Error Detection and Recovery
Basics of Error Detection
What is the primary purpose of error detection?
A) To detect and correct errors in programs
B) To prevent bugs from occurring
C) To detect errors in data transmission or storage
D) To optimize program performance
Answer: C) To detect errors in data transmission or storage
Which of the following is a common error detection technique?
A) Parity check
B) Loop unrolling
C) Pipeline scheduling
D) Address mapping
Answer: A) Parity check
Which error detection method involves counting the number of 1s in a binary sequence?
A) Parity check
B) Checksum
C) CRC (Cyclic Redundancy Check)
D) Hamming code
Answer: A) Parity check
In a single parity bit error detection scheme, what happens when an odd number of errors occur?
A) Errors are not detected
B) Errors are corrected
C) Errors are always detected
D) Errors are ignored
Answer: A) Errors are not detected
Which type of error detection is commonly used in network communication protocols like Ethernet?
A) Cyclic Redundancy Check (CRC)
B) Parity bit
C) Hamming code
D) Gray code
Answer: A) Cyclic Redundancy Check (CRC)
Error Recovery Techniques
What is the primary goal of error recovery?
A) To restore a system to a correct state after an error
B) To identify bugs in the system
C) To stop a program after an error occurs
D) To minimize the system performance overhead
Answer: A) To restore a system to a correct state after an error
Which of the following is an error recovery strategy used in parsers?
A) Panic mode
B) Deadlock avoidance
C) Paging
D) Pipelining
Answer: A) Panic mode
Which error recovery technique discards input symbols until a synchronizing token is found?
A) Panic mode recovery
B) Backtracking
C) Forward recovery
D) Checkpointing
Answer: A) Panic mode recovery
What is backtracking in error recovery?
A) Reverting to a previous correct state to attempt recovery
B) Randomly generating solutions
C) Scanning the code for logical errors
D) Moving forward without considering the error
Answer: A) Reverting to a previous correct state to attempt recovery
Which of the following is NOT an error recovery technique in parsers?
A) Error correction
B) Panic mode recovery
C) Forward error correction
D) Phrase-level recovery
Answer: C) Forward error correction
Parity, Checksums, and CRC
How does a parity bit work in error detection?
A) By checking the number of set bits (1s) in the data
B) By correcting all single-bit errors
C) By comparing two copies of data
D) By counting the number of bytes
Answer: A) By checking the number of set bits (1s) in the data
Which type of parity is used when the number of 1s should be odd?
A) Odd parity
B) Even parity
C) Dynamic parity
D) Continuous parity
Answer: A) Odd parity
A Cyclic Redundancy Check (CRC) is used to detect errors in which type of system?
A) Data communication
B) Video processing
C) Graphics rendering
D) Audio playback
Answer: A) Data communication
Which of the following is true about checksums?
A) They can detect burst errors
B) They are primarily used for detecting hardware failures
C) They ensure both error detection and correction
D) They use cryptographic algorithms
Answer: A) They can detect burst errors
Which of the following best describes CRC (Cyclic Redundancy Check)?
A) A polynomial-based error detection scheme
B) A bitwise inversion technique
C) An encryption algorithm
D) A hardware optimization technique
Answer: A) A polynomial-based error detection scheme
Error Correction
Which method is used to both detect and correct errors?
A) Hamming code
B) Parity bit
C) CRC
D) Checksum
Answer: A) Hamming code
What does the Hamming code correct?
A) Single-bit errors
B) Two-bit errors
C) Burst errors
D) All types of errors
Answer: A) Single-bit errors
In Hamming code, how many parity bits are needed to detect and correct a single error in 7 data bits?
A) 4
B) 3
C) 2
D) 1
Answer: A) 4
Which error correction technique is commonly used in memory systems?
A) ECC (Error Correction Code)
B) CRC (Cyclic Redundancy Check)
C) Parity check
D) Checksum
Answer: A) ECC (Error Correction Code)
Hamming distance is used to measure what?
A) The minimum number of changes required to correct an error
B) The distance between two points in memory
C) The execution speed of a program
D) The size of data
Answer: A) The minimum number of changes required to correct an error
Error Detection in Compilers
What is a common method for detecting syntax errors in a compiler?
A) Using a parser
B) Using a tokenizer
C) Using a garbage collector
D) Using a scheduler
Answer: A) Using a parser
Which phase of the compiler is responsible for error detection related to semantics?
A) Semantic analysis phase
B) Lexical analysis phase
C) Code generation phase
D) Syntax analysis phase
Answer: A) Semantic analysis phase
Which error detection strategy is used to check for undefined variables in a program?
A) Static analysis
B) Dynamic analysis
C) Memory optimization
D) Instruction scheduling
Answer: A) Static analysis
Which error recovery method skips tokens until a synchronizing token is found in parsing?
A) Panic mode
B) Backtracking
C) Correction mode
D) Recursive descent
Answer: A) Panic mode
What type of error does the lexical analysis phase of a compiler typically detect?
A) Invalid tokens or symbols
B) Memory allocation issues
C) Logic errors
D) Stack overflow errors
Answer: A) Invalid tokens or symbols
Error Recovery in Parsing
Which parser error recovery method uses insertions, deletions, and replacements of symbols to fix errors?
