A.A condition where the operating system runs faster than the hardware
B.A situation where processes compete for the CPU scheduler
C.A condition where a process races to finish before the time quantum expires
D.A situation where several processes access and manipulate the same data concurrently and the outcome depends on the order of execution
Correct Answer: A situation where several processes access and manipulate the same data concurrently and the outcome depends on the order of execution
Explanation:
A race condition occurs when the final state of shared data depends on the specific order in which instructions are executed by concurrent processes.
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2Which of the following is NOT a requirement for a solution to the Critical Section Problem?
A.Bounded Waiting
B.processor Speed
C.Progress
D.Mutual Exclusion
Correct Answer: processor Speed
Explanation:
The solution to the critical section problem must satisfy Mutual Exclusion, Progress, and Bounded Waiting. It should not rely on the relative speed of the processors.
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3What does 'Mutual Exclusion' imply in the context of the Critical Section Problem?
A.All processes must execute their critical sections simultaneously
B.If a process is executing in its critical section, then no other processes can be executing in their critical sections
C.Processes must share the same memory address space
D.The operating system excludes processes from using the CPU
Correct Answer: If a process is executing in its critical section, then no other processes can be executing in their critical sections
Explanation:
Mutual exclusion ensures that only one process at a time is active within the critical section to prevent data inconsistency.
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4What is a Semaphore?
A.A protected integer variable that can only be accessed via two atomic operations
B.A hardware instruction
C.A specialized CPU register
D.A queue of processes waiting for I/O
Correct Answer: A protected integer variable that can only be accessed via two atomic operations
Explanation:
A semaphore is a synchronization tool (an integer variable) accessed only through two standard atomic operations: wait() and signal().
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5In a Semaphore, what does the 'wait' (or P) operation do?
A.Sets the semaphore value to zero
B.Increments the semaphore value
C.Reads the semaphore value without changing it
D.Decrements the semaphore value
Correct Answer: Decrements the semaphore value
Explanation:
The wait operation (P) decrements the semaphore value. If the value becomes negative, the process is blocked.
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6What is the main disadvantage of a Spinlock?
A.It causes context switching
B.It is difficult to implement
C.It requires busy waiting, wasting CPU cycles
D.It cannot handle multiple processes
Correct Answer: It requires busy waiting, wasting CPU cycles
Explanation:
Spinlocks cause the calling process to loop continuously (busy wait) while waiting for the lock to become available, which wastes CPU time.
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7A binary semaphore is also known as a:
A.Spinlock
B.Mutex lock
C.Monitor
D.Counting semaphore
Correct Answer: Mutex lock
Explanation:
A binary semaphore can range only between 0 and 1, functioning similarly to a Mutex (Mutual Exclusion) lock.
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8Which hardware instruction is commonly used to implement mutual exclusion?
A.JumpAndLink
B.TestAndSet
C.PushAndPop
D.LoadAndStore
Correct Answer: TestAndSet
Explanation:
TestAndSet is an atomic hardware instruction that tests a value and sets it, used to implement locks for mutual exclusion.
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9What is the 'Bounded Waiting' requirement?
A.There exists a bound on the number of times other processes are allowed to enter their critical sections after a process has made a request to enter its critical section
B.The critical section size must be bounded
C.Processes must wait in a queue indefinitely
D.A process must wait for a fixed amount of time
Correct Answer: There exists a bound on the number of times other processes are allowed to enter their critical sections after a process has made a request to enter its critical section
Explanation:
Bounded waiting ensures that a waiting process will eventually get into the critical section; it prevents starvation.
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10In the Producer-Consumer problem using a bounded buffer, when does the Producer wait?
A.When the Consumer is sleeping
B.When the mutex is unlocked
C.When the buffer is empty
D.When the buffer is full
Correct Answer: When the buffer is full
Explanation:
If the buffer is full, the producer cannot add new items and must wait until the consumer consumes an item.
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11Which of the following is a high-level synchronization construct that ensures mutual exclusion automatically?
A.Spinlock
B.Semaphore
C.Peterson's Solution
D.Monitor
Correct Answer: Monitor
Explanation:
A Monitor is a high-level abstraction where the compiler ensures that only one process can be active within the monitor at a time.
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12In the Dining Philosophers problem, deadlock occurs if:
A.One philosopher picks up both chopsticks
B.Philosophers eat sequentially
C.The philosophers do not speak to each other
D.All philosophers pick up their left chopstick simultaneously
Correct Answer: All philosophers pick up their left chopstick simultaneously
Explanation:
If every philosopher picks up the left chopstick at the same time, they will all wait indefinitely for the right chopstick, causing a circular wait (deadlock).
