operating system full MCQ interviews question and answer
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
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| operating system full MCQ interviews question and answer |
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
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
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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
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9. What is an ISR?
a) Information Service Request
b) Interrupt Service Request
c) Interrupt Service Routine
d) Information Service Routine
answer : ==: c
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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
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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
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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
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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
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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
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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
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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
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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
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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
22. The chmod command invokes the ____ system call.
a) chmod
b) ch
c) read
d) change
answer : ==: a
23. For reading input, which of the following system call is used?
a) write
b) rd
c) read
d) change
answer : ==: c
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
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, sleek).
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)
. 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.
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.
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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.
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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.
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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.
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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.
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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.
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
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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
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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
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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
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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
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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
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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
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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
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9. An un-interruptible unit is known as ____________
a) single
b) atomic
c) static
d) none of the mentioned
answer : ==: b
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10. TestAndSet instruction is executed ____________
a) after a particular process
b) periodically
c) atomically
d) none of the mentioned
answer : ==: c
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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
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12. What are the two atomic operations permissible on semaphores?
a) wait
b) stop
c) hold
d) none of the mentioned
answer : ==: a
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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
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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
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15. The wait operation of the semaphore basically works on the basic _______ system call.
a) stop()
b) block()
c) hold()
d) wait()
answer : ==: b
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16. The signal operation of the semaphore basically works on the basic _______ system call.
a) continue()
b) wakeup()
c) getup()
d) start()
answer : ==: b
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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
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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
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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
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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.
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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
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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
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24. What are the two kinds of semaphores?
a) mutex & counting
b) binary & counting
c) counting & decimal
d) decimal & binary
answer : ==: b
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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
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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
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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
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31. Spinlocks are intended to provide __________ only.
a) Mutual Exclusion
b) Bounded Waiting
c) Aging
d) Progress
answer : ==: b
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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52. In the write ahead logging a _____________ is maintained.
a) a memory
b) a system
c) a disk
d) a log record
answer : ==: d
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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
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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
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56. Consider a transaction T1 that committed prior to checkpoint. The record appears in the log before the 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
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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
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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
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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
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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
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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
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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
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