📝 Monitors Usage in Process synchronization (55 MCQs)

📖 From Operating System • 5. Process Synchronization • 55 questions available

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What is Monitors Usage in Process synchronization?

Definition:
Monitor usage involves defining condition variables with wait and signal operations inside the monitor to allow processes to suspend and resume based on logical predicates beyond simple mutual exclusion.

Example:
In a producer-consumer monitor, $notFull.wait()$ suspends the producer when $count==N$ , and $notEmpty.signal()$ wakes a consumer when $count > 0$ .

Reason:
Condition variables enable expressive synchronization semantics within the safe confines of the monitor, separating the concern of mutual exclusion from conditional waiting.

Easy

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📝 All Monitors Usage in Process synchronization MCQs

Q1. An abstract data type (ADT) encapsulates data with a set of functions that are:

A.Dependent on the specific implementation

B.Independent of any specific implementation of the ADT ✅

C.Only accessible to external processes

D.Always implemented as semaphores

💡 Difficulty: easy | ✅ Correct: B

📖 Explanation: An ADT encapsulates data and operations, making the operations independent of the implementation details. This allows programmers to use the ADT without knowing how it is implemented internally, promoting modularity and code reuse.

Q2. A monitor type is an ADT that includes a set of programmer-defined operations provided with:

A.Parallel execution

B.Mutual exclusion within the monitor ✅

C.No synchronization

D.Semaphore-based locking

💡 Difficulty: easy | ✅ Correct: B

📖 Explanation: A monitor type is specifically designed as an ADT that provides mutual exclusion within the monitor. This means that only one process can be active inside the monitor at any given time, ensuring that shared data is accessed safely.

Q3. What does a monitor type declare in addition to function bodies?

A.Only semaphore variables

B.Only condition variables

C.Variables whose values define the state of an instance ✅

D.Only shared global variables

💡 Difficulty: easy | ✅ Correct: C

📖 Explanation: A monitor type declares the variables whose values define the state of an instance of that type. These variables represent the shared data that the monitor is designed to protect and synchronize access to, along with the functions that operate on them.

Q4. In a monitor, functions defined within the monitor can access which variables?

A.Only global variables

B.Any variables in the system

C.Only variables declared locally within the monitor and formal parameters ✅

D.Only semaphore variables

💡 Difficulty: easy | ✅ Correct: C

📖 Explanation: Functions defined within a monitor can only access variables declared locally within the monitor and their formal parameters. This encapsulation ensures that the monitor's data is protected and can only be modified through the monitor's defined operations.

Q5. The local variables of a monitor can be accessed by which functions?

A.Any function in the system

B.Only the local functions within the monitor ✅

C.Only external functions

D.No functions can access them

💡 Difficulty: easy | ✅ Correct: B

📖 Explanation: Local variables of a monitor can only be accessed by the local functions defined within that monitor. This strict encapsulation is fundamental to the monitor construct, as it ensures that the monitor's data is only modified through controlled, synchronized operations.

Q6. What fundamental guarantee does the monitor construct provide?

A.That multiple processes can be active simultaneously

B.That only one process at a time is active within the monitor ✅

C.That no processes can enter the monitor

D.That processes enter the monitor in a specific order

💡 Difficulty: medium | ✅ Correct: B

📖 Explanation: The monitor construct ensures that only one process at a time is active within the monitor. This implicit mutual exclusion is a key feature of monitors, as it relieves programmers from explicitly coding synchronization constraints like semaphore wait() and signal() operations.

Q7. Why does the programmer not need to code synchronization constraints explicitly when using a monitor?

A.Because semaphores are automatically used

B.Because the monitor construct ensures only one process is active at a time ✅

C.Because the compiler handles all synchronization

D.Because processes never interfere with each other

💡 Difficulty: medium | ✅ Correct: B

📖 Explanation: The monitor construct implicitly ensures mutual exclusion by only allowing one process to be active within the monitor at a time. This means the programmer does not need to explicitly code synchronization mechanisms like semaphores to protect shared data, reducing the risk of synchronization errors.

Q8. What additional synchronization mechanism is provided within monitors for modeling complex synchronization schemes?

