Dynamic Loading:
o
Routine is not loaded until it is called
o
Better memory-space utilization; unused routine is never loaded.
o
Useful when large amounts of code are needed to handle
infrequently occurring cases.
o
No special support from the operating system is required
implemented through program design.
Dynamic Linking:
Linking postponed until execution time.
o
Small piece of code, stub, used to locate the appropriate
memory-resident library routine.
o
Stub replaces itself with the address of the routine, and executes
the routine.
o
Operating system needed to check if routine is in processes’
memory address.
o
Dynamic linking is particularly useful for libraries.
Overlays:
·
Keep in memory only those instructions and data that are needed at
any given time.
·
Needed when process is larger than amount of memory allocated to
it.
Implemented by user, no special support needed from operating system,
programming design of overlay structure is complex.
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