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  2. 2. Definition A computer program use just to evaluate scripts according to the respective grammar. In computer Science, its a text analyzing process to determine if it belongs to a certain language or not. Mostly used as a part of High-Level-Language translators(Interpreter or Compiler). But some Standalone Parsers are available for specific purposes.(for e.g.
  3. 3. What and How it works? It first receives input in the form of  sequential source program or  Stream of characters (String). Break them into small chunks or parts (tokens).  For Example in English Language: He is running to school Subject Verb Object And produces a data-structure that is usually a tree.
  4. 4. What is not Parsing? Parser does not evaluate one thing into another. If just change its representation from one form to another. Parser is not responsible for summarizing or extract the original body of text.Word Processing Programs also uses a parser to checkspelling and grammatical mistakes.
  5. 5. But What is Compiler ??? Compiler is a Language Translator or a computer program that translates a Human understandable instruction set into Computer understandable form Or simply, the output of compiler is .exe file,Object code or RTL(Register Transfer Language)
  6. 6. Compiler VS Parser From the previous discussion it can be concluded that:  The output of Parser is a Data-Structure that is useless for the for both Liveware and hardware.  But this will be a very useful input for some component of the compiler.  Whereas, the output of the compiler is understandable and can be executed by Computer hardware
  7. 7. Phases of Compiler
  8. 8. Phases of Compiler These 3 phases can be called as they are actually parsing the source Program
  9. 9. Lexical Analysis As the name shows, Its done by Lexical Analyzer. Reads the characters from the input stream or source program. Group them in tokens. Each token describe some important element. CONFUSED….!!! Lets see an exmaple.
  10. 10. Token Example int a = 10 ; That’s the code for declaring and initializing a variable “a”. When this LOC passed through t Lexical Box following thing happens Identifier Constant int a = 10 ; Data Type Assignment Symbol Operator Each of this term is called as Token. For e.g. “a” is a token of “Identifier type”. The Character Sequence “int” is called as the its Lexeme.
  11. 11. Can we proceed further OR
  12. 12. Syntax Analyzer According to many sources, this phase is actually responsible for Parsing. So, the input of this phase is the Tokens formed in the previous phase i.e. Lexical Analysis. In this phase, the recently formed token acquire a Hierarchical Data Structure, that’s called Tree in Computer Science.
  13. 13. Before Moving Further First Explore this New Buzz Word Tree. Definition: Its an hierarchical Data Structure that is also known as the Collection of some related nodes.
  14. 14. Terminologies Node is structure that contains some value or condition. In the tree on right side “2” is a parent node that has two child nodes “7” and “5”.