Formal Languages Questions
A pushdown automaton (PDA) is a type of automaton that consists of a finite control, an input tape, and a stack. It can read symbols from the input tape, perform state transitions based on the current state and input symbol, and manipulate the stack by pushing or popping symbols. PDAs are used to recognize context-free languages.
On the other hand, a context-free grammar (CFG) is a formal grammar that consists of a set of production rules, non-terminal symbols, and terminal symbols. It is used to generate strings in a language by applying the production rules to non-terminal symbols. CFGs are used to describe context-free languages.
The main difference between a PDA and a CFG is that a PDA is a computational model that recognizes or accepts strings in a language, while a CFG is a generative model that describes the structure of strings in a language. In other words, a PDA determines whether a given string belongs to a language, while a CFG generates all possible strings in a language.
In summary, a pushdown automaton is a computational model that recognizes context-free languages, while a context-free grammar is a generative model that describes context-free languages.