Question

Explain Internal and External Fragmentations.

Answer 1

Internal fragmentation is the wasted space within each allocated block because of rounding up from the actual requested allocation to the allocation granularity. External fragmentation is the various free spaced holes that are generated in either your memory or disk space.

Answer 2

● Internal fragmentation occurs when the memory is divided into fixed sized blocks. Whenever a process request for the memory, the fixed sized block is allocated to the process. In case the memory assigned to the process is somewhat larger than the memory requested, then the difference between assigned and requested memory is the Internal fragmentation.

● External fragmentation occurs when there is a sufficient amount of space in the memory to satisfy the memory request of a process. But the process’s memory request can not be satisfied as the memory available is in a non-contiguous manner. Either you apply first-fit or best-fit memory allocation strategy it will cause external fragmentation.

When a process is loaded and removed from the memory the free space creates the hole in the memory space, and there are many such holes in the memory space, this is called External fragmentation.

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Difference between Internal fragmentation and External fragmentation :-

◆ The basic reason behind the occurrences of internal and external fragmentation is that internal fragmentation occurs when memory is partitioned into fixed-sized blocks whereas external fragmentation occurs when memory is partitioned into variable size blocks.

◆ When the memory block allotted to the process comes out to be slightly larger than requested memory, then the free space left in the allotted memory block causes internal fragmentation. On the other hands, when the process is removed from the memory it creates free space causing a hole in the memory which is called external fragmentation.

◆ The problem of internal fragmentation can be solved by partitioning the memory into variable sized blocks and assign the best fit block to the requesting process. However, the solution for external fragmentation is compaction, but it is expensive to implement, so the processes must be allowed to acquire physical memory in a non-contiguous manner, to achieve this the technique of paging and segmentation is introduced.