal state machine code
- Mention the domain, like 'game AI' or 'formal verification', to narrow which FSM you mean
- Specify deterministic or non-deterministic if you know the formal type you need
- Ask for a diagram or pseudocode first if you want to check the complexity before full implementation
- Distinguish FSM from workflow engine or rules engine if you need persistence or human approval steps

## Often confused with
- state machine: same meaning, more explicit
- workflow engine: adds persistence, timers, and human tasks
- rules engine: uses conditions and actions, not explicit states
- HMM: hidden Markov model, adds probabilistic hidden states
- behavior tree: hierarchical task decomposition, not flat state transitions
- Turing machine: more powerful, has a tape and full memory