memory management

Question

True or False

S1: In Fixed partition we have both internal and external fragmentation

S2: In variable partition, we have only external fragmentation

Answer 1

Both the statements are correct

Comments

for 2nd case,

supoose i have 50KB memory space. 2 processes( A & B) of 25 KB are there then we allocate first 25KB to A and remaining 25 KB to B.

After 10ms A completes it work and now another process C(20 KB) comes then we allocate C to first block

now in the 1st block we have 5KB empty so is it external fragm. only?

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after allocating C you will have 3 blocks here,

1st --> 20KB

2nd --> 5KB

3rd --> 25KB

caz it is variable length partitions so you don't have 5KB left in 1st block you actually have 5 KB block separate which is external fragmentation

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got it..thanks :)

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In fixed partitioning we have both the frag. problem.

External frag. is removed when along with fixed partitioning of logical space(into pages) and physical space(into frames), physical memory is non contiguous which is paging supports system view of memory

Answer 2

s1 is false becoz fixed size partitioning never suffers for ext frag ,only internal frag is there.

s1 is true.

Comments

S1 is true.

Suppose there are 4 blocks. Each block is of size 4MB

Each block is filled with a 2MB processes. Thus, 8MB is actually free in memory but a new 4MB process cannot be allocated to the free space. This is external fragmentation.

Also, here, note that a 4MB block is allocated 2MB process. This is internal fragmentation.

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Internal Fragmentation even affects the memory management techniques like paging, let alone the fixed partition.