GATE CSE 2015 | Set 2 | Question: 30

Question

Consider $6$ memory partitions of sizes $200$ $\text{KB}$, $400$ $\text{KB}$, $600$ $\text{KB}$, $500$ $\text{KB}$, $300$ $\text{KB}$ and $250$ $\text{KB}$, where $\text{KB}$refers to $\text{kilobyte}$. These partitions need to be allotted to four processes of sizes $357$ $\text{KB}$, $210$ $\text{KB}$, $468$ $\text{KB}$, $491$ $\text{KB}$ in that order. If the best-fit algorithm is used, which partitions are NOT allotted to any process?

• A. $200$ $\text{KB}$ and $300$ $\text{KB}$
• B. $200$ $\text{KB}$ and $250$ $\text{KB}$
• C. $250$ $\text{KB}$ and $300$ $\text{KB}$
• D. $300$ $\text{KB}$ and $400$ $\text{KB}$

Comments

Level : Easy 

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Solution

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Option  : (A)  :- 200KB ,300KB

Answer 1

Option (A) is correct because we have $6$ memory partitions of sizes $200 \ KB, 400 \ KB, 600 \ KB, 500 \ KB, 300 \ KB$ and $250 \ KB$ and the partition allotted to the process using best fit is given below:

• $357 \ KB$ process allotted at partition $400 \ KB.$
• $210 \ KB$ process allotted at partition $250 \ KB$
• $468 \ KB$ process allotted at partition $500  \ KB$
• $491 \ KB$ process allotted at partition $600 \ KB$

So, we have left only two partitions $200 \ KB$ and $300 \ KB$

Comments

Answer A

BEST FIT :- We select smallest sufficient partition among free available partition

WORST FIT:-we select largest sufficient partition  among the free available partition

FIRST FIT :-we select first sufficient partition from the top of the memory

NEXT FIT :-we select first sufficient partition from the last of the memory

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Alternate approach, For the best-fit strategy we can do this as well:

Arrange the given partitions in ascending order so we have

200KB

250KB

300KB

400KB

500KB

600KB
Now allocating the processes to blocks we have

200KB -

250KB - 210KB

300KB -

400KB - 357KB

500KB - 468KB

600KB - 491KB
So 200KB and 300KB are the two blocks which are left.

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"IN THAT ORDER" is important.
Allocation with Best fit remains the same even if we do not consider "in that order" for this question, however, it may give different results for different values of process sizes.

 

Answer 2

Ans A

Best fit policy is choose smallest big enough chunk of memory.

Comments

@Vikrant Singh

sir, how to understand that question is of Fixed partition or variable?

means holes created can be filled or not ?

Answer 3

Option A is the correct Answer

Only partitions 200KB and 300KB are left vacant --> 

Answer 4

https://youtu.be/lLiIW-tnGeI

Answer 5

best fit means the tight enough in simple enough actually my words means the smallest enogh to need to allocate the part.

for 357kb small ==> 400kb,210kb small enough ==> 250kb , 468kb ==> 500kb , 491kb ==> 600kb so remaining the 200 and 300kb remains .. so ans is A