Assignment 2

Total of 50 marks. Answer the following questions on paper. Show your work for any calculations.

Treat this assignment as an open-book individual exam. You may consult any of your class notes or other books or documents, paper or electronic. However, you may NOT discuss questions or share answers with any other person until after the assignment is due.

1. How many interrupt levels are available on Intel machines running DOS or Windows? [1]
2. What is the advantage of preemptive multitasking over non-preemptive multitasking? [2]
3. How would you find and remove a hung process in Windows? In UNIX? [4]
4. What are two reasons for defragmenting a disk? [2]
5. Why are memory and disk blocks usually allocated in sizes of powers of two? [2]
6. What is the main difference between segments and pages? [1]
7. Give one advantage of paging over segmentation and one advantage of segmentation over paging. [2]
8. A 32-bit address is divided into a page number and a displacement which produces a page size of 16 KB.
   1. How many pages could be referenced? [3]
   2. How much space would the page table use if each entry is four bytes? [1]
9. Why do modular object-oriented programs run faster than monolithic programs with GOTO statements? [2]
10. What is the advantage of having a separate register to point to the page table or segment table? [1]
11. What two characteristics of pages do page replacement policies use to remove pages? [2]
12. In which hardware device would you normally find real memory? virtual memory? [2]
13. What is the advantage of direct memory access? [1]
14. Why do disks and tape transfer data in blocks of characters rather than a single character at a time? [2]
15. What is the purpose of a buffer? [2]
16. Which two system files make up the core of MS-DOS? [2]
17. How do you refer to an I/O device in DOS? in UNIX? [2]
18. Which file loads DOS device drivers? [1]
19. What steps do you need to take to install a new hardware device on a PC running Windows? [5]
20. What is the capacity of a hard disk with 512 bytes per sector, 200 sectors per track, 1000 cylinders and 4 double-sided platters? [2]
21. What must be done to a new hard disk before installing two different operating systems like Linux and Windows? [2]
22. When Windows is not shut down properly (e.g. if the power is cut), files and file tables can be damaged.
    What two programs can be used to repair the file system? [2]
23. What is the purpose of a cache? [2]
24. What are two reasons that memory performance is much faster than disk performance? [2]