General Concepts of Error Recovery
What is the main goal of error recovery in compilers?
A) To fix all errors in the source code
B) To allow the parser to continue parsing after an error
C) To generate optimized machine code
D) To improve the efficiency of code execution
Answer: B) To allow the parser to continue parsing after an error
Which of the following is NOT an error recovery strategy in syntax analysis?
A) Panic mode
B) Phrase-level recovery
C) Backtracking
D) Data flow analysis
Answer: D) Data flow analysis
Which error recovery strategy discards input symbols until a synchronizing token is found?
A) Panic mode recovery
B) Phrase-level recovery
C) Backpatching
D) Intermediate code generation
Answer: A) Panic mode recovery
What is the primary advantage of panic mode recovery?
A) It guarantees that the parser will never enter an infinite loop
B) It provides highly accurate error messages
C) It optimizes code while fixing errors
D) It fixes both syntax and semantic errors
Answer: A) It guarantees that the parser will never enter an infinite loop
In which recovery strategy does the parser make local corrections to the input?
A) Phrase-level recovery
B) Panic mode recovery
C) Backtracking
D) Code generation
Answer: A) Phrase-level recovery
In panic mode recovery, the parser skips tokens until:
A) A predefined synchronizing token is found
B) The entire line is skipped
C) The program terminates
D) The source code is corrected automatically
Answer: A) A predefined synchronizing token is found
A significant drawback of panic mode recovery is:
A) It skips large portions of input, potentially missing multiple errors
B) It causes infinite loops in the parser
C) It requires excessive memory
D) It corrects all errors incorrectly
Answer: A) It skips large portions of input, potentially missing multiple errors
Which of the following is a typical synchronizing token used in panic mode recovery?
A) Semicolon (;)
B) Arithmetic operator (+)
C) Parentheses (())
D) Equal sign (=)
Answer: A) Semicolon (;)
Phrase-level recovery attempts to:
A) Make immediate local corrections to the source code at the point of error
B) Skip input until a synchronizing token is found
C) Reanalyze the entire input from the beginning
D) Terminate the program upon error detection
Answer: A) Make immediate local corrections to the source code at the point of error
Which of the following is the main advantage of phrase-level error recovery?
A) It tries to correct errors without discarding significant input
B) It guarantees that no further errors will occur
C) It optimizes the performance of the code
D) It provides detailed semantic corrections
Answer: A) It tries to correct errors without discarding significant input
Panic Mode Error Recovery
Which of the following describes panic mode recovery in syntax analysis?
A) Discarding input symbols until a synchronizing token is found
B) Making small, local corrections at the point of the error
C) Backtracking to previous input
D) Reanalyzing the entire input from the beginning
Answer: A) Discarding input symbols until a synchronizing token is found
Panic mode error recovery is generally preferred because:
A) It is simple and ensures the parser will not get stuck
B) It corrects both syntax and semantic errors efficiently
C) It fixes all errors in the input code
D) It requires minimal memory
Answer: A) It is simple and ensures the parser will not get stuck
What is a drawback of panic mode recovery?
A) It may skip over large parts of the input, causing multiple errors to be missed
B) It provides detailed correction for all syntax errors
C) It requires significant memory usage
D) It always introduces new errors in the process
Answer: A) It may skip over large parts of the input, causing multiple errors to be missed
In panic mode recovery, a synchronizing token is used to:
A) Help the parser resume parsing after skipping erroneous input
B) Correct the source code at the point of error
C) Detect the next semantic error
D) Terminate the parsing process
Answer: A) Help the parser resume parsing after skipping erroneous input
Which of the following tokens is commonly used as a synchronizing token in panic mode recovery?
A) if
B) else
C) Semicolon (;)
D) Plus (+)
Answer: C) Semicolon (;)
In panic mode recovery, if a closing parenthesis is missing, the parser may skip input until it finds:
A) A semicolon (;)
B) An opening curly brace ({)
C) An operator (+, -, etc.)
