pushdown automaton

A pushdown automaton (PDA) is a type of computational model used to recognize certain patterns, especially those involving nested structures like balanced parentheses. It extends a basic machine (finite automaton) by including a stack—a temporary storage area—allowing it to keep track of information needed for decision-making. As it reads input, it can push or pop symbols from the stack, helping it understand complex patterns that require memory of previous inputs. PDAs are fundamental in parsing context-free languages, which are common in programming language syntax.