Operating Systems 03

21. Resources are allocated to the process on non-shareable basis is

[Paper II June 2012]

(A) mutual exclusion

(B) hold and wait

(C) no pre-emption

(D) circular wait

22. Cached and interleaved memories are ways of speeding up memory access between CPU’s and slower RAM. Which memory models are best suited (i.e. improves the performance most) for which programs?     [Paper II June 2012]

(i) Cached memory is best suited for small loops.

(ii) Interleaved memory is best suited for small loops

(iii) Interleaved memory is best suited for large sequential code.

(iv) Cached memory is best suited for large sequential code.

(A) (i) and (ii) are true.

(B) (i) and (iii) are true.

(C) (iv) and (ii) are true.

(D) (iv) and (iii) are true.

23. Consider the following page trace: 4,3, 2, 1, 4, 3, 5, 4, 3, 2, 1, 5

Percentage of page fault that would occur if FIFO page replacement algorithm is used with number of frames for the JOB m = 4 will be                       [Paper II June 2012]

(A) 8                (B) 9

(C) 10             (D) 12

24. Given memory partitions of 100 K, 500 K, 200 K, 300 K and 600 K (in order) and processes of 212 K, 417 K, 112 K, and 426 K (in order), using the first-fit algorithm, in which partition would the process requiring 426 K be placed ?                  [Paper II December 2012]

(A) 500 K

(B) 200 K

(C) 300 K

(D) 600 K

25. The problem of indefinite blockage of low-priority jobs in general priority scheduling algorithm can be solved using:   [Paper II December 2012]

(A) Parity bit

(B) Aging

(C) Compaction

(D) Timer

26. Which of the following memory allocation scheme suffers from external fragmentation?

[Paper II December 2012]

(A) Segmentation

(B) Pure demand paging

(C) Swapping

(D) Paging

27. In UNIX, which of the following command is used to set the task priority?      

[Paper II December 2012]

(A) init

(B) nice

(C) kill

(D) PS

SOLUTIONS

21. A

22.

23. C
The first 4 page references will cause page faults and they are brought into the 4 page frames available. The sequence is shown below
4 - page fault, brought to frame. Page Frame : 4
3 - page fault, brought to frame. Page Frame : 4, 3
2 - page fault, brought to frame. Page Frame : 4, 3, 2
1 - page fault, brought to frame. Page Frame : 4, 3, 2, 1
4 - available in the frame, no page fault occurs. Page Frame : 4, 3, 2, 1
3 - available in the page frame, no page fault occurs. Page Frame : 4, 3, 2, 1
When the fame is full and a page fault occurs, then the page that was first brought in is removed and the referred page is brought in to the frame.
5 - not in the page frame, page fault. 4 is removed and 5 is brought is. Page Frame : 5, 3, 2, 1
4 - not in the page frame, page fault. 3 is removed and 4 is brought is. Page Frame : 5, 4, 2, 1
3 - not in the page frame, page fault. 2 is removed and 3 is brought is. Page Frame : 5, 4, 3, 1
2 - not in the page frame, page fault. 1 is removed and 2 is brought is. Page Frame : 5, 4, 3, 2
1 - not in the page frame, page fault. 5 is removed and 1 is brought is. Page Frame : 1, 4, 3, 2
5 - not in the page frame, page fault. 4 is removed and 5 is brought is. Page Frame : 1, 5, 3, 2

24. A
100 K, 500 K, 200 K, 300 K and 600 K (in order) and processes of 212 K, 417 K, 112 K, and 426 K
According the to the first fit algorithm, the memmory will be scanned to find out the memory portion that is enough for the arriving process, The first such portion found is allocated to the process. In the given example when process of size 212K arrives it is placed in memory portion with size 500K. This leaves an unused space of 288K. Now 417K arrioves it is placed inportion with size 600K, leaving 183K unused. Now 112K arrives and this can be placed in the un used sopace of 183K. Atlast the process of 426K arrives, we dont have memory block large enough to hold this, so we need to remove some already allocated process and allocate that block. 500k block is the one suitable if we do a linear search.
25. B

26. A

27. B
init - Init is the parent of all processes. Its primary role is to create processes from a script stored in the file
nice - run a program with modified scheduling priority
kill - terminate a process

ps - report process status