D) An identifier
Answer: A) A semicolon (;)
The primary advantage of panic mode error recovery is:
A) Simplicity and assurance that the parser will not enter an infinite loop
B) Detailed and accurate error reporting
C) Optimization of the source code
D) Elimination of all semantic errors
Answer: A) Simplicity and assurance that the parser will not enter an infinite loop
Panic mode error recovery is useful for:
A) Quickly skipping over erroneous input to resume parsing
B) Making detailed corrections to every error in the input
C) Optimizing the input code for efficiency
D) Fixing semantic errors in the source code
Answer: A) Quickly skipping over erroneous input to resume parsing
Which of the following describes a limitation of panic mode recovery?
A) It may skip over large portions of input, missing multiple errors
B) It guarantees that all errors will be corrected
C) It introduces infinite loops into the parsing process
D) It consumes excessive memory during error detection
Answer: A) It may skip over large portions of input, missing multiple errors
Panic mode recovery is most effective when:
A) The goal is to resume parsing quickly after an error is detected
B) The goal is to correct all errors in the source code
C) The parser must backtrack to reanalyze the input
D) The input has no syntax errors
Answer: A) The goal is to resume parsing quickly after an error is detected
Phrase-Level Error Recovery
Phrase-level recovery attempts to:
A) Make localized corrections to the source code at the point of error
B) Skip all remaining input after an error is detected
C) Reanalyze the entire input from the beginning
D) Terminate the program upon error detection
Answer: A) Make localized corrections to the source code at the point of error
Which of the following is a common phrase-level recovery technique?
A) Inserting missing symbols
B) Discarding input until a synchronizing token is found
C) Backtracking through the input
D) Optimizing the input code for efficiency
Answer: A) Inserting missing symbols
The main advantage of phrase-level recovery is:
A) It tries to correct errors without skipping significant input
B) It guarantees that no further errors will occur
C) It optimizes the performance of the code
D) It provides detailed semantic corrections
Answer: A) It tries to correct errors without skipping significant input
In phrase-level recovery, the parser may attempt to correct the error by:
A) Inserting or deleting symbols to allow parsing to continue
B) Skipping all remaining input
C) Entering an infinite loop until the error is resolved
D) Reanalyzing the entire input
Answer: A) Inserting or deleting symbols to allow parsing to continue
What is a drawback of phrase-level recovery?
A) It can introduce new errors during recovery
B) It skips large portions of input
C) It is difficult to implement
D) It optimizes code prematurely
Answer: A) It can introduce new errors during recovery
Phrase-level recovery involves making corrections:
A) At the point of the error with minimal disruption to parsing
B) By skipping all input until a synchronizing token is found
C) By reanalyzing the entire input
D) By discarding the entire line of code
Answer: A) At the point of the error with minimal disruption to parsing
Which of the following is a risk of phrase-level recovery?
A) It may introduce further syntax errors while correcting an error
B) It skips large portions of the source code
C) It always terminates the parsing process after an error
D) It consumes excessive memory during recovery
Answer: A) It may introduce further syntax errors while correcting an error
Phrase-level recovery is most appropriate when:
A) The error can be corrected with small, localized changes
B) Large portions of the input need to be skipped
C) The parser needs to reanalyze the input from the beginning
D) The source code contains no syntax errors
Answer: A) The error can be corrected with small, localized changes
An example of phrase-level error recovery is:
A) Inserting a missing semicolon to allow parsing to continue
B) Skipping input until a synchronizing token is found
C) Reanalyzing the entire input from the beginning
D) Generating optimized machine code after an error is found
Answer: A) Inserting a missing semicolon to allow parsing to continue
Which of the following is NOT a characteristic of phrase-level recovery?
A) Making local corrections to allow parsing to continue
B) Skipping large portions of the input
C) Introducing minor changes at the point of error
D) Attempting to fix the error without terminating parsing
Answer: B) Skipping large portions of the input
More Specific MCQs on Error Handling Strategies
Phrase-level recovery typically corrects errors by:
A) Inserting or deleting symbols
B) Skipping entire sections of code
C) Reanalyzing the entire input
D) Terminating the program immediately
Answer: A) Inserting or deleting symbols
Panic mode recovery is effective in:
A) Ensuring that the parser never enters an infinite loop
B) Correcting all errors accurately
C) Recovering from semantic errors
D) Generating optimized code
Answer: A) Ensuring that the parser never enters an infinite loop
What is a common disadvantage of both panic mode and phrase-level recovery?
