========
Concepts
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Processes
=========

A program in execution

Address Space
	All memory that a process can read or write.

Thread
	One position of execution in a process. Does not have it's own address space.

Virtual Memory
==============

- Allows multiple programs to have the same view of having a completely 'empty' machine (memory starting at address 0).

- Provides protection -- processes can not write to each other's memory.

System Calls
============

- Often implemented via software interrupts.
- Actual code is in an area with the 'system' bit set, which makes it privileged. 

Engineering
===========

Monolithic
----------

- The all-in-one approach, with one binary.
- Debugging and management can be a problem.
- Eg. Linux.

Microkernels
------------

- Keep only the most necessary bits in kernel mode.
- Most kernel functionality in user mode, managed by the microkernel.