Difference Between Pushdown Automata and Finite Automata

Automata is a theoretical concept which is taught in computer science and mathematics. The topics included in automata include abstract machines. These machines have to deal with computational problems and resolve them. Automata theory is used to develop methods which can be used in the description and analysis of the dynamic behavior of the discrete system. There are two types of automata which are Pushdown automata and finite automata. In this article, we will discuss the difference between Pushdown Automata and Finite Automata.

What is Pushdown Automata?

Pushdown automata is a finite state machine which also consists of additional stack storage. The reason behind adding an additional stack is to make decisions related to transitions. Input symbols and current state are not used while transitioning. The tuples used in pushdown automata are listed below:

• Q ? This tuple consists of a set of states.
• ? ? This tuple consists of a set of symbols
• ? ? This tuple denotes a set of pushdown symbols which can be pushed or popped from the stack
• q0 ? is a tuple which denotes the initial state
• Z ? This is a tuple which is present in the stack at the initial stage
• F ? This tuple denotes the final set of states.
• ? ? This tuple denotes the transition function

What is Finite Automata?

Finite automata is used to calculate the transitions of state which are related to the input symbols. The transitions in finite automata depend upon the current state and input symbols. The five tuples included in the finite automata are listed below ?

• Q ? This tuple denotes the finite set of states
• ? ? This tuple denotes the set of input symbols
• q ? This tuple denotes the initial state
• F ? This symbol denotes the set of final states
• ? ? This symbol denotes the transition function

Difference between Pushdown Automata and Finite Automata

The table below shows the difference between Finite Automata and Pushdown Automata.

Pushdown Automata: Finite Automata: Which is better?

Pushdown Automata supports Type-2 grammar and has the ability to support languages that are free from context. It also has the ability to store a long set of alphabets due to additional stack storage. Finite Automat supports Type-3 grammar and uses regular languages. It does not have any additional storage space for alphabets.

Conclusion

Automata is a concept which is included as one of the topics in computer science and mathematics. They are used in abstract machines which can perform calculations and resolve computational problems. Two major types of automata are pushdown automata and finite automata.

FAQs on Pushdown Automata Vs. Finite Automata

1. Which automata has the additional space to store more alphabets and information?

Pushdown automata comes with an additional stack for storage and it can store more information in comparison to finite automata. Finite automata have a limited amount of memory and do not have an additional stack.

2. Which automata has better input processing capabilities?

Finite automata can process one input symbol at a time. The transition between states depends upon the current input symbol that is being processed. Pushdown automata also processes one input symbol at a time but it can also perform operations on the stack. The transition between symbols depends upon the current as well as the top symbol.

3. What types of languages are supported by pushdown automata and finite automata?

Pushdown automata have the ability of supporting a large number of languages. Pushdown automata supports context-free languages. Comparatively finite automata support only regular languages.

4. Which automata has a large storage space?

Pushdown automata has large storage space as additional stack is also available. Such a stack is not available with the finite automata.

5. What are the components of Pushdown Automata?

The components included in pushdown automata are as follows ?

• Input tape ? It is divided into many cells or symbols and it consists of a read-only input head.
• Finite control ? It includes a pointer which has the point of the symbol that is to be read.
• Stack ? It has the ability to push and remove items from a single end.