# Operating System

QUESTION 3 [17 Marks) (a) Figure 1 shows a diagram of disk storage containing two files, Filel and File2. 1 2 4 File Index block 16 File File2 5 6 7 8 4 9 10 11 12 13 14 15 16 1.8. 17, 18 17 18 19 20 Figure 1 Disk storage i. Redraw Figure 3 and add arrows in the diagram if Filel and File2 start at block 16 and block 4, respectively. [4] State the name of disk allocation technique that is being used. [1] ii. (b) Figure 2 shows a bit map for free space management for a hypothetical Operating System whereby bit O indicates that the block is used and bit 1 indicates that the block is free. Suppose the size of a block is 12KB. Block No 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 Bit Map 1001011010 001011 Figure 2 i. List the block numbers that are allocated to a file named DATA.txt, if the size of the file is 68KB. (3) Is there any block that suffers from fragmentation in storing the DATA.txt? If the answer is a YES, state the block number. Based on the answer, calculate the file size used and the size of the fragmentation in that block. [3] (c) While checking for block consistency, the result of scanning 16 blocks of storage is shown in Figure 3. Block number 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 Blockin used 110 00101 0 3 0 1 0 0 Free block 1001 11103010101 Figure 3 1 i. Based on Figure 3, determine the consistency error(s) exist by stating to the block number of the storage. Justify your answer. [3] ii. For the error(s) stated in (i), suggest a solution to overcome the error(s). [3] QUESTION 3 [17 Marks) (a) Figure 1 shows a diagram of disk storage containing two files, Filel and File2. 1 2 4 File Index block 16 File File2 5 6 7 8 4 9 10 11 12 13 14 15 16 1.8. 17, 18 17 18 19 20 Figure 1 Disk storage i. Redraw Figure 3 and add arrows in the diagram if Filel and File2 start at block 16 and block 4, respectively. [4] State the name of disk allocation technique that is being used. [1] ii. (b) Figure 2 shows a bit map for free space management for a hypothetical Operating System whereby bit O indicates that the block is used and bit 1 indicates that the block is free. Suppose the size of a block is 12KB. Block No 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 Bit Map 1001011010 001011 Figure 2 i. List the block numbers that are allocated to a file named DATA.txt, if the size of the file is 68KB. (3) Is there any block that suffers from fragmentation in storing the DATA.txt? If the answer is a YES, state the block number. Based on the answer, calculate the file size used and the size of the fragmentation in that block. [3] (c) While checking for block consistency, the result of scanning 16 blocks of storage is shown in Figure 3. Block number 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 Blockin used 110 00101 0 3 0 1 0 0 Free block 1001 11103010101 Figure 3 1 i. Based on Figure 3, determine the consistency error(s) exist by stating to the block number of the storage. Justify your answer. [3] ii. For the error(s) stated in (i), suggest a solution to overcome the error(s). [3]