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13What is Peterson's Solution used for?
A.Managing memory fragmentation
B.Solving the Critical Section problem for two processes
C.Scheduling threads
D.Handling hardware interrupts
Correct Answer: Solving the Critical Section problem for two processes
Explanation:
Peterson's solution is a classic software-based solution to the critical section problem restricted to two processes.
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14In Peterson's solution, which variables are shared between processes?
A.semaphore and mutex
B.turn and flag
C.lock and key
D.start and finish
Correct Answer: turn and flag
Explanation:
Peterson's solution uses an integer variable 'turn' to indicate whose turn it is, and a boolean array 'flag' to indicate if a process is ready to enter the critical section.
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15What problem is the Readers-Writers problem primarily concerned with?
A.Ensuring exclusive access for writers while allowing multiple concurrent readers
B.Allowing multiple writers to write simultaneously
C.Synchronizing two writers only
D.Preventing readers from reading shared data
Correct Answer: Ensuring exclusive access for writers while allowing multiple concurrent readers
Explanation:
The problem allows multiple readers to read at the same time but requires that if a writer is writing, no other process (reader or writer) can access the shared data.
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16What happens to threads that call 'wait' on a Condition Variable in a Monitor?
A.They enter a busy-wait loop
B.They continue executing
C.They are terminated
D.They are suspended and placed in a waiting queue
Correct Answer: They are suspended and placed in a waiting queue
Explanation:
When a thread executes wait() on a condition variable, it releases the monitor lock and is suspended until another thread signals it.
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17Which of the following is NOT shared by threads of the same process?
A.Open files
B.Code section
C.Program Counter and Stack
D.Global variables
Correct Answer: Program Counter and Stack
Explanation:
Each thread has its own thread of execution, which requires a private Program Counter (PC), set of registers, and Stack. They share code, data, and files.
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18What is a Heavyweight Process compared to a Thread?
A.A thread with a large stack
B.A kernel-level thread
C.A process with a single thread of control
D.A process with no memory
Correct Answer: A process with a single thread of control
Explanation:
A traditional process (Heavyweight) has a single thread of control. Threads are often called Light Weight Processes (LWP).
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19Which multithreading model maps many user-level threads to a single kernel thread?
A.One-to-One Model
B.Many-to-One Model
C.Many-to-Many Model
D.Two-Level Model
Correct Answer: Many-to-One Model
Explanation:
The Many-to-One model maps multiple user threads to a single kernel thread. If one blocks, the entire process blocks.
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20What is a limitation of the Many-to-One multithreading model?
A.It does not support user-level threads
B.The entire process blocks if one thread makes a blocking system call
C.It consumes too many kernel resources
D.It is too complex to implement
Correct Answer: The entire process blocks if one thread makes a blocking system call
Explanation:
Since there is only one kernel thread, the OS sees the process as a single unit. If that unit blocks (e.g., for I/O), no other user thread in that process can run.
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21Which multithreading model provides more concurrency than Many-to-One but doesn't require a kernel thread for every user thread?
A.Single Thread Model
B.One-to-One Model
C.Many-to-Many Model
D.Independent Model
Correct Answer: Many-to-Many Model
Explanation:
The Many-to-Many model multiplexes many user-level threads to a smaller or equal number of kernel threads.
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22What is 'Scheduler Activation'?
A.A hardware interrupt that starts the scheduler
B.The process of activating the CPU clock
C.A signal to kill a process
D.A mechanism for communication between the user-thread library and the kernel
Correct Answer: A mechanism for communication between the user-thread library and the kernel
Explanation:
Scheduler activations provide a communication channel (often via upcalls) to maintain the correct number of kernel threads for the application's user threads.
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23Which standard defines the API for thread creation and synchronization (Pthreads)?
A.Win32
B.POSIX
C.Java
D.ANSI
Correct Answer: POSIX
Explanation:
Pthreads refers to POSIX Threads, a standard (IEEE 1003.1c) defining an API for thread creation and synchronization.
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24What is the function of pthread_join()?
A.Creates a new thread
B.Unlocks a mutex
C.Waits for a specific thread to terminate
D.Terminates a thread
Correct Answer: Waits for a specific thread to terminate
Explanation:
The pthread_join() function suspends execution of the calling thread until the target thread terminates.
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25A Precedence Graph is a directed acyclic graph used to:
A.Describe the execution dependencies among concurrent processes
B.Visualize the memory usage of a process
C.Map virtual memory to physical memory
D.Show the hierarchy of file systems
Correct Answer: Describe the execution dependencies among concurrent processes
Explanation:
Precedence graphs illustrate constraints on the order in which a collection of tasks or processes can execute.