A) They may both introduce further errors
B) They always terminate the parsing process
C) They skip large portions of input
D) They provide detailed semantic corrections
Answer: A) They may both introduce further errors
Which of the following is NOT an advantage of panic mode error recovery?
A) Simplicity in implementation
B) Preventing infinite loops in parsing
C) Generating highly accurate error reports
D) Allowing the parser to continue after an error
Answer: C) Generating highly accurate error reports
Panic mode recovery uses what kind of token to resume parsing?
A) Synchronizing token
B) Semantic token
C) Optimizing token
D) Backtracking token
Answer: A) Synchronizing token
In phrase-level recovery, corrections are made:
A) Locally at the point of error
B) By skipping input
C) By reanalyzing the entire input
D) Only after the entire program is parsed
Answer: A) Locally at the point of error
Phrase-level recovery may involve which of the following actions?
A) Inserting or deleting tokens
B) Skipping large sections of input
C) Backtracking through the input
D) Reanalyzing the entire source code
Answer: A) Inserting or deleting tokens
Which of the following strategies is more likely to skip a large portion of the input?
A) Panic mode recovery
B) Phrase-level recovery
C) Intermediate code generation
D) Syntax-directed translation
Answer: A) Panic mode recovery
Which error recovery strategy is simpler but less precise in terms of fixing errors?
A) Panic mode recovery
B) Phrase-level recovery
C) Semantic analysis
D) Machine code generation
Answer: A) Panic mode recovery
The main drawback of phrase-level recovery is that:
A) It may introduce new syntax errors while correcting
B) It requires reanalysis of the entire input
C) It always skips the remaining input
D) It guarantees no further errors
Answer: A) It may introduce new syntax errors while correcting
More Detailed MCQs
In panic mode recovery, what happens if no synchronizing token is found?
A) The parser may skip the entire input
B) The parser will enter an infinite loop
C) The program will terminate
D) The parser will reanalyze the entire input
Answer: A) The parser may skip the entire input
In phrase-level recovery, how does the parser handle missing symbols?
A) It inserts missing symbols at the point of error
B) It skips the input until a synchronizing token is found
C) It discards the entire input
D) It backtracks through the input
Answer: A) It inserts missing symbols at the point of error
Which of the following is an important consideration in choosing a synchronizing token in panic mode recovery?
A) It should be a token that frequently appears in valid input
B) It should be a token that never appears in valid input
C) It should be unique to the program
D) It should terminate the program
Answer: A) It should be a token that frequently appears in valid input
Phrase-level recovery is better suited for:
A) Situations where small corrections can resolve the error
B) Large programs with many errors
C) Situations where the input needs to be skipped entirely
D) Programs with no syntax errors
Answer: A) Situations where small corrections can resolve the error
Which of the following tokens might be used as a synchronizing token in panic mode recovery?
A) end
B) Semicolon (;)
C) Assignment (=)
D) Colon (:)
Answer: B) Semicolon (;)
In phrase-level recovery, the parser typically:
A) Makes localized corrections to continue parsing
B) Skips all remaining input
C) Terminates the parsing process
D) Backtracks through the input
Answer: A) Makes localized corrections to continue parsing
One of the challenges of implementing phrase-level recovery is:
A) It may require introducing new errors to correct old ones
B) It guarantees the correction of all errors
C) It skips large portions of input
D) It simplifies the error correction process significantly
Answer: A) It may require introducing new errors to correct old ones
Which strategy is preferred when rapid error detection and continued parsing are required?
A) Panic mode recovery
B) Phrase-level recovery
C) Semantic analysis
D) Code optimization
Answer: A) Panic mode recovery
The primary objective of both panic mode and phrase-level recovery is to:
A) Continue parsing despite errors
B) Correct all errors in the input
C) Skip all remaining input after an error is detected
D) Terminate the program upon error detection
Answer: A) Continue parsing despite errors
A disadvantage of both panic mode and phrase-level recovery is:
A) They may introduce further errors
B) They consume excessive memory
C) They always terminate the program
D) They guarantee no further errors
Answer: A) They may introduce further errors