External Fragmentation Explained

External fragmentation is a common issue in memory management within operating systems. It occurs when the system has enough total free memory to satisfy a memory allocation request, but this free memory is broken into small, non-contiguous pieces (often called 'holes'). Because these holes are not adjacent to each other, a large contiguous block cannot be formed, and thus the memory cannot be allocated despite the sufficient total free space.

Analyzing the Options

Option 1 Analysis:

This option correctly defines external fragmentation. It highlights the key condition: 'When enough total memory space exists to satisfy a request, but it is not contiguous, storage is fragmented into a large number of small holes.' This accurately captures the essence of the problem where the size is sufficient, but the continuity is lacking.

Option 2 Analysis:

This option is incorrect. It states that the memory *is* contiguous while also mentioning fragmentation. External fragmentation specifically happens when the required memory is *not* contiguous, even if the total available memory is large enough.

Option 3 Analysis:

This option, 'When memory is empty,' is too vague and incorrect. External fragmentation is about the *state* and *distribution* of free memory, not simply whether it is empty. Memory can be empty but still fragmented internally or externally.

Option 4 Analysis:

The statement 'Always' is incorrect. External fragmentation is a conditional state that arises due to specific patterns of memory allocation and deallocation, particularly with dynamic memory management techniques. It doesn't constantly occur.

Conclusion on External Fragmentation

Based on the analysis, external fragmentation occurs precisely when the total available memory is sufficient for a request, but it is scattered into multiple, non-adjacent blocks, preventing the allocation of a single, continuous block.