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26What defines 'Co-operating Processes'?
A.Processes that do not share data
B.Processes running on different computers
C.Processes that can affect or be affected by other executing processes
D.Processes that are completely independent
Correct Answer: Processes that can affect or be affected by other executing processes
Explanation:
Co-operating processes share state (data or resources) and can influence one another's execution, requiring synchronization.
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27In the context of process hierarchy, what system call is typically used in Unix/Linux to create a new process?
A.fork()
B.create()
C.spawn()
D.new()
Correct Answer: fork()
Explanation:
The fork() system call creates a new process (child) which is a copy of the calling process (parent).
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28If a Semaphore S has a value of 10, and 5 P (wait) operations and 3 V (signal) operations are performed, what is the final value of S?
29What is the 'Bakery Algorithm' designed to solve?
A.Memory allocation
B.Deadlock recovery
C.The Producer-Consumer problem
D.The Critical Section problem for N processes
Correct Answer: The Critical Section problem for N processes
Explanation:
The Bakery Algorithm is a solution to the critical section problem for N processes, based on the idea of taking tickets in a bakery.
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30Which of the following is true regarding User-Level Threads (ULT)?
A.They require hardware support
B.Context switching is faster than Kernel-Level Threads
C.The kernel is aware of all ULTs
D.They cannot run on any OS
Correct Answer: Context switching is faster than Kernel-Level Threads
Explanation:
ULT management is done by a thread library in user space. Context switching is faster because it does not require kernel intervention (mode switching).
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31In the One-to-One multithreading model, what is the main drawback?
A.It is not standard
B.It does not support multiprocessors
C.It blocks the whole process on I/O
D.Creating a user thread requires creating a corresponding kernel thread, which creates overhead
Correct Answer: Creating a user thread requires creating a corresponding kernel thread, which creates overhead
Explanation:
While offering good concurrency, the overhead of creating a kernel thread for every user thread can burden the system.
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32What is an 'Upcall' in the context of Scheduler Activations?
A.increasing the priority of a thread
B.Uploading data to the cloud
C.A notification from the kernel to the thread library
D.A call from a user thread to the kernel
Correct Answer: A notification from the kernel to the thread library
Explanation:
The kernel uses an upcall to inform the application (thread library) about specific events, such as a processor becoming available or a thread blocking.
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33Which synchronization primitive is typically used to solve the Reader-Writer problem to prevent writer starvation?
A.TestAndSet
B.Disable Interrupts
C.Spinlocks
D.Semaphores with a priority queue
Correct Answer: Semaphores with a priority queue
Explanation:
Standard semaphores might lead to starvation; complex solutions or monitors often use priority mechanisms to ensure writers eventually get access.
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34What is 'Priority Inversion'?
A.Inverting the bits of the semaphore
B.The scheduler runs processes in reverse order
C.A lower priority process holds a lock needed by a higher priority process
D.Assigning priority 0 to the most important process
Correct Answer: A lower priority process holds a lock needed by a higher priority process
Explanation:
Priority inversion occurs when a high-priority task is indirectly preempted by a medium-priority task because a low-priority task holds a shared resource.
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35How does the 'Swap' hardware instruction assist in synchronization?
A.It moves a process to swap space
B.It switches between user and kernel mode
C.It changes the process ID
D.It swaps the content of two memory words atomically
Correct Answer: It swaps the content of two memory words atomically
Explanation:
The Swap instruction atomically exchanges the contents of two variables, which can be used to implement a lock (e.g., swapping a lock variable with 'true').
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36In a Monitor, if process P executes x.signal() and process Q was waiting on x, and Q immediately executes while P waits, this strategy is called:
A.Signal and Wait (Hoare semantics)
B.Broadcast
C.Signal and Continue (Mesa semantics)
D.Busy Waiting
Correct Answer: Signal and Wait (Hoare semantics)
Explanation:
In Hoare semantics (Signal and Wait), the signaler blocks to let the waiting thread run immediately.
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37Which component allows a thread to have its own copy of data?
A.Shared Memory
B.TLS (Thread Local Storage)
C.Global Heap
D.Semaphore
Correct Answer: TLS (Thread Local Storage)
Explanation:
Thread Local Storage (TLS) allows each thread to have its own instance of a variable, separate from other threads.
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38The problem where a producer tries to put an item into a full buffer is handled by:
A.Putting the producer to sleep
B.Killing the consumer
C.Discarding the item
D.Overwriting the oldest item
Correct Answer: Putting the producer to sleep
Explanation:
In standard synchronization solutions, the producer waits (sleeps) on a semaphore or condition variable until space is available.
