15-453 Formal Languages, Automata, and Computation
Lecture 10: Pushdown Automata

We formally introduce pushdown automata (PDAs) as a computational model. PDAs are non-deterministic (like NFAs), but they can push and pop symbols of a stack while they read a word. This makes the equivalent in power to context-free grammars. We give some examples aof PDAs and show that every context-free language is recognized by a PDA. The other direction will be the subject of the next lecture.