## Are PDAs more powerful than NFA?

Pushdown automata (PDAs) can be thought of as combining an NFA “control-unit” with a “memory” in the form of an infinite stack. PDAs are more powerful than FAs, being able to recognize languages that FAs cannot.

## Is push down related to stack?

The term “pushdown” refers to the fact that the stack can be regarded as being “pushed down” like a tray dispenser at a cafeteria, since the operations never work on elements other than the top element. A stack automaton, by contrast, does allow access to and operations on deeper elements.

**What are genuine differences between FAs and PDAs?**

Pushdown automata has the additional stack for storing long sequence of alphabets. Finite Automata doesn’t has any space to store input alphabets.

**Which is more powerful PDA or Npda?**

The CFG which accepts deterministic PDA accepts non-deterministic PDAs as well. Similarly, there are some CFGs which can be accepted only by NPDA and not by DPDA. Thus NPDA is more powerful than DPDA.

### Who invented Pushdown automata?

Pushdown acceptors were first formalized by Chomsky [Ch5] and Evey [Ev], although the notion of a pushdown tape has been used since 1954. [Ch5] N. Chomsky, context-free grammars and pushdown storage, MIT Res. Lab.

### What is the 7 tuple for PDA?

PDA can be betokened formally by a 7-tuple (Q, ∑, S, δ, q0, I, F) where, Q is the number of states. It is finite.

**Why is Npda more powerful than DPDA?**

Power of NPDA is more than DPDA. It is not possible to convert every NPDA to corresponding DPDA. Language accepted by DPDA is subset of language accepted by NPDA. The languages accepted by DPDA are called DCFL (Deterministic Context Free Languages) which are subset of NCFL (Non Deterministic CFL) accepted by NPDA.

**Which is slower NFA or DFA?**

NFA advantages over a DFA: the representation uses less memory. NFA disadvantages compared to an NFA: Slower to arrive at an answer.