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).

Bovet, Cesati, Understanding the Linux Kernel

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
Frans Kaashoek

An operating system, as we use the term, means a collection of programs that are sufficient to use the computer to do a wide variety of jobs. A general purpose operating system, to be complete, ought to handle all the jobs that many users may want to do.

The kernel is one of the programs in an operating system - the program that allocates the machine's resources to the other programs that are running. The kernel also takes care of starting and stopping other programs.

Richard Stallman