Context-free grammar

Context free grammar (CFG )

Syntax analysis or parsis( from parser tree ) is the second phase of compiler .We have seen than a lexical analyzer can identify tokens with the help of regular expressions and pattern rules.But a lexical analyzer can not check the syntax of a given sentence due to the limitation of the regular expressions. Regular expressions can not check balancing tokens,Such as parenthesis. Therefor , this phase uses context free grammar which is recognize by push down automata.

CFG, On the other hand,is a super set of regular grammar.

It implies that every regular grammar is also context free but there exist some problem ,which are beyond the scope of regular grammar .CFG is a helpful tool in describing the syntax of programming language.

CFG stands for context free grammar, It is a formal grammar which is used to generate all possible patterns of string in a given formal language . It defined four topples. As

G = (V, T ,P , S )

G = is the grammar , set of production rule, it is used to generate the string of language.

T = T is the final set of a non-terminal symbol,It denoted by capital letters .

V = final set of non- terminal symbol.

S = s is start system.

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