Explain the difference between internal fragmentation and external fragmentation. Provide examples for each.
The Correct Answer and Explanation is :
Internal Fragmentation and External Fragmentation are two types of memory fragmentation that occur in computer systems, affecting how memory is allocated and utilized.
Internal Fragmentation:
Internal fragmentation occurs when memory is allocated in fixed-size blocks, but the process or data being stored doesn’t fully utilize the allocated memory. This leaves unused memory within the allocated space, which is wasted. The wasted memory is internal to the allocated block.
Example of Internal Fragmentation:
Suppose a system allocates memory in blocks of 128 KB. If a process only requires 100 KB, the remaining 28 KB inside the block is wasted. Even though the system might have enough memory available elsewhere, that 28 KB cannot be used by other processes because it is part of a block that has already been allocated.
External Fragmentation:
External fragmentation occurs when free memory is scattered in small blocks throughout the system, preventing larger blocks of memory from being allocated efficiently, even though the total free memory is enough. This is a result of the dynamic allocation and deallocation of memory, which causes gaps between allocated memory blocks.
Example of External Fragmentation:
Imagine a system with 1 MB of memory, where memory is allocated in various-sized blocks. After several allocations and deallocations, you might have small free blocks of memory (e.g., 50 KB, 100 KB, and 30 KB). Despite the total free memory being 180 KB, no single block of memory large enough for a new 200 KB request exists. This is due to the fragmentation of free memory across the system.
Key Differences:
- Internal Fragmentation happens within allocated blocks and is caused by fixed-size allocation.
- External Fragmentation occurs when free memory is fragmented into smaller chunks, making it difficult to allocate larger blocks.
Both types of fragmentation can lead to inefficient memory usage, but they are addressed with different strategies. For internal fragmentation, systems may use variable-sized blocks or memory compaction to minimize waste. For external fragmentation, techniques like memory compaction, paging, or segmentation are often used to mitigate the problem.