What is parsing? Write down the drawback of top down parsing of backtracking.

Parsing is the process of analyzing a text, made of a sequence of tokens, to determine its grammatical structure with respect to a given formal grammar. 

 

Parsing is also known as syntactic analysis and parser is used for analyzing a text. The task of the parser is essentially to determine if and how the input can be derived from the start symbol of the grammar. The input is a valid input with respect to a given formal grammar if it can be derived from the start symbol of the grammar.

Drawbacks of top down parsing

Following are drawbacks of top down parsing of backtracking:
(i) Semantic actions cannot be performed while making a prediction. The actions must be delayed until the prediction is known to be a part of a successful parse.
(ii) Precise error reporting is not possible. A mismatch merely triggers backtracking. A source string is known to be erroneous only after all predictions have failed.