Fragmented state When fragmented, the
number of seek operations
increases and access
speed decreases.
Optimized state When optimized, the
number of seek
operations decreases
and access speed
increases.
③
②
Optimization
(Defragmentation)
①
③
②
④
④
①
⑤
⑤
Formula for calculating storage capacity
Example
If a floppy disk with the following specifications is formatted, how
many MB is the storage capacity?
No. of tracks per surface
No. of sectors per track
Sector length (bytes)
Storage surface
Computer system
Storage capacity per sector × No. of sectors per track ×
No. of tracks per surface × No. of storage surfaces
Chapter 8
●Calculating the capacity of magnetic disks
The following formula can be used to calculate the storage capacity of a
magnetic disk, and the number of sectors needed to record data.
: 80
: 18
: 512
: Both sides
512 bytes × 18 sectors / per track × 80 tracks / per surface × 2 surfaces =
1,474,560 bytes ≒ 1.4MB
Therefore, the storage capacity is 1.4MB.
Formula for calculating number of sectors needed to store data
Data length ÷ Storage capacity per sector ··· Round to nearest integer
Example
For a floppy disk that has 512 bytes per sector, how many total
sectors are needed to store 500 bytes, 1,400 bytes, and 1,600
bytes of data?
500 bytes ÷ 512 bytes = 0.976 ···· (rounded to nearest integer) = 1 sector
1,400 bytes ÷ 512 bytes = 2.734 ···· (rounded to nearest integer) = 3 sectors
1,600 bytes ÷ 512 bytes = 3.125 ···· (rounded to nearest whole integer) = 4 sectors
1 sector + 3 sectors + 4 sectors = 8 sectors
Therefore, 8 sectors are needed.
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