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[MCQ] Operating Systems

Module 01

1.Timer is used to prevent a single
a)Job
b)Time
c)Computer
d)Information
Answer : a

2. To run a program this Setup involves an amount of
a)Money
b)Resources
c)Users
d)Time
Answer :d

3. Time sharing technique handles
a)Single Interactive Job
b)Multiple Interactive Job
c)Recent Interactive Job
d)Old Interactive Job
Answer:b

4.Interrupts make an operating system more
a)Rigid
b)Expensive
c)Reliable
d)Flexible
Answer:d

5. With the use of multiprogramming batch processing work can be

a)Efficient
b)Rigid
c)Expensive
d)Flexible
Answer : a

6. The initial program that is run when the computer is powered up is called __________
a) boot program
b) bootloader
c) initializer
d) bootstrap program
Answer: d
Explanation: None.

7. How does the software trigger an interrupt?
a) Sending signals to CPU through bus
b) Executing a special operation called system call
c) Executing a special program called system program
d) Executing a special program called interrupt trigger program
Answer: b
Explanation: None.

8. What is a trap/exception?
a) hardware generated interrupt caused by an error
b) software generated interrupt caused by an error
c) user generated interrupt caused by an error
d) none of the mentioned
Answer: b
Explanation: None.

9. What is an ISR?
a) Information Service Request
b) Interrupt Service Request
c) Interrupt Service Routine
d) Information Service Routine
Answer: c
Explanation: None.

10. What is an interrupt vector?
a) It is an address that is indexed to an interrupt handler
b) It is a unique device number that is indexed by an address
c) It is a unique identity given to an interrupt
d) None of the mentioned
Answer: a
Explanation: None.

11. DMA is used for __________
a) High speed devices(disks and communications network)
b) Low speed devices
c) Utilizing CPU cycles
d) All of the mentioned
Answer: a
Explanation: None.

12. In a memory mapped input/output __________
a) the CPU uses polling to watch the control bit constantly, looping to see if a device is ready
b) the CPU writes one data byte to the data register and sets a bit in control register to show that a byte is available
c) the CPU receives an interrupt when the device is ready for the next byte
d) the CPU runs a user written code and does accordingly
Answer: b
Explanation: None.

13. In a programmed input/output(PIO) __________
a) the CPU uses polling to watch the control bit constantly, looping to see if a device is ready
b) the CPU writes one data byte to the data register and sets a bit in control register to show that a byte is available
c) the CPU receives an interrupt when the device is ready for the next byte
d) the CPU runs a user written code and does accordingly
Answer: a
Explanation: None.

14. In an interrupt driven input/output __________
a) the CPU uses polling to watch the control bit constantly, looping to see if a device is ready
b) the CPU writes one data byte to the data register and sets a bit in control register to show that a byte is available
c) the CPU receives an interrupt when the device is ready for the next byte
d) the CPU runs a user written code and does accordingly
Answer: c
Explanation: None.

15. In the layered approach of Operating Systems __________
a) Bottom Layer(0) is the User interface
b) Highest Layer(N) is the User interface
c) Bottom Layer(N) is the hardware
d) Highest Layer(N) is the hardware
Answer: b
Explanation: None.

16. How does the Hardware trigger an interrupt?
a) Sending signals to CPU through a system bus
b) Executing a special program called interrupt program
c) Executing a special program called system program
d) Executing a special operation called system call
Answer: a
Explanation: None.

17. Which operation is performed by an interrupt handler?
a) Saving the current state of the system
b) Loading the interrupt handling code and executing it
c) Once done handling, bringing back the system to the original state it was before the interrupt occurred
d) All of the mentioned
Answer: d
Explanation: None.

18. A system call is a routine built into the kernel and performs a basic function.
a) True
b) False
Answer: a
Explanation: All UNIX systems offer around 200 special functions known as system calls. A system call is a routine built into the kernel and performs a very basic function that requires communication with the CPU, memory and devices.

19. When we execute a C program, CPU runs in ____ mode.
a) user
b) kernel
c) supervisory
d) system
Answer: a
Explanation: When we execute a C program, the CPU runs in user mode. It remains it this particular mode until a system call is invoked.

20. In ____ mode, the kernel runs on behalf of the user.
a) user
b) kernel
c) real
d) all
Answer: b
Explanation: Whenever a process invokes a system call, the CPU switches from user mode to kernel mode which is a more privileged mode. The kernel mode is also called as supervisor mode. In this mode, the kernel runs on behalf of the user and has access to any memory location and can execute any machine instruction.

21. All UNIX and LINUX systems have one thing in common which is ____
a) set of system calls
b) set of commands
c) set of instructions
d) set of text editors
Answer: a
Explanation: As we know that, all UNIX and LINUX systems have one thing in common; they use the same set of system calls.

22. The chmod command invokes the ____ system call.
a) chmod
b) ch
c) read
d) change
Answer: a
Explanation: Many commands and system calls share the same names. For example, the chmod command invokes the chmod system call.

23. For reading input, which of the following system call is used?
a) write
b) rd
c) read
d) change
Answer: c
Explanation: The standard C library offers a set of separate functions to read a block of data. For example, to read a block of data fread is used, for reading a line fgets is used and for reading a character fgetc is used. All these functions invoke the system call -read, which is available for reading input.

24. Which of the following system call is used for opening or creating a file?
a) read
b) write
c) open
d) close
Answer: c
Explanation: To read or write to a file, we first need to open it. For this purpose, open system call is used. Open has two forms ; the first forms assumes that the file already exists and the second form creates the file if it doesn’t.

25. There are ___ modes of opening a file.
a) 4
b) 3
c) 2
d) 1
Answer: b
Explanation: There are three modes of opening a file, out of which only one mode is required to be specified while opening the file. The three modes are, O_RDONLY, O_WRONLY, O_RDWR.

26. Which of the following mode is used for opening a file in both reading and writing?
a) O_RDONLY
b) O_WRONLY
c) O_RDWR
d) O_WDR
Answer: c
Explanation: There are three modes of opening a file namely:

 O_RDONLY    -    opens files for reading
 O_WRONLY    -    opens file for writing 
 O_RDWR      -   opens file for reading and writing

27. open system call returns the file descriptor as ___
a) int
b) float
c) char
d) double
View Answer
Answer: c
Explanation: open returns the file descriptor as an int. This is the lowest number available for allocation and is used as an argument by the other four calls (read, write, close, lseek).

28. Which of the following system call is used for closing a file?
a) open
b) lseek
c) close
d) write
Answer: c
Explanation: A program automatically closes all open files before termination, but it’s a good practice to close them explicitly. The close system call is used for closing a file.
int close (int fd)

29. close system call returns ____
a) 0
b) -1
c) 1
d) 0 and -1
Answer: d
Explanation: The return type of close system call is an integer. It either returns 0 if the file is closed successfully or -1 otherwise.

30. ____ system call is used for writing to a file.
a) read
b) write
c) close
d) seek
Answer: b
Explanation: write system call is required for writing to a file which has previously been opened with the open system call. write system call returns the number of characters written.

31. write system call returns -1 when ___________
a) if disk fills up while write is in progress
b) when file doesn’t exist
c) if the file size exceeds the system’s limit
d) if disk fills up while write is in progress and if the file size exceeds
Answer: d
Explanation: write system call returns the number of characters written. However, it will return -1 if if disk fills up while write is in progress or if the file size exceeds the system’s limit.

32. ____ system call is used for positioning the offset pointer.
a) read
b) write
c) open
d) lseek
Answer: d
Explanation: The lseek system call moves the file offset pointer to a specified point. It doesn’t do any physical I/O rather it determines the position in the file where the next I/O operation will take place.

33. Which of the following offset is used with lseek system call to set the offset pointer to the end of the file?
a) SEEK_SET
b) SEEK_END
c) SEEK_CUR
d) SEEK_CR
Answer: b
Explanation: The offset signifies the position of the offset pointer which can take one of these three values:

 SEEK_SET    -    offset pointer set to the beginning of file
 SEEK_END    -    offset pointer set to the end of file
 SEEK_CUR    -    offset pointer remains at current location

34. Which of the following system call is used for truncating a file?
a) truncate
b) ftruncate
c) trunk
d) truncate and ftruncate
Answer: d
Explanation: The truncate and ftruncate calls can truncate a file to any length. These calls are often used in combination with lseek to overwrite a certain segment of a file.

35. truncate needs the ___ of the file as an argument but ftruncate works with _______
a) pathname, file descriptor
b) file descriptor, pathname
c) pathname, pathname
d) file descriptor, file descriptor
Answer: a
Explanation: The truncate and ftruncate calls can truncate a file to any length. truncate needs the pathname of the file as an argument but ftruncate works with the file descriptor.

Module 01

1. The systems which allow only one process execution at a time, are called __________
a) uniprogramming systems
b) uniprocessing systems
c) unitasking systems
d) none of the mentioned
Answer: b
Explanation: Those systems which allows more than one process execution at a time, are called multiprogramming systems. Uniprocessing means only one processor.

2. In operating system, each process has its own __________
a) address space and global variables
b) open files
c) pending alarms, signals and signal handlers
d) all of the mentioned
Answer: d
Explanation: In Operating Systems, each process has its own address space which contains code, data, stack and heap segments or sections. Each process also has a list of files which is opened by the process as well as all pending alarms, signals and various signal handlers.

3. In Unix, Which system call creates the new process?
a) fork
b) create
c) new
d) none of the mentioned
Answer: a
Explanation: In UNIX, a new process is created by fork() system call. fork() system call returns a process ID which is generally the process id of the child process created.

4. A process can be terminated due to __________
a) normal exit
b) fatal error
c) killed by another process
d) all of the mentioned
Answer: d
Explanation: A process can be terminated normally by completing its task or because of fatal error or killed by another process or forcefully killed by a user. When the process completes its task without any error then it exits normally. The process may exit abnormally because of the occurrence of fatal error while it is running. The process can be killed or terminated forcefully by another process.

5. What is the ready state of a process?
a) when process is scheduled to run after some execution
b) when process is unable to run until some task has been completed
c) when process is using the CPU
d) none of the mentioned
Answer: a
Explanation: Ready state of the process means process has all necessary resources which are required for execution of that process when CPU is allocated. Process is ready for execution but waiting for the CPU to be allocated.

6. What is interprocess communication?
a) communication within the process
b) communication between two process
c) communication between two threads of same process
d) none of the mentioned
Answer: b
Explanation: Interprocess Communication (IPC) is a communication mechanism that allows processes to communicate with each other and synchronise their actions without using the same address space. IPC can be achieved using shared memory and message passing.