A.Semaphores

B.Mutexes

C.Condition variables ✅

D.Atomic operations

💡 Difficulty: medium | ✅ Correct: C

📖 Explanation: The monitor construct alone is not sufficient for modeling all synchronization schemes. For more complex synchronization, condition variables are provided. These allow processes to wait for specific conditions to become true before proceeding, enabling more flexible and powerful synchronization.

Q9. A programmer who needs to write a tailor-made synchronization scheme can define condition variables using which syntax?

A.condition x, y; ✅

B.semaphore x, y;

C.mutex x, y;

D.var x, y: condition;

💡 Difficulty: medium | ✅ Correct: A

📖 Explanation: Condition variables are declared using the syntax `condition x, y;`. This declares two condition variables named x and y. These variables can then be used with the `wait()` and `signal()` operations to implement complex synchronization schemes within the monitor.

Q10. Which operations can be invoked on a condition variable?

A.Only wait()

B.Only signal()

C.Both wait() and signal() ✅

D.Neither wait() nor signal()

💡 Difficulty: medium | ✅ Correct: C

📖 Explanation: The only operations that can be invoked on a condition variable are `wait()` and `signal()`. These operations are specifically designed to synchronize processes within a monitor. `wait()` suspends a process, while `signal()` resumes a suspended process.

Q11. What does the `x.wait()` operation do to the process invoking it?

A.It continues execution

B.It suspends the process until another process invokes `x.signal()` ✅

C.It signals other waiting processes

D.It exits the monitor

💡 Difficulty: medium | ✅ Correct: B

📖 Explanation: The `x.wait()` operation suspends the process invoking it. The process remains suspended until another process invokes `x.signal()`. This is the fundamental mechanism for condition synchronization, allowing a process to wait for a specific condition to become true.

Q12. What does the `x.signal()` operation do when invoked on a condition variable?

A.It resumes exactly one suspended process ✅

B.It resumes all suspended processes

C.It blocks the signaling process

D.It has no effect regardless of suspended processes

💡 Difficulty: medium | ✅ Correct: A

📖 Explanation: The `x.signal()` operation resumes exactly one suspended process that is waiting on condition variable x. This is a controlled way to wake up processes, ensuring that only one process is resumed at a time, which helps prevent race conditions.

Q13. What happens if the `x.signal()` operation is invoked and no process is suspended on condition x?

A.The signaling process is suspended

B.The operation has no effect ✅

C.A deadlock occurs

D.A default process is resumed

💡 Difficulty: medium | ✅ Correct: B

📖 Explanation: If no process is suspended on condition x, the `signal()` operation has no effect. The state of x remains unchanged, as if the operation had never been executed. This is a key difference from semaphore signal operations, which always affect the semaphore state.

Q14. How does the `signal()` operation on a condition variable differ from the `signal()` operation on a semaphore?

A.Both always affect the state

B.The condition variable signal has no effect if no process is waiting, while semaphore signal always affects state ✅

C.Semaphore signal has no effect if no process is waiting

D.They are identical

💡 Difficulty: medium | ✅ Correct: B

📖 Explanation: The key difference is that `signal()` on a condition variable has no effect if no process is suspended on that condition. In contrast, `signal()` on a semaphore always affects the semaphore state, incrementing its value regardless of whether processes are waiting.

Q15. When the `x.signal()` operation is invoked by process P and there exists a suspended process Q associated with condition x, what must happen?

A.P continues execution

B.Q continues execution

C.P must wait ✅

D.Both P and Q continue simultaneously

💡 Difficulty: medium | ✅ Correct: C

📖 Explanation: If process P invokes `x.signal()` and process Q is suspended on condition x, P must wait. This is necessary because if both P and Q were active simultaneously within the monitor, mutual exclusion would be violated. Only one process can be active in the monitor at a time.

Q16. In the Signal and Wait approach, what happens when P executes signal and Q is waiting?

