# Automata Theory
Confidence: high
Last verified: 2026-05-22
Generation: human_only


## TL;DR

Automata theory studies abstract machines and the problems they can solve. Finite automata (regular languages) → Pushdown automata (context-free) → Turing machines (computable). Powers: regular expressions, parsers, compilers, and the theoretical limits of computation.

## Core Explanation

Chomsky hierarchy: Type 3 (regular, regex, DFA/NFA), Type 2 (context-free, programming language syntax), Type 1 (context-sensitive), Type 0 (recursively enumerable, Turing-complete). Finite automaton: states + transitions + start state + accept states. NFA (nondeterministic) equivalent to DFA (deterministic) — subset construction converts NFA→DFA (exponential blowup possible).

## Further Reading

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