7. A set of processes is deadlock if __________
a) each process is blocked and will remain so forever
b) each process is terminated
c) all processes are trying to kill each other
d) none of the mentioned
Answer: a
Explanation: Deadlock is a situation which occurs because process A is waiting for one resource and holds another resource (blocking resource). At the same time another process B demands blocking a resource as it is already held by a process A, process B is waiting state unless and until process A releases occupied resource.

8. A process stack does not contain __________
a) Function parameters
b) Local variables
c) Return addresses
d) PID of child process
Answer: d
Explanation: Process stack contains Function parameters, Local variables and Return address. It does not contain the PID of child process.

9. Which system call can be used by a parent process to determine the termination of child process?
a) wait
b) exit
c) fork
d) get
Answer: a
Explanation: wait() system call is used by the parent process to determine termination of child process. The parent process uses wait() system call and gets the exit status of the child process as well as the pid of the child process which is terminated.

10. The address of the next instruction to be executed by the current process is provided by the __________
a) CPU registers
b) Program counter
c) Process stack
d) Pipe
Answer: b
Explanation: The address of the next instruction to be executed by the current process is provided by the Program Counter. After every instruction is executed, the Program Counter is incremented by 1 i.e. address of the next instruction to be executed. CPU fetches instruction from the address denoted by Program Counter and execute it.

11. A Process Control Block(PCB) does not contain which of the following?
a) Code
b) Stack
c) Bootstrap program
d) Data
Answer: c
Explanation: Process Control Block (PCB) contains information related to a process such as Process State, Program Counter, CPU Register, etc. Process Control Block is also known as Task Control Block. Bootstrap program is a program which runs initially when the system or computer is booted or rebooted.

12. The number of processes completed per unit time is known as __________
a) Output
b) Throughput
c) Efficiency
d) Capacity
Answer: b
Explanation: The number of processes completed per unit time is known as Throughput. Suppose there are 4 processes A, B, C & D they are taking 1, 3, 4 & 7 units of time respectively for their executions. For 10 units of time, throughput is high if process A, B & C are running first as 3 processes can execute. If process C runs first then throughput is low as maximum only 2 processes can execute. Throughput is low for processes which take a long time for execution. Throughput is high for processes which take a short time for execution.

13. The state of a process is defined by __________
a) the final activity of the process
b) the activity just executed by the process
c) the activity to next be executed by the process
d) the current activity of the process
Answer: d
Explanation: The state of a process is defined by the current activity of the process. A process state changes when the process executes. The process states are as New, Ready, Running, Wait, Terminated.

14. Which of the following is not the state of a process?
a) New
b) Old
c) Waiting
d) Running
Answer: b
Explanation: There is no process state such as old. When a process is created then the process is in New state. When the process gets the CPU for its execution then the process is in Running state. When the process is waiting for an external event then the process is in a Waiting state.

15. What is a Process Control Block?
a) Process type variable
b) Data Structure
c) A secondary storage section
d) A Block in memory
Answer: b
Explanation: A Process Control Block (PCB) is a data structure. It contains information related to a process such as Process State, Program Counter, CPU Register, etc. Process Control Block is also known as Task Control Block.

16. The entry of all the PCBs of the current processes is in __________
a) Process Register
b) Program Counter
c) Process Table
d) Process Unit
Answer: c
Explanation: The entry of all the PCBs of the current processes is in Process Table. The Process Table has the status of each and every process that is created in OS along with their PIDs.

17. What is the degree of multiprogramming?
a) the number of processes executed per unit time
b) the number of processes in the ready queue
c) the number of processes in the I/O queue
d) the number of processes in memory
Answer: d
Explanation: Multiprogramming means the number of processes are in the ready states. To increase utilization of CPU, Multiprogramming is one of the most important abilities of OS. Generally, a single process cannot use CPU or I/O at all time, whenever CPU or I/O is available another process can use it. By doing this CPU utilization is increased.

18. A single thread of control allows the process to perform __________
a) only one task at a time
b) multiple tasks at a time
c) only two tasks at a time
d) all of the mentioned
Answer: a
Explanation: A single thread of control allows the process to perform only one task at a time. In the case of multi-core, multiple threads can be run simultaneously and can perform multiple tasks at a time.

19. What is the objective of multiprogramming?
a) Have a process running at all time
b) Have multiple programs waiting in a queue ready to run
c) To increase CPU utilization
d) None of the mentioned
Answer: c
Explanation: The objective of multiprogramming is to increase CPU utilization. Generally, a single process cannot use CPU or I/O at all time, whenever CPU or I/O is available another process can use it. Multiprogramming offers this ability to OS by keeping multiple programs in a ready queue.

20. Which of the following do not belong to queues for processes?
a) Job Queue
b) PCB queue
c) Device Queue
d) Ready Queue
Answer: b
Explanation: PCB queue does not belong to queues for processes. PCB is a process control block which contains information related to process. Each process is represented by PCB.

21. When the process issues an I/O request __________
a) It is placed in an I/O queue
b) It is placed in a waiting queue
c) It is placed in the ready queue
d) It is placed in the Job queue
Answer: a
Explanation: When the process issues an I/O request it is placed in an I/O queue. I/O is a resource and it should be used effectively and every process should get access to it. There might be multiple processes which requested for I/O. Depending on scheduling algorithm I/O is allocated to any particular process and after completing I/O operation, I/O access is returned to the OS.

22. What will happen when a process terminates?
a) It is removed from all queues
b) It is removed from all, but the job queue
c) Its process control block is de-allocated
d) Its process control block is never de-allocated
Answer: a
Explanation: When a process terminates, it removes from all queues. All allocated resources to that particular process are deallocated and all those resources are returned back to OS.

23. What is a long-term scheduler?
a) It selects processes which have to be brought into the ready queue
b) It selects processes which have to be executed next and allocates CPU
c) It selects processes which heave to remove from memory by swapping
d) None of the mentioned
Answer: a
Explanation: A long-term scheduler selects processes which have to be brought into the ready queue. When processes enter the system, they are put in the job queue. Long-term scheduler selects processes from the job queue and puts them in the ready queue. It is also known as Job Scheduler.

24. If all processes I/O bound, the ready queue will almost always be ______ and the Short term Scheduler will have a ______ to do.
a) full, little
b) full, lot
c) empty, little
d) empty, lot
Answer: c
Explanation: If all processes are I/O bound, the ready queue will almost empty and the short-term scheduler will have a little to do. I/O bound processes spend more time doing I/O than computation.

25. What is a medium-term scheduler?
a) It selects which process has to be brought into the ready queue
b) It selects which process has to be executed next and allocates CPU
c) It selects which process to remove from memory by swapping
d) None of the mentioned
Answer: c
Explanation: A medium-term scheduler selects which process to remove from memory by swapping. The medium-term scheduler swapped out the process and later swapped in. Swapping helps to free up memory.

26. What is a short-term scheduler?
a) It selects which process has to be brought into the ready queue
b) It selects which process has to be executed next and allocates CPU
c) It selects which process to remove from memory by swapping
d) None of the mentioned
Answer: b
Explanation: A short-term scheduler selects a process which has to be executed next and allocates CPU. Short-term scheduler selects a process from the ready queue. It selects processes frequently.

27. The primary distinction between the short term scheduler and the long term scheduler is __________
a) The length of their queues
b) The type of processes they schedule
c) The frequency of their execution
d) None of the mentioned
Answer: c
Explanation: The primary distinction between the short-term scheduler and long-term scheduler is the frequency of their execution. Short-term scheduler executes frequently while long-term scheduler executes much less frequently.

28. The only state transition that is initiated by the user process itself is __________
a) block
b) wakeup
c) dispatch
d) none of the mentioned
Answer: a
Explanation: The only state transition that is initiated by the user process itself is block. Whenever a user process initiates an I/O request it goes into block state unless and until the I/O request is not completed.

29. In a time-sharing operating system, when the time slot given to a process is completed, the process goes from the running state to the __________
a) Blocked state
b) Ready state
c) Suspended state
d) Terminated state
Answer: b
Explanation: In a time-sharing operating system, when the time slot given to a process is completed, the process goes from the running state to the Ready State. In a time-sharing operating system unit time is defined for sharing CPU, it is called a time quantum or time slice. If a process takes less than 1 time quantum, then the process itself releases the CPU.

30. In a multiprogramming environment __________
a) the processor executes more than one process at a time
b) the programs are developed by more than one person
c) more than one process resides in the memory
d) a single user can execute many programs at the same time
Answer: c
Explanation: In a multiprogramming environment more than one process resides in the memory. Whenever a CPU is available, one process amongst all present in memory gets the CPU for execution. Multiprogramming increases CPU utilization.

31. Suppose that a process is in “Blocked” state waiting for some I/O service. When the service is completed, it goes to the __________
a) Running state
b) Ready state
c) Suspended state
d) Terminated state
Answer: b
Explanation: Suppose that a process is in “Blocked” state waiting for some I/O service. When the service is completed, it goes to the ready state. Process never goes directly to the running state from the waiting state. Only processes which are in ready state go to the running state whenever CPU allocated by operating system.

32. The context of a process in the PCB of a process does not contain __________
a) the value of the CPU registers
b) the process state
c) memory-management information
d) context switch time
Answer: d
Explanation: The context of a process in the PCB of a process does not contain context switch time. When switching CPU from one process to another, the current context of the process needs to be saved. It includes values of the CPU registers, process states, memory-management information.

33. Which of the following need not necessarily be saved on a context switch between processes?
a) General purpose registers
b) Translation lookaside buffer
c) Program counter
d) All of the mentioned
Answer: b
Explanation: Translation Look-aside Buffer (TLB) need not necessarily be saved on a context switch between processes. A special, small, fast-lookup hardware cache is called Translation Look-aside Buffer. TLB used to reduce memory access time.

34. Which of the following does not interrupt a running process?
a) A device
b) Timer
c) Scheduler process
d) Power failure
Answer: c
Explanation: Scheduler process does not interrupt a running process. Scheduler process selects an available process from a pool of available processes and allocates CPU to it.

35. Which process can be affected by other processes executing in the system?
a) cooperating process
b) child process
c) parent process
d) init process
Answer: a
Explanation: A cooperating process can be affected by other processes executing in the system. Also it can affect other processes executing in the system. A process shares data with other processes, such a process is known as a cooperating process.

36. When several processes access the same data concurrently and the outcome of the execution depends on the particular order in which the access takes place is called ________
a) dynamic condition
b) race condition
c) essential condition
d) critical condition
Answer: b
Explanation: When several processes access the same data concurrently and the outcome of the execution depends on the particular order in which access takes place is called race condition.