A.P continues and Q waits

B.P waits until Q leaves the monitor or waits for another condition ✅

C.Q immediately resumes and P continues

D.Both P and Q continue simultaneously

💡 Difficulty: medium | ✅ Correct: B

📖 Explanation: In the Signal and Wait approach, the signaling process P waits until Q leaves the monitor or waits for another condition. This ensures that mutual exclusion is maintained and allows Q to proceed with its execution before P continues.

Q17. In the Signal and Continue approach, what happens when P executes signal and Q is waiting?

A.P waits for Q

B.Q waits until P leaves the monitor or waits for another condition ✅

C.Both P and Q are active simultaneously

D.P is suspended indefinitely

💡 Difficulty: medium | ✅ Correct: B

📖 Explanation: In the Signal and Continue approach, Q waits until P leaves the monitor or waits for another condition. This allows P, which is already executing, to continue first, maintaining the natural flow of execution while still ensuring only one process is active at a time.

Q18. Which approach is considered more reasonable because P was already executing in the monitor?

A.Signal and Wait

B.Signal and Continue ✅

C.Neither is reasonable

D.Both are equally reasonable

💡 Difficulty: medium | ✅ Correct: B

📖 Explanation: The Signal and Continue approach is often considered more reasonable because P was already executing in the monitor. Since P had already acquired the monitor lock and was active, allowing it to continue is the natural choice, minimizing context switching and maintaining the flow of execution.

Q19. What is the potential problem with the Signal and Continue approach?

A.The logical condition for which Q was waiting may no longer hold by the time Q is resumed ✅

B.Q may never be resumed

C.P may never leave the monitor

D.The monitor may deadlock

💡 Difficulty: medium | ✅ Correct: A

📖 Explanation: The potential problem with Signal and Continue is that by the time Q is resumed, the logical condition for which Q was waiting may no longer hold. During the time P continues executing, the state of the shared data might change, invalidating the condition that Q was waiting for.

Q20. What compromise was adopted in the language Concurrent Pascal regarding signal handling?

A.P continues executing

B.Q continues executing

C.P immediately leaves the monitor, and Q is immediately resumed ✅

D.Both P and Q are suspended

💡 Difficulty: medium | ✅ Correct: C

📖 Explanation: In Concurrent Pascal, when thread P executes the signal operation, it immediately leaves the monitor. This allows Q to be immediately resumed. This compromise balances the need for P to finish its work with the need for Q to proceed, without requiring complex scheduling decisions.

Q21. Which programming languages have incorporated the monitor concept as described?

A.Only Java

B.Only C#

C.Both Java and C# ✅

D.Neither Java nor C#

💡 Difficulty: medium | ✅ Correct: C

📖 Explanation: Both Java and C# have incorporated the monitor concept. Java implements monitors through synchronized methods and blocks, while C# provides similar functionality through lock statements and the Monitor class. These languages were designed with concurrency in mind and used monitors as a fundamental synchronization mechanism.

Q22. Which language provides some type of concurrency support using a mechanism similar to monitors?

A.Java

B.C#

C.Erlang

D.All of the above ✅

💡 Difficulty: medium | ✅ Correct: D

📖 Explanation: Java, C#, and Erlang all provide concurrency support using mechanisms similar to monitors. Java and C# directly incorporate the monitor concept, while Erlang provides similar concurrency support through its own actor-based model, which shares some characteristics with monitors.

Q23. What is the primary purpose of condition variables in a monitor?

A.To replace semaphores

B.To provide additional synchronization mechanisms for complex schemes ✅

C.To increase the speed of execution

D.To reduce memory usage

💡 Difficulty: medium | ✅ Correct: B

📖 Explanation: Condition variables are provided to handle complex synchronization schemes that cannot be modeled with the basic monitor construct alone. They allow processes to wait for specific conditions and be signaled when those conditions become true, providing more flexible synchronization.

Q24. When a process invokes `x.wait()`, what state does it enter?

A.Running state

B.Ready state

C.Suspended state ✅

D.Terminated state

💡 Difficulty: medium | ✅ Correct: C

📖 Explanation: When a process invokes `x.wait()`, it enters a suspended state. The process is blocked and cannot continue execution until another process invokes `x.signal()` on the same condition variable. This is the mechanism for condition synchronization within monitors.

