..........happens when the memory is split into fixed -sized blocks

External fragmentation : memory in a partition not used by a process is not available to other processes

External fragmentation : job loading and
unloading produces empty holes scattered throughout memory

in Fixed Partitions Hardware requirements: base register and limit register

in Variable Partitions Hardware requirements base register and limit register

Solve the external fragmentation problem by making the units small

Page size is often a power of 2

in Address translation physical address is PFN+offset

The (M) Modify bit says whether the page has been accessed

The(V) Valid bit says whether or not the PTE can be used

The virtual page number (VPN) determines physical page

A simple technique is a three-level page table

in Two-Level Page Tables Virtual addresses (VAs) have three parts

in Paging Limitations Can still have External fragmentation

segmentation = 1 segment/process

segmentation = many segments/process

page (logical) => page frame (physical)

in Hardware support multiple base/limit pairs, two per segment

Cooperative Process: One process's execution has an effect on the execution of other processes.

Independent Process: the execution of one process has impact on the execution of the others

Processes can execute concurrently or in series