37. If a process is executing in its critical section, then no other processes can be executing in their critical section. What is this condition called?
a) mutual exclusion
b) critical exclusion
c) synchronous exclusion
d) asynchronous exclusion
Answer: a
Explanation: If a process is executing in its critical section, then no other processes can be executed in their critical section. This condition is called Mutual Exclusion. Critical section of the process is shared between multiple processes. If this section is executed by more than one or all of them concurrently then the outcome of this is not as per desired outcome. For this reason the critical section of the process should not be executed concurrently.

38. Which one of the following is a synchronization tool?
a) thread
b) pipe
c) semaphore
d) socket
Answer: c
Explanation: Semaphore is a synchronization tool. Semaphore is a mechanism which synchronizes or controls access of threads on critical resources. There are two types of semaphores i) Binary Semaphore ii) Counting Semaphore.

39. A semaphore is a shared integer variable __________
a) that can not drop below zero
b) that can not be more than zero
c) that can not drop below one
d) that can not be more than one
Answer: a
Explanation: A semaphore is a shared integer variable that can not drop below zero. In binary semaphore, if the value of the semaphore variable is zero that means there is a process that uses a critical resource and no other process can access the same critical resource until it is released. In Counting semaphore, if the value of the semaphore variable is zero that means there is no resource available.

40. Mutual exclusion can be provided by the __________
a) mutex locks
b) binary semaphores
c) both mutex locks and binary semaphores
d) none of the mentioned
Answer: c
Explanation: Mutual exclusion can be provided by both mutex locks and binary semaphore. Mutex is a short form of Mutual Exclusion. Binary semaphore also provides a mechanism for mutual exclusion. Binary semaphore behaves similar to mutex locks.

41. When high priority task is indirectly preempted by medium priority task effectively inverting the relative priority of the two tasks, the scenario is called __________
a) priority inversion
b) priority removal
c) priority exchange
d) priority modification
Answer: a
Explanation: When a high priority task is indirectly preempted by a medium priority task effectively inverting the relative priority of the two tasks, the scenario is called priority inversion.

42. Process synchronization can be done on __________
a) hardware level
b) software level
c) both hardware and software level
d) none of the mentioned
Answer: c
Explanation: Process synchronization can be done on both hardware and software level. Critical section problems can be resolved using hardware synchronisation. But this method is not simple for implementation so software synchronization is mostly used.

43. A monitor is a module that encapsulates __________
a) shared data structures
b) procedures that operate on shared data structure
c) synchronization between concurrent procedure invocation
d) all of the mentioned
Answer: d
Explanation: A monitor is a module that encapsulates shared data structures, procedures that operate on shared data structure, synchronization between concurrent procedure invocation.

44. To enable a process to wait within the monitor __________
a) a condition variable must be declared as condition
b) condition variables must be used as boolean objects
c) semaphore must be used
d) all of the mentioned
Answer: a
Explanation: To enable a process to wait within the monitor a condition variable must be declared as condition.

45. Restricting the child process to a subset of the parent’s resources prevents any process from __________
a) overloading the system by using a lot of secondary storage
b) under-loading the system by very less CPU utilization
c) overloading the system by creating a lot of sub-processes
d) crashing the system by utilizing multiple resources
Answer: c
Explanation: Restricting the child process to a subset of the parent’s resources prevents any process from overloading the system by creating a lot of sub-processes. A process creates a child process, child process requires certain resources to complete its task. A child process can demand required resources directly from the system, but by doing this system will be overloaded. So to avoid overloading of the system, the parent process shares its resources among children.

46. A parent process calling _____ system call will be suspended until children processes terminate.
a) wait
b) fork
c) exit
d) exec
Answer: a
Explanation: A parent process calling wait system call will be suspended until children processes terminate. A parameter is passed to wait system call which will obtain exit status of child as well as wait system call returns PID of terminated process.

47. Cascading termination refers to termination of all child processes if the parent process terminates ______
a) Normally
b) Abnormally
c) Normally or abnormally
d) None of the mentioned
Answer: c
Explanation: Cascading termination refers to termination of all child processes if the parent process terminates Normally or Abnormally. Some systems don’t allow child processes to exist if the parent process has terminated. Cascading termination is normally initiated by the operating system.

47. With _____________ only one process can execute at a time; meanwhile all other process are waiting for the processor. With ______________ more than one process can be running simultaneously each on a different processor.
a) Multiprocessing, Multiprogramming
b) Multiprogramming, Uniprocessing
c) Multiprogramming, Multiprocessing
d) Uniprogramming, Multiprocessing
Answer: d
Explanation: With Uniprogramming only one process can execute at a time; meanwhile all other processes are waiting for the processor. With Multiprocessing more than one process can run simultaneously each on different processors. The Uniprogramming system has only one program inside the core while the Multiprocessing system has multiple processes inside multiple cores. The core is one which executes instructions and stores data locally into registers.

48. In UNIX, each process is identified by its __________
a) Process Control Block
b) Device Queue
c) Process Identifier
d) None of the mentioned
Answer: c
Explanation: In Unix, each process is identified by its Process Identifier or PID. The PID provides unique value to each process in the system so that each process can be identified uniquely.

49. In UNIX, the return value for the fork system call is _____ for the child process and _____ for the parent process.
a) A Negative integer, Zero
b) Zero, A Negative integer
c) Zero, A nonzero integer
d) A nonzero integer, Zero
Answer: c
Explanation: In Unix, the return value of the fork system call is Zero for the child process and Non-zero value for parent process. A fork system call returns the PID of a newly created (child) process to the parent and returns Zero to that newly created (child) process.

50. The child process can __________
a) be a duplicate of the parent process
b) never be a duplicate of the parent process
c) cannot have another program loaded into it
d) never have another program loaded into it
Answer: a
Explanation: The child process can be a duplicate of the parent process. The child process created by fork consists of a copy of the address space of the parent process.

51. The child process completes execution, but the parent keeps executing, then the child process is known as __________
a) Orphan
b) Zombie
c) Body
d) Dead
Answer: b
Explanation: The child process completes execution, but the parent keeps executing, then the child process is known as Zombie. When a child process terminates, its resources get deallocated but its entry in the Process Control Block (PCB) remains there until its parent calls wait system call.

Module 3.1

1. Concurrent access to shared data may result in ____________
a) data consistency
b) data insecurity
c) data inconsistency
d) none of the mentioned
Answer: c
Explanation: None.

2. A situation where several processes access and manipulate the same data concurrently and the outcome of the execution depends on the particular order in which access takes place is called ____________
a) data consistency
b) race condition
c) aging
d) starvation
Answer: b
Explanation: None.

3. The segment of code in which the process may change common variables, update tables, write into files is known as ____________
a) program
b) critical section
c) non – critical section
d) synchronizing
Answer: b
Explanation: None.

4. Which of the following conditions must be satisfied to solve the critical section problem?
a) Mutual Exclusion
b) Progress
c) Bounded Waiting
d) All of the mentioned
Answer: d
Explanation: None.

5. Mutual exclusion implies that ____________
a) if a process is executing in its critical section, then no other process must be executing in their critical sections
b) if a process is executing in its critical section, then other processes must be executing in their critical sections
c) if a process is executing in its critical section, then all the resources of the system must be blocked until it finishes execution
d) none of the mentioned
Answer: a
Explanation: None.

6. Bounded waiting implies that there exists a bound on the number of times a process is allowed to enter its critical section ____________
a) after a process has made a request to enter its critical section and before the request is granted
b) when another process is in its critical section
c) before a process has made a request to enter its critical section
d) none of the mentioned
Answer: a
Explanation: None.

7. A minimum of _____ variable(s) is/are required to be shared between processes to solve the critical section problem.
a) one
b) two
c) three
d) four
Answer: b
Explanation: None.

8. In the bakery algorithm to solve the critical section problem ____________
a) each process is put into a queue and picked up in an ordered manner
b) each process receives a number (may or may not be unique) and the one with the lowest number is served next
c) each process gets a unique number and the one with the highest number is served next
d) each process gets a unique number and the one with the lowest number is served next
Answer: b
Explanation: None.

9. An un-interruptible unit is known as ____________
a) single
b) atomic
c) static
d) none of the mentioned
Answer: b
Explanation: None.

10. TestAndSet instruction is executed ____________
a) after a particular process
b) periodically
c) atomically
d) none of the mentioned
Answer: c
Explanation: None.

11. Semaphore is a/an _______ to solve the critical section problem.
a) hardware for a system
b) special program for a system
c) integer variable
d) none of the mentioned
Answer: c
Explanation: None.

12. What are the two atomic operations permissible on semaphores?
a) wait
b) stop
c) hold
d) none of the mentioned
Answer: a
Explanation: None.

13. What are Spinlocks?
a) CPU cycles wasting locks over critical sections of programs
b) Locks that avoid time wastage in context switches
c) Locks that work better on multiprocessor systems
d) All of the mentioned
Answer: d
Explanation: None.

14. What is the main disadvantage of spinlocks?
a) they are not sufficient for many process
b) they require busy waiting
c) they are unreliable sometimes
d) they are too complex for programmers
Answer: b
Explanation: None.

15. The wait operation of the semaphore basically works on the basic _______ system call.
a) stop()
b) block()
c) hold()
d) wait()
Answer: b
Explanation: None.

16. The signal operation of the semaphore basically works on the basic _______ system call.
a) continue()
b) wakeup()
c) getup()
d) start()
Answer: b
Explanation: None.

17. If the semaphore value is negative ____________
a) its magnitude is the number of processes waiting on that semaphore
b) it is invalid
c) no operation can be further performed on it until the signal operation is performed on it
d) none of the mentioned
Answer: a
Explanation: None.

18. The code that changes the value of the semaphore is ____________
a) remainder section code
b) non – critical section code
c) critical section code
d) none of the mentioned
Answer: c
Explanation: None.

19. The following program consists of 3 concurrent processes and 3 binary semaphores. The semaphores are initialized as S0 = 1, S1 = 0, S2 = 0.
Process P0

while(true)
{
    wait(S0);
    print '0';
    release(S1);
    release(S2);
}
 
Process P1
wait(S1);
release(S0);
 
Process P2
wait(S2);
release(S0);

How many times will P0 print ‘0’?
a) At least twice
b) Exactly twice
c) Exactly thrice
d) Exactly once
Answer: a
Explanation: None.