Q25. In the Signal and Wait approach, after P waits, how can P resume execution?

A.P never resumes

B.P resumes automatically after a fixed time

C.P resumes when Q leaves the monitor or waits for another condition ✅

D.P resumes when any process signals

💡 Difficulty: medium | ✅ Correct: C

📖 Explanation: In Signal and Wait, P waits until Q leaves the monitor or waits for another condition. Once Q releases the monitor (by completing its work or waiting on another condition), P can resume execution. This ensures that the monitor's mutual exclusion is maintained.

Q26. What is the main advantage of using monitors over semaphores for synchronization?

A.Monitors are faster

B.Monitors provide automatic mutual exclusion and structured synchronization ✅

C.Monitors use less memory

D.Monitors are simpler to implement

💡 Difficulty: hard | ✅ Correct: B

📖 Explanation: The main advantage of monitors is that they provide automatic mutual exclusion and structured synchronization. Programmers don't need to manually handle semaphore operations for lock acquisition and release, which reduces the risk of errors like deadlocks and race conditions.

Q27. How does a condition variable's signal operation handle the case of multiple waiting processes?

A.It resumes all waiting processes

B.It resumes exactly one suspended process ✅

C.It resumes the first process that invoked wait

D.It resumes the last process that invoked wait

💡 Difficulty: hard | ✅ Correct: B

📖 Explanation: The `signal()` operation on a condition variable resumes exactly one suspended process. This controlled wake-up ensures that only one process proceeds, preventing potential race conditions. The specific process resumed is determined by the system's scheduling policy.

Q28. What is the effect on a condition variable when `signal()` is invoked and no process is waiting?

A.The condition variable is set to a signaling state

B.The operation has no effect ✅

C.The signaling process is suspended

D.The condition variable is reset to its initial state

💡 Difficulty: hard | ✅ Correct: B

📖 Explanation: When `signal()` is invoked on a condition variable and no process is waiting, the operation has no effect. The condition variable remains in the same state, as if the signal operation had never been executed. This is a fundamental difference from semaphore signal operations.

Q29. Consider the scenario: Process P calls `x.signal()` and process Q is waiting on x. In the Signal and Continue approach, what is the immediate effect?

A.Q is resumed immediately and P continues

B.P continues execution and Q waits ✅

C.P is suspended and Q is resumed

D.Both P and Q are suspended

💡 Difficulty: hard | ✅ Correct: B

📖 Explanation: In Signal and Continue, P continues execution, and Q must wait until P leaves the monitor or waits for another condition. This preserves the idea that the currently executing process should continue, while still maintaining mutual exclusion by not allowing Q to enter the monitor until P leaves.

Q30. Consider the scenario: Process P calls `x.signal()` and process Q is waiting on x. In the Signal and Wait approach, what is the immediate effect?

A.P continues execution and Q waits

B.P waits and Q is resumed ✅

C.Both P and Q continue

D.Both P and Q are suspended

💡 Difficulty: hard | ✅ Correct: B

📖 Explanation: In Signal and Wait, P waits, and Q is resumed. This approach prioritizes the waiting process Q, allowing it to proceed immediately. P will be resumed after Q leaves the monitor or waits for another condition, ensuring mutual exclusion is maintained.

Q31. The monitor construct ensures that only one process at a time is active within the monitor. This is known as:

A.Parallel execution

B.Implicit mutual exclusion ✅

C.Explicit semaphore control

D.Conditional synchronization

💡 Difficulty: hard | ✅ Correct: B

📖 Explanation: This feature is called implicit mutual exclusion. The programmer does not need to explicitly code mutual exclusion mechanisms (like semaphores), as the monitor construct automatically ensures that only one process is active within the monitor at any given time.

Q32. In a monitor, a function can access which types of variables?

A.Global variables and local variables

B.Local variables and formal parameters ✅

C.Only formal parameters

D.Only semaphore variables

💡 Difficulty: hard | ✅ Correct: B

📖 Explanation: A function defined within a monitor can only access variables declared locally within the monitor and its formal parameters. This encapsulation ensures that the monitor's internal state is protected and can only be modified through the monitor's own functions, preventing unintended interference.

