Introduction to Operating Systems Week 4 NPTEL Assignment Answers 2025
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✅ Subject: Introduction to Operating Systems
📅 Week: 4
🎯 Session: NPTEL 2025 July-October
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NPTEL Introduction to Operating Systems Week 4 Assignment Answers 2025
1. Let the number of bits for Interrupt gate descriptor be 48, ie 32:16 (segment selector:offset). Each entry in the interrupt descriptor table is 5 Bytes. What will the total size of the IDT in bytes ?
- 1256
- 1024
- 1020
- 1280
Answer : See Answers
2. State True or False
The user to kernel stack switching is done using Task Segment Descriptor, by changing SS to SS1 and ESP to ESP1
- True
- False
Answer :
3. Which of the following is FALSE. An interrupt occurs in the protected mode.
- Determine the IRQ number from the interrupt controller
- Switch from user to kernel stack
- Save the process states
- None of these
Answer :
4. Interrupt vector number used for system call is xv6 ___________ .
- 16
- 32
- 48
- 64
Answer :
5. What does the the system call sys_uptime() return?
- Time the when system call is invoked
- Time since the start of the process
- The number of clock ticks interrupts that have occurred since the start
- Maximum time the interrupt taken to complete execution
Answer :
6. The signal sent from the processor to the device after receiving an interrupt is
- Interrupt-acknowledge
- Return signal
- Service signal
- Permission signal
Answer :
7. The return address from the interrupt-service routine is stored on the
- Interrupt handler
- Processor register
- Kernel stack
- Memory
Answer : See Answers
8. Which of the following are TRUE in a multiprogrammed OS?
a. More than one program can be in the ready state at the same time.
b. When a program exits, other programs are loaded into ready queue immediately.
c. After a software interrupt occurred, a process in the ready queue may switch to running state
d. If a higher priority process is present in the ready queue, then the running process will immediately switching from running to ready state.- a, b, c
- a, b, d
- a, c, d
- a, b, c, d
Answer :
9. Which of the following does not interrupt a running process?
- A device
- Timer
- Power Failure
- None of the above
Answer :
10. State True/False for each of the following statements.
1. In a multitasking operating system, interrupt (either software, hardware, or exception) is required for the operating system to execute.
2. A context switching occurs whenever the OS executes.- True,True
- True,False
- False, True
- False, False
Answer :
11. Which of the following need not necessarily be saved when context switch occurs?
- Registers
- TLB
- Program counter
- None of the above
Answer :
12. Consider a system having n CPUs, k processes, and k > n. Calculate the upper bound for the number of processes in the READY, RUNNING and BLOCKED states
- k, k, k
- n, n, n
- k, k , n
- k, n, k
Answer : See Answers
13. State True or False
Double fault is a fault that occurs when a CPU is trying to call an exception handler.- True
- False
Answer :
14. Devices that turn on interrupt in xv6?
- UART
- IDE
- Keyboard
- All of these
Answer :
15. Match the following
a. Trapframe 1. Overflow
b. Trap 2. Difficult to recover
c. Fault 3. Restore the context
d. Abort 4. Segment not present- a-3, b-1 c-4, d-2
- a-3, b-4,c-1, d-3
- a-4, b-1, c-3, d-2
- a-4, b-3, c-2, d -1
Answer : See Answers