20. Each process Pi, i = 0,1,2,3,……,9 is coded as follows.
repeat

 P(mutex)
 {Critical Section}
 V(mutex)
 forever

The code for P10 is identical except that it uses V(mutex) instead of P(mutex). What is the largest number of processes that can be inside the critical section at any moment (the mutex being initialized to 1)?
a) 1
b) 2
c) 3
d) None of the mentioned
Answer: c
Explanation: Any one of the 9 processes can get into critical section after executing P(mutex) which decrements the mutex value to 0. At this time P10 can enter critical section by incrementing the value to 1. Now any of the 9 processes can enter the critical section by again decrementing the mutex value to 0. None of the remaining processes can get into their critical sections.

21. Two processes, P1 and P2, need to access a critical section of code. Consider the following synchronization construct used by the processes.

Process P1 :
while(true)
{
w1 = true;
while(w2 == true);
Critical section
w1 = false;
}
Remainder Section
 
Process P2 :
while(true)
{
w2 = true;
while(w1 == true);
Critical section
w2 = false;
}
Remainder Section

Here, w1 and w2 have shared variables, which are initialized to false. Which one of the following statements is TRUE about the above construct?
a) It does not ensure mutual exclusion
b) It does not ensure bounded waiting
c) It requires that processes enter the critical section in strict alternation
d) It does not prevent deadlocks but ensures mutual exclusion
Answer: d
Explanation: None.

22. What will happen if a non-recursive mutex is locked more than once?
a) Starvation
b) Deadlock
c) Aging
d) Signaling
Answer: b
Explanation: If a thread which had already locked a mutex, tries to lock the mutex again, it will enter into the waiting list of that mutex, which results in a deadlock. It is because no other thread can unlock the mutex.

23. What is a semaphore?
a) is a binary mutex
b) must be accessed from only one process
c) can be accessed from multiple processes
d) none of the mentioned
Answer: c
Explanation: None.

24. What are the two kinds of semaphores?
a) mutex & counting
b) binary & counting
c) counting & decimal
d) decimal & binary
Answer: b
Explanation: None.

25. What is a mutex?
a) is a binary mutex
b) must be accessed from only one process
c) can be accessed from multiple processes
d) none of the mentioned
Answer: b
Explanation: None.

26. At a particular time of computation the value of a counting semaphore is 7.Then 20 P operations and 15 V operations were completed on this semaphore. The resulting value of the semaphore is? (GATE 1987)
a) 42
b) 2
c) 7
d) 12
Answer: b
Explanation: P represents Wait and V represents Signal. P operation will decrease the value by 1 every time and V operation will increase the value by 1 every time

27. A binary semaphore is a semaphore with integer values ____________
a) 1
b) -1
c) 0.8
d) 0.5
Answer: a
Explanation: None.

28. The following pair of processes share a common variable X.
Process A

int Y;
A1: Y = X*2;
A2: X = Y;   
 
Process B
int Z;
B1: Z = X+1;
B2: X = Z;

X is set to 5 before either process begins execution. As usual, statements within a process are executed sequentially, but statements in process A may execute in any order with respect to statements in process B.
How many different values of X are possible after both processes finish executing?
a) two
b) three
c) four
d) eight
Answer: c
Explanation: Here are the possible ways in which statements from A and B can be interleaved.
A1 A2 B1 B2: X = 11
A1 B1 A2 B2: X = 6
A1 B1 B2 A2: X = 10
B1 A1 B2 A2: X = 10
B1 A1 A2 B2: X = 6
B1 B2 A1 A2: X = 12.

29. The program follows to use a shared binary semaphore T.

Process A  
int Y;            
A1: Y = X*2;      
A2: X = Y;        
signal(T);        
 
Process B
int Z;
B1: wait(T);
B2: Z = X+1;
X = Z;

T is set to 0 before either process begins execution and, as before, X is set to 5.
Now, how many different values of X are possible after both processes finish executing?
a) one
b) two
c) three
d) four
Answer: a
Explanation: The semaphore T ensures that all the statements from A finish execution before B begins. So now there is only one way in which statements from A and B can be interleaved:
A1 A2 B1 B2: X = 11.

30. Semaphores are mostly used to implement ____________
a) System calls
b) IPC mechanisms
c) System protection
d) None of the mentioned
Answer: b
Explanation: None.

31. Spinlocks are intended to provide __________ only.
a) Mutual Exclusion
b) Bounded Waiting
c) Aging
d) Progress
Answer: b
Explanation: None.

32. The bounded buffer problem is also known as ____________
a) Readers – Writers problem
b) Dining – Philosophers problem
c) Producer – Consumer problem
d) None of the mentioned
Answer: c
Explanation: None.

33. In the bounded buffer problem, there are the empty and full semaphores that ____________
a) count the number of empty and full buffers
b) count the number of empty and full memory spaces
c) count the number of empty and full queues
d) none of the mentioned
Answer: a
Explanation: None.

34. In the bounded buffer problem ____________
a) there is only one buffer
b) there are n buffers ( n being greater than one but finite)
c) there are infinite buffers
d) the buffer size is bounded
Answer: b
Explanation: None.

35. To ensure difficulties do not arise in the readers – writers problem _______ are given exclusive access to the shared object.
a) readers
b) writers
c) readers and writers
d) none of the mentioned
Answer: b
Explanation: None.

36. The dining – philosophers problem will occur in case of ____________
a) 5 philosophers and 5 chopsticks
b) 4 philosophers and 5 chopsticks
c) 3 philosophers and 5 chopsticks
d) 6 philosophers and 5 chopsticks
Answer: a
Explanation: None.

37. A deadlock free solution to the dining philosophers problem ____________
a) necessarily eliminates the possibility of starvation
b) does not necessarily eliminate the possibility of starvation
c) eliminates any possibility of any kind of problem further
d) none of the mentioned
Answer: b
Explanation: None.

38. All processes share a semaphore variable mutex, initialized to 1. Each process must execute wait(mutex) before entering the critical section and signal(mutex) afterward.
Suppose a process executes in the following manner.
signal(mutex);

.....
critical section
.....
wait(mutex);

In this situation :
a) a deadlock will occur
b) processes will starve to enter critical section
c) several processes maybe executing in their critical section
d) all of the mentioned
Answer: c
Explanation: None.

39. All processes share a semaphore variable mutex, initialized to 1. Each process must execute wait(mutex) before entering the critical section and signal(mutex) afterward.
Suppose a process executes in the following manner.

wait(mutex);
.....
critical section
.....
wait(mutex);

a) a deadlock will occur
b) processes will starve to enter critical section
c) several processes maybe executing in their critical section
d) all of the mentioned
Answer: a
Explanation: None.

40. Consider the methods used by processes P1 and P2 for accessing their critical sections whenever needed, as given below. The initial values of shared boolean variables S1 and S2 are randomly assigned. (GATE 2010)
Method used by P1 :

while(S1==S2);
Critical section
S1 = S2;
 
Method used by P2 :
while(S1!=S2);
Critical section
S2 = not(S1);

Which of the following statements describes properties achieved?
a) Mutual exclusion but not progress
b) Progress but not mutual exclusion
c) Neither mutual exclusion nor progress
d) Both mutual exclusion and progress
Answer: d
Explanation: None.

41. A monitor is a type of ____________
a) semaphore
b) low level synchronization construct
c) high level synchronization construct
d) none of the mentioned
Answer: c
Explanation: None.

42. A monitor is characterized by ____________
a) a set of programmer defined operators
b) an identifier
c) the number of variables in it
d) all of the mentioned
Answer: a
Explanation: None.

43. A procedure defined within a ________ can access only those variables declared locally within the _______ and its formal parameters.
a) process, semaphore
b) process, monitor
c) semaphore, semaphore
d) monitor, monitor
Answer: d
Explanation: None.

44. The monitor construct ensures that ____________
a) only one process can be active at a time within the monitor
b) n number of processes can be active at a time within the monitor (n being greater than 1)
c) the queue has only one process in it at a time
d) all of the mentioned
Answer: a
Explanation: None.

45. What are the operations that can be invoked on a condition variable?
a) wait & signal
b) hold & wait
c) signal & hold
d) continue & signal
Answer: a
Explanation: None.

46. Which is the process of invoking the wait operation?
a) suspended until another process invokes the signal operation
b) waiting for another process to complete before it can itself call the signal operation
c) stopped until the next process in the queue finishes execution
d) none of the mentioned
Answer: a
Explanation: None.

47. If no process is suspended, the signal operation ____________
a) puts the system into a deadlock state
b) suspends some default process execution
c) nothing happens
d) the output is unpredictable
Answer: c
Explanation: None.

48. A collection of instructions that performs a single logical function is called ____________
a) transaction
b) operation
c) function
d) all of the mentioned
Answer: a
Explanation: None.

49. A terminated transaction that has completed its execution successfully is ____________ otherwise it is __________
a) committed, destroyed
b) aborted, destroyed
c) committed, aborted
d) none of the mentioned
Answer: c
Explanation: None.

50. The state of the data accessed by an aborted transaction must be restored to what it was just before the transaction started executing. This restoration is known as ________ of transaction.
a) safety
b) protection
c) roll – back
d) revert – back
Answer: c
Explanation: None.

51. Write ahead logging is a way ____________
a) to ensure atomicity
b) to keep data consistent
c) that records data on stable storage
d) all of the mentioned
Answer: d
Explanation: None.

52. In the write ahead logging a _____________ is maintained.
a) a memory
b) a system
c) a disk
d) a log record
Answer: d
Explanation: None.

53. An actual update is not allowed to a data item ____________
a) before the corresponding log record is written out to stable storage
b) after the corresponding log record is written out to stable storage
c) until the whole log record has been checked for inconsistencies
d) all of the mentioned
Answer: a
Explanation: None.

54. The undo and redo operations must be _________ to guarantee correct behaviour, even if a failure occurs during recovery process.
a) idempotent
b) easy
c) protected
d) all of the mentioned
Answer: a
Explanation: Idempotent – Multiple executions of an operation have the same result as does one execution.

55. The system periodically performs checkpoints that consists of the following operation(s) ____________
a) Putting all the log records currently in main memory onto stable storage
b) putting all modified data residing in main memory onto stable storage
c) putting a log record onto stable storage
d) all of the mentioned
Answer: d
Explanation: None.

56. Consider a transaction T1 that committed prior to checkpoint. The <T1 commits> record appears in the log before the <checkpoint> record. Any modifications made by T1 must have been written to the stable storage either with the checkpoint or prior to it. Thus at recovery time ____________
a) There is a need to perform an undo operation on T1
b) There is a need to perform a redo operation on T1
c) There is no need to perform an undo and redo operation on T1
d) All of the mentioned
Answer: c
Explanation: None.

