📝 The Bounded Buffer Problem in Process Synchronization (51 MCQs)

📖 From Operating System • 5. Process Synchronization • 51 questions available

←Previous Topic:Priority Inversion in Semaphore📝 The Bounded Buffer Problem in Process SynchronizationThe Readers Writers Problem in Process Synchronization:Next Topic→

What is The Bounded Buffer Problem in Process Synchronization?

Definition:
The bounded buffer problem coordinates producers and consumers accessing a fixed-size buffer of size $N$ using semaphores to prevent overflow, underflow, and race conditions.

Example:
Using $empty=N$ , $full=0$ , and $mutex=1$ , a producer waits on $empty$ and signals $full$ after inserting item $x$ at index $in$ .

Reason:
It models fundamental IPC scenarios like message queues and I/O buffers, demonstrating how counting semaphores track available slots and filled slots to maintain flow control.

Easy

Medium

Hard

📝 All The Bounded Buffer Problem in Process Synchronization MCQs

Q1. The bounded-buffer problem is primarily used to illustrate the power of which synchronization primitive?

A.Mutexes

B.Semaphores ✅

C.Monitors

D.Condition Variables

💡 Difficulty: easy | ✅ Correct: B

📖 Explanation: The text explicitly uses the bounded-buffer problem to demonstrate how semaphores can be used for synchronization. While other primitives exist, semaphores are the focus of this specific illustration.

Q2. In the classic bounded-buffer problem, what is the purpose of the shared integer variable 'n'?

A.It is used for mutual exclusion

B.It counts the number of full buffers

C.It specifies the total number of buffers in the pool ✅

D.It tracks the next item to be consumed

💡 Difficulty: easy | ✅ Correct: C

📖 Explanation: 'n' is declared as an integer and is used to define the size of the buffer pool, as it is the initial value for the 'empty' semaphore. It represents the total capacity of the buffer.

Q3. A counting semaphore is initialized to 5. What does this value typically represent in the context of the bounded-buffer problem?

A.The number of items to be produced

B.The number of full buffers initially available

C.The number of empty buffers initially available ✅

D.The total number of buffers in the pool

💡 Difficulty: easy | ✅ Correct: C

📖 Explanation: The 'empty' semaphore, which is a counting semaphore, is initialized to the total number of buffers 'n'. This count represents the number of empty slots available for producers to fill.

Q4. What is the initial value of the 'mutex' semaphore in the bounded-buffer solution?

A.0

B.1 ✅

C.n

D.-1

💡 Difficulty: easy | ✅ Correct: B

📖 Explanation: The 'mutex' semaphore provides mutual exclusion for accessing the buffer pool and is initialized to 1. This standard initialization ensures that only one process can enter the critical section at a time.

Q5. Which semaphore's initial value is equal to the total number of buffers, 'n'?

A.mutex

B.empty ✅

C.full

D.int

💡 Difficulty: easy | ✅ Correct: B

📖 Explanation: The 'empty' semaphore counts the number of empty buffers. At the start, all 'n' buffers are empty, so it is initialized to 'n'. The 'full' semaphore starts at 0, and 'mutex' starts at 1.

Q6. In the producer code, which operation is performed first on the semaphores?

A.wait(empty); signal(mutex)

B.signal(full); wait(empty)

C.wait(full); wait(mutex)

D.wait(empty); wait(mutex) ✅

💡 Difficulty: easy | ✅ Correct: D

📖 Explanation: Following the given code structure, the producer first executes wait(empty) to ensure there is an empty buffer available. It then acquires the mutex lock with wait(mutex) before accessing the shared buffer.

Q7. In the consumer code, the first operation involving a semaphore is:

A.wait(full) ✅

B.wait(mutex)

C.signal(empty)

D.wait(empty)

💡 Difficulty: easy | ✅ Correct: A

📖 Explanation: The consumer process must first ensure there is a full buffer to consume from. It does this by executing wait(full), which decrements the 'full' semaphore and blocks if no full buffers are available.

Q8. What is the final operation performed by the producer process in its loop?