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39Why is disabling interrupts not a viable solution for mutual exclusion in multiprocessor systems?
A.It is too slow
B.It only disables interrupts on one processor, not all
C.It causes the OS to crash
D.It requires too much power
Correct Answer: It only disables interrupts on one processor, not all
Explanation:
Disabling interrupts prevents the current CPU from switching tasks, but other CPUs can still access shared memory, failing to guarantee mutual exclusion.
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40What is 'Busy Waiting'?
A.A process repeatedly checking a condition until it becomes true
B.A process waiting for I/O
C.The CPU executing a NOP instruction
D.A process waiting in a queue
Correct Answer: A process repeatedly checking a condition until it becomes true
Explanation:
Busy waiting involves a continuous loop that consumes CPU cycles while checking if a lock or condition is available.
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41Which of the following is a valid state for a Java thread?
A.WAITING
B.RUNNING
C.BLOCKED
D.All of the above
Correct Answer: All of the above
Explanation:
Java threads can be in states such as NEW, RUNNABLE (Running), BLOCKED, WAITING, TIMED_WAITING, or TERMINATED.
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42In the context of threads, what is 'cancellation'?
A.Deleting the thread library
B.Stopping the CPU
C.Terminating a thread before it has completed
D.Removing a semaphore
Correct Answer: Terminating a thread before it has completed
Explanation:
Thread cancellation involves terminating a thread (the target thread) before it has finished its task (e.g., clicking 'Stop' in a web browser).
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43Deferred cancellation of a thread means:
A.The thread is cancelled after 1 minute
B.The thread cancels the parent process
C.The thread is cancelled immediately
D.The thread checks periodically if it should terminate
Correct Answer: The thread checks periodically if it should terminate
Explanation:
In deferred cancellation, the target thread periodically checks a flag to see if it should terminate, allowing it to clean up resources safely.
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44A solution to the Dining Philosophers problem using a monitor restricts a philosopher to pick up chopsticks only if:
A.The right neighbor is eating
B.They have a ticket
C.Both neighbors are not eating
D.The left neighbor is eating
Correct Answer: Both neighbors are not eating
Explanation:
To prevent deadlock and ensure mutual exclusion, a philosopher is allowed to change state to 'EATING' only if both left and right neighbors are not in 'EATING' state.
Incorrect! Try again.
45Which type of semaphore can take any non-negative integer value?
A.Mutex
B.Spinlock
C.Counting Semaphore
D.Binary Semaphore
Correct Answer: Counting Semaphore
Explanation:
Counting semaphores can range over an unrestricted domain and are used to control access to a given number of resources.
Incorrect! Try again.
46What defines a 'Thread Safe' function?
A.It can be called from multiple threads simultaneously without producing incorrect results
B.It creates a new thread
C.It uses no memory
D.It runs very fast
Correct Answer: It can be called from multiple threads simultaneously without producing incorrect results
Explanation:
Thread safety ensures that shared data structures are manipulated in a manner that guarantees safe execution by multiple threads at the same time.
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47In the 'Sleeping Barber' problem (a variation of producer-consumer), what happens if the customer arrives and the waiting room is full?
A.The customer waits outside
B.The barber cuts two heads at once
C.The customer wakes the barber
D.The customer leaves
Correct Answer: The customer leaves
Explanation:
In the standard Sleeping Barber problem, if there are no free chairs in the waiting room, the customer leaves the shop.
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48What is the benefit of the 'Grand Central Dispatch' (GCD) technology in macOS/iOS?
A.It replaces the kernel
B.It manages thread pools and scheduling automatically
C.It creates infinite threads
D.It increases clock speed
Correct Answer: It manages thread pools and scheduling automatically
Explanation:
GCD is an extension that allows application developers to identify sections of code to run in parallel, while the OS manages the threads.
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49Concurrency vs Parallelism: Which statement is true?
A.Concurrency requires multiple processors
B.Parallelism is software only
C.They are exactly the same
D.Parallelism requires multiple processors/cores, Concurrency does not
Correct Answer: Parallelism requires multiple processors/cores, Concurrency does not
Explanation:
Concurrency is about dealing with lots of things at once (logical), while Parallelism is about doing lots of things at once (physical hardware execution).
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50What is the primary purpose of a Condition Variable?
A.To allow threads to wait for a specific condition to become true
B.To increment a counter
C.To store the process ID
D.To lock a file
Correct Answer: To allow threads to wait for a specific condition to become true
Explanation:
Condition variables are synchronization primitives that enable threads to wait until a particular condition (state) occurs.
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