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In a file allocation system, which of the following allocation scheme(s) can be used if no external fragmentation is allowed?

1. Contiguous
3. Indexed
1. $1$ and $3$ only
2. $2$ only
3. $3$ only
4. $2$ and $3$ only

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Both Linked and Indexed allocation free from external fragmentation

Refer: Galvin

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In galvin, allocation methods in file system chapter 11.

@srestha@Bikram plz let me know if i am wrong

Internal Fragmentation

1) It occurs when memory is divided into fixed-sized partitions.

2) it occurs contiguous & non contiguous allocation

3)non contiguous allocation avoid external fragmentation.

External Fragmentation

1)It occurs when memory is divided into variable-sized partitions based on size of process.

2) it does not occur when memory allocated in non contiguous manner.

Plz search Wikipedia for it.
Option D: Both Indexed and Linked file allocation schemes do not suffer from external fragmentation,  Whereas Contiguous allocation suffer from external fragmentation & Internal fragmentation may exist in the last disk block of a file.
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Internal Fragmentation will be there in all the allocations.

in dynamic memory allocation, memory pools drastically cut internal fragmentation by spreading the space overhead over a larger number of objects.

IF we have a file of size 1020 B and block size is 512 B

Then every allocation technique will give Internal fragmentation as last block wil  be partially filled

So all techniques suffer from Internal fragmentation is right ???

Yes, all will suffer from internal fragmentation given File size is not a multiple of Block size.

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