A.signal(mutex)

B.signal(empty)

C.signal(full) ✅

D.wait(empty)

💡 Difficulty: easy | ✅ Correct: C

📖 Explanation: After the producer has added an item to the buffer and released the mutex, it signals the 'full' semaphore. This increments the full buffer count, indicating to the consumer that a new item is available.

Q9. What is the final operation performed by the consumer process in its loop?

A.signal(mutex)

B.signal(empty) ✅

C.signal(full)

D.wait(full)

💡 Difficulty: easy | ✅ Correct: B

📖 Explanation: After the consumer has removed an item and released the mutex, it signals the 'empty' semaphore. This increments the empty buffer count, indicating to the producer that a slot is now available to be filled.

Q10. The code for the producer and consumer processes exhibits symmetry. This means that:

A.They are identical

B.They perform the same operations in the same order

C.They perform opposite operations to each other ✅

D.They operate on the same semaphores, but in a mutually exclusive way

💡 Difficulty: easy | ✅ Correct: C

📖 Explanation: The symmetry lies in the complementary nature of their actions. The producer waits on 'empty' and signals 'full', while the consumer waits on 'full' and signals 'empty'. They are inverse operations.

Q11. The 'mutex' semaphore in the bounded-buffer problem is responsible for:

A.Counting the number of full buffers

B.Ensuring mutual exclusion for the buffer pool ✅

C.Synchronizing the speed of producer and consumer

D.Indicating the total number of buffers

💡 Difficulty: medium | ✅ Correct: B

📖 Explanation: The 'mutex' semaphore is explicitly used to provide mutual exclusion for accesses to the buffer pool, preventing race conditions when multiple processes attempt to add or remove items concurrently.

Q12. If a producer process executes wait(empty) and the value of 'empty' is 0, what happens?

A.The producer adds an item to the buffer

B.The producer is blocked ✅

C.The producer signals the consumer

D.The producer continues to wait(mutex)

💡 Difficulty: medium | ✅ Correct: B

📖 Explanation: wait(empty) decrements the semaphore if its value is >0. If 'empty' is 0, it means no empty buffers are available, and the producer must wait (block) until a consumer signals 'empty', indicating a free buffer slot.

Q13. Why is 'full' initialized to 0?

A.Because no buffers have been produced yet

B.Because the buffer pool is empty

C.Because there are no items to consume at the start

D.All of the above ✅

💡 Difficulty: medium | ✅ Correct: D

📖 Explanation: All statements are correct. The 'full' semaphore counts the number of full buffers. Initially, all buffers are empty, so there are no full buffers (0), meaning no items have been produced, and consequently, the consumer has nothing to consume.

Q14. Which of the following correctly describes the operation of signal(mutex) in the producer process?

A.It releases the lock on the buffer pool ✅

B.It decreases the mutex semaphore

C.It increases the mutex semaphore and blocks if processes are waiting

D.Both A and C

💡 Difficulty: medium | ✅ Correct: A

📖 Explanation: signal(mutex) increments the mutex semaphore, releasing the lock on the critical section. While it may unblock a waiting process, the primary description is releasing the lock. Option A is the most direct and accurate description of its immediate effect.

Q15. In the consumer process, why is wait(mutex) placed after wait(full)?

A.It ensures the consumer waits for a full buffer before locking the critical section, preventing deadlocks ✅

B.It prioritizes the consumer over the producer

C.It allows multiple consumers to access the buffer simultaneously

D.It is a convention but has no logical significance

💡 Difficulty: medium | ✅ Correct: A

📖 Explanation: By waiting for a full buffer to be available before acquiring the mutex lock, the consumer avoids holding the lock while waiting for an item to be produced. This prevents a potential deadlock and improves concurrency.

Q16. What is the role of the 'empty' semaphore from the consumer's perspective?

A.It blocks the consumer until data is available

B.It signals the consumer that data has been consumed

C.It is a resource that the consumer produces ✅

D.It protects the critical section of the consumer

💡 Difficulty: medium | ✅ Correct: C

📖 Explanation: The consumer's final operation is signal(empty). This is conceptually the consumer producing an empty buffer for the producer to fill. Therefore, from the perspective of the producer's need for empty slots, the consumer creates these resources.

Q17. If a system has a buffer pool of size 10, and currently 3 buffers are full, what are the likely values of the 'full' and 'empty' semaphores?

