# Automata Theory Questions and Answers – Applications – Parsers

This set of Automata Theory Multiple Choice Questions & Answers (MCQs) focuses on “Applications – Parsers”.

1. To derive a string using the production rules of a given grammar, we use:
a) Scanning
b) Parsing
c) Derivation
d) All of the mentioned

Explanation: Parsing is required to check the acceptability of a string. Further, comes the syntactical phase which is taken care by other phases of compiler.

2. Which of the following parser reaches the root symbol of the tree at last?
a) Top down parser
b) Bottom up parser
c) TOP down and Bottom up parser
d) None of the mentioned

Explanation: Bottom up parser starts from the bottom with the string and comes up to the start symbolusing a parse tree or a derivation tree.

3. Left corner parsing methof uses which of the following?
a) Top down parser
b) Bottom up parser
c) TOP down and Bottom up parser
d) None of the mentioned

Explanation: It is a hybrid method which works bottom up along the left edges of each subtree, and top down on the rest of the parse tree.

4. Which of the following parser performs top down parsing?
a) LALR parser
b) LL parser
c) Recursive Accent parser
d) None of the mentioned

Explanation: Bottom up parsing is done by shift reduce parsers like LALR parsers, Operator precedence parsers, simple precedence parsers, etc.

5. Which of the following is true for shift reduce parsers?
a) Scans and parses the input in one forward pass over the text, without any backup
b) A shift command advances in the input stream by one symbol
c) LALR parser
d) All of the mentioned

Explanation: The mentioned are the correct and proper functions of a shift reduce parsers. The parsing methods are most commonly used for parsing programming languages, etc.
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6. State true or false:
Statement: LALR parsers uses tables rather than mutually recursive functions.
a) true
b) false

Explanation: It is exactly the opposite case where LALR parsers uses mutually recursive functions instead of tables. It is a simplified version of canonical left to right parser.

7. LALR in LALR parser stands for:
a) Left aligned left right parser
b) Look ahead left to right parser
c) Language Argument left to right parser
d) None of the mentioned

Explanation: LALR stands for Look ahead left to right parsers. It has more language recognition power than LR(0) parser.

8. Which of the following can be a LALR parser generator?
a) YACC
b) GNU Bison
c) YACC and GNU Bison
d) None of the mentioned

Explanation: YACC is a computer code for UNIX operating system which generates a LALR parser. On the other hand GNU Bison or Bison can generate LALR and GLR parsers.

9. Which of the following parsers do not relate to Bottom up parsing?
a) LL parser
b) Recursive descent parser
c) Earley parsers
d) All of the mentioned

Explanation: All the following mentioned are top down parsers and begin their operation from the starting symbol.

10. Which of the following is true for a predictive parser?
a) Recursive Descent parser
b) no backtracking
c) Recursive Descent parser and no backtracking
d) None of the mentioned