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GATE CS 2011 Official Paper

Option 2 : Deterministic push down automata (DPDA) and Non-deterministic push down automata (NPDA)

The correct answer is **option 2**

**Option 1:**** SAME **expressive power

NFA and DFA have the same expressive power.

__Option 2:__ DIFFERENT expressive power

Some languages are accepted by NPDA but not by deterministic PDA. **Therefore expressive power of DPDA < expressive power of NPDA**.

So, deterministic pushdown automata (DPDA) and non-deterministic pushdown automata (NPDA) have DIFFERENT expressive power

__Option 3:__ SAME expressive power

Deterministic single-tape Turing machine and Non-deterministic single-tape Turing machine have the same expressive power

__Option 4:__ SAME expressive power

Multi-tape Turing machines has same power as single tape Turing machines.