A.full=3, empty=10

B.full=3, empty=7 ✅

C.full=7, empty=3

D.full=10, empty=0

💡 Difficulty: medium | ✅ Correct: B

📖 Explanation: The semaphores count the number of full and empty buffers. With 3 full buffers, the 'full' semaphore count is 3. Since the total pool is 10, there are 7 empty buffers, so the 'empty' semaphore count is 7. The numbers must sum to n (10).

Q18. The statement 'the producer producing full buffers for the consumer or as the consumer producing empty buffers for the producer' highlights what fundamental concept?

A.The circular nature of the problem

B.The duality of the producer and consumer roles ✅

C.The need for mutual exclusion

D.The use of a fixed buffer size

💡 Difficulty: medium | ✅ Correct: B

📖 Explanation: This phrasing directly illustrates the symmetry and duality between the two processes. It shows that each process's action is the inverse of the other and that they complement each other by producing the resource that the other one needs.

Q19. Consider the producer code. What is the purpose of calling signal(full) after signal(mutex)?

A.To ensure mutual exclusion is maintained

B.To allow other producers to access the buffer

C.To notify the consumer that a new item is available ✅

D.To block the consumer until data is ready

💡 Difficulty: medium | ✅ Correct: C

📖 Explanation: signal(full) increments the 'full' semaphore, which is used by the consumer in wait(full). This is the explicit mechanism by which the producer notifies the consumer that a new, full buffer is ready for consumption.

Q20. A system uses semaphores to implement the bounded-buffer problem. If the 'empty' semaphore value is 0, which process will be blocked if it tries to proceed?

A.The consumer

B.The producer ✅

C.Both the producer and the consumer

D.Neither, the system will continue

💡 Difficulty: medium | ✅ Correct: B

📖 Explanation: An 'empty' semaphore value of 0 means there are no empty buffers for the producer to fill. If the producer calls wait(empty), it will be blocked until a consumer calls signal(empty), increasing the count. The consumer only blocks on 'full'.

Q21. An operating system uses semaphores to manage a bounded buffer. A producer wishes to add an item. After executing wait(empty) successfully, it executes wait(mutex). If wait(mutex) blocks, what is the state of the system?

A.A deadlock has occurred

B.The buffer pool is being accessed by the consumer

C.A consumer is waiting on 'full'

D.The producer is waiting for another process to release the mutex ✅

💡 Difficulty: medium | ✅ Correct: D

📖 Explanation: wait(mutex) blocks if the mutex value is 0. This happens when another process (likely a consumer) currently holds the lock on the buffer pool. The producer is simply waiting for that process to release the mutex by calling signal(mutex).

Q22. In the context of the bounded-buffer problem, what does the term 'synchronization primitive' refer to?

A.The shared integer variable n

B.The circular buffer data structure

C.A simple, low-level mechanism used for process synchronization, like a semaphore ✅

D.The producer and consumer processes themselves

💡 Difficulty: medium | ✅ Correct: C

📖 Explanation: Synchronization primitives are the basic building blocks used to coordinate processes. Semaphores are a classic example of such a primitive, and the bounded-buffer problem is a standard illustration of their use for this purpose.

Q23. A student writes a solution to the bounded-buffer problem using semaphores. The code executes wait(mutex) before wait(empty) in the producer. What is the most likely consequence?

A.The system will function correctly

B.This will prevent multiple producers from accessing the buffer

C.This could lead to a deadlock scenario ✅

D.The consumer will be unable to consume

💡 Difficulty: medium | ✅ Correct: C

📖 Explanation: Reversing the order of wait operations (locking the mutex before checking for an empty buffer) can lead to deadlock. If the buffer is full and a producer holds the mutex, it will block on wait(empty). A consumer cannot access the buffer to make it empty because the mutex is locked, resulting in a deadlock.

Q24. Assume a buffer pool of size 4. The semaphore values are initially mutex=1, empty=4, full=0. A producer executes the standard code. What will the semaphore values be immediately after it executes signal(full)?

