n Memory references are dynamically translated into
physical addresses at run time
u a process may be swapped in and out of main
memory such that it occupies different regions
n A process may be broken up into pieces (pages or
segments) that do not need to be located
contiguously in main memory
n Hence: all pieces of a process do not need to be
loaded in main memory during execution
u computation may proceed for some time if the next
instruction to be fetch (or the next data to be accessed) is
in a piece located in main memory