Q33. Why is the monitor construct not sufficient for modeling all synchronization schemes?

A.Because it cannot handle multiple processes

B.Because some schemes require more complex condition synchronization ✅

C.Because it only works with semaphores

D.Because it cannot prevent deadlocks

💡 Difficulty: hard | ✅ Correct: B

📖 Explanation: The basic monitor construct is not sufficient for modeling all synchronization schemes because some schemes require more complex synchronization than simple mutual exclusion. Condition variables were introduced to address this limitation, allowing processes to wait for specific conditions before proceeding.

Q34. What is the role of condition variables in monitor-based synchronization?

A.To provide mutual exclusion

B.To allow processes to wait for specific conditions and be signaled when those conditions become true ✅

C.To replace all other synchronization mechanisms

D.To speed up monitor execution

💡 Difficulty: hard | ✅ Correct: B

📖 Explanation: Condition variables enable more complex synchronization by allowing processes to wait for specific conditions to become true. When a process needs to wait for a condition, it executes `wait()`. When another process makes the condition true, it executes `signal()` to resume the waiting process.

Q35. What is the fundamental difference between semaphore `signal()` and condition variable `signal()` regarding state changes?

A.Both always change the state

B.Semaphore `signal()` always changes state; condition variable `signal()` may not ✅

C.Condition variable `signal()` always changes state; semaphore `signal()` may not

D.Neither changes the state

💡 Difficulty: hard | ✅ Correct: B

📖 Explanation: The fundamental difference is that semaphore `signal()` always affects the semaphore state (incrementing its value), while condition variable `signal()` only affects the state if a process is waiting. If no process is waiting, the condition variable's state remains unchanged, and the signal operation is effectively ignored.

Q36. In Concurrent Pascal's compromise for signal handling, why does P immediately leave the monitor?

A.To allow Q to be immediately resumed ✅

B.To improve performance

C.To prevent deadlock

D.To satisfy both signal and wait approaches

💡 Difficulty: hard | ✅ Correct: A

📖 Explanation: In Concurrent Pascal, P immediately leaves the monitor so that Q can be immediately resumed. This compromise ensures that the waiting process Q gets to proceed without delay, while P has completed its operation and releases the monitor. This balances the needs of both processes.

Q37. What is the potential issue with Signal and Continue where Q waits until P leaves the monitor?

A.P may never leave the monitor

B.The condition Q was waiting for may no longer hold by the time Q resumes

C.Q may starve

D.All of the above ✅

💡 Difficulty: hard | ✅ Correct: D

📖 Explanation: Signal and Continue has several potential issues: P may never leave the monitor (causing Q to wait indefinitely), the condition Q was waiting for may change while P continues, and Q could potentially starve if P repeatedly continues and prevents Q from being scheduled.

Q38. In Signal and Wait, why does P need to wait after signaling?

A.To allow Q to execute while ensuring only one process is active in the monitor ✅

B.To prevent Q from executing

C.To improve system performance

D.To satisfy compiler requirements

💡 Difficulty: hard | ✅ Correct: A

📖 Explanation: In Signal and Wait, P waits after signaling to ensure that only one process is active in the monitor at a time. If P continued, both P and Q would be active simultaneously, violating the monitor's fundamental mutual exclusion property. Waiting allows Q to proceed while maintaining synchronization.

Q39. In Signal and Continue, why does Q wait after being signaled?

A.To allow P to complete its work in the monitor ✅

B.To prevent P from executing

C.To improve system performance

D.To satisfy compiler requirements

💡 Difficulty: hard | ✅ Correct: A

📖 Explanation: In Signal and Continue, Q waits after being signaled to allow P to complete its work in the monitor. Since P was already executing, this approach maintains the natural flow of execution and ensures that P's work is completed before Q proceeds, while still preserving mutual exclusion.

Q40. What is the condition variable state when `x.signal()` is invoked and no process is suspended?