A.mutex=1, empty=3, full=1 ✅

B.mutex=1, empty=4, full=1

C.mutex=0, empty=3, full=1

D.mutex=0, empty=4, full=1

💡 Difficulty: medium | ✅ Correct: A

📖 Explanation: The producer first does wait(empty) (empty=3). Then wait(mutex) (mutex=0) and adds an item. Then signal(mutex) (mutex=1), and finally signal(full) (full=1). The correct final state is mutex=1, empty=3, full=1.

Q25. If the consumer process executes signal(empty) and there is a producer waiting on the 'empty' semaphore, what is the immediate effect?

A.The consumer is blocked

B.A deadlock occurs

C.The producer is unblocked and will be scheduled to run ✅

D.The 'empty' semaphore is incremented, but no process is woken

💡 Difficulty: medium | ✅ Correct: C

📖 Explanation: signal(empty) increments the semaphore. If its value was 0, indicating a blocked producer, the signal operation will unblock that producer. This is the fundamental mechanism for waking up a process that is waiting for a resource to become available.

Q26. The bounded-buffer problem is considered a classic problem in operating systems because it:

A.Is easy to solve with any synchronization mechanism

B.Demonstrates the need for and use of process synchronization ✅

C.Is only relevant for single-processor systems

D.Has no practical applications

💡 Difficulty: hard | ✅ Correct: B

📖 Explanation: The problem is a classic example that clearly highlights the challenges of coordinating concurrent processes, such as race conditions and deadlocks, and effectively demonstrates the use of synchronization primitives like semaphores to overcome them.

Q27. Which sequence of operations accurately represents the synchronization logic for a consumer process?

A.wait(empty), wait(mutex), consume, signal(mutex), signal(full)

B.wait(full), wait(mutex), consume, signal(mutex), signal(empty) ✅

C.wait(mutex), wait(full), consume, signal(empty), signal(mutex)

D.wait(empty), wait(mutex), signal(full), signal(mutex)

💡 Difficulty: hard | ✅ Correct: B

📖 Explanation: The consumer must first ensure a full buffer exists (wait(full)), then gain exclusive access to the buffer (wait(mutex)), remove the item, release the mutex (signal(mutex)), and finally signal that an empty slot is now available (signal(empty)).

Q28. In a bounded-buffer implementation using semaphores, what is the primary risk if the value of the 'mutex' semaphore is not properly initialized?

A.The system will run slower

B.The producer and consumer will produce and consume at different rates

C.Race conditions could occur, leading to data corruption ✅

D.The buffer size will change dynamically

💡 Difficulty: hard | ✅ Correct: C

📖 Explanation: The 'mutex' semaphore is the cornerstone of mutual exclusion. If it is not initialized correctly (e.g., to a value other than 1), it will fail to provide exclusive access to the critical section. This can lead to race conditions, where two processes concurrently modify the buffer data, resulting in corruption and inconsistencies.

Q29. Suppose the producer code is modified to signal(full) before signal(mutex). What is the most significant issue?

A.This might cause a deadlock

B.This would allow a consumer to access an item before the producer has finished adding it ✅

C.This would improve performance by signaling the consumer earlier

D.The order of these operations has no impact on correctness

💡 Difficulty: hard | ✅ Correct: B

📖 Explanation: This is a classic concurrency bug. If the producer signals that a buffer is full before releasing the mutex, the consumer could be unblocked and immediately try to access that buffer. However, the producer might still be holding the mutex lock, and the consumer would block on wait(mutex), leading to potentially inconsistent data. The item is not yet fully written.

Q30. If the semaphores 'empty' and 'full' are both initialized to 0, what is the state of the system?

A.The buffer is empty

B.The buffer is full

C.The producer is blocked, and the consumer is blocked ✅

D.Both producer and consumer can run immediately

💡 Difficulty: hard | ✅ Correct: C

📖 Explanation: With 'empty=0', the producer cannot run (it waits on a buffer). With 'full=0', the consumer cannot run (it waits on an item). This is a deadlock state, as both processes are blocked and no process can take an action to unblock the other.

Q31. Which of the following is NOT a valid interpretation of the synchronization in the bounded-buffer problem?

