Fixed vs Dynamic Partitioning

Fixed Partitioning: Memory Divided Into Set Sizes Upfront

Physical Memory divided in advance into fixed-size partitions:
+----------+----------+----------+----------+
| 100k     | 100k     | 100k     | 100k     |
+----------+----------+----------+----------+

Fixed partitioning divides memory into a set number of partitions, decided in advance, before any process is loaded. Each process is placed into a partition large enough to hold it - simple to implement, but the partition sizes are set upfront and cannot easily be changed afterward.

The Waste Problem With Fixed Partitions

A small process placed into a large, fixed-size partition wastes all the unused space inside that partition - this specific kind of waste is exactly what's called internal fragmentation, covered in detail in the next note.

Dynamic Partitioning: Sized Exactly to Fit Each Process

Physical Memory, dynamically sized to fit exactly:
+--------+------------+----------+---------+
| OS     | Process A  | Process B| (free)  |
+--------+------------+----------+---------+
  (partition sizes exactly match each process's actual needs)

Dynamic partitioning creates a partition of exactly the size a process actually needs, at the moment it's loaded - no wasted space within any single partition, since each block precisely matches its process's real requirement.

The Trade-off Dynamic Partitioning Introduces Instead

As processes of varying sizes are repeatedly loaded and later removed, the free memory between remaining processes becomes broken up into many small, scattered gaps - this different kind of waste is external fragmentation, also covered in detail in the next note.

Comparing the Two Approaches