Suppose there are six files F1, F2, F3, F4, F5, F6 with corresponding sizes 150 KB, 225 KB, 75 KB, 60 KB, 275 KB and 65 KB respectively. The files are to be stored on a sequential device in such a way that optimizes access time. In what order should the files be stored ?a)F5, F2, F1, F3, F6, F4b)F4, F6, F3, F1, F2, F5c)F1, F2, F3, F4, F5, F6d)F6, F5, F4, F3, F2, F1Correct answer is option 'B'. Can you explain this answer?

Question

Answer

For access time optimization sort the files in incresing order of file size. So, option (B) is correct.

Answer

Explanation:

To optimize access time, the files should be stored in such a way that reduces seek time. Seek time is the time taken by the device to position the read/write head to the desired location on the storage medium.

Seek time is influenced by the following factors:
1. Distance: The distance the read/write head needs to move to access the file.
2. Order: The order in which the files are stored on the device.

To minimize seek time, we should arrange the files in increasing order of their sizes, as smaller files will require less movement of the read/write head.

Calculating the seek time for each option:

Let's calculate the seek time for each option and choose the one with the minimum seek time.

a) F5, F2, F1, F3, F6, F4:
Seek Time = Distance(F5, F2) + Distance(F2, F1) + Distance(F1, F3) + Distance(F3, F6) + Distance(F6, F4)

b) F4, F6, F3, F1, F2, F5:
Seek Time = Distance(F4, F6) + Distance(F6, F3) + Distance(F3, F1) + Distance(F1, F2) + Distance(F2, F5)

c) F1, F2, F3, F4, F5, F6:
Seek Time = Distance(F1, F2) + Distance(F2, F3) + Distance(F3, F4) + Distance(F4, F5) + Distance(F5, F6)

d) F6, F5, F4, F3, F2, F1:
Seek Time = Distance(F6, F5) + Distance(F5, F4) + Distance(F4, F3) + Distance(F3, F2) + Distance(F2, F1)

Calculating the seek time:

To calculate the seek time, we need to determine the distance between each pair of files. Assuming the read/write head starts at the first file and moves linearly to the subsequent files, the distance between two files can be calculated as the absolute difference between their sizes.

Seek Time for option a:
Distance(F5, F2) = |275 - 225| = 50
Distance(F2, F1) = |225 - 150| = 75
Distance(F1, F3) = |150 - 75| = 75
Distance(F3, F6) = |75 - 65| = 10
Distance(F6, F4) = |65 - 60| = 5

Seek Time (a) = 50 + 75 + 75 + 10 + 5 = 215

Seek Time for option b:
Distance(F4, F6) = |60 - 65| = 5
Distance(F6, F3) = |65 - 75| = 10
Distance(F3, F1) = |75 - 150| = 75
Distance(F1, F2) = |150 - 225| = 75
Distance(F2, F5) = |225 -

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