Difference between Internal and External Fragmentation

By Mohit Uniyal|Updated : November 10th, 2022

Difference between Internal and External Fragmentation is that in internal fragmentation, fixed-size storage is designated, whereas, in external fragmentation, variable-size storage is designated. Fragmentation is a process when program memory is used insufficiently for data storage, and ability or efficiency—and occasionally both—are reduced.

Difference between Internal and External Fragmentation PDF

Comparison of internal and external fragmentation helps understand the fragmentation process deeply. Here, we will see the difference between internal and external fragmentation on various factors and explore them individually.

Difference between Internal and External Fragmentation

Internal and External Fragmentation are types of fragmentation in Operating systems. For the GATE exam, candidates must thoroughly understand the comparison of internal and External fragmentation.

Key Differences between Internal and External Fragmentation

Internal FragmentationExternal Fragmentation
Internal fragmentation occurs when a difference exists between the allotted and required memory space. External fragmentation occurs when memory allocation is impossible for noncontiguous memory blocks.
This happens when fixed-size memory blocks are present for allocation.This happens when variable-size memory blocks are present for allocation.
Best Fit Block Search is used to find the solution.Compaction is used to find a solution.
When paging is present, this type of fragmentation occurs.When segmentation is present, this type of fragmentation occurs.
Fixed partitioning makes the occurrence of internal fragmentation.Dynamic partitioning makes the occurrence of external fragmentation.
This method occurs when the worst fit allocation of the memory method is used.When the best and first fit allocation of the memory method is used, this method occurs.

What is Internal Fragmentation?

Internal fragmentation is a type of fragmentation. In this method, mounted-sized block division of the memory occurs. The difference between allotted and required memory blocks makes internal fragmentation. let us understand the internal fragmentation from the figure shown below:

Internal Segmentation

It is shown that there is a difference between the required and the allocated space. This is the process of internal segmentation.

What is External Segmentation?

The external segmentation occurs in the OS when memory space in noncontiguous with abundant space to allocate the blocks. External fragmentation happens when usable storage is divided into smaller portions and is interspersed with designated memory space. Let us understand it with the figure shown below:

External Segmentation

Here, the assigned space is less than the fragments. The memory space is left because there is sufficient memory space. It is an important topic in the GATE CSE syllabus. Here, it is essential to know that assigned space is not adjacent to each other.

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FAQs on Difference between Internal and External Fragmentation

  • The main difference between Internal and External Fragmentation is that Best Fit Block Search is used in internal fragmentation, whereas compaction is used in external fragmentation to find the solution. Both are types of fragmentation.

  • As per the partitioning, the difference between internal and external fragmentation is that in internal fragmentation, Fixed partitioning is available, whereas, in external fragmentation, dynamic partitioning is present.

  • Internal fragmentation is a method to do the mounted-sized block division of memory. In this method, fixed-size memory blocks are assigned to the fragments. The difference exists between allotted and required memory.

  • External fragmentation is a process of fragmentation where noncontiguous memory allocation is done. In this method, the desired memory space is less than available. The allocation in external fragmentation occurs in non-adjacent spaces.

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