Introduction and Overview

Question 1

Define an operating system (OS)

Answer 1

An operating system (OS) is a software that connects user application software with the computer hardware.

Question 2

Virtualization

Answer 2

The operating system provides an illusion to every running computer program that it has exclusive control of the Central Processing Unit (CPU) and memory, while many other programs actually share them. This feature of an OS is known as virtualization.

Question 3

Concurrency

Answer 3

The OS feature of executing multiple programs simultaneously (concurrently) without any failures is called concurrency.

Question 4

Persistency

Answer 4

The OS feature that preserves all computer data even after the machine is rebooted, be it intentionally or accidentally, is called persistency.

Question 5

Define a typical UNIX system

Answer 5

The structure/architecture of a UNIX system can be divided into 2 levels - the user-space level and the kernel-space level.

• The user-space level is made up of applications and libraries.
• The kernel-space level is made up of 2 layers - an (inner) Portable OS layer, which contains system calls like