57. Serializable schedules are ones where ____________
a) concurrent execution of transactions is equivalent to the transactions executed serially
b) the transactions can be carried out one after the other
c) a valid result occurs after execution transactions
d) none of the mentioned
Answer: a
Explanation: None.

58. A locking protocol is one that ____________
a) governs how locks are acquired
b) governs how locks are released
c) governs how locks are acquired and released
d) none of the mentioned
Answer: c
Explanation: None.

59. The two phase locking protocol consists of ____________
a) growing & shrinking phase
b) shrinking & creation phase
c) creation & growing phase
d) destruction & creation phase
Answer: a
Explanation: None.

60. The growing phase is a phase in which?
a) A transaction may obtain locks, but does not release any
b) A transaction may obtain locks, and releases a few or all of them
c) A transaction may release locks, but does not obtain any new locks
d) A transaction may release locks, and does obtain new locks
Answer: a
Explanation: None.

61. The shrinking phase is a phase in which?
a) A transaction may obtain locks, but does not release any
b) A transaction may obtain locks, and releases a few or all of them
c) A transaction may release locks, but does not obtain any new locks
d) A transaction may release locks, and does obtain new locks
Answer: c
Explanation: None.

62. Which of the following concurrency control protocols ensure both conflict serializability and freedom from deadlock?
I) 2-phase locking
II) Timestamp ordering
a) I only
b) II only
c) Both I and II
d) Neither I nor II
Answer: b
Explanation: None.

Module 3.2

1. What is a reusable resource?
a) that can be used by one process at a time and is not depleted by that use
b) that can be used by more than one process at a time
c) that can be shared between various threads
d) none of the mentioned
Answer: a
Explanation: None.

2. Which of the following condition is required for a deadlock to be possible?
a) mutual exclusion
b) a process may hold allocated resources while awaiting assignment of other resources
c) no resource can be forcibly removed from a process holding it
d) all of the mentioned
Answer: d
Explanation: None.

3. A system is in the safe state if ____________
a) the system can allocate resources to each process in some order and still avoid a deadlock
b) there exist a safe sequence
c) all of the mentioned
d) none of the mentioned
Answer: a
Explanation: None.

4. The circular wait condition can be prevented by ____________
a) defining a linear ordering of resource types
b) using thread
c) using pipes
d) all of the mentioned
Answer: a
Explanation: None.

5. Which one of the following is the deadlock avoidance algorithm?
a) banker’s algorithm
b) round-robin algorithm
c) elevator algorithm
d) karn’s algorithm
Answer: a
Explanation: None.

6. What is the drawback of banker’s algorithm?
a) in advance processes rarely know how much resource they will need
b) the number of processes changes as time progresses
c) resource once available can disappear
d) all of the mentioned
Answer: d
Explanation: None.

7. For an effective operating system, when to check for deadlock?
a) every time a resource request is made
b) at fixed time intervals
c) every time a resource request is made at fixed time intervals
d) none of the mentioned
Answer: c
Explanation: None.

8. A problem encountered in multitasking when a process is perpetually denied necessary resources is called ____________
a) deadlock
b) starvation
c) inversion
d) aging
Answer: b
Explanation: None.

9. Which one of the following is a visual ( mathematical ) way to determine the deadlock occurrence?
a) resource allocation graph
b) starvation graph
c) inversion graph
d) none of the mentioned
Answer: a
Explanation: None.

10. To avoid deadlock ____________
a) there must be a fixed number of resources to allocate
b) resource allocation must be done only once
c) all deadlocked processes must be aborted
d) inversion technique can be used
Answer: a
Explanation: None.

11. The number of resources requested by a process ____________
a) must always be less than the total number of resources available in the system
b) must always be equal to the total number of resources available in the system
c) must not exceed the total number of resources available in the system
d) must exceed the total number of resources available in the system
Answer: c
Explanation: None.

12. The request and release of resources are ___________
a) command line statements
b) interrupts
c) system calls
d) special programs
Answer: c
Explanation: None.

13. What are Multithreaded programs?
a) lesser prone to deadlocks
b) more prone to deadlocks
c) not at all prone to deadlocks
d) none of the mentioned
Answer: b
Explanation: Multiple threads can compete for shared resources.

14. For a deadlock to arise, which of the following conditions must hold simultaneously?
a) Mutual exclusion
b) No preemption
c) Hold and wait
d) All of the mentioned
Answer: d
Explanation: None.

15. For Mutual exclusion to prevail in the system ____________
a) at least one resource must be held in a non sharable mode
b) the processor must be a uniprocessor rather than a multiprocessor
c) there must be at least one resource in a sharable mode
d) all of the mentioned
Answer: a
Explanation: If another process requests that resource (non – shareable resource), the requesting process must be delayed until the resource has been released.

16. For a Hold and wait condition to prevail ____________
a) A process must be not be holding a resource, but waiting for one to be freed, and then request to acquire it
b) A process must be holding at least one resource and waiting to acquire additional resources that are being held by other processes
c) A process must hold at least one resource and not be waiting to acquire additional resources
d) None of the mentioned
Answer: b
Explanation: None.

17. Deadlock prevention is a set of methods ____________
a) to ensure that at least one of the necessary conditions cannot hold
b) to ensure that all of the necessary conditions do not hold
c) to decide if the requested resources for a process have to be given or not
d) to recover from a deadlock
Answer: a
Explanation: None.

18. For non sharable resources like a printer, mutual exclusion ____________
a) must exist
b) must not exist
c) may exist
d) none of the mentioned
Answer: a
Explanation: A printer cannot be simultaneously shared by several processes.

19. For sharable resources, mutual exclusion ____________
a) is required
b) is not required
c) may be or may not be required
d) none of the mentioned
Answer: b
Explanation: They do not require mutually exclusive access, and hence cannot be involved in a deadlock.

20. To ensure that the hold and wait condition never occurs in the system, it must be ensured that ____________
a) whenever a resource is requested by a process, it is not holding any other resources
b) each process must request and be allocated all its resources before it begins its execution
c) a process can request resources only when it has none
d) all of the mentioned
Answer: d
Explanation: c – A process may request some resources and use them. Before it can can request any additional resources, however it must release all the resources that it is currently allocated.

21. The disadvantage of a process being allocated all its resources before beginning its execution is ____________
a) Low CPU utilization
b) Low resource utilization
c) Very high resource utilization
d) None of the mentioned
Answer: b
Explanation: None.

22. To ensure no preemption, if a process is holding some resources and requests another resource that cannot be immediately allocated to it ____________
a) then the process waits for the resources be allocated to it
b) the process keeps sending requests until the resource is allocated to it
c) the process resumes execution without the resource being allocated to it
d) then all resources currently being held are preempted
Answer: d
Explanation: None.

23. One way to ensure that the circular wait condition never holds is to ____________
a) impose a total ordering of all resource types and to determine whether one precedes another in the ordering
b) to never let a process acquire resources that are held by other processes
c) to let a process wait for only one resource at a time
d) all of the mentioned
Answer: a
Explanation: None.

24. Each request requires that the system consider the _____________ to decide whether the current request can be satisfied or must wait to avoid a future possible deadlock.
a) resources currently available
b) processes that have previously been in the system
c) resources currently allocated to each process
d) future requests and releases of each process
Answer: a
Explanation: None.

25. Given a priori information about the ________ number of resources of each type that maybe requested for each process, it is possible to construct an algorithm that ensures that the system will never enter a deadlock state.
a) minimum
b) average
c) maximum
d) approximate
Answer: c
Explanation: None.

26. A deadlock avoidance algorithm dynamically examines the __________ to ensure that a circular wait condition can never exist.
a) resource allocation state
b) system storage state
c) operating system
d) resources
Answer: a
Explanation: Resource allocation states are used to maintain the availability of the already and current available resources.

27. A state is safe, if ____________
a) the system does not crash due to deadlock occurrence
b) the system can allocate resources to each process in some order and still avoid a deadlock
c) the state keeps the system protected and safe
d) all of the mentioned
Answer: b
Explanation: None.

28. A system is in a safe state only if there exists a ____________
a) safe allocation
b) safe resource
c) safe sequence
d) all of the mentioned
Answer: c
Explanation: None.

29. All unsafe states are ____________
a) deadlocks
b) not deadlocks
c) fatal
d) none of the mentioned
Answer: b
Explanation: None.

30. A system has 12 magnetic tape drives and 3 processes : P0, P1, and P2. Process P0 requires 10 tape drives, P1 requires 4 and P2 requires 9 tape drives.
Process    

P0            
P1                             
P2                             
 
Maximum needs (process-wise: P0 through P2 top to bottom)    
10             
4   
9
 
Currently allocated (process-wise)
5
2
2

Which of the following sequence is a safe sequence?
a) P0, P1, P2
b) P1, P2, P0
c) P2, P0, P1
d) P1, P0, P2
Answer: d
Explanation: None.

31. If no cycle exists in the resource allocation graph ____________
a) then the system will not be in a safe state
b) then the system will be in a safe state
c) all of the mentioned
d) none of the mentioned
Answer: b
Explanation: None.

32. The resource allocation graph is not applicable to a resource allocation system ____________
a) with multiple instances of each resource type
b) with a single instance of each resource type
c) single & multiple instances of each resource type
d) none of the mentioned
Answer: a
Explanation: None.

33. The Banker’s algorithm is _____________ than the resource allocation graph algorithm.
a) less efficient
b) more efficient
c) equal
d) none of the mentioned

34. The data structures available in the Banker’s algorithm are ____________
a) Available
b) Need
c) Allocation
d) All of the mentioned
Answer: d
Explanation: None.

35. The content of the matrix Need is ____________
a) Allocation – Available
b) Max – Available
c) Max – Allocation
d) Allocation – Max
View Answer

36. A system with 5 processes P0 through P4 and three resource types A, B, C have A with 10 instances, B with 5 instances, and C with 7 instances. At time t0, the following snapshot has been taken:

Process
P0               
P1               
P2           
P3           
P4       
 
Allocation (process-wise : P0 through P4 top TO bottom) 
A   B   C
0   1   0
2   0   0
3   0   2
2   1   1
0   0   2
 
MAX (process-wise: P0 through P4 top TO bottom)
A   B   C
7   5   3
3   2   2
9   0   2
2   2   2
4   3   3
 
Available
A   B   C
3   3   2

The sequence <P1, P3, P4, P2, P0> leads the system to ____________
a) an unsafe state
b) a safe state
c) a protected state
d) a deadlock
Answer: b
Explanation: None.