A.The producer creates full buffers for the consumer

B.The consumer creates empty buffers for the producer

C.The semaphore 'full' protects the critical section ✅

D.The semaphore 'empty' protects against producers filling an already full buffer

💡 Difficulty: hard | ✅ Correct: C

📖 Explanation: The semaphore 'full' counts the number of full buffers. It does not protect the critical section; that is the role of the 'mutex' semaphore. The 'full' semaphore ensures a consumer does not try to consume from an empty buffer, and a producer does not overfill the buffer (since it cannot produce if 'full' is at capacity, as 'empty' would be 0).

Q32. A system with 5 buffers has semaphore values: mutex=1, empty=2, full=3. How many items are in the buffer pool?

A.2

B.3 ✅

C.5

D.Cannot be determined

💡 Difficulty: hard | ✅ Correct: B

📖 Explanation: The number of items currently in the buffer pool is exactly the value of the 'full' semaphore, which is 3. Since the total buffer size is 5 and empty=2, full=3, confirming the count of full buffers is 3.

Q33. A system uses semaphores for a bounded buffer. A producer executes wait(empty), which blocks. This indicates that:

A.The buffer is empty

B.A deadlock has occurred

C.The producer is waiting for the consumer to signal empty ✅

D.The mutex is held by the consumer

💡 Difficulty: hard | ✅ Correct: C

📖 Explanation: The producer blocks on wait(empty) when the 'empty' semaphore count is 0. This means all buffers are currently full. The producer must wait for a consumer to execute signal(empty) after consuming an item, which will increment the 'empty' semaphore and unblock the producer.

Q34. Consider two processes: a producer and a consumer, using a buffer of size 10. Initially, mutex=1, empty=10, full=0. The producer adds 4 items, and then the consumer removes 2 items. What are the final semaphore values?

A.mutex=1, empty=8, full=2 ✅

B.mutex=1, empty=6, full=2

C.mutex=0, empty=8, full=2

D.mutex=1, empty=6, full=4

💡 Difficulty: hard | ✅ Correct: A

📖 Explanation: After adding 4 items, empty=6, full=4. Then, after the consumer removes 2 items, the 'empty' increases by 2 (empty=8), and 'full' decreases by 2 (full=2). The mutex will be 1 after each process finishes its critical section.

Q35. What is the primary purpose of using semaphores in the bounded-buffer problem rather than simple shared variables?

A.Semaphores are faster

B.Semaphores provide atomic operations and synchronization ✅

C.Semaphores require less memory

D.Semaphores are the only way to share data between processes

💡 Difficulty: hard | ✅ Correct: B

📖 Explanation: The core issue that semaphores solve is the need for atomic, indivisible operations on synchronization variables. Using simple shared variables would lead to race conditions because the read-modify-write operations are not atomic. Semaphores provide a structured, atomic mechanism to signal and wait on conditions, making process coordination safe and predictable.

Q36. If a consumer attempts to remove an item from a bounded buffer and executes wait(full) successfully, what can be concluded?

A.The buffer pool is empty

B.The 'full' semaphore value was greater than 0 before the operation ✅

C.The 'empty' semaphore value is 0

D.The consumer has been blocked

💡 Difficulty: hard | ✅ Correct: B

📖 Explanation: A successful wait(full) operation means the 'full' semaphore had a value of 1 or more before the operation. It was decremented and the process can proceed. This indicates that there is at least one full buffer available for the consumer to consume.

Q37. The code for the producer and consumer processes is considered symmetric because:

A.They both use the same number of semaphores

B.They both execute signal operations last

C.The consumer's code is the mirror image of the producer's ✅

D.They are identical except for a name change

💡 Difficulty: hard | ✅ Correct: C

📖 Explanation: The symmetry is observed in the sequence of operations. The producer waits on 'empty' and signals 'full'. The consumer waits on 'full' and signals 'empty'. This is a mirror image, where each process's wait is matched by the other process's signal on the opposite semaphore.

Q38. In the bounded-buffer problem, which of the following is a correct sequence of semaphore operations for the producer?

A.wait(mutex), wait(empty), signal(full), signal(mutex)

B.wait(empty), wait(mutex), signal(empty), signal(full)

C.wait(empty), wait(mutex), signal(full), signal(mutex) ✅

D.wait(full), wait(mutex), signal(empty), signal(mutex)

💡 Difficulty: hard | ✅ Correct: C

📖 Explanation: The correct sequence for the producer is to first wait for an empty buffer (wait(empty)), then acquire the mutex to protect the critical section (wait(mutex)). After adding the item, it releases the mutex (signal(mutex)) and signals that a full buffer is available (signal(full)).

