1. All processes in the main memory are asleep.
2. All "ready-to-run" processes are swapped out.
3. There is no space in the swap device for the new incoming process that are swapped out of the main memory.
4. There is no space in the main memory for the new incoming process.
1. Memory architecture must based on Pages,
2. The machine must support the 'restartable' instructions.
It's the nature of the processes that they refer only to the small subset of the total data space of the process. i.e. the process frequently calls the same subroutines or executes the loop instructions.
The set of pages that are referred by the process in the last "n", references, where "n" is called the window of the working set of the process.
The window of the working set of a process is the total number in which the process had referred the set of pages in the working set of the process.