36. The wait-for graph is a deadlock detection algorithm that is applicable when ____________
a) all resources have a single instance
b) all resources have multiple instances
c) all resources have a single 7 multiple instances
d) all of the mentioned
Answer: a
Explanation: None.

37. An edge from process Pi to Pj in a wait for graph indicates that ____________
a) Pi is waiting for Pj to release a resource that Pi needs
b) Pj is waiting for Pi to release a resource that Pj needs
c) Pi is waiting for Pj to leave the system
d) Pj is waiting for Pi to leave the system
Answer: a
Explanation: None.

38. If the wait for graph contains a cycle ____________
a) then a deadlock does not exist
b) then a deadlock exists
c) then the system is in a safe state
d) either deadlock exists or system is in a safe state
Answer: b
Explanation: None.

39. If deadlocks occur frequently, the detection algorithm must be invoked ________
a) rarely
b) frequently
c) rarely & frequently
d) none of the mentioned
Answer: b
Explanation: None.

40. What is the disadvantage of invoking the detection algorithm for every request?
a) overhead of the detection algorithm due to consumption of memory
b) excessive time consumed in the request to be allocated memory
c) considerable overhead in computation time
d) all of the mentioned
Answer: c
Explanation: None.

41. A deadlock eventually cripples system throughput and will cause the CPU utilization to ______
a) increase
b) drop
c) stay still
d) none of the mentioned
Answer: b
Explanation: None.

42. Every time a request for allocation cannot be granted immediately, the detection algorithm is invoked. This will help identify ____________
a) the set of processes that have been deadlocked
b) the set of processes in the deadlock queue
c) the specific process that caused the deadlock
d) all of the mentioned
Answer: a
Explanation: None.

43. A computer system has 6 tape drives, with ‘n’ processes competing for them. Each process may need 3 tape drives. The maximum value of ‘n’ for which the system is guaranteed to be deadlock free is?
a) 2
b) 3
c) 4
d) 1
Answer: a
Explanation: None.

44. A system has 3 processes sharing 4 resources. If each process needs a maximum of 2 units then, deadlock ____________
a) can never occur
b) may occur
c) has to occur
d) none of the mentioned
Answer: a
Explanation: None.

45. ‘m’ processes share ‘n’ resources of the same type. The maximum need of each process doesn’t exceed ‘n’ and the sum of all their maximum needs is always less than m+n. In this setup, deadlock ____________
a) can never occur
b) may occur
c) has to occur
d) none of the mentioned
Answer: a
Explanation: None.

46. A deadlock can be broken by ____________
a) abort one or more processes to break the circular wait
b) abort all the process in the system
c) preempt all resources from all processes
d) none of the mentioned
Answer: a
Explanation: None.

47. The two ways of aborting processes and eliminating deadlocks are ____________
a) Abort all deadlocked processes
b) Abort all processes
c) Abort one process at a time until the deadlock cycle is eliminated
d) All of the mentioned
Answer: c
Explanation: None.

48. Those processes should be aborted on occurrence of a deadlock, the termination of which?
a) is more time consuming
b) incurs minimum cost
c) safety is not hampered
d) all of the mentioned
Answer: b
Explanation: None.

49. The process to be aborted is chosen on the basis of the following factors?
a) priority of the process
b) process is interactive or batch
c) how long the process has computed
d) all of the mentioned
Answer: d
Explanation: None.

50. Cost factors for process termination include ____________
a) Number of resources the deadlock process is not holding
b) CPU utilization at the time of deadlock
c) Amount of time a deadlocked process has thus far consumed during its execution
d) All of the mentioned
Answer: c
Explanation: None.

60. If we preempt a resource from a process, the process cannot continue with its normal execution and it must be ____________
a) aborted
b) rolled back
c) terminated
d) queued
Answer: b
Explanation: None.

61. To _______ to a safe state, the system needs to keep more information about the states of processes.
a) abort the process
b) roll back the process
c) queue the process
d) none of the mentioned
Answer: b
Explanation: None.

62. If the resources are always preempted from the same process __________ can occur.
a) deadlock
b) system crash
c) aging
d) starvation
Answer: d
Explanation: None.

63. What is the solution to starvation?
a) the number of rollbacks must be included in the cost factor
b) the number of resources must be included in resource preemption
c) resource preemption be done instead
d) all of the mentioned
Answer: a
Explanation: None.

Module 04

1. What is Address Binding?
a) going to an address in memory
b) locating an address with the help of another address
c) binding two addresses together to form a new address in a different memory space
d) a mapping from one address space to another
Answer: d
Explanation: None.

2. Binding of instructions and data to memory addresses can be done at ____________
a) Compile time
b) Load time
c) Execution time
d) All of the mentioned
Answer: d
Explanation: None.

3. If the process can be moved during its execution from one memory segment to another, then binding must be ____________
a) delayed until run time
b) preponed to compile time
c) preponed to load time
d) none of the mentioned
Answer: a
Explanation: None.

4. What is Dynamic loading?
a) loading multiple routines dynamically
b) loading a routine only when it is called
c) loading multiple routines randomly
d) none of the mentioned
Answer: b
Explanation: None.

5. What is the advantage of dynamic loading?
a) A used routine is used multiple times
b) An unused routine is never loaded
c) CPU utilization increases
d) All of the mentioned
Answer: b
Explanation: None.

6. The idea of overlays is to ____________
a) data that are needed at any given time
b) enable a process to be larger than the amount of memory allocated to it
c) keep in memory only those instructions
d) all of the mentioned
Answer: d
Explanation: None.

7. The ___________ must design and program the overlay structure.
a) programmer
b) system architect
c) system designer
d) none of the mentioned
Answer: a
Explanation: None.

8. The ___________ swaps processes in and out of the memory.
a) Memory manager
b) CPU
c) CPU manager
d) User
Answer: a
Explanation: None.

9. If a higher priority process arrives and wants service, the memory manager can swap out the lower priority process to execute the higher priority process. When the higher priority process finishes, the lower priority process is swapped back in and continues execution. This variant of swapping is sometimes called?
a) priority swapping
b) pull out, push in
c) roll out, roll in
d) none of the mentioned
Answer: c
Explanation: None.

10. If binding is done at assembly or load time, then the process _____ be moved to different locations after being swapped out and in again.
a) can
b) must
c) can never
d) may

Answer: c
Explanation: None.

11. In a system that does not support swapping ____________
a) the compiler normally binds symbolic addresses (variables) to relocatable addresses
b) the compiler normally binds symbolic addresses to physical addresses
c) the loader binds relocatable addresses to physical addresses
d) binding of symbolic addresses to physical addresses normally takes place during execution
Answer: a
Explanation: None.

12. Which of the following is TRUE?
a) Overlays are used to increase the size of physical memory
b) Overlays are used to increase the logical address space
c) When overlays are used, the size of a process is not limited to the size of the physical memory
d) Overlays are used whenever the physical address space is smaller than the logical address space
Answer: c
Explanation: None.

13. The address generated by the CPU is referred to as ____________
a) Physical address
b) Logical address
c) Neither physical nor logical
d) None of the mentioned
Answer: b
Explanation: None.

14. The address loaded into the memory address register of the memory is referred to as ____________
a) Physical address
b) Logical address
c) Neither physical nor logical
d) None of the mentioned
Answer: a
Explanation: None.

15. The run time mapping from virtual to physical addresses is done by a hardware device called the ____________
a) Virtual to physical mapper
b) Memory management unit
c) Memory mapping unit
d) None of the mentioned
Answer: b
Explanation: None.

16. The base register is also known as the ____________
a) basic register
b) regular register
c) relocation register
d) delocation register
Answer: c
Explanation: None.

17. The size of a process is limited to the size of ____________
a) physical memory
b) external storage
c) secondary storage
d) none of the mentioned
Answer: a
Explanation: None.

18. CPU fetches the instruction from memory according to the value of ____________
a) program counter
b) status register
c) instruction register
d) program status word
Answer: a
Explanation: None.

19. A memory buffer used to accommodate a speed differential is called ____________
a) stack pointer
b) cache
c) accumulator
d) disk buffer
Answer: b
Explanation: None.

20. Which one of the following is the address generated by CPU?
a) physical address
b) absolute address
c) logical address
d) none of the mentioned
Answer: c
Explanation: None.

21. Run time mapping from virtual to physical address is done by ____________
a) Memory management unit
b) CPU
c) PCI
d) None of the mentioned
Answer: a
Explanation: None.

22. Memory management technique in which system stores and retrieves data from secondary storage for use in main memory is called?
a) fragmentation
b) paging
c) mapping
d) none of the mentioned
Answer: b
Explanation: None.

23. The main memory accommodates ____________
a) operating system
b) cpu
c) user processes
d) all of the mentioned
Answer: a
Explanation: None.

24. What is the operating system?
a) in the low memory
b) in the high memory
c) either low or high memory (depending on the location of interrupt vector)
d) none of the mentioned
Answer: c
Explanation: None.

25. In contiguous memory allocation ____________
a) each process is contained in a single contiguous section of memory
b) all processes are contained in a single contiguous section of memory
c) the memory space is contiguous
d) none of the mentioned
Answer: a
Explanation: None.

26. The relocation register helps in ____________
a) providing more address space to processes
b) a different address space to processes
c) to protect the address spaces of processes
d) none of the mentioned
Answer: c
Explanation: None.

27. With relocation and limit registers, each logical address must be _______ the limit register.
a) less than
b) equal to
c) greater than
d) none of the mentioned
Answer: a
Explanation: None.

28. In internal fragmentation, memory is internal to a partition and ____________
a) is being used
b) is not being used
c) is always used
d) none of the mentioned
Answer: b
Explanation: None.

29. A solution to the problem of external fragmentation is ____________
a) compaction
b) larger memory space
c) smaller memory space
d) none of the mentioned
Answer: a
Explanation: None.

30. Another solution to the problem of external fragmentation problem is to ____________
a) permit the logical address space of a process to be noncontiguous
b) permit smaller processes to be allocated memory at last
c) permit larger processes to be allocated memory at last
d) all of the mentioned
Answer: a
Explanation: None.

31. If relocation is static and is done at assembly or load time, compaction _________
a) cannot be done
b) must be done
c) must not be done
d) can be done
Answer: a
Explanation: None.

32. The disadvantage of moving all process to one end of memory and all holes to the other direction, producing one large hole of available memory is ____________
a) the cost incurred
b) the memory used
c) the CPU used
d) all of the mentioned
Answer: a
Explanation: None.

