Concepts

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.