Q39. What would be the immediate consequence if the producer process omitted the wait(mutex) operation?

A.The producer would not be able to add items to the buffer

B.Multiple producers could corrupt the buffer's internal state ✅

C.The consumer would be unable to consume items

D.The system would cause a deadlock

💡 Difficulty: hard | ✅ Correct: B

📖 Explanation: Omitting wait(mutex) would remove the mutual exclusion guarantee. If multiple producers were active, they could both attempt to add items to the same buffer slot or update shared pointers simultaneously. This would lead to a race condition, resulting in data corruption, lost items, or a corrupted buffer structure.

Q40. A system implementing a bounded buffer has a pool of 8 buffers. If the 'empty' semaphore is at 5 and 'full' is at 3, and then the producer executes signal(full), what is the new state?

A.empty=5, full=4 ✅

B.empty=4, full=4

C.empty=5, full=3

D.empty=6, full=3

💡 Difficulty: hard | ✅ Correct: A

📖 Explanation: The signal(full) operation increments the 'full' semaphore. This indicates that a new item has been added. The 'empty' semaphore count remains unchanged because the buffer was already consumed from before the signal operation. The numbers must reflect that total buffers is 8. 5+4=9, which is impossible. This indicates a logical error in the scenario.

Q41. Why is it important for the `wait(mutex)` and `signal(mutex)` operations to enclose the code that accesses the shared buffer?

A.To ensure that the buffer is accessed in a first-come, first-served manner

B.To provide mutual exclusion and prevent race conditions during buffer manipulation ✅

C.To allow both producer and consumer to access the buffer simultaneously

D.To optimize the code for faster execution

💡 Difficulty: hard | ✅ Correct: B

📖 Explanation: The mutex semaphore is specifically designed to provide mutual exclusion. By enclosing the buffer access code with wait(mutex) and signal(mutex), we ensure that only one process (either a producer or a consumer) can manipulate the buffer's internal state at any given time. This is critical for preventing race conditions.

Q42. What is a potential consequence if a producer process fails to call `signal(full)` after adding an item?

A.The consumer will not be notified of the new item and may block even if a full buffer is available ✅

B.The system will immediately crash

C.The item will be lost from the buffer

D.The producer will be unable to add more items

💡 Difficulty: hard | ✅ Correct: A

📖 Explanation: signal(full) is the mechanism by which the producer notifies the consumer that a new full buffer is ready. Without it, the 'full' semaphore count would not reflect the newly added item. The consumer, when it calls wait(full), could block unnecessarily even though there is data to consume.

Q43. The bounded-buffer problem is a classic example used to illustrate the concept of:

A.Memory management

B.Process synchronization ✅

C.CPU scheduling

D.File systems

💡 Difficulty: hard | ✅ Correct: B

📖 Explanation: The problem is specifically designed to highlight the challenges of coordinating processes that share a resource (the buffer). It is a quintessential example of a synchronization problem, demonstrating how to use primitives like semaphores to ensure correct and orderly access to shared data.

Q44. Which of the following best describes the role of the 'full' semaphore for the consumer process?

A.It blocks the consumer until there is an item to consume ✅

B.It allows the consumer to access the critical section

C.It is a resource that the consumer must signal

D.It indicates the number of items the consumer has consumed

💡 Difficulty: hard | ✅ Correct: A

📖 Explanation: The consumer's first operation is wait(full). This is a blocking operation. If the 'full' semaphore is 0, the consumer is blocked, representing the condition where there are no items to consume. This directly controls the consumer's progress based on the availability of data.

Q45. If a buffer of size 6 is used, and the semaphores are initialized correctly, what is the maximum number of processes that can be blocked on the 'full' semaphore at any given time?