A.The condition variable is set to 0

B.The condition variable is set to 1

C.The state remains unchanged ✅

D.The condition variable is reset

💡 Difficulty: hard | ✅ Correct: C

📖 Explanation: When `x.signal()` is invoked and no process is suspended on condition x, the state of the condition variable remains unchanged. The operation effectively does nothing, and the condition variable continues as if the signal had never been called.

Q41. What is the primary reason for using condition variables in monitors rather than just semaphores?

A.Condition variables provide more flexible and structured condition synchronization ✅

B.Condition variables are faster

C.Condition variables use less memory

D.Condition variables are easier to implement

💡 Difficulty: hard | ✅ Correct: A

📖 Explanation: Condition variables provide more flexible and structured condition synchronization because they are specifically designed for waiting and signaling within monitors. Unlike semaphores, condition variables allow fine-grained control over condition checking and signaling, making them more suitable for complex synchronization schemes.

Q42. When a process is suspended on a condition variable, how can it be resumed?

A.Only by invoking `signal()` on the same condition variable ✅

B.Only by invoking `signal()` on any condition variable

C.By the operating system automatically

D.By invoking `wait()` on the same condition variable

💡 Difficulty: hard | ✅ Correct: A

📖 Explanation: A process suspended on a condition variable can only be resumed when another process invokes `signal()` on the same condition variable. This targeted signaling ensures that only the appropriate waiting processes are resumed, maintaining synchronization correctness.

Q43. What is a disadvantage of the Signal and Continue approach?

A.P cannot continue its work

B.Q may be delayed indefinitely

C.The condition Q was waiting for might change before Q is resumed ✅

D.P leaves the monitor immediately

💡 Difficulty: hard | ✅ Correct: C

📖 Explanation: A key disadvantage is that the condition Q was waiting for might change before Q is resumed. While P continues executing, it may modify shared data, invalidating the condition that caused Q to wait. When Q finally resumes, it must recheck the condition, potentially requiring it to wait again.

Q44. What is a disadvantage of the Signal and Wait approach?

A.P may be delayed indefinitely ✅

B.Q may not get to execute

C.The condition P was waiting for might change

D.P cannot signal again

💡 Difficulty: hard | ✅ Correct: A

📖 Explanation: A key disadvantage is that P may be delayed indefinitely if Q never leaves the monitor or waits for another condition. If Q enters an infinite loop or deadlocks, P will never resume execution. This potential for indefinite delay makes Signal and Wait less predictable.

Q45. How does the Concurrent Pascal compromise address the issues with both Signal and Wait and Signal and Continue?

A.By having P leave the monitor immediately, allowing Q to resume ✅

B.By having Q leave the monitor immediately

C.By having both P and Q continue simultaneously

D.By having neither process continue

💡 Difficulty: hard | ✅ Correct: A

📖 Explanation: The Concurrent Pascal compromise addresses the issues by having P immediately leave the monitor after signaling, allowing Q to resume immediately. This ensures Q does not have to wait and P's work is completed, avoiding the problems of both approaches.

Q46. The monitor concept is most similar to which software engineering principle?

A.Code reuse

B.Encapsulation ✅

C.Inheritance

D.Polymorphism

💡 Difficulty: hard | ✅ Correct: B

📖 Explanation: The monitor concept is most similar to encapsulation. Monitors encapsulate shared data and the functions that operate on it, hiding the internal state and protecting it from unauthorized access. This is a fundamental principle of object-oriented programming, where encapsulation ensures data integrity and modularity.

Q47. What is the significance of Java and C# incorporating the monitor concept?

A.It shows monitors are only used in academic settings

B.It demonstrates the practical importance of monitors in modern programming languages ✅

C.It indicates monitors are obsolete

D.It means semaphores are no longer needed

💡 Difficulty: hard | ✅ Correct: B

📖 Explanation: The incorporation of monitors in Java and C# demonstrates the practical importance of monitors in modern programming languages. These languages were designed for concurrent programming and used monitors as a fundamental synchronization mechanism, validating the monitor concept's utility in real-world applications.

Q48. In the context of monitors, what does the entry queue in Figure 5.16 represent?