A) Phrase-level recovery
B) Panic mode
C) Predictive parsing
D) Bottom-up parsing
Answer: A) Phrase-level recovery
In which method does the parser continue parsing even after detecting an error, attempting to fix the input?
A) Error correction
B) Backtracking
C) Top-down parsing
D) Forward correction
Answer: A) Error correction
Which method is the simplest form of error recovery in parsers?
A) Panic mode recovery
B) Backtracking
C) Dynamic programming
D) Look-ahead parsing
Answer: A) Panic mode recovery
In panic mode error recovery, what happens to the tokens after an error is detected?
A) They are discarded until a synchronization token is found
B) They are modified to fix the error
C) They are stored in a buffer
D) They are re-analyzed using different rules
Answer: A) They are discarded until a synchronization token is found
Which error recovery method involves retrying to parse the input after making certain modifications to correct the error?
A) Error correction
B) Predictive parsing
C) Recursive descent parsing
D) Look-ahead parsing
Answer: A) Error correction
Advanced Topics
Which recovery technique uses checkpoints in systems to restore the state in case of errors?
A) Checkpointing
B) Memory mapping
C) Backtracking
D) Forward recovery
Answer: A) Checkpointing
Which error recovery strategy corrects errors as they occur rather than detecting them first?
A) Forward error correction
B) Backward recovery
C) Panic mode
D) Checkpointing
Answer: A) Forward error correction
What is the purpose of forward recovery in systems?
A) To continue operation by handling errors as they occur
B) To revert to a previous correct state
C) To abort and restart the operation
D) To stop the program immediately after an error
Answer: A) To continue operation by handling errors as they occur
In a distributed system, what technique is used to recover from a partial system failure?
A) Distributed rollback
B) Local rollback
C) Forward error correction
D) Panic mode
Answer: A) Distributed rollback
Which of the following can prevent error propagation in a system?
A) Error isolation
B) Stack allocation
C) Loop unrolling
D) Instruction pipelining
Answer: A) Error isolation’
Miscellaneous
What is the main goal of backward error recovery?
A) To restore the system to a previous valid state
B) To predict future errors
C) To prevent errors from occurring
D) To isolate hardware faults
Answer: A) To restore the system to a previous valid state
In backward error recovery, which of the following is used to revert to a previous correct state?
A) Checkpointing
B) Instruction pipelining
C) Stack optimization
D) Predictive parsing
Answer: A) Checkpointing
What is the primary difference between error detection and error correction?
A) Error correction involves fixing errors after they are detected
B) Error detection involves fixing errors as they occur
C) Error correction prevents errors from occurring
D) Error detection only applies to software, while error correction applies to hardware
Answer: A) Error correction involves fixing errors after they are detected
Which type of system can continue functioning in the presence of errors using error detection and recovery techniques?
A) Fault-tolerant system
B) Distributed system
C) Time-sharing system
D) Real-time system
Answer: A) Fault-tolerant system
In systems with error recovery, what is the role of redundancy?
A) To provide alternative ways of storing or transmitting data
B) To improve system performance
C) To speed up processing
D) To reduce memory usage
Answer: A) To provide alternative ways of storing or transmitting data
Additional Concepts
What is the purpose of recovery blocks in error recovery systems?
A) To provide an alternative sequence of instructions to be executed in case of failure
B) To isolate different parts of the memory
C) To improve the system’s performance
D) To reduce the system’s memory footprint
Answer: A) To provide an alternative sequence of instructions to be executed in case of failure
Which of the following is a strategy for handling errors in distributed systems?
A) Global checkpointing
B) Stack unrolling
C) Phrase-level recovery
D) Bottom-up parsing
Answer: A) Global checkpointing
In a rollback-recovery protocol, which action is taken after detecting an error?
A) The system is restored to a previous checkpoint
B) The system continues without addressing the error
C) The system generates a warning and continues
D) The system pauses all processes
Answer: A) The system is restored to a previous checkpoint
What is a “shadow page” in database systems in the context of error recovery?
A) A copy of the page used to restore data in case of a failure
B) A backup server for processing data
C) An alternative algorithm for error detection
D) A page used to store metadata
Answer: A) A copy of the page used to restore data in case of a failure
What type of fault is often corrected using error detection and recovery techniques?
A) Transient fault
B) Permanent fault
C) Logic fault
D) Performance fault
Answer: A) Transient fault
Which of the following is a non-maskable error that cannot be corrected by recovery techniques?
A) Hardware failure
B) Transient fault
C) Stack overflow
D) Logic error
Answer: A) Hardware failure
Which system ensures minimal data loss and downtime using recovery techniques?
A) Fault-tolerant system
B) Multithreaded system
C) Paging system
D) Pipelined system
Answer: A) Fault-tolerant system
What is the primary goal of using redundant arrays in RAID systems for error recovery?
A) To recover data in case of drive failure
B) To improve access speed
C) To reduce power consumption
D) To optimize cache usage
Answer: A) To recover data in case of drive failure
In compiler error recovery, what does the “parse tree” represent?
A) The hierarchical structure of the source code
B) The list of all variables
C) The sequence of executed commands
D) The result of dynamic memory allocation
Answer: A) The hierarchical structure of the source code
What happens when an error is detected in a real-time system?
A) The system attempts to recover while maintaining timing constraints
B) The system halts all operations
C) The system reboots automatically
D) The system performs an immediate shutdown
Answer: A) The system attempts to recover while maintaining timing constraints