Pushdown automata is a finite automata with extra memory called stack which helps pushdown automata to recognize Context Free Languages.

A pushdown autimaton is a way to implement a context-free grammar in a similar way we design DFA for a regular grammar. A DFA can remember a finite amount of information, but a PDA can remember an infinite amount of information.

Basically a pushdown autimaton is-

"Finite state machine" + "a stack"

A pushdown autimaton has three components-

an input tape,

a control unit, and

a stack with infinite size.

A pushdown automata (PDA) can be defined as:

Q:is a set of states

q0:is the initial state

Z: is the initial pushdown symbol

F: is the set of final states etc.

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