A.Processes waiting for the monitor's mutex ✅

B.Processes waiting for condition variables

C.Processes that have finished execution

D.Processes not yet created

💡 Difficulty: hard | ✅ Correct: A

📖 Explanation: The entry queue in a monitor represents processes waiting to enter the monitor. Since only one process can be active in the monitor at a time, other processes that call monitor functions are queued in the entry queue, waiting for their turn to acquire the monitor lock and execute their operations.

Q49. What is the state of a condition variable when it is first declared?

A.It has no associated queue ✅

B.It has one waiting process

C.It has multiple waiting processes

D.It is initialized with a signal

💡 Difficulty: hard | ✅ Correct: A

📖 Explanation: When a condition variable is first declared, it has no associated queue of waiting processes. It is in an initial state where no process is suspended on it. The queue is dynamically created as processes execute `wait()` and is emptied as processes are resumed by `signal()` operations.

Q50. What does a process do when it invokes `x.wait()` in terms of monitor locks?

A.It releases the monitor lock and suspends ✅

B.It keeps the monitor lock and suspends

C.It releases the monitor lock and continues

D.It keeps the monitor lock and continues

💡 Difficulty: hard | ✅ Correct: A

📖 Explanation: When a process invokes `x.wait()`, it releases the monitor lock and then suspends. This is necessary because the lock must be released to allow other processes to enter the monitor and potentially signal the condition. The process will reacquire the lock when it is resumed.

Q51. What is the result if a process in a monitor invokes `x.wait()` without having released the monitor lock?

A.It continues execution

B.It causes a deadlock

C.It releases the lock automatically ✅

D.It signals other processes

💡 Difficulty: hard | ✅ Correct: C

📖 Explanation: When `x.wait()` is invoked, the monitor lock is automatically released by the system. This is a built-in feature of the wait operation. The process then suspends, and the lock becomes available for other processes to enter the monitor, preventing deadlock and ensuring progress.

Q52. How does the monitor construct handle the situation where a process is suspended on a condition variable?

A.It holds the monitor lock until the process resumes

B.It releases the monitor lock and other processes can enter ✅

C.It terminates the process

D.It signals all other processes

💡 Difficulty: hard | ✅ Correct: B

📖 Explanation: When a process is suspended on a condition variable, the monitor releases the monitor lock, allowing other processes to enter the monitor. This is essential for preventing deadlock, as the suspended process cannot make progress, and other processes must be able to enter the monitor to signal the condition.

Q53. The language Erlang provides concurrency support using:

A.Exactly the same monitor mechanism as Java

B.A similar mechanism to monitors ✅

C.No synchronization support

D.Only semaphores

💡 Difficulty: hard | ✅ Correct: B

📖 Explanation: Erlang provides concurrency support using a mechanism similar to monitors, though it is based on an actor model rather than traditional monitors. This demonstrates that the principles behind monitors are widely applicable and have influenced the design of multiple programming languages for concurrent programming.

Q54. What is the purpose of having multiple condition variables within a single monitor?

A.To synchronize different types of conditions separately ✅

B.To increase the number of processes in the monitor

C.To replace the need for monitor functions

D.To make the monitor faster

💡 Difficulty: hard | ✅ Correct: A

📖 Explanation: Multiple condition variables allow a single monitor to manage different types of conditions separately. For example, in a bounded buffer, separate condition variables could be used for 'buffer full' and 'buffer empty' conditions, allowing processes to wait for specific conditions and be signaled appropriately.

Q55. Which synchronization construct is most directly related to the condition variables in monitors?

A.Semaphores ✅

B.Mutexes

C.Reader-writer locks

D.Spinlocks

💡 Difficulty: hard | ✅ Correct: A

📖 Explanation: Condition variables in monitors are most directly related to semaphores, as both provide waiting and signaling mechanisms. However, condition variables are specifically designed for use within monitors and have different semantics (no effect if no waiting process) compared to general semaphores.

🔗 Related Topics (MCQs)

📝 Process Synchronization in operating system MCQs 📝 The Critical Section Problem in Process Synchronization MCQs 📝 Peterson's Solution MCQs 📝 Synchronization hardware in operating system MCQs 📝 Mutex Locks in Process Synchronization MCQs

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