External scheduler

• Responsible to define what process will run in a thread at each time
• Interrupts and resumes tasks (context switching)
• Runs in the most privileged protection ring

Context switching

• It's the act of saving the state (registers, program counter, etc.) of a running process and loading the saved state of another process so it can run.
• Without saving and restoring states, processes wouldn't resume correctly after being paused.