Operating Systems

Question 1

What is the kernel?

Answer 1

The kernel is the central part of an operating system that manages system resources and provides services to other parts of the operating system and to applications running on the computer.

Question 2

What is a context switch?

Answer 2

A context switch is a switch from user mode to kernel mode.

This switch is very computationally expensive as items need to be moved in and out of registry and memory, therefore operating systems should strive to avoid “switching” as much as possible.

Question 3

What are the four types of kernel?

Answer 3

Monolithic
Layered
Microkernel
Modular

Question 4

Monolithic

Answer 4

All services are implemented by a contextually large kernel and any new feature is added to the kernel.

In other words, everything is connected to everything.

Question 5

Layered

Answer 5

Services are implemented by a contextually large kernel, with a layered organisation.

For example, a process stored in layer 6 may only communicate with processes from layer 7.

Question 6

Microkernel

Answer 6

Services are instead implemented instead by servers, with a contextually small “micro” kernel delivering messages between them.

So, the kernel, instead of being the one that does everything, instead takes the role of a message handler, directing processes to dedicated “servers”.