ISRO2020-46

Question

A magnetic disk has $100$ cylinders, each with $10$ tracks of $10$ sectors. If each sector contains $128$ bytes, what is the maximum capacity of the disk in kilobytes?

• A. $1,280,000$
• B. $1280$
• C. $1250$
• D. $128,000$

Comments

option c) 1250

Answer 1

$\underline{\textbf{Answer:}\Rightarrow}\;\mathbf{c.}$

Magnetic disk capacity $=100\times 10 \times 10 \times 128 \\= 1280000\;\text{Bytes}\\=\dfrac{12380000}{1024} \;\text{KB}\\= 1250\;\text{KB}$

Comments

what is the actual meaning of cylinders.

Number of platters or Number of Tracks in a platter.

Because the defn of cylinder is taking same track from all platters.

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No!

The cylinder is always the number of tracks and not the platters.

We have a separate word for platters which is "platter" only.

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So, according to qsn 100 cylinders means 100 tracks ??

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Yes, definitely.

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A magnetic disk has 100 cylinders, each with 10 tracks of 10 sectors

#platters = ??

#tracks = 100 or 10

please confirm this 

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Don't confused.

The number of cylinders = 100.

Number of tracks = 10

Number of sectors = 10

I know why are you getting confused.

See, its better we don't talk about the platter until its exclusively mentioned.

Because people can talk about platters in 2 ways, i.e, one side data one or two side data one platter.

So, better not to think if its not mentioned.

Think about only if its given in the question.

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though I follow this approach but I feel qsn statment is ambiguous.

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From Wikipedia, 

standard says,

1. kilobyte should be unambiguously referred as $1000$ bytes.

2. kibibytes  should be unambiguously referred as $1024$ bytes.

Which makes option (B) correct. 

@`JEET

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It has to be divided with $1024$ only.

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since in (SI) 1kB=1000byte and in base2 1KB or 1KiB=1024bytes.

ans should be B

i will claim this question.

Answer 2

Magnetic disk has 100 cylinder. Each cylinder contains 10 tracks.

Each track contain 10 sector & each sector contains 128 B of data.

Total Capacity = (No. of cylinder) * (No. of track in each cylinder) * (No. of sector in each track) * (Capacity of each sector)

= 100 * 10 * 10 * 128 B = 1280000 B = (1280000 / 1024 ) KB = 1250 KB.

So, maximum capacity is 1250 KB.

Answer 3

Capacity of disk= # of cylinder $*$ # of tracks/cylinder $*$ # of sector/track $*$ # of bytes/sector

$C= 100*10*10*128=1280000 B$

$C=1280000/1024 = 1250 KB$

Option c) is correct