A.1

B.6

C.5 ✅

D.Unlimited

💡 Difficulty: hard | ✅ Correct: C

📖 Explanation: The maximum number of processes that can be blocked on 'full' is the total number of potential producers minus one or the total buffer capacity minus one. A process blocks on 'full' when it tries to wait on a semaphore with value 0. If 'full' is at 0, all buffers are empty. All consumers trying to consume will block. The maximum is the buffer size minus one, or the number of producers. The maximum is n-1 (5) if there are n buffers.

Q46. A system uses the bounded-buffer solution. The producer and consumer both execute at the same time. What ensures that the producer does not add an item to a buffer that is being consumed?

A.The 'empty' semaphore

B.The 'full' semaphore

C.The 'mutex' semaphore ✅

D.The integer 'n'

💡 Difficulty: hard | ✅ Correct: C

📖 Explanation: The 'mutex' semaphore ensures mutual exclusion. Before either process can access the buffer, it must acquire the 'mutex' lock. This guarantees that the buffer's internal pointers and data are in a consistent state and that the producer and consumer do not interfere with each other's operations on the same buffer location.

Q47. Which of the following statements is TRUE about the shared data structures in the bounded-buffer problem?

A.'mutex' and 'empty' are counting semaphores

B.'n' is a semaphore variable

C.'full' is initialized to 1

D.'mutex' is initialized to 1 ✅

💡 Difficulty: hard | ✅ Correct: D

📖 Explanation: The 'mutex' semaphore is a binary semaphore initialized to 1. 'empty' and 'full' are counting semaphores, initialized to 'n' and 0 respectively. 'n' is a simple integer. Only 'mutex' is correctly stated as being initialized to 1.

Q48. In the bounded-buffer problem, the code for producer and consumer processes are executed in a loop. The 'while(true)' construct indicates that:

A.The processes will run indefinitely ✅

B.The processes will only run once

C.The processes will stop when the buffer is full or empty

D.This is a pseudo-code representation and not a real program

💡 Difficulty: hard | ✅ Correct: A

📖 Explanation: The 'while(true)' loop is a standard way of representing an infinite loop in pseudo-code. It indicates that the producer and consumer processes are meant to run continuously, producing and consuming items in an ongoing cycle, as they would in a real-world, long-running system.

Q49. The semaphore solution to the bounded-buffer problem with a buffer size of 'n' assumes that:

A.Only one producer and one consumer process exist

B.The buffer is a simple array of 'n' locations

C.All items are of the same size

D.The 'mutex', 'empty', and 'full' semaphores are all initialized correctly ✅

💡 Difficulty: hard | ✅ Correct: D

📖 Explanation: The correctness of the entire solution hinges on proper initialization. The code provided in the text explicitly initializes these semaphores to 1, n, and 0, respectively. This is a fundamental requirement for the solution to work as intended.

Q50. Which of the following correctly identifies the order of semaphore operations in the producer's code?

A.wait(empty), wait(mutex), signal(mutex), signal(full) ✅

B.wait(mutex), wait(empty), signal(full), signal(mutex)

C.wait(full), wait(mutex), signal(mutex), signal(empty)

D.wait(empty), wait(full), signal(mutex), signal(empty)

💡 Difficulty: hard | ✅ Correct: A

📖 Explanation: The correct order is wait(empty) to check for an empty slot, wait(mutex) to lock the critical section, then after adding the item, signal(mutex) to release the lock, and finally signal(full) to notify the consumer. This is the standard, correct, and safe ordering for the producer.

Q51. A bounded buffer has a pool of 10 buffers. Initially, 'full' = 0 and 'empty' = 10. After the producer has performed all its operations and added 3 items, and the consumer has then performed all its operations and removed 1 item, the value of 'full' and 'empty' will be:

A.full=2, empty=8 ✅

B.full=3, empty=7

C.full=2, empty=7

D.full=4, empty=6

💡 Difficulty: hard | ✅ Correct: A

📖 Explanation: After adding 3 items: full=3, empty=7. Then after removing 1 item: full=2, empty=8. The total is always 10. The producer's operations decrement 'empty' and increment 'full'. The consumer's operations decrement 'full' and increment 'empty'.

🔗 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

←Previous Topic:Priority Inversion in Semaphore📝 The Bounded Buffer Problem in Process SynchronizationThe Readers Writers Problem in Process Synchronization:Next Topic→