Welcome to the XV Quiz for CSL 3030 - Operating Systems!

• Answer the multiple-choice questions by selecting the correct option.
• For theoretical questions, provide concise and accurate explanations.
• Feel free to use this quiz for self-assessment or educational purposes.

1. What is XV6?
   • a. A programming language
   • b. A Unix-like operating system
   • c. A file system
   • d. An assembly language

2. XV6 is based on which earlier operating system?
   • a. Windows
   • b. Linux
   • c. BSD
   • d. DOS

3. Which file system is used in XV6?
   • a. FAT32
   • b. NTFS
   • c. ext4
   • d. simple

4. How are system calls implemented in XV6?
   • a. As functions in the C standard library
   • b. As interrupts
   • c. Through the command line
   • d. As external programs

5. In XV6, what is the maximum number of processes that can run simultaneously?
   • a. 128
   • b. 256
   • c. 512
   • d. 1024

6. What is the name of the shell used in XV6?
   • a. Bash
   • b. Zsh
   • c. Sh
   • d. Fish

7. How does XV6 handle process scheduling?
   • a. Round-robin scheduling
   • b. Priority-based scheduling
   • c. First-Come-First-Serve (FCFS)
   • d. Random scheduling

8. Which memory management technique is used in XV6?
   • a. Paging
   • b. Segmentation
   • c. Virtual Memory
   • d. None of the above

9. How are interrupts handled in XV6?
   • a. Through polling
   • b. Using hardware interrupts
   • c. Using software interrupts
   • d. Both b and c

10. Does XV6 support multithreading?
    • a. Yes
    • b. No

11. Who developed XV6?
    • a. Microsoft
    • b. Google
    • c. MIT
    • d. IBM

12. Briefly explain the different states a process can be in within the XV6 operating system.

13. Describe the structure of the file system in XV6. Include the key components and their roles.

14. Explain the difference between system calls and library functions in the context of XV6. Provide examples of each.

15. How does memory paging work in XV6? Discuss the benefits of using paging in memory management.

16. Name and briefly explain three essential shell commands in the XV6 operating system.

17. Discuss the concept of process synchronization in XV6. Why is it essential, and what mechanisms are used to achieve it?

18. Explain the role of interrupts in the XV6 operating system. How are interrupts handled, and what is their significance in system operation?

19. What is virtual memory, and how is it implemented in XV6? Discuss the advantages of using virtual memory.

20. Outline the steps involved in the boot process of XV6. What happens from the moment the computer is powered on to when the XV6 kernel is loaded into memory?

1. b. A Unix-like operating system

2. b. Linux

3. d. simple

4. a. As functions in the C standard library

5. a. 128

6. c. Sh

7. a. Round-robin scheduling

8. a. Paging

9. d. Both b and c

10. b. No

11. c. MIT

12. Answer a. Unused: process before the allocation of resources any resources b. Embryo: when new process is created and is not allocated a stack and a page table c. Sleeping: when sleep() syscall is used d. Runnable: When the process is ready to be executed but not currently in the CPU e. Running: When the process is getting executed in the CPU f. Zombie: When a process has finished executing but the resources that were used by it are not freed

13. Answer The XV6 file system is orgaised in 7 layers in an heirarchial structure, the layers are: File Descriptor: file descriptor layer abstracts many Unix resources (e.g., pipes, devices, files, etc.) using the file system interface Pathname: The pathname layer provides hierarchical path names like /bin/ys/xys/xyz, and resolves them with recursive lookup Directory: A directory can contain a group of files or other directories Inode: The inode layer provides individual files, each with a unique i-number Logging: The logging layer allows higher layers to wrap updates to several blocks in a transaction, and ensures that the blocks are updated atomically in the face of crashes Buffer Cache: The Buffer Cache layer caches disk blocks and synchronizes access to them, making sure that only one kernel process at a time can modify the data stored in any particular block. Disk: Disk hardware traditionally presents the data on the disk as a numbered sequence of 512-byte blocks

14. System calls in XV6 are implemented in the kernel mode library functions are executed in user mode. System calls will have certain previledges and user calls will be unpreviledged

15. In xv6, paging is used for memory management. xv6 uses 32 bit VA, so memory size can go upto 4GB. A page size of 4KB is maintained, and a 2 level page table is used. Paging helps in non- contiguous memory allocation, by dividing memory into frames and programs into pages of equal sizes.

16. 1. ls - shows files and directories in a directory
    2. echo - used for printing whatever we give with it.
    3. grep - find/match some text in file

17. In the xv6 operating system, process synchronization is achieved using locks. This is crucial for maintaining memory consistency and preventing race conditions. Additionally, it helps prevent deadlock situations where processes wait indefinitely for each other to release resources.

18. When an interrupt occurs, the processor execution of current program is stopped and an interrupt handler begins execution. This handler is responsible for dealing and resolving the interrupt. Once this is over, the program again starts (if it has not been terminated). Its register values are saved at the time of interrupt, so that these can be restored at this instant.

19. XV6 has no implementation of virtual memory, It is useful to implement the concept of virtual memory in order to increase the degree of multi-programming

20. BIOS Initialization Boot Loader Execution Kernel Loading Initial Setup Device Initialization Kernel creates the first process, called the init process, which is responsible for initializing the system and starting user applications User Environment Setup Shell Process initialisation and execution by Init process User Interaction using Shell