33. Which of the following page replacement algorithms suffers from Belady’s Anomaly?
a) Optimal replacement
b) LRU
c) FIFO
d) Both optimal replacement and FIFO
Answer: c
Explanation: None.

34. A process refers to 5 pages, A, B, C, D, E in the order : A, B, C, D, A, B, E, A, B, C, D, E. If the page replacement algorithm is FIFO, the number of page transfers with an empty internal store of 3 frames is?
a) 8
b) 10
c) 9
d) 7
Answer: c
Explanation: None.

35. In question 2, if the number of page frames is increased to 4, then the number of page transfers ____________
a) decreases
b) increases
c) remains the same
d) none of the mentioned
Answer: b
Explanation: None.

36. A memory page containing a heavily used variable that was initialized very early and is in constant use is removed, then the page replacement algorithm used is ____________
a) LRU
b) LFU
c) FIFO
d) None of the mentioned
View Answer
Answer: c
Explanation: None.

37. A virtual memory system uses First In First Out (FIFO) page replacement policy and allocates a fixed number of frames to a process. Consider the following statements.
P : Increasing the number of page frames allocated to a process sometimes increases the page fault rate
Q : Some programs do not exhibit locality of reference
Which of the following is TRUE?
a) Both P and Q are true, and Q is the reason for P
b) Both P and Q are true, but Q is not the reason for P
c) P is false but Q is true
d) Both P and Q are false
Answer: c
Explanation: None.

38. When using counters to implement LRU, we replace the page with the ____________
a) smallest time value
b) largest time value
c) greatest size
d) none of the mentioned
Answer: a
Explanation: Whenever a reference to a page is made, the contents of the clock register are copied into the time-of-use field in the page-table entry for that page. In this way, we always have the time of the last reference to each page.

39. In the stack implementation of the LRU algorithm, a stack can be maintained in a manner ____________
a) whenever a page is used, it is removed from the stack and put on bottom
b) the bottom of the stack is the LRU page
c) the top of the stack contains the LRU page and all new pages are added to the top
d) none of the mentioned
Answer: b
Explanation: None.

40. There is a set of page replacement algorithms that can never exhibit Belady’s Anomaly, called ____________
a) queue algorithms
b) stack algorithms
c) string algorithms
d) none of the mentioned
View Answer
Answer: b
Explanation: None.

41. Applying the LRU page replacement to the following reference string.
1 2 4 5 2 1 2 4
The main memory can accommodate 3 pages and it already has pages 1 and 2. Page 1 came in before page 2.
How many page faults will occur?
a) 2
b) 3
c) 4
d) 5
Answer: c
Explanation: None.

42. Increasing the RAM of a computer typically improves performance because ____________
a) Virtual memory increases
b) Larger RAMs are faster
c) Fewer page faults occur
d) None of the mentioned
Answer: c
Explanation: None.

43. Physical memory is broken into fixed-sized blocks called ________
a) frames
b) pages
c) backing store
d) none of the mentioned
Answer: a
Explanation: None.

44. Logical memory is broken into blocks of the same size called _________
a) frames
b) pages
c) backing store
d) none of the mentioned
Answer: b
Explanation: None.

45. Every address generated by the CPU is divided into two parts. They are ____________
a) frame bit & page number
b) page number & page offset
c) page offset & frame bit
d) frame offset & page offset
Answer: b
Explanation: None.

46. The __________ is used as an index into the page table.
a) frame bit
b) page number
c) page offset
d) frame offset
Answer: b
Explanation: None.

47. The _____ table contains the base address of each page in physical memory.
a) process
b) memory
c) page
d) frame
Answer: c
Explanation: None.

48. In segmentation, each address is specified by ____________
a) a segment number & offset
b) an offset & value
c) a value & segment number
d) a key & value
Answer: a
Explanation: None.

49. In paging the user provides only ________ which is partitioned by the hardware into ________ and ______
a) one address, page number, offset
b) one offset, page number, address
c) page number, offset, address
d) none of the mentioned
Answer: a
Explanation: None.

50. Each entry in a segment table has a ____________
a) segment base
b) segment peak
c) segment value
d) none of the mentioned
Answer: a
Explanation: None.

51. The segment base contains the ____________
a) starting logical address of the process
b) starting physical address of the segment in memory
c) segment length
d) none of the mentioned
Answer: b
Explanation: None.

52. The segment limit contains the ____________
a) starting logical address of the process
b) starting physical address of the segment in memory
c) segment length
d) none of the mentioned
Answer: c
Explanation: None.

Module 05

1. To organise file systems on disk _______________
a) they are split into one or more partitions
b) information about files is added to each partition
c) they are made on different storage spaces
d) all of the mentioned
Answer: b
Explanation: None.

2. The directory can be viewed as a _________ that translates file names into their directory entries.
a) symbol table
b) partition
c) swap space
d) cache
Answer: a
Explanation: None.

3. What will happen in the single level directory?
a) All files are contained in different directories all at the same level
b) All files are contained in the same directory
c) Depends on the operating system
d) None of the mentioned
Answer: b
Explanation: None.

4. What will happen in the single level directory?
a) all directories must have unique names
b) all files must have unique names
c) all files must have unique owners
d) all of the mentioned
Answer: b
Explanation: None.

5. What will happen in the two level directory structure?
a) each user has his/her own user file directory
b) the system doesn’t its own master file directory
c) all of the mentioned
d) none of the mentioned
Answer: a
Explanation: None.

6. When a user job starts in a two level directory system, or a user logs in _____________
a) the users user file directory is searched
b) the system’s master file directory is not searched
c) the master file directory is indexed by user name or account number, and each entry points to the UFD for that user
d) all of the mentioned
Answer: c
Explanation: None.

7. When a user refers to a particular file?
a) system MFD is searched
b) his own UFD is not searched
c) both MFD and UFD are searched
d) every directory is searched
Answer: c
Explanation: None.

8. What is the disadvantage of the two level directory structure?
a) it does not solve the name collision problem
b) it solves the name collision problem
c) it does not isolate users from one another
d) it isolates users from one another
Answer: d
Explanation: None.

9. In the tree structured directories _____________
a) the tree has the stem directory
b) the tree has the leaf directory
c) the tree has the root directory
d) all of the mentioned
Answer: c
Explanation: None.

10. The current directory contains, most of the files that are _____________
a) of current interest to the user
b) stored currently in the system
c) not used in the system
d) not of current interest to the system
Answer: a
Explanation: None.

11. Which of the following are the types of Path names?
a) absolute & relative
b) local & global
c) global & relative
d) relative & local
Answer: a
Explanation: None.

12. An absolute path name begins at the _____________
a) leaf
b) stem
c) current directory
d) root
Answer: d
Explanation: None.

13. A relative path name begins at the _____________
a) leaf
b) stem
c) current directory
d) root
Answer: c
Explanation: None.

14. In a tree structure, when deleting a directory that is not empty?
a) The contents of the directory are safe
b) The contents of the directory are also deleted
c) contents of the directory are not deleted
d) none of the mentioned
Answer: b
Explanation: None.

15. When two users keep a subdirectory in their own directories, the structure being referred to is _____________
a) tree structure
b) cyclic graph directory structure
c) two level directory structure
d) acyclic graph directory
Answer: d
Explanation: None.

16. A tree structure ______ the sharing of files and directories.
a) allows
b) may restrict
c) restricts
d) none of the mentioned
Answer: c
Explanation: None.

17. With a shared file _____________
a) actual file exists
b) there are two copies of the file
c) the changes made by one person are not reflected to the other
d) the changes made by one person are reflected to the other
Answer: d
Explanation: None.

18. In UNIX, what is a link?
a) a directory entry
b) a pointer to another file or subdirectory
c) implemented as an absolute or relative path name
d) all of the mentioned
Answer: d
Explanation: None.

19. The operating system _______ the links when traversing directory trees, to preserve the acyclic structure of the system.
a) considers
b) ignores
c) deletes
d) none of the mentioned
Answer: b
Explanation: None.

20. The deletion of a link ________ the original file.
a) deletes
b) affects
c) does not affect
d) none of the mentioned
Answer: c
Explanation: None.

21. When keeping a list of all the links/references to a file, and the list is empty, implies that _____________
a) the file has no copies
b) the file is deleted
c) the file is hidden
d) none of the mentioned
Answer: b
Explanation: None.

22. When a cycle exists, the reference count maybe non zero, even when it is no longer possible to refer to a directory or file, due to _______
a) the possibility of one hidden reference
b) the possibility of two hidden references
c) the possibility of self referencing
d) none of the mentioned
Answer: c
Explanation: None.

23. ______ is a unique tag, usually a number identifies the file within the file system.
a) File identifier
b) File name
c) File type
d) None of the mentioned
Answer: a
Explanation: None.

24. To create a file ____________
a) allocate the space in file system
b) make an entry for new file in directory
c) allocate the space in file system & make an entry for new file in directory
d) none of the mentioned
Answer: c
Explanation: None.

25. By using the specific system call, we can ____________
a) open the file
b) read the file
c) write into the file
d) all of the mentioned
Answer: d
Explanation: None.

26. File type can be represented by ____________
a) file name
b) file extension
c) file identifier
d) none of the mentioned
Answer: b
Explanation: None.

27. Which file is a sequence of bytes organized into blocks understandable by the system’s linker?
a) object file
b) source file
c) executable file
d) text file
Answer: a
Explanation: None.

28. What is the mounting of file system?
a) crating of a filesystem
b) deleting a filesystem
c) attaching portion of the file system into a directory structure
d) removing the portion of the file system into a directory structure
Answer: c
Explanation: None.

29. Mapping of file is managed by ____________
a) file metadata
b) page table
c) virtual memory
d) file system
Answer: a
Explanation: None.

30. Mapping of network file system protocol to local file system is done by ____________
a) network file system
b) local file system
c) volume manager
d) remote mirror
Answer: a
Explanation: None.

31. Which one of the following explains the sequential file access method?
a) random access according to the given byte number
b) read bytes one at a time, in order
c) read/write sequentially by record
d) read/write randomly by record
Answer: b
Explanation: None.

32. When will file system fragmentation occur?
a) unused space or single file are not contiguous
b) used space is not contiguous
c) unused space is non-contiguous
d) multiple files are non-contiguous
Answer: a
Explanation: None.

33. What is the mount point?
a) an empty directory at which the mounted file system will be attached
b) a location where every time file systems are mounted
c) is the time when the mounting is done
d) none of the mentioned
Answer: a
Explanation: None.

