3 articles
Pushdown automaton
A pushdown automaton (PDA) is a finite-state machine with a stack as its only auxiliary memory, recognizing exactly the context-free languages, including nested structures like palindromes.
Stack machine
A stack machine, also called a stack computer, is a computer or virtual machine whose instructions take operands from a last-in, first-out stack rather than named registers.
Tree automaton
A tree automaton is a finite-state machine that accepts trees rather than strings by labeling subtrees with states; it recognizes regular tree languages and underpins XML schema validation.