Determinism

Deterministic finite state machine (DFSM) is a state machine that always gives the same output for the same input. This means:

• no two transitions from the same state happen under exactly the same conditions; and
• no transitions happen without empty input (so-called epsilon input).

DFSM are also known as deterministic finite automata or deterministic finite acceptors (both abbreviated as DFA).

All other state machines are non-deterministic (NDFSM).

There are algorithms to convert an NDFSM to a DFSM, but they're also beyond the scope of this article.