Which memory allocation approach is particularly susceptible to external fragmentation in operating systems?

Introduction / Context:
Fragmentation in memory management appears as either internal or external. External fragmentation occurs when free space exists but is divided into small noncontiguous blocks that are insufficient for a request, even though the total free space is adequate. Recognizing which schemes suffer most helps explain design choices like paging or hybrid strategies.

Given Data / Assumptions:

• Segmentation allocates variable-size segments.
• Pure paging uses fixed-size frames/pages.
• Multiple fixed partitions allocate fixed-size blocks (leading to internal, not external, fragmentation).
• Swapping is a mechanism, not an allocation scheme by itself.

Concept / Approach:

Variable-size allocations (e.g., segmentation or dynamic partitions) create gaps as segments are loaded and removed; over time, free memory becomes fragmented externally. Paging, by contrast, eliminates external fragmentation by using uniform page/frame sizes (though it can suffer internal fragmentation in the last page). Fixed partitions also avoid external fragmentation but suffer internal waste when processes do not perfectly fill a partition.

Step-by-Step Solution:

Verification / Alternative check:

OS textbooks emphasize that paging eliminates external fragmentation while segmentation, dynamic partitioning, and heap-like allocators suffer from it.

Why Other Options Are Wrong:

• pure demand paging: fixed-size pages avoid external fragmentation.
• multiple contiguous fixed partitions: mostly internal fragmentation.
• swapping: a process placement mechanism, not the allocation granularity determining fragmentation type.

Common Pitfalls:

• Confusing internal with external fragmentation or conflating swapping with allocation policy.

Final Answer:

segmentation.