Explain Type-2 and Type-3 Grammar in TOC?

The Chomsky hierarchy is given below −

Type 2 − Context Free Grammar (CFG)

• Type 2 grammars are generated by context free languages.
• The language that is generated by the grammar is recognized by Push Down Automata.
• Type 2 must be in Type 1.
• Left-hand side of production can have only one variable.

• |alpha| =1

  There is no restriction on beta.

  The production rules are in the form of −

  A->alpha

  Where, A is any single non-terminal and is any combination of terminals and nonterminals.

Example

S->AB

A->a

B->b

Type 3 − Regular grammar

• Type 3 grammars are generated by regular languages.
• These languages are exactly all those languages that can be accepted by finite state automata.
• Type 3 is the most restricted grammar.

• It is in the form of

  V->VT*/T* Or V->T*V/T*

Example

S->ab