OS Definition

An operating sytem is software that manages the computer hardware ... [it provides] an environment in which a user can execute prgrams in a convenient and efficent manner.
Silbershatz, Galvin, Gagne, Operating System Concepts.

An operating system must fulfill two main objectives:

1. Interact with the hardware components servicing all low-level programmable elements included in the hardware platform.
2. Provide an execution environment to all applications that run on the computer system (the so-called user programs).

What is an operating system?

1. a piece of software that turns the hardware into something useful
2. layered picture: hardware, OS, applications
3. Three main functions: fault isolate applications, abstract hardware, manage hardware