What are the two types of fragmentation Illustrate them with block diagrams?

Answer 1

Ans) In computer storage, fragmentation is a phenomenon in which storage space is used inefficiently, reducing capacity and often performance. Fragmentation leads to storage space being "wasted", and the term also refers to the wasted space itself.

There are three different but related forms of fragmentation: external fragmentation, internal fragmentation, and data fragmentation, which can be present in isolation or conjunction. Fragmentation is often accepted in return for improvements in speed or simplicity.

Internal fragmentation: Due to the rules governing memory allocation, more computer memory is sometimes allocated than is needed. For example, memory can only be provided to programs in chunks divisible by 4, 8 or 16, and as a result if a program requests perhaps 23 bytes, it will actually get a chunk of 24. When this happens, the excess memory goes to waste. In this scenario, the unusable memory is contained within an allocated region, and is thus termed internal fragmentation. Slack space is a very important source of evidence in computer forensic investigation.

External fragmentation

External fragmentation arises when free memory is separated into small blocks and is interspersed by allocated memory. It is a weakness of certain storage allocation algorithms, when they fail to order memory used by programs efficiently. The result is that, although free storage is available, it is effectively unusable because it is divided into pieces that are too small individually to satisfy the demands of the application. The term "external" refers to the fact that the unusable storage is outside the allocated regions. External fragmentation also occurs in file systems as many files of different sizes are created, change size, and are deleted. The effect is even worse if a file which is divided into many small pieces is deleted, because this leaves similarly small regions of free spaces.

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0x1000

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Comments

Start with all memory available for allocation.

A

B

C

Allocated three blocks A, B, and C, of size 0x1000.

A

C

Freed block B. Notice that the memory that B used cannot be included for an allocation larger than B's size.