34. When a file system is mounted over a directory that is not empty then _____________
a) the system may not allow the mount
b) the system must allow the mount
c) the system may allow the mount and the directory’s existing files will then be made obscure
d) all of the mentioned
Answer: c
Explanation: None.

35. In UNIX, exactly which operations can be executed by group members and other users is definable by _____________
a) the group’s head
b) the file’s owner
c) the file’s permissions
d) all of the mentioned
Answer: b
Explanation: None.

36. A process _____ lower the priority of another process if both are owned by the same owner.
a) must
b) can
c) cannot
d) none of the mentioned
Answer: b
Explanation: None.

37. In distributed file system ________________ directories are visible from the local machine.
a) protected
b) local
c) private
d) remote
Answer: d
Explanation: None.

38. In the world wide web, a ____ is needed to gain access to the remote files, and separate operations are used to transfer files.
a) laptop
b) plugin
c) browser
d) player
Answer: c
Explanation: None.

39. Anonymous access allows a user to transfer files _____________
a) without having an account on the remote system
b) only if he accesses the system with a guest account
c) only if he has an account on the remote system
d) none of the mentioned
Answer: a
Explanation: The world wide web uses anonymous file exchange almost exclusively.

40. The machine containing the files is the _______ and the machine wanting to access the files is the ______
a) master, slave
b) memory, user
c) server, client
d) none of the mentioned
Answer: c
Explanation: None.

41. Distributed naming services/Distributed information systems have been devised to _____________
a) provide information about all the systems
b) provide unified access to the information needed for remote computing
c) provide unique names to all systems in a network
d) all of the mentioned
Answer: b
Explanation: None.

42. Domain name system provides _____________
a) host-name-to-network-address translations for the entire internet
b) network-address-to-host-name translations for the entire internet
c) binary to hex translations for the entire internet
d) all of the mentioned
Answer: a
Explanation: None.

43. To recover from failures in the network operations _____________ information may be maintained.
a) ip address
b) state
c) stateless
d) operating system
Answer: b
Explanation: None.

44. The series of accesses between the open and close operations is a _____________
a) transaction
b) procedure
c) program
d) file session
Answer: d
Explanation: None.

Module 06

1. I/O hardware contains ____________
a) Bus
b) Controller
c) I/O port and its registers
d) All of the mentioned
Answer: d
Explanation: None.

2. The data-in register of I/O port is ____________
a) Read by host to get input
b) Read by controller to get input
c) Written by host to send output
d) Written by host to start a command
Answer: a
Explanation: None.

3. The host sets _____ bit when a command is available for the controller to execute.
a) write
b) status
c) command-ready
d) control
Answer: c
Explanation: None.

4. When hardware is accessed by reading and writing to the specific memory locations, then it is called ____________
a) port-mapped I/O
b) controller-mapped I/O
c) bus-mapped I/O
d) none of the mentioned
Answer: d
Explanation: It is called memory-mapped I/O.

5. Device drivers are implemented to interface ____________
a) character devices
b) block devices
c) network devices
d) all of the mentioned
Answer: d
Explanation: None.

6. Which hardware triggers some operation after certain programmed count?
a) programmable interval timer
b) interrupt timer
c) programmable timer
d) none of the mentioned
Answer: a
Explanation: None.

7. The device-status table contains ____________
a) each I/O device type
b) each I/O device address
c) each I/O device state
d) all of the mentioned
Answer: d
Explanation: None.

8. Which buffer holds the output for a device?
a) spool
b) output
c) status
d) magic
Answer: a
Explanation: None.

9. Which one of the following connects high-speed high-bandwidth device to memory subsystem and CPU.
a) Expansion bus
b) PCI bus
c) SCSI bus
d) None of the mentioned
Answer: a
Explanation: None.

10. A process is moved to wait queue when I/O request is made with ____________
a) non-blocking I/O
b) blocking I/O
c) asynchronous I/O
d) synchronous I/O
Answer: b
Explanation: None.

11. In _______ information is recorded magnetically on platters.
a) magnetic disks
b) electrical disks
c) assemblies
d) cylinders
Answer: a
Explanation: None.

12. The heads of the magnetic disk are attached to a _____ that moves all the heads as a unit.
a) spindle
b) disk arm
c) track
d) none of the mentioned
Answer: b
Explanation: None.

13. The set of tracks that are at one arm position make up a ___________
a) magnetic disks
b) electrical disks
c) assemblies
d) cylinders
Answer: d
Explanation: None.

14. The time taken to move the disk arm to the desired cylinder is called the ____________
a) positioning time
b) random access time
c) seek time
d) rotational latency
Answer: c
Explanation: None.

15. The time taken for the desired sector to rotate to the disk head is called ____________
a) positioning time
b) random access time
c) seek time
d) rotational latency
Answer: d
Explanation: None.

16. When the head damages the magnetic surface, it is known as _________
a) disk crash
b) head crash
c) magnetic damage
d) all of the mentioned
Answer: b
Explanation: None.

17. A floppy disk is designed to rotate ___________ as compared to a hard disk drive.
a) faster
b) slower
c) at the same speed
d) none of the mentioned
Answer: b
Explanation: None.

18. What is the host controller?
a) controller built at the end of each disk
b) controller at the computer end of the bus
c) all of the mentioned
d) none of the mentioned
Answer: b
Explanation: None.

19. ______ controller sends the command placed into it, via messages to the _____ controller.
a) host, host
b) disk, disk
c) host, disk
d) disk, host
Answer: c
Explanation: None.

20. What is the disk bandwidth?
a) the total number of bytes transferred
b) total time between the first request for service and the completion on the last transfer
c) the total number of bytes transferred divided by the total time between the first request for service and the completion on the last transfer
d) none of the mentioned
Answer: c
Explanation: None.

21. Whenever a process needs I/O to or from a disk it issues a ______________
a) system call to the CPU
b) system call to the operating system
c) a special procedure
d) all of the mentioned
Answer: b
Explanation: None.

22. If a process needs I/O to or from a disk, and if the drive or controller is busy then ____________
a) the request will be placed in the queue of pending requests for that drive
b) the request will not be processed and will be ignored completely
c) the request will be not be placed
d) none of the mentioned
Answer: a
Explanation: None.

23. Consider a disk queue with requests for I/O to blocks on cylinders.
98 183 37 122 14 124 65 67
Considering FCFS (first cum first served) scheduling, the total number of head movements is, if the disk head is initially at 53 is?
a) 600
b) 620
c) 630
d) 640
Answer: d
Explanation: None.

24. Consider a disk queue with requests for I/O to blocks on cylinders.
98 183 37 122 14 124 65 67
Considering SSTF (shortest seek time first) scheduling, the total number of head movements is, if the disk head is initially at 53 is?
a) 224
b) 236
c) 245
d) 240
Answer: b
Explanation: None.

25. Random access in magnetic tapes is _________ compared to magnetic disks.
a) fast
b) very fast
c) slow
d) very slow
Answer: d
Explanation: None.

26. Magnetic tape drives can write data at a speed ________ disk drives.
a) much lesser than
b) comparable to
c) much faster than
d) none of the mentioned
Answer: b
Explanation: None.

27. On media that use constant linear velocity (CLV), the _____________ is uniform.
a) density of bits on the disk
b) density of bits per sector
c) the density of bits per track
d) none of the mentionedAnswer: c
Explanation: The farther a track is from the center of the disk.

28. SSTF algorithm, like SJF __________ of some requests.
a) may cause starvation
b) will cause starvation
c) does not cause starvation
d) causes aging
Answer: a
Explanation: None.

29. In the ______ algorithm, the disk arm starts at one end of the disk and moves toward the other end, servicing requests till the other end of the disk. At the other end, the direction is reversed and servicing continues.
a) LOOK
b) SCAN
c) C-SCAN
d) C-LOOK
Answer: b
Explanation: None.

30. In the _______ algorithm, the disk head moves from one end to the other, servicing requests along the way. When the head reaches the other end, it immediately returns to the beginning of the disk without servicing any requests on the return trip.
a) LOOK
b) SCAN
c) C-SCAN
d) C-LOOK
Answer: c
Explanation: None.

31. In the ______ algorithm, the disk arm goes as far as the final request in each direction, then reverses direction immediately without going to the end of the disk.
a) LOOK
b) SCAN
c) C-SCAN
d) C-LOOK
Answer: a
Explanation: None.

32. The process of dividing a disk into sectors that the disk controller can read and write, before a disk can store data is known as ____________
a) partitioning
b) swap space creation
c) low-level formatting
d) none of the mentioned
Answer: c
Explanation: None.

33. The data structure for a sector typically contains ____________
a) header
b) data area
c) trailer
d) all of the mentioned
Answer: d
Explanation: None.

34. The header and trailer of a sector contain information used by the disk controller such as _________ and _________
a) main section & disk identifier
b) error correcting codes (ECC) & sector number
c) sector number & main section
d) disk identifier & sector number
Answer: b
Explanation: None.

35. The two steps the operating system takes to use a disk to hold its files are _______ and ________
a) partitioning & logical formatting
b) swap space creation & caching
c) caching & logical formatting
d) logical formatting & swap space creation
Answer: a
Explanation: None.

36. The _______ program initializes all aspects of the system, from CPU registers to device controllers and the contents of main memory, and then starts the operating system.
a) main
b) bootloader
c) bootstrap
d) rom
Answer: c
Explanation: None.

37. For most computers, the bootstrap is stored in ________
a) RAM
b) ROM
c) Cache
d) Tertiary storage
Answer: b
Explanation: None.

38. A disk that has a boot partition is called a _________
a) start disk
b) end disk
c) boot disk
d) all of the mentioned
Answer: c
Explanation: None.

39. Defective sectors on disks are often known as __________
a) good blocks
b) destroyed blocks
c) bad blocks
d) none of the mentioned
Answer: c
Explanation: None.

40. In SCSI disks used in high end PCs, the controller maintains a list of _________ on the disk. The disk is initialized during ________ formatting which sets aside spare sectors not visible to the operating system.
a) destroyed blocks, high level formatting
b) bad blocks, partitioning
c) bad blocks, low level formatting
d) destroyed blocks, partitioning
Answer: c
Explanation: None.

41. The scheme used in the above question is known as _______ or ________
a) sector sparing & forwarding
b) forwarding & sector utilization
c) backwarding & forwarding
d) sector utilization & backwarding
Answer: a
Explanation: None.

42. An unrecoverable error is known as _________
a) hard error
b) tough error
c) soft error
d) none of the mentioned
Answer: a
Explanation: None.

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