Push-Down Automata
The push-down automaton as a 7-tuple, the move label convention, instantaneous descriptions and the turnstile, acceptance by final state and by empty stack and their equivalence for nondeterministic PDAs, and constructions for a^n b^n, a^n b^2n, ww^R (nondeterministic, with a diagram), wcw^R, equal numbers of a and b, balanced parentheses and a^i b^j c^k with i = j or j = k. Every PDA was simulated nondeterministically on all strings up to length